minerals Article Indium Mineralization in the Volcanic Dome-Hosted Ánimas–Chocaya–Siete Suyos Polymetallic Deposit, Potosí, Bolivia Lisard Torró 1,* , Malena Cazorla 2, Joan Carles Melgarejo 2 , Antoni Camprubí 3, Marta Tarrés 2, Laura Gemmrich 2, Marc Campeny 2,4, David Artiaga 2, Belén Torres 2, Álvaro Martínez 5, Diva Mollinedo 6, Pura Alfonso 7 and Osvaldo R. Arce-Burgoa 8,† 1 Geological Engineering Program, Faculty of Sciences and Engineering, Pontifical Catholic University of Peru (PUCP), Av. Universitaria 180, San Miguel, Lima 15088, Peru 2 Departament de Mineralogia, Petrologia i Geologia Aplicada, Universitat de Barcelona (UB), C/Martí i Franquès s/n, 08028 Barcelona, Spain; malecama.97@gmail.com (M.C.); joan.carles.melgarejo.draper@ub.edu (J.C.M.); martatm10@hotmail.com (M.T.); lauragemmrich.macia@gmail.com (L.G.); mcampenyc@bcn.cat (M.C.); dartiaga@ub.edu (D.A.); belentcgeo@gmail.com (B.T.) 3 Instituto de Geología, Universidad Nacional Autónoma de México. Ciudad Universitaria, Coyoacán, CDMX 04510, Mexico; camprubitaga@gmail.com 4 Departament de Mineralogia, Museu de Ciències Naturals de Barcelona, 08003 Barcelona, Spain 5 Department of Earth Sciences, University of Geneva, Rue des Maraîchers 13, 1205 Geneva, Switzerland; alvaro@bizkaia.eu 6 Facultad de Ciencias Geológicas, Universidad Mayor San Andrés, Av. Villazón N◦ 1995, Plaza del Bicentenario–Zona Central, La Paz 2314, Bolivia; diva.moshi@gmail.com 7 Departament d’Enginyeria Minera, Industrial i TIC, Universitat Politècnica de Catalunya, Av. de les Bases de Manresa 61-73, Manresa, 08242 Barcelona, Spain; maria.pura.alfonso@upc.edu 8 Colegio de Geólogos de Bolivia, Edificio Señor de la Exaltación Nro. 4683, Av. Hernando Siles entre calles 1 y 2, Zona de Obrajes, Casilla 8941, La Paz, Bolivia; oarce.cgb@gmail.com * Correspondence: lisardtorro@hotmail.com; Tel.: +51-912-617-691 † Current address: Eloro Resources Ltd. Av. La Floresta 497, Of. 101, San Borja, Lima 15037, Perú.  Received: 31 August 2019; Accepted: 29 September 2019; Published: 1 October 2019  Abstract: A volcanic dome complex of Miocene age hosts the In-bearing Ánimas–Chocaya–Siete Suyos district in SW Bolivia. Ore mineralization occurs as banded and massive infillings in sub-vertical, NE-SW striking veins. In this article, a detailed petrographic study is combined with in situ mineral geochemistry determinations in ore from the Arturo, Chorro and Diez veins in the Siete Suyos mine, the Ánimas, Burton, Colorada, and Rosario veins in the Ánimas mine and the Nueva vein in the Chocaya mine. A three-stage paragenetic sequence is roughly determined for all of them, and includes (1) an early low-sulfidation stage that is dominated by cassiterite, pyrrhotite, arsenopyrite, and high-Fe sphalerite (FeS > 21 mol. %); (2) a second intermediate-sulfidation stage dominated by pyrite + marcasite ± intermediate product, sphalerite (FeS < 21 mol. %), stannite, and local famatinite; and, (3) a late intermediate-sulfidation stage dominated by galena and Ag-Pb-Sn sulfosalts. Electron-probe microanalyses reveal high indium enrichment in stage-2 sphalerite (up to 9.66 wt.% In) and stannite (up to 4.11 wt.% In), and a moderate enrichment in rare wurtzite (up to 1.61 wt.% In), stage-1 sphalerite (0.35 wt.% In), cassiterite (up to 0.25 wt.% In2O3), and ramdohrite (up to 0.24 wt.% In). Therefore, the main indium mineralization in the district can be associated to the second, intermediate-sulfidation stage, chiefly in those veins in which sphalerite and stannite are more abundant. Atomic concentrations of In and Cu in sphalerite yield a positive correlation at Cu/In = 1 that agrees with a (Cu+ + In3+)↔ 2Zn2+ coupled substitution. The availability of Cu in the mineralizing fluids during the crystallization of sphalerite is, in consequence, essential for the incorporation of indium in its crystal lattice and would control the distribution of indium enrichment Minerals 2019, 9, 604; doi:10.3390/min9100604 www.mdpi.com/journal/minerals Minerals 2019, 9, 604 2 of 42 at different scales. The highest concentrations of indium in sphalerite, which is found in the Diez vein in the Siete Suyos mine, occur in crustiform bands of sphalerite with local “chalcopyrite disease” texture, which has not been observed in the other studied veins. In stannite, the atomic concentrations of In are negatively correlated with those of Cu and Sn at Cu + In = 2 and Sn + In = 1. Thus, atomic proportions and correlations suggest the contextualization of the main indium mineralization in the sphalerite–stannite–roquesite pseudoternary system. Keywords: critical metals; high-tech metals; indium; sphalerite; Bolivian-type deposits 1. Introduction The high-tech metal indium (In) is classified as a critical raw material due to its high economic importance and elevated risk of supply [1–10]. In nature, this metal mostly occurs in the crystal lattice of base-metal sulfides and oxides in substitution of cations with similar radii (i.e., Zn, Fe, Cu, Sn, As) and only a few, and rare, discrete indium minerals have been defined [11–14]. High concentrations of In have been described in sphalerite, cassiterite, chalcopyrite, stannite, tennantite, and tin sulfosalts [14]. Indium is not exploited as a primary commodity, but rather as a co-product or by-product of base metals, chiefly in zinc [15–19], but also in tin [20] and copper [21] ores. The occurrence of In is reported in ore deposits that span a broad range of ages and mineralization styles [11,14]. High concentrations are described prominently in exhalative deposits hosted in volcanic (e.g., [22,23]) and sedimentary sequences (e.g., [24]), granite-hosted (including greisen-type, e.g., [25,26]), vein-stockwork Sn-W, porphyry Sn and xenothermal Sn-W-Cu-Zn-Pb-Ag veins (e.g., [27–30]), skarn (e.g., [18,31]), ,and epithermal (e.g., [15,16,32,33]) deposits. A number of polymetallic mineral deposits from the central Andes in Peru, Bolivia, and northern Argentina are listed as major In hosts [11,34,35]. Chief among them are xenothermal polymetallic-vein deposits hosted by the Andean tin belt [29,36–39]. Whole-rock geochemical analysis of ore samples (including composites) from SW Bolivia deposits has revealed In contents as high as 5740 ppm for Potosí, 3080 ppm for Huari Huari, 2730 ppm for Bolivar, and 2510 ppm for Ánimas-Siete Suyos deposits [37]. Ishihara et al. [37], by means of electron microprobe analyses (EPMA) on one sample from the Potosí deposit, determined that “black sphalerite” is the major host for In (up to 1.27 wt.%) and it occurs along with local “petrukite-bearing zones”. A femto-second laser ablation inductively coupled plasma mass spectrometry (fs-LA-ICP-MS) study combined with EPMA by Murakami and Ishihara [29] yielded concentrations of In as high as 7.89 wt.% in Fe-rich (“black”) sphalerite in a sample from the Huari Huari deposit, and concentrations up to 5.08 wt.% In in a sample from the Potosí deposit; in addition, these authors determined concentrations up to 18 wt.% In in an undetermined Zn-In mineral. In the Santa Fe mining district, the contents of In in ore are up to 200 ppm and concentrations of In as high as 2.03 wt.% In were determined in sakuraiite [38]. In the Huari Huari deposit, an EPMA study that is based on a large number of ore samples distributed along the mineralized zones allowed for Torró et al. [39] to determine that an early generation of sphalerite rich in Cu, and in part co-crystallized with stannite, was the main host for In, and pointed out that the highest concentrations of this metal are found in a central position of the deposit complex. Although the In-bearing Ánimas–Chocaya–Siete Suyos district (also referred to as Chocaya or Gran Chocaya district) is not considered of world-class significance, it was regarded by Ahlfeld and Schneider-Scherbina [40] as the southernmost large Bolivian tin deposit. Tin was indeed the main commodity that was mined in the district until the 1950s, when lead and silver became the main products. Being discovered in 1800, the beginnings of large-scale mining in this district are intimately linked to the name of two of the so-called tin barons in Bolivia, Avelino Aramayo, and Simón I. Patiño. The Ánimas mine was first exploited by the Aramayo Mines Company from 1870. The Chocaya (or Chocaya La Vieja) mine was first mined by the Minera y Agrícola Oploca Company (Santiago Minerals 2019, 9, 604 3 of 42 de Chile, Chile; which in 1926 became part of the Patiño Group) since 1884. Both of the companies were nationalized in 1952 and were renamed as Telamayu and Santa Ana, and they belong to the Corporación Minera de Bolivia (COMIBOL). Since the early 1990s to this day, mines in the district are operated by mining cooperatives mostly for lead, zinc, and silver. In this work, we present in situ chemical analyses of ore minerals from the In-bearing Ánimas–Chocaya–Siete Suyos district. Such chemical determinations are systematically linked to petrographic observations and contextualized along thorough paragenetic sequences built for selected veins. By doing so, we seek a better understanding of the temporal and spatial distribution of In in xenothermal deposits hosted in volcanic-dome complexes following a similar research scheme as Torró et al. [39] did for the Huari Huari sediment-hosted polymetallic vein deposit. The results of this research should serve as a basis for the exploration of In in other xenothermal vein deposits, in particular those that are hosted in volcanic-dome complexes, and they might be of help for the optimization of metallurgical flowsheets for ore processing with economic concentrations in this metal. This article corresponds to a group of papers of various Bolivian tin deposits with the same collective aim [33,39–41]. 2. Geologic Setting 2.1. Geodynamic Setting The highlands of the Andes cover about one-third of the Bolivian territory, with the remaining two-thirds being covered by tropical lowlands. In Bolivia, the Andean Cordillera splits into two parallel mountain chains, the Western and Eastern Cordilleras, which are separated by the Altiplano (i.e., the high plains between 3600 and 4500 m above the sea level) [40,42–46]. The geology of both Cordilleras is contrasting. The Eastern Cordillera is composed of a pile of thrusted, folded and variably metamorphosed marine Paleozoic and both marine and non-marine Cretaceous sedimentary rocks that underwent deformation during the Caledonian (Ordovician), Hercynian (Devonian to Triassic), and Andean (Cretaceous to Cenozoic) orogenic cycles [45]. The restricted outcrops of igneous rocks of variable ages occur throughout the Eastern Cordillera [47,48]. In stark contrast, the Western Cordillera is mostly composed of late Miocene to Recent intermediate (andesitic and dacitic) volcanic rocks that intruded and overlaid Jurassic and Cretaceous sedimentary and volcanic rocks. On the one hand, Cenozoic igneous rocks in the Altiplano and Western Cordillera are described to record a high mantle input and belong to the I-type, magnetite-series. Igneous rocks in the Eastern Cordillera, on the other hand, mostly resulted from sediment melting in a thickened continental crust, have peraluminous, reduced signatures, and belong to the S-type, ilmenite-series [47,49,50]. The third of the physiographic units of the Andes in Bolivia, the Altiplano, is an internally drained basin that contains a thick succession of sedimentary rocks derived from both Cordilleras since the Upper Cretaceous [51]. The maximum width of the Altiplano (that is, the maximum separation between the Cordilleras in surface; ~300 km) occurs in the so-called “elbow of the Andes”, which is also known as the Bolivian orocline or Arica Deflection [52]. North of the orocline, the Andes run NW-SE, whereas south of the orocline they run N-S. The general geology and the metallogeny of the Central Andes have both been controlled by a quasi-continuous subduction along the western margin of the South American plate over the last ca. 250 M.y. [53–59]. Several Paleogene and Neogene polymetallic mineralized belts juxtapose to morphotectonic provinces in the Andean orogen [56,59]. The Andean tin belt, in which the studied deposit is located, is confined to the Eastern Cordillera through Bolivia with short extensions into southern Peru and northern Argentina [40,45,56,60–62]. Mineralization in the Andean tin belt is genetically connected to reduced, peraluminous magmas of mostly late Oligocene to Miocene ages, although a late Triassic-early Jurassic mineralization episode is described in NW Bolivia, north of the Bolivian orocline [56,63–65]. Age aside, there are marked differences in the mineralization styles and depths of emplacement along the tin belt north and south of the Bolivian orocline. North of the orocline, Minerals 2019, 9, 604 4 of 42 the Sn-W mineralization forms veins within granite batholiths or at their contacts with sedimentary hosts. South of the orocline, Sn, Sn-W, and Sn-polymetallic mineralizations are “shallower” and related to porphyritic intrusions, dome complexes, hydrothermal breccia pipes, and collapse calderas. These eventMuianelrlayls d20e1v9,e 9l,o xp FeOdR aPEdEvRa RnEcVeIdEWa r gillic lithocaps within the epithermal environment over h4i gofh 4-2g rade mesoctohlelarpmsae lc(aolrdexreans.o tThheersme aelv[e6n0tu])avllyei ndedveeploopseidts a[6d1v,a6n3c,e6d6 –a6r8g]i.llic lithocaps within the epithermal 2.2. Geenovliorgoynmofetnhte oDveepr ohsiigth-grade mesothermal (or xenothermal [60]) vein deposits [61,63,66–68]. T2.h2.e GÁeonliomgya osf– tCheh Doecpaoysait– Siete Suyos district is located in the Potosí Department, 150 km south of the city ofTPhoet Áosníimanads–nCehaorctahyea–tSoiwetne Souf yAotso dchisatraictt aislt liotucadteesd bine ttwhee ePnot4o1s5í 0Daepnadrt4m30en0tm, 1.5a0.s k.lm. A sopuptrho oxfi mate coordthinea tceitsyo foft hPeomtoasií namndin neseaarr eth2e0 ◦t5o7w′5n1 ”ofS A66to◦c1h8a′ 24at” Waltiftourdeths ebÁetnwiemena s4m15in0 ea, n2d0 ◦54370′60” mS.6a.6s◦.l1. 7′43” W forAtphperoSxieimteaSteu cyoosrdminiantes, aonf tdhe2 m0◦a5i8n′ m29in”eSs a6r6e◦ 2109°′5571'5”1W" S 6fo6°r1t8h'2e4"C Who fcoar ythaem Áinnime.aPs hmyinsieo, g20r°a5p7h'6y" cally, this dSi s6t6r°ic1t7's4i3t"s Won ftohre thwee sStieetren Sfluaynoks omfinthe,e aEnads t2e0r°n58C'2o9r"d Sil l6e6r°a1,9c'5l1o"s eWto fothr ethter ipClheojcuanyca timonineth. at is drawPnhybsyiotghraepEhayscatellryn, tChios rddisiltlreicrta s,ittsh oenW thees wteersnteCrno frldanilkle orfa t,haen Edasttheren sCoourtdhilelerrna,e cnlodseo tfo tthhee tArilptliep lano (Figujruen1c)ti.oTnh tehadt iisst rdircatwisni bnyc ltuhde eEdasitnertnh eCoQrudielclehrias,l tahme Wineinstgergnr Couorpd[il6le1r]aw, ainthdi nthteh seouAtnhedrena enn(do or fB tohlei vian) tin beAltlt(iFpilganuor e(F1i)g.ure 1). The district is included in the Quechisla mining group [61] within the Andean (or Bolivian) tin belt (Figure 1). FigurFeig1u.reR 1e.g Rioengaiolngael ogleoogloicgaiclaml mapaps hshoowwiinngg tthhee llooccaattiioonn oof fththe estsutduyd yareaar e(aÁn(Áimnaism-Cahso-Ccahyoac-Saiyeate- Siete Suyos district; white box). Inset shows the location of the map within the Western Cordillera (Andean Suyos district; white box). Inset shows the location of the map within the Western Cordillera (Andean morphotectonic units are after Arce-Burgoa [61]). morphotectonic units are after Arce-Burgoa [61]). Mineralization in the Ánimas–Chocaya–Siete Suyos district is genetically associated with the MChioncearyaal ivzoaltciaonnici ncaltdheeraÁ cnoimmpalesx–,C whhoiccha yisa a–bSoieutte 9 Skumy ions ddiaimsteritcert aisndg eMnieotciecnael liyn aagsseo [4c0ia,6t0e,d61w]. iAth the Chocpaiylea ovfo llacvaan aicndca pldyreorcalacsotimc pdelepxo,siwtsh oifc hdaicsitaicb ocoumt 9poksmitioinn ids iapmrotertuedreadn bdyM a icoecnetnrael idnomagee o[f4 t0h,6e 0,61]. A pilseaomfel acvoma panosditipoynr (oFcilgausrteic 2d). eTphoes vitoslcoafndica ccoitmicpcleoxm isp hoossitteiodn biys Oprrdootrvuicdiaend sbanydastcoennetsr aanl d oslmateeso, f the samewchoimchp aorsei tfiaounlte(Fdi ganudr efo2l)d.eTdh aelovnogl csuancciecscsiovme pclloesxe iasnhtioclsinteed anbdy sOyrndcloinveic sitarnucstaunredss wtointhe sNaWn-dSEs lates, whichstraikreinfga auxlitaeld plandes f[o69ld].e Idn tahleo anrgeas oufc sctuesdsyi,v Oercdlovsiecian triocclkins earaen udncsoynnfocrlimnaebslytr ouvcetrulariens bwy igtehnNtlyW -SE strikidnigppaixniga ilnptelrabneedsde[d69 s]a.ndInstotnhees aarneda tuofffss otuf dthye, QOuredhouvai cFioarnmaroticokns, oaf rOeliugnocceonnef-oMrmiocaebnley aogve e[6rl9a–in by gentl7y2]d. iOpprdinovgiciinatne rabnedd dQeudehsuaan dFostromnaetisoann sdertiuesff ws oerfet hbeotQh uinethruudaeFdo arnmda ctioovne,reodf Obyl igefofucesinvee- Manido cene age [6e9x–p7lo2s]i.vOe rddeopvosicitisa nasasnocdiaQteude thou taheF oCrhmocaatiyoan vsoelrciaensicw cearledebroat shyisntetmru d(Feidguarned 2Aco) v[6e0re,6d1,b6y9]e. ffDuacsiitvee and lavas show porphyritic textures described by subhedral quartz, plagioclase, biotite, sanidine, and exploasuigvieted epphoesniotcsraysstsso c(iaantded lteosstehr eaCmhooucnatys aovf olhcoarnnibclecnadlde eraands yshtyepmers(Fthiegnuer)e i2nA )a [6fi0n,6e-1g,6ra9i]n.eDd acite lavasgsrhoouwndpmoarspsh oyfr tihtiec staemxteu croems dpeosscitriiobne d[6b9]y. subhedral quartz, plagioclase, biotite, sanidine, and augite phenocrysts (and lesser amounts of hornblende and hypersthene) in a fine-grained groundmass of the same composition [69]. Minerals 2019, 9, 604 5 of 42 Minerals 2019, 9, x FOR PEER REVIEW 5 of 42 Fiigurre 2.. ((A)) Geollogiicall map showiing tthe diisttrriibuttiion off veiins iin tthe Ániimas–Siiette Suyos–Chocaya miiniing diissttrriicctt.. TThhe elolocactaitoinon ofo tfhtihsi smmapa pis ishsohwonw inn iFnigFuigreu r1e. (1B. ) (CBo) nCcoenpctuepalt ugaelogloegoilco gmicodmeol dofe lthoef ÁthneimÁnasim–Saies–teS iSeuteySous–yCohs–oCcahyoac adyeapdoesipt.o sTiht.eT thraecter aocfe tohfet hcerocsrso sssecsteicotnio nono nsusrufrafcaec eisi sshshoowwnn inin ((A)).. Modiffiied from Arce-Burgoa [61].. Lvl. = lleevveell. . Miinneerraalliizzaattiioonn aanndd hhyyddrrootthheerrmaall aalltteerraattiioonn aaffffeecctteedd bbootthh vvoollccaanniicc ccoompplleexx aanndd Orrddoovviicciiaann hhoosstt rroocckkss.. Hyyddrrootthheerrmaallllyy aalltteerreedd rroocckkss eexxtteenndd aaccrroossss oovveerr 88 kkm22 ((ssuurrffaaccee pprroojjeeccttiioonn)),, tthhuuss ffoorrmiinngg aann iirrrreegguullaarr NNEE-S-SWWb ebletl[t6 0[6,609,6].9H]. yHdyrodtrhoetrhmeraml aallt earlatteiroantiiosnm iosr empoerrev apseivrveainsirvoec kins orfotchkesC ohfo cthaye aCvhoolccaanyiac vcoomlcapnleicx ,ccohmiepfllyexin, tchheiebflays ailnt utffheb rbecacsiaal (Ftuigffu rbere2cBc)i,aa n(Fdigituirsep o2Bor),l yadnedv eilto pise dpoinorOlyr ddoevviceilaonperodc kins, Oprrodboavbilcyiadnu reotcoktsh, epirronbeaabrllyy ndoune- rteoa ctthiveier cnheaararlcyt enrowni-trheahcytdivreo tchhearmraactleflru widisth. Inhtyednrsoethqeuramrtazl- sfeluriicditse. I(nfitneen-sger aqinueadrtmz-suesrciocivteit e()fianned-glroacianleqdu amrtuzs-ctoovuirtme)a lainnde alsosceaml bqluaagretsz-gtroaudremoaulitnwea radssteomlebslasgpeesr vgarsaidvee oquutawrtazr-dse troic ilteessa npde,rvfuarstihvee r,qtuoaprtrzo-pseyrliictiitce( manods,t lfyucrthhloerr,i tteo) apsrsoepmybliltaicg e(ms. oNstelvye crhthloerleitses), laoscsaelmsbhlaalgloews. Nqueavretzrt-hkealoelsins,i tleocaasls sehmabllloawge qsuaarertdz-eksacroilbineditein asthseemSbieltaegSeus yaores danesdcrÁibneimd ians tmhein Seiset[e6 9S]u.yIonsg aennde rÁaln, ismucahs mdiisntreisb u[t6i9o]n. oIfnh ygdenroetrhael,r msuacl ha ltderisattrioibnuatisosnem obfl ahgyeds rfiottshtehramt aolf maletesorathtieornm aalsstienmdbelpagoessit sfuitns dtehralyt inogf mesothermal tin deposits underlying advanced argillic (epithermal) lithocaps in the Bolivian tin belt Minerals 2019, 9, 604 6 of 42 advanced argillic (epithermal) lithocaps in the Bolivian tin belt [67]. Reported K-Ar ages in the area are 13.8 ± 0.2 Ma (unweighted mean value) for biotite grains from unaltered volcanic rocks, and of 12.5 ± 0.2 Ma for a sericitized sample (whole-rock age) [73]. Volcanic and basement metamorphosed sedimentary rocks are crosscut by a NE-SW striking network of steeply-dipping veins that extends for over 5 km between the Siete Suyos (to the NE) and Chocaya mines (to the SW; Figure 2A) [60,61,69,74]. The main veins in the Siete Suyos mine are named Esperanza, San Patricio, Salvadora, Arturo, Diez, Nueva, Colorada, and Inca (1 to 7) and they have been worked from level 0 at 4202 m.a.s.l. to level 28 at 3564 m.a.s.l. The Colorada and Inca veins extend into the Ánimas mine (Figure 2A). In addition to these, important veins in the Ánimas mine also include the Ánimas, Rosario and Burton veins—the latter being formerly considered the Ag- and Pb-richest vein in Bolivia [40]. Some of them are exploited at depth intervals of ~900 m (e.g., Burton and Colorada veins; Figure 2B) between the surface and level 780, at 3407 m.a.s.l. (note that the name of the levels differs for the Ánimas and Siete Suyos mines, so that, for example, level 19 in the Siete Suyos mine is at the same topographic elevation as level 302 in the Ánimas mine). The longest of these veins is Colorada, which extends for over 2450 m along strike. In the Chocaya mine, the main veins are named Inocentes, Nueva, San Bartolomé, and Candelaria, among which Nueva is the longest as it extends about 770 m along strike and more than 150 m in depth. Noteworthy, single veins in the three mines are often hosted by both Ordovician (lower segment of the vein) and volcanic complex (upper segment of the vein) rocks (Figure 2B). Buerger and Maury [74] and Sugaki et al. [69] noted contrasting metalliferous contents for veins along the Ánimas–Chocaya–Siete Suyos district. In the Siete Suyos mine, Sugaki et al. [69] described that both veins were largely composed of cassiterite and pyrite (Colorada, Inca, and Nueva) and veins that consisted mostly of pyrite, sphalerite, stannite and galena, with lesser amounts of cassiterite (Esperanza, Salvadora, Arturo, and Diez). In contrast, the ore mineral assemblages described in veins from the Ánimas mine are dominated by sulfides (chiefly sphalerite, pyrite, wurtzite, galena) and contain only minor amounts of cassiterite, except for the Colorada vein (which is cassiterite-rich). Ore mineral assemblages in veins from the Chocaya mine are dominated by sphalerite, wurtzite, galena, pyrite, and silver-antimony sulfosalts. According to Sugaki et al. [69], the described ore mineral assemblages depict a metalliferous concentric zoning with (1) a NE-SW trending ellipsoidal core rich in Sn, which contains the Colorada, Inca and Nueva veins in the Siete Suyos mine and their extensions into the Ánimas mine; (2) an intermediate zone that surrounds this core, which is centered in the Ánimas mine and enriched in Zn, Ag and, to a lesser extent, in Sn; and (3) a farther, external zone centered in the Chocaya mine that is rich in Ag, Zn and Pb. Homogenization temperatures (Th) and salinities of fluid inclusions in vein quartz along the district exhibit significant differences, perhaps in association with the metalliferous zoning: higher values are reported in the Sn-rich core (Th: 220 to 360 ◦C; 4.6 to 11.9 wt.% NaCl equiv.) than in the intermediate (Th: 170 to 270 ◦C; 3.8 to 4.9 wt.% NaCl equiv.) and external (Th: 170 to 270 ◦C; 3.7 to 5.2 wt.% NaCl equiv.) zones [69]. 3. Materials and Methods The study area is comprised within the quadrangle defined by coordinates 20◦55′50” S 66◦20′30” W and 20◦59′20” S 66◦17′12” W. The study is based on 82 rock samples from the Ánimas–Siete Suyos–Chocaya district, including in situ surface (n = 50) and mining gallery (underground; n = 32) samples. Studied samples are representative of the different metalliferous domains defined by Sugaki et al. [69] in the Ánimas (n = 35), Siete Suyos (n = 24), and Chocaya (n = 23) mine areas. Sampled veins in mine galleries include Ánimas (levels 100, 125, 175, and 200), Arturo (levels 19, 20, and 21), Burton (level 232), Chorro (levels 14 and 16), Colorada (levels 264 and 302), Diez (level 15), Jalisco (level 75), Nueva (level 125), and Rosario (levels 175, 200, 232, 302). The availability of underground samples for each vein has been restricted to active galleries at the time of each sampling campaign during 2012, 2015, and 2018. As a consequence, for example, no samples from veins at mine levels below the 302 level in the Chocaya and Ánimas mines (Figure 2B) are available in this study, as Minerals 2019, 9, 604 7 of 42 the respective galleries have been flooded for decades. This study also includes mineralogical and geochemical data on two underground samples from the Siete Suyos mine area that were picked up from pre-feed stockpiles and whose allocation to a particular vein and the level is unknown. A list of the samples, the mine from which they were sampled and their geographic (coordinates) or relative (vein and gallery level) location is given in Table S1 in Supplementary Material. The samples were prepared as polished thick (n = 58) and thin (n = 3) sections for their study under the optical microscope using reflected and transmitted light. A selection of these samples was examined on an environmental SEM Thermo Fisher Quanta 650 FEI equipment with an EDAX-Octane Pro EDS microanalysis system that is available at Centro de Caracterización de Materiales of the Pontifical Catholic University of Peru (CAM-PUCP). The operating conditions were 20 keV accelerating voltage and 5 nA in backscattered electron (BSE) mode. Mineral chemistry analyses of sulfide minerals were performed on 58 polished sections while using five-channel JEOL JXA-8230 electron microprobe equipment (Jeol Ltd., Tokyo, Japan) available at Centres Científics i Tecnològics of the Univeristy of Barcelona (CCiT-UB), operated at 20 kV acceleration voltage, 20 nA beam current and with a beam diameter of 5 µm. Analytical standards and lines used for analyses were: sphalerite (Zn, Kα), chalcopyrite (Cu, Kα), FeS2 (Fe and S, Kα), Ag (Ag, Lα), Sb (Sb, Lα), Bi (Bi, Mβ), CdS (Cd, Lβ), PbS (Pb, Mα), GaAs (As, Lα), Sn (Sn, Lα), InSb (In, Lα) Ge (Ge, Lα), and Ta (Ta, Lβ). The detection limits (d.l.) for each element, representative analyses of the different minerals investigated, and the normalization constants used for formula calculations are shown in Table S2 in Supplementary Material. Mineralogical determinations were also carried out by means of X-ray Diffraction (XRD; n = 8). The samples were ground in an agate mortar and were manually pressed by means of a glass plate to obtain a flat surface in cylindrical standard sample holders of 16 mm diameter and 2.5 mm height. The diffractograms were obtained in a Bruker D8 Discover powder diffractometer in Bragg-Brentano θ/2θ geometry of 240 mm of radius, nickel filtered Cu Kα radiation (k = 1.5418 Å), and 45 kV–40 mA at the CAM-PUCP. The software PANalytical X’Pert Highscore© 2.0.1 (Version 2.0.1, PANalytical, Almelo, The Netherlands) was used to subtract the background of the patterns, to detect the peaks, and to assign mineral phases to each peak. 4. Mineralogy and Textures 4.1. Siete Suyos Mine The mineralogy and micro-textures of the Arturo, Chorro and Diez veins in the Ánimas mine are described below. The Arturo vein is mostly composed of sulfides, between which sphalerite is the most abundant, and quartz. Sphalerite flooded the central portion of the vein and the interstitial space in the anhedral pyrite, arsenopyrite, cassiterite, and quartz association that rims the vein (Figure 3A–E). Pyrite occurs as grains with sizes between some tens of micrometers and 0.5 mm, and it shows evidence for extensive corrosion, such as engulfment and secondary porosity, which are lined with sphalerite and quartz (Figure 3A–C). A few pyrite grains preserve straight faces that recall pseudo-hexagonal shapes of the crystals previous to their corrosion and replacement; trails of micrometer-sized inclusions that are roughly parallel to crystal faces that reproduce hexagonal patterns are relatively common (Figure 3B,C). Cassiterite is a relatively minor phase in the Arturo vein and occurs as anhedral grains of less than 100 µm across that have been extensively replaced by sphalerite (Figure 3D–G); they are often intergrown with pyrite and quartz (Figure 3F,G). Arsenopyrite is even scarcer than cassiterite and it has been extensively replaced by pyrite and sphalerite, thus emphasizing its early precipitation (Figure 3G). Traces of galena are observed filling porosity within and as thin veinlets across pyrite and sphalerite (Figure 3E,I). Additionally, filling porosity, mostly within sphalerite, are trace amounts of sulfosalts, which include fizélyite [Ag5Pb14Sb21S48], owyheeite [Ag3+xPb10-2xSb11+xS28, −0.13 < x > +0.20], miargyrite [AgSbS2], pyrargyrite [Ag3SbS3], diaphorite [Ag3Pb2Sb3S8], and hocartite Minerals 2019, 9, 604 8 of 42 [Ag2(Fe2+,Zn)SnS4], either as monomineralic or polyminerallic infillings (Figure 3H,I). In polyminerallic infillings, miargyrite is veined by fizélyite (Figure 3H) and galena, diaphorite and pyrargyrite were replaced by hocartite (Figure 3I). Minerals 2019, 9, x FOR PEER REVIEW 8 of 42 FiFgiugruer3e. 3P. Phhoototommicicroroggrarapphhss( (rreeflfelecctteeddl liigghtt;; A––C)) aand bbaacckk--ssccaatttteerreedd eelelecctrtoronn imimagagese s(D(D–I–)I o)fo tfextetuxtrualr al feafetuatruerseisn inth teheA Artruturorov veienini nint htheeS SieieteteS Suuyyooss miinnee.. ((A)) Geenneerraal laassppeecct toof fththe emmininerearlaizliaztaiotino nata tthteh e ArAturtruorvoe ivne,iwn,i twh iatnhh aendhraeldpraylr ipteycrirtyes tcarlysswtailtsh iwn iathgirno uan dgrmoausnsdomf asspsh aolfe rsiptehaanledriqteu aarntzd. (qBu)aCrtozr. ro(Bd)e d pyCriotrerogdraeidn pthyarittes hgorwains ctohnast psihcouwous sceonngspuilcfumoeuns teanngdulsfemceonntd aanryd psoecroonsidtyar;ys opmoreoosiftyth; esosmtrae igohf tth(neo t cosrtrroadigehdt) c(nryost tacol rfraocdeseda)n dcrtyhsetaal rrfaacnegse manedn tthoef marircarnogmeemteern-ts izoef dmpiocrroomsietytedr-rsaizweda ppsoeruosdioty-h dexraawgo na al shpaspeeu.d(oC-)hCexoargroondaeld sphaypriet.e (Cgr)a Cinorwroitdhedtr apiylsriotef gmraicinro wmiethte trr-asiilzse odf pmoircorosimtyetpear-rsailzleedl t pootrhoesictryy pstaarlafllaecle s betfoo rtehec ocrrryosstiaoln f.a(cDes) bMefinoruet ecocarrsossitieorni.t e(Dre)l iMctsinwutiteh cinasasisteprhitael erreiltiectgsr owuitnhdinm aa sssp; hnaolteeritthee gcroomunpdomsitaisosn; al zonnointeg tihnes pcohmalperoistiet.io(nEa)lA znohneindgr ailnc asspshitaelreirtieteg. r(aEin) sAhnighhedlyrarle pcalascseitderbitye sgprhaainles rihteig;hthlye arespselamcebdla gbey is custpbhyalaervieter;y ththei nasvseeminbleltagthea its hcuost tbsys oam veergya tlheinna v. e(Fin)leFto trhmaet rhloysetsu hsoemdrea gl acalesnsait.e (rFit)e Fcorrymstearllsy ienutehregdrroawl n wictahsspiyterriittee acnrydsqtaulsa ritnzt;ebrgortohwcnas wsiittehr ipteyrainted apnydr iqteuaarrtez;p baortthly craespslitaecreidte bayndsp phyarlieteri taer.e (pGa)rtAlyr sreenpolapcyerdi te crybsyt aslpshsahleorwitep. a(rGti)a Al rrespenlaocpeymrietnet cbryysptaylrsi tsehoanwd pbaortthialm rienpelraaclesmweenrte beyx tpeynrsitive ealnydr ebpoltahc emdinbeyrasplsh waleerreit e; caesxsitteenrsiitveeolyc cruerpslaacsesdc abtyte rsepdhamleinriutet;e craesliscittesr. it(eH )ocDcuetrasi laos f socwatytehreeedi tem, ifinzuétely irteeliacntsd. m(Hi)a rDgyetraitiel tohf at owyheeite, fizélyite and miargyrite that line porosity in sphalerite and cassiterite; miargyrite is locally line porosity in sphalerite and cassiterite; miargyrite is locally veined by fizélyite (inset). (I) Infilling veined by fizélyite (inset). (I) Infilling in porosity within sphalerite, lined with galena, hocartite, in porosity within sphalerite, lined with galena, hocartite, diaphorite and pyrargyrite. Key: apy = diaphorite and pyrargyrite. Key: apy = arsenopyrite; cst = cassiterite; dia = diaphorite; fiz = fizélyite; arsenopyrite; cst = cassiterite; dia = diaphorite; fiz = fizélyite; gn = galena; hoc = hocartite; owy = gn = galena; hoc = hocartite; owy = owyheeite; py = pyrite; pyr = pyrargyrite; qz = quartz; sl = owspyhhaeleeirtiet;ep. y = pyrite; pyr = pyrargyrite; qz = quartz; sl = sphalerite. Minerals 2019, 9, 604 9 of 42 In the Chorro vein, sphalerite is the main ore mineral (up to 70% modal) and it occurs along appreciable amounts of sulfosalts (Figure 4). Quartz is the only identified gangue mineral; it forms euhedral to anhedral crystals some tens of micrometers long. In general, the vein texture can be described as a mass of sphalerite and sulfosalts that flooded the interstitial space between the crystals of quartz and that contains remnants of earlier minerals (Figure 4A–D). Cassiterite, which is relatively scarce in the Chorro vein, is one of the mineral phases found as anhedral remnants due to its replacement by sphalerite and sulfosalts (Figure 4E,F,H,I). Other phases in a similar textural position are arsenopyrite, which forms subhedral crystals that are up to 200 µm across (Figure 4B), and pyrite, which forms anhedral grains up to 250 µm across (Figure 4C). Massive aggregates of anhedral sphalerite show abundant secondary porosity that is often lined with sulfosalts and galena (Figure 4A,B), and locally replaced by stannite (Figure 4A,E). Garland-like arrays of galena and sulfosalt crystals are locally observed within sphalerite. Sphalerite is, in addition, observed as minute anhedral isolated grains within a mass of sulfosalts in a reactive sequence (Figure 4I,J,L). Minor amounts of galena are lining porosity within pyrite grains (Figure 4G). In the sulfosalt + galena assemblages after sphalerite, galena is found as anhedral corroded and isolated grains with sizes that are up to some tens of micrometers (Figure 4H,I). A wealth of sulfosalts has been identified in samples from the Chorro vein, namely miargyrite, franckeite [Fe2+(Pb,Sn2+)6Sn4+ 2Sb2S14], boulangerite [Pb5Sb4S11], teallite [PbSnS2], ramdohrite [Pb5.9Fe0.1Mn0.1In0.1Cd0.2Ag2.8Sb10.8S24], diaphorite, hocartite, and fizélyite. Miargyrite occurs as anhedral aggregates that flooded interstitial spaces between subhedral crystals of quartz and corroded grains of pyrite, sphalerite, and cassiterite (Figure 4C). Miargyrite is locally veined by other sulfosalts (i.e., ramdohrite and diaphorite; Figure 4K). Franckeite, boulangerite, teallite, and fizélyite mostly form up to 100 µm long needles and bladed crystals (Figure 4F,H,J,L). The ore mineralogy in the Diez vein is dominated by sulfides, among which sphalerite is the most abundant, with a modal proportion ~75% in the studied samples (Figure 5A–F). The general structure of the vein includes a 2 mm-wide rim that is dominated by anhedral pyrite and subhedral arsenopyrite with sizes that mostly range between 100 and 200 µm, and that are often intergrown with euhedral quartz (Figure 5A,E). Such pyrite belongs to a first stage of mineralization and it is accordingly labelled as pyrite-I. Pyrite-I and arsenopyrite are replaced by sphalerite mostly along irregular replacement fronts; sphalerite is also flooding interstitial spaces between arsenopyrite and pyrite-I and fills corrosion porosity within them (Figure 5A,E). The vein core is almost exclusively composed of massive sphalerite that shows a conspicuous overlying of parallel bands with oscillatory composition that depicts crustiform and drusy patterns that extend inward the vein from the pyrite-I–arsenopyrite–quartz assemblage (Figure 5B,C,F). Close to the contact with the outer pyrite-I–arsenopyrite–quartz “substrate”, sphalerite hosts a myriad of micrometer-sized chalcopyrite blebs (chalcopyrite disease texture) that disappear towards the inner bands of sphalerite (Figure 5D). Porosity within massive sphalerite is lined with stannite and, to a lesser extent, with tetrahedrite-group minerals (Figure 5A,E). Stannite also occurs as replacement bands across the bands of sphalerite (Figure 5F). Such an assemblage is cut by 2 mm-thick stringers that are composed of quartz, sulfides and sulfosalts. In general, such veinlets show outer sectors of massive quartz and a central suture of pyrite and sulfosalts (mostly jamesonite [Pb4FeSb6S14], andorite [AgPbSb3S6] and boulangerite; Figure 5G). Accordingly, such pyrite within is labelled as pyrite-II. Pyrite-II occurs as anhedral grains that host abundant inclusions of up to 50 µm long needle-like and bladed euhedral jamesonite (Figure 5G–I). Pyrite-II is often wrapped by jamesonite crystals that are partly replaced by an andorite and boulangerite assemblage (Figure 5H). Andorite is rather scarce in such assemblage and it mostly appears as islands that are surrounded by boulangerite, thus suggesting its replacement by the latter (Figure 5I). Minerals 2019, 9, 604 10 of 42 Minerals 2019, 9, x FOR PEER REVIEW 10 of 42 FigFuigreur4e. P4h. oPthoomtoicmroicgrroagprhasph(rse fl(reecftleedctleidg hlti;gAht–; CA)–aCn)d abnadck -bsaccakt-tsecraetdteerleedc treolencitmroang eims (aDge–sL )(Dof–tLe)x toufr al featteuxrteusrainl ftehaetuCrheso rinro thvee iCnhionrtrhoe vSeiient einS tuhyeo Ssiemtein Seu.y(oAs) mCionrer.o (dAe)d Csoprhroadleerdit espwhiatlheraibteu wnditahn atbsuencodnadnta ry posroecsoitnydaanryd pcuotrobsyityv eainndle tcsulti nbeyd vweiinthlettes allilniteeda nwdithfr atenaclklieteit ea;nsdp hfraalnercikteeitseh; oswphsalloecraitler espholawces mloecnatl to replacement to stannite. (B) Subhedral crystals of arsenopyrite partly replaced by abundant stannite. (B) Subhedral crystals of arsenopyrite partly replaced by abundant sphalerite, which in turn is sphalerite, which in turn is partially replaced by an assemblage of fine-grained sulfosalts. (C) partially replaced by an assemblage of fine-grained sulfosalts. (C) Corroded pyrite grains and sphalerite Corroded pyrite grains and sphalerite extensively replaced by miargyrite. (D) Fine-grained quartz, extensively replaced by miargyrite. (D) Fine-grained quartz, sulfosalts and galena in a garland-like sulfosalts and galena in a garland-like arrangement; the central space and the periphery are flooded arrbayn gsepmhaelnetr;itteh. e(Ece) nAtrnahl esdpraacle carnydstathlse opfe rciapshsietreyritaer eshfloowodinegd benygsuplfhmaleenrti tefi.ll(eEd) Awnithhe dstraanlncirtye satanlds of cassspihtearlietreitseh; oinw aindgdietinognu, lsfpmhealnetrifitel leisd pwarittlhy srteapnlancieted aanndd svpehinaeledr ibtye ;diniapahdodriittieo nan, dsp rhaamledroitheriitse.p (aFr)t ly repAlancheeddraanld cavsesiinteerditbe yredpilaapchedo rbitye abnoudlaranmgedriothe raitned. (tFe)alAlitneh. e(dGr)a lAcnahsesditrearli tpeyrreiptela wceidthb iyncblouusiloannsg eorfi te andgatleeanlal.i t(eH. )( GRe)liActns hoef dsprahlapleyrritiete awndit chasinsictleuristieo inns ao mf gaassle onfa g.a(lHen)aR, ferlainctcskeoiftes pahndal beroiutelaanngderictaes; snioteteri te in tahmat agsasleonfag iasl epnarat,lyfr raenpclkaeceitde bayn dthbe osuullfaonsgaeltrsi.t (eI;) nPootreosthitayt wgiatlheinna ainsdp vaeritnlyletrse paclarocessd sbpyhatlheeristeu llifnoesdal ts. (I) wPoitrho sai tfyinwe-igthraininaendd avsseeinmlbetlsagaec roofs sgaslpehnaal,e treiatelliltien eadndw firthanackfieniete-g; rgaailneenda, atsesaelmlitbe laangde ofrfagnaclkeeniate, taelaslol ite andocfcruapnyc kienitteer;sgtiatlieanl as,ptaecael libteetawnedenfr asnucbkheeidteraal lsqouoarctczu pcryyisntatelsr.s t(iJt)i aSlusbphaecderbael twqueaerntzs uabnhde danrahleqduraalr tz crysspthaalsle. r(iJt)e Scurybshtaelds rraelpqlaucaerdt zbyan hdocaanrhtieted, rfarlanspckheailtee raitnedc bryosutlaalnsgreerpitlea. c(eKd) bMyiahrogcyarritteit ve,eifnraend cbkye iftienea-nd bougrlaaningeedr irtaem. (dKo)hMritiea ragnydr idteiavpehionreidte.b (yL)fi Anen-hgerdairnale dquraarmtzd, osphhriatleerainted adnida pchasosriitteer.it(eL w) Aithnihne ad rmalasqsu oafr tz, sphdaialeprhitoeraitne,d ficzaéslsyiitteer iatnedw riathmindoahmriates.s Koefyd: iapyh o=r aitres,efinozéplyriittee;a bnodur a=m boduolharnigt e.riKtee;y c:sta p= yca=ssairtesreinteo;p dyirai te; bou= d=iabpohuolrainteg; efrkit e=; fcrastnc=kecaitses; igtenr =it eg;adleinaa=; hdoica =p hocraitret;itfer;k fi=z =f rfaiznéclkyietiet;e m; gian = mgialregnyari;the;o pcy= =h poycraitret;i te; fizq=z fi= zqéulyaritez; rmamia = rmamiadroghyrriittee; ;spl =y s=phpaylerirtiete; ;q szsa=ls q=u fainretzly; rinatmerg=rorwamn dsuolhforistael;ts;l s=tns =p hstaalnenriitte;; stesa l=s = finteelaylliintete. r grown sulfosalts; stn = stannite; tea = teallite. Minerals 2019, 9, 604 11 of 42 Minerals 2019, 9, x FOR PEER REVIEW 11 of 42 FiguFrigeu5r.e P5h. oPthoomtoimcriocrgorgarpahpshs( r(erflefelecctetedd liligghhtt;; AA,,EE,,FF)) aanndd bbaacckk-s-sccaatttetreerde deleelcetrcotrno inmiamgeasg e(Bs,C(B,F,C–I,F) –oIf ) of texttuerxatlufreaal tuferaetsuirnetsh ienD tiheez vDeiienzi nvtehine Sinie ttehSeu Syioestem Sinuey.o(sA m) Ainneh. e(Adr)a Al pnyhreidteraaln dpysuribteh eadnrda lsaurbshenedorpayl rite arsenopyrite grains in a groundmass composed of sphalerite and stannite. (B) Conspicuous grains in a groundmass composed of sphalerite and stannite. (B) Conspicuous compositional compositional sub-parallel banding describing crustiform and polygonal patterns in sphalerite; subb-priagrhatlelre lzbonanesd icnogrredsepsocnrdib tino gInc-r uanstdi foCrum-ricahn dcopmoploysgiotinonasl. p(Cat)t eOrnpesni-nspsapceh ainlefrililtien;g borfi gahltteerrnaztoe nes corrbeasnpdosn odf Itno- Iann-da Cnud-rCicuh- (rbicrhighcotemr)p woisthit iCoun-s a. n(dC I)nO-ppoeonr -(sdpaarkceeri)n sfiplhlianlegriotef; ainlt tehren baotettboman ldefst ocofrInne-r,a nd Cu-srpichhal(ebrritieg hint ecro)nwtaictth wCituh- qaunadrtIzn, -hpoosotirng(d marykreiard) scphhalacloepriytrei;tei nbltehbes.b (oDt)t oSmphlaelfetrictoe rinne cro, nstpahcta lweritihte in contqaucatrwtz,i tphyqriutea ratnzd, haorssetinnogpymriytrei, awditchh aalbcuonpdyarnitte cbhlaelcbosp. y(Drit)eS bplehbasl etrhiatet fiandceo onftfa ocut twwiatrhdq. u(Ea)r tPzy,rpitye rite andaanrds eanrosepnyorpityer,itwe igthivainbgu nwdaayn ttoc mhaalscsoivpey rsiptheablelerbitse tihnawtafradd tehoeff veoiunt;w paorrdos. i(tyE )inP ysprihtealaenridte airss menoosptlyy rite givilningewd awyittho smtaansnsiitve eanspdh taetlrearhiteedirnitwe.a (rFd) Pthaeravlleeiln b;apnodrso osift yspihnasleprhitael ewriitthe cisonmtroassttliyngli ncoemdpwoistihtiosnta innn ite andtetremtrsa hofe Idnr aitned. C(Fu), cPuatr bayll setlabnannitde.s (Gof) Qspuhaartlze rsittreinwgeirt haccrosnst rsapshtainlegritceo wmitpho as iptiyornitei,n jatmeremsosniotef aInda nd Cu,bcouutlabnygsetraitnen ciotere. .( (GH)) QPyuraitret zwsitrhi nmgiecroamcreotesrs-sipzheda ljearmiteswoniitthe ainpclyursiitoen,sja; imn ethsoe npieteripahnedryb ouf playnrgite rite corec.ry(sHta)lsP, jyarmitesowniteh ims picarotlmy reetperla-sciezde dbyj amndeosroitnei.t (eI)i nJacmluessionnitse; nineetdhlesp aenrdip bhlaedryes orfeplyacreitde bcyr yasnt als, jameassoenmitbeliasgpe aorft blyourelapnlagceeridteb aynadn adnodroirteit.e(. IK)eJya:m aepsyo =n aitresenneoepdyleristea;n adndb l=a adnedsorreiptela; bceodu =b yboaunlansgsemritbel; age of bcopuyl a=n cghearlictoepaynridtea; njmdso r=i tjea.mKeseoyn:itea;p pyy= = aprysreinteo; pqyzr i=t eq;uaanrdtz;= sla =n dspohriatlee;ribteo;u st=n b= osutalnannigtee;r ittde ;=c py = chteatlrcaohpedyrriittee-;grjmousp =mijanmeraelsso. nite; py = pyrite; qz = quartz; sl = sphalerite; stn = stannite; td = tetrahedrite-group minerals. 4.2. Ánimas Mine 4.2. ÁnimThase Mmiinneeralogy and micro-textures of samples from the Ánimas, Burton, Colorada, and Rosario veTihnes imn itnher Áalnoigmyaas nmdinme iacreo -dtesxctruibresd obfelsoawm. ples from the Ánimas, Burton, Colorada, and Rosario veins in Itnh ethÁen Áimnaims ams inveeianr, ethdee socrreib medinbeerlaol wa.ssemblage is chiefly composed of pyrite, cassiterite, spInhathleeriÁten, iamnda sstvaeninni,tteh-gerooruepm minineerarallass wseimthb sliaggneifiiscacnhti eaflmyocuonmtsp oofs seudlfoofspalytsr,i taen,dca tshsei tmeraitine, gsapnhgauleer ite, andmstinanernailt ies- gquroaurtpz (mFiignuerreasl s6 wanidth 7)s.i gInn tihfiec aonuttearm seocutonrtss oof fthseu vlfeoisna, lptsy,riatne,d cathsseitmeriatien, agnadn qguuaertmz ifnoremra l is quacrotzm(mFiognu irnetse6rsapnerdse7d). aInndt ihneteorulotcekresde ccrtuorsstifoofrmth ebavnedins,, spoymriet ete,ncsa sosfi mteircirteo,maentdersq uthairctkz efaocrhm (Fciogmurme on inte6rAsp,Be)r.s ePdyraitned winithteinrl othckise dbacnrduesdti faorrrmangbeamndenst, s(opmyreitet-eIn) smoofsmtlyi coroccmurest earss athnihcekdreaalc hcry(Fstiaglus rwe i6tAh ,B). abundant porosity that is lined with micrometer-sized cassiterite crystals and a variety of sulfides Pyriatnedw siutlhfoinsatlhtsi s(Fbiagnudree 6dBa–rDr)a.n Pgyermitee-nI its( opfyternit efi-nI)elmy oinsttelyrgorocwcunr swaitsha vnahreiadbrlae lacmryosutnatlss owf imtharacbausinted, ant porososi ttyhatth uatnidselri ntheed pweittrhogmraicprhoimc metiecrr-ossizcoepdec sahssoiwtesr istleigchrtylyst awlshiatnerd saecvtoarrsie wtyitohf ssturolfindge pslaeoncdhsrouilsfmos;a lts (Figure 6B–D). Pyrite-I is often finely intergrown with variable amounts of marcasite, so that under the petr ographic microscope shows slightly whiter sectors with strong pleochroism; such pyrite–marcasite Minerals 2019, 9, 604 12 of 42 assemblage is locally recrystallized to “clean” pyrite (pyrite-II) that tends to form euhedral crystals. Cavities in corroded pyrite-I–marcasite crystals are often nicely arranged drawing beehive-like patterns that suggest the pseudomorphic replacement of former crystals with pseudo-hexagonal habit (Figure 6D). Infillings along joints and porosity within pyrite-I often show an outer lining of cassiterite and central stannite (Figure 6D). Cassiterite is more abundant at the shallow levels of the vein (100 and 125 levels) and it is increasingly replaced by stannite-group minerals (Figure 6E,F) at greater depths; stannite-group minerals are indeed much abundant at the 175 and 200 mining levels (Figure 6G), representing up to 50% (modal) of the mineralization in some of the studied samples. Pyrite-I is also either replaced along borders or veined by stannite (Figure 6F,G). Arsenopyrite is up to 5% (modal) in all of the studied samples and it normally forms euhedral crystals up to 300 µm across (long axis) epitaxial to pyrite-I (±marcasite, Figure 6H) or intergrown and included within pyrite-I and quartz (Figure 6I–K). In Figure 6J, a euhedral crystal of a monazite-group mineral and arsenopyrite within pyrite-I impinge upon one another. Sphalerite is found in all the studied samples (up to 20% modal) and it mostly concentrates along the central domains of the vein and subsidiary veinlets. It is commonly observed interstitial to quartz, pyrite and cassiterite (Figure 6I) or replacing (along irregular fronts or veinlets) pyrite-I (Figure 6I,L). Sphalerite and stannite-group minerals form intricate intergrowths and mutual veining that suggest that, at least in part, these two sulfides coevally crystallized (Figure 7A). Galena is rather scanty in the studied samples and systematically appears as minute anhedral crystals lining porosity within corroded crystals of the sulfides mentioned above and cassiterite. In addition, galena is observed as an infilling of stringers and cracks that cut the sulfosalt assemblage above. Samples from the Ánimas vein host a wealth of sulfosalts, which mostly occur lining porosity and filling interstitial space between pyrite, cassiterite, arsenopyrite, and quartz. Jamesonite occurs as minute needles of less than 5 µm in diameter and some tens of micrometers in length, or as subparallel 200 µm long bladed crystals that form columnar masses (Figure 7A–E,G). Jamesonite is replaced along rims and twining planes on {100} by other sulfosalts and also by sphalerite and stannite (Figure 7E–G). Tetrahedrite-group minerals (tetrahedrite and freibergite; see below) form anhedral aggregates that adapt to the morphology of the available space or form irregular replacement fronts on stannite, sphalerite, and jamesonite (Figure 7A,B,E,H). Andorite and miargyrite show common mutual boundaries and fine intergrowths (Figure 7D,G), some of which recall myrmekitic textures (Figure 7F). Minute miargyrite crystals are observed along the contacts between tetrahedrite-group minerals and pyrite (Figure 7H). Pyrargyrite is rare in the Ánimas vein and it mostly occurs along contacts between andorite and miargyrite or replacing them (Figure 7G). Local fizélyite occupies interstitial space between boulangerite subhedral crystals (Figure 7I). Minor amounts of staročeskéite [Ag0.70Pb1.60(Bi1.35Sb1.35)Σ2.70S6] are observed lining porosity in cassiterite along with stannite and other sulfosalts; when found along with stannite, staročeskéite concentrates along the rims of the porosity or veins stannite, thus pointing to a later crystallization. Traces of other sulfosalts, such as franckeite, oscarkempffite [Ag10Pb4(Sb17Bi9)S48], ramdohrite, semseyite [Pb9Sb8S21], and terrywallaceite [AgPb(Sb,Bi)3S6] have also been identified in the Ánimas vein. The studied sample from the Burton vein (Figure 8) is mostly composed of pyrite (~75% modal). Pyrite occurs as highly corroded anhedral grains with abundant porosity often arranged describing orbicular, crustiform and polygonal patterns (Figure 8A–E). Scattered euhedral quartz crystals between 100 µm and 1 mm in length show mutual straight boundaries with pyrite (Figure 8C). Remnants of arsenopyrite crystals up to 300 µm across are encapsulated by pyrite (Figure 8A,E,F). Cassiterite, which is a trace mineral in the sample, occurs as anhedral grains up to 150 µm in diameter that show pervasive engulfment and porosity due to replacement by later sulfides and sulfosalts (Figure 8G). The conspicuous porosity within and the corrosion gulfs around pyrite are mostly lined with stannite, which is relatively abundant (~20% modal; Figure 8A–E); stannite is also common as interstitial space infillings between pyrite and quartz (Figure 8C). In similar textural positions as stannite occur tetrahedrite-group minerals and chalcopyrite (Figure 8A,B,D–G). Stannite and tetrahedrite-group minerals show complex intergrowths in which the first is apparently veined and replaced along Minerals 2019, 9, 604 13 of 42 very iMrrineegrauls l2a0r19f,r 9o, xn FtsORb yPEtEhRe RsEeVcIEoWn d . Tetrahedrite-group minerals host micrometer-sized in1c3l uofs i4o2 ns of chalcopyrite (Figure 8B) and both minerals form complex intergrowths in which chalcopyrite veins tetrahseizderdit ien-cglruosuiopnsm oifn cehraallcso, pthyuristes u(Fgigguerseti n8Bg) aanladt ebrocthry mstianlelirzaalst ifoonrmo fctohmepfloerxm inetrer(Fgrigowurtehs8 Ein, Fw).hPicohr osity in pycrhitaelciospaylrsiotefi vleleinds wteittrhahterdarcietea-gmroouupn mtsinoefrgaalsl,e tnhau,so ssucgagreksetimngp ffia ltaete, ra ncrdysmtailalirzgaytiroint eo,fw thhei cfohrmpaerrt ially repla(cFeidgusrtea n8nEi,tFe). (FPiogruosriety8 Hin, Ip).yrite is also filled with trace amounts of galena, oscarkempffite, and miargyrite, which partially replaced stannite (Figure 8H,I). FigurFeig6u. rBea 6c. kB-asccka-tstceartetedreedle ecltercotrnonim imagageess( A(A––DD,,FF,,JJ,,KK)) aanndd pphhotootmomicriocrgoragprhaps h(rsef(lreecflteedc tliegdhtl;i gEh,Gt;–EI,,LG) –I,L) of texotfu treaxltuferaalt uferaetsuriens tihne thÁen Áimniamsavs evienini nint htheeÁ Ánniimmaass mmiinnee. .(A(A) )InItnetresprseprseerds emdicmroibcarnodbsa nodf spyorfitpe yrite and cassiterite; in addition, cassiterite lines porosity in pyrite, which shows beehive-like replacement and cassiterite; in addition, cassiterite lines porosity in pyrite, which shows beehive-like replacement textures. (B) Detail of cassiterite mineralization along cracks, cavities and rims of pyrite. (C) Vugs in textupreysr.it(eB a)reD leinteadil wofitcha csassistietreirtietem anind ear caelinztaratil oinnfialll oonf sgtacnrnaictke.s (,Dca) vCiatvieitsieasn ind pryimritse odfepnoytrei thee.x(aCg)onVaul gs in pyritestarurectluinreesd awndit hdrcaaws sbiteeerhiitveea-lnikde atecxetnutrreas;l cinavfiiltlieosf asrtea nfinllietde. w(Dith) Ccaasvsiitteieristei,n sptaynrnititee daenndo ttreahceesx oafg onal structguarleesnaa.n (dE)d Draetwailb oefe shuivbhe-eldikraelt ceaxstsuitreersit;ec acrvyistiteaslsa rreepfilalcleedd bwyi tshtacnansisteit,e wrihteic,hs taalnson riteepalancdedtr paycreisteo. f(Fg)a lena. (E) DeCtasisl iotefrsiuteb rheelidctrsa alfctaers spietervriatseivcer yresptalalscerempelnatc beyd sbtyansntaitne.n (iGte), Pwerhvicahsivaels roeprelapcleamceedntp oyf rpityer.it(eF c)rCysatsaslsit erite relictsbya ftsetarnpneirtev.a s(Hiv)e Dreeptalailc eomf eintebrgyrostwan npityer.it(eG–m) Parecravsaitsei vpesreeupdloamceomrpehnitc oaffpteyr ripteyrcrrhyosttitael stbabyusltaarn nite. (H) Dcertyasitlaolsf, iwntheircghr oawren epyitraixteia–llmy aorvcaersgitreowpsne ubdy osmubohrpedhriacl acfrteyrstpalys rrohf oatritsentaobpyurliatre.c r(Iy)s tSaplsh,awlerhitiec h are epitaxreiaplllayceomveerngt roofw ann basysseumbbhlaegder aolf ceruyhsetadlrsaol farasresneonpoypryitrei taen.d( Is)uSbphheadlrearli taenrde apnlahceedmrael nptyorfitaen craysssteamls.b lage of eu(hJ)e dCroarlroadresde npoypriyteri tceryasntadl wsuitbhh iendclruaslioannsd ofa nahrseednoraplyrpityer iatnedc rmyosntaalzsi.te,( Ja)nCd ocrarvoitdieesd lipnyedri tweitchr ystal with minicalrugsyiroitnes. o(Kf )a rAsernseonpoypryirtietea nindtemrgoronwazni tew,iathn dpycarivtei,t iethsel inlaetdterw sithhowmiinagr gay rpitsee.u(dKo-)hAexrasgeonnoapl yrite morphology. (L) Pervasive replacement of anhedral pyrite grains by sphalerite; both minerals show intergrown with pyrite, the latter showing a pseudo-hexagonal morphology. (L) Pervasive replacement abundant cavities that denote corrosion. Key: apy = arsenopyrite; cst = cassiterite; gn = galena; mc = of anhmeadrcraaslitpey; mritiea =g rmaiianrsgybryitsep; mhanlze =ri mteo; nbaoztihtem-grinouepra mlsinsheroawls; apbyu =n pdyarnitte;c qazv i=t iqeusatrhtza;t sdl =e nspohtealceorirtreo; sion. Key: satnp y= s=tananrsiteen. opyrite; cst = cassiterite; gn = galena; mc = marcasite; mia = miargyrite; mnz = monazite-group minerals; py = pyrite; qz = quartz; sl = sphalerite; stn = stannite. Minerals 2019, 9, 604 14 of 42 Minerals 2019, 9, x FOR PEER REVIEW 14 of 42 FigFuigruer7e. 7P. Phhoototommicircoroggrarapphhss( (rreeflfleecctteedd lliigghhtt;; AA––CC)) aanndd bbaacckk-s-sccaatttetereredd eleelcetcrtorno nimimagaegse (sD(–DI)– oI)f toefxtteuxrtaul ral feafetuatruesreosf osfu slufolfsoaslatlstsin int htheeÁ Ánnimimaass vveeiinn iinn tthhee ÁÁnniimmaass mmiinnee. .(A(A) )InIntetresrtsittiiatila slpsapcaec beebtwetewenee enuheuedhreadl ral quqaurtazrtzc rcyrsytsatlaslsfi lflielldedw witihtha ann aasssseemmbbllaaggee ooff ssuullffiiddeess aanndd ssuulflofosasaltlst;s ;eaeralyrl yspshpahlearlietrei ties ivseivneeidn ebdy by stasntannitnei,tew, whihchichin intu turnrni sisv veeinineedda anndd ccuutt bbyy aannhheeddrraall ccrryysstatalsl soof ftettertarhaehderditreit-eg-rgoruopu mp imneinraelrsa, lasn, danordioter ite and euhedral jamesonite. (B) Relicts of pyrite and cassiterite replaced by an assemblage of stannite, and euhedral jamesonite. (B) Relicts of pyrite and cassiterite replaced by an assemblage of stannite, tetrahedrite-group minerals and jamesonite. (C) Beehive-like pyrite (pseudomorphic replacement of tetrahedrite-group minerals and jamesonite. (C) Beehive-like pyrite (pseudomorphic replacement pseudo-hexagonal crystals) showing abundant porosity, lined with sulfosalts (mostly andorite and ofmpisaerugdyroi-the)e. x(Dag)o Cnoarlrocdryesdt aplysr)itseh corwysitnagls,a wbiuthn dpaonrotspitoyr loinsietdy ,wliinthe danwdoitrhites, umlfioarsgayltrsit(em, aonsdt lsytaannnditoer; ite anidn madidaritgioynri, taen). a(sDse)mCbolargroed oefd japmyersiotenictrey, smtaialsr,gywriitteh apnodr oasnidtyorliitnee rdepwlaictheda pnydroitreit efr,ommi aitrsg byorirtdee,ras nd stainnwniatred; sin. Nadotdei ttihoen r,eapnlaacsesmemenbt loagf ecaosfsijtaemritees obny itseta, nmniiater giny rtihtee abnodttoamnd loefrti tceorrenperla ocre dthpe yimritaegfer. o(mE) its boBrdlaedresdi ncwryasrtdalss. oNf ojtaemtehseonreitpel aacnedm esnutbhoefdcraasl sictreyrsittealsb yosf tacnasnsiitteeriinte threepblaoctetdom byle fsttacnonrniteer aonrdt he imtaegtrea.h(eEd)rBitlea-dgreoducpr ymstianlesraolfs;j anmoetes oanlsitoe taentrdahseudbrhiteed-grarol ucrpy smtainlseroaflsc avsesiinteinrigte srteapnlnaictee.d (Fb)y Isnttaenrnstiitteiaal nd tetsrpaahceed breittew-geeronu ppyrmitein aenrda lqs;unarottze carlyssotatlest lrianheedd wriitteh- garnoduopritme iannedr amlsiavregiynriinteg. (sGta)n Mniitneu. te(F i)ncInlutseirosntist ial spoafc egableetnwae ceonnpceynrittreataen adloqnuga rctrzacckrys,s tcaolnstlaicntesd anwdit hvoaindds oinri taena ansdsemmibalraggyer iotef .m(Gia)rgMyrinitue,t epiynrcalrugsyirointes of gaalennda jacomnecseonntirtea;t enaoltoe npgycrarargckyrsi,tceo rnetpalcatcsinagn danvdooidristei nanadn amsisaermgybrliateg.e Tohfem loiacragtiyorni teo,f pthyirsa rimgyargitee ias nd jamsheoswonni tien; Fn.o (tHe )p Iynrtaerrgstyitriiatle srpeapclea cbientgwaeennd opryirtietea nanddm eipairtgaxyirailt ea.rsTehneoploycraittei olinneodf twhiisthi mteatrgaeheisdsrihteo-wn ing(Fro).u(pH )mIninteerrasltsi tianl dsp asctaenbneittew; emeniaprgyyrirtietea nisd eopbsitearxvieadl aarlsoengo ptyhrei tecolinntaecdt wbietthwteeetnra hpeydrritiete -agnrdo up mitneetrraahlsedarnidte-sgtaronunpit em; miniearraglsy r(iitnesiest)o. b(sIe) rvInetderasltoitniagl tshpeacoe nbtaectwt beetnw seuelnfidpeysr itaendan qdutaerttrza hleinderdit ew-gitrho up mibnoeuralalsng(ienrsiteet,) .fi(zIé)lIynite rasntidti aglaslepnaac;e gbaeletwnae ecnonscuelnfitdraetseas nadloqnug atrhtez rlimnesd owf tihthe bcaovuiltayn agnedri tcer,afickzsé liyni ttehea nd gaflieznéaly; igtea laennda bcounlcaenngterraite saassloemngbltahgee.r iKmesy:o afnthd e=c anvditoyriaten;d apcrya =c kasrsienntohpeyfirizteé;l ybiotue a=n bdoubloaunlgaenrgiter; ite asscestm =b clagssei.teKriteey; :fiazn =d f=izéalnyidteo;r igtne ;=a pgayle=naa;r jsmens o=p jyarmites;obnoitue; =mbiao u= lamnigaregryitrei;tec; spt y= =c apsysriitter; itpey;rfi =z = fizpéylyriatreg;ygrnite=; qgza l=e nqau;ajrmtzs; s=l =ja smpehsaolenriitte;; mstnia == stmanianritgey; rtidte =; tpeytr=ahpeydriite ;gpryour p=. pyrargyrite; qz = quartz; sl = sphalerite; stn = stannite; td = tetrahedrite group. Minerals 2019, 9, 604 15 of 42 Minerals 2019, 9, x FOR PEER REVIEW 15 of 42 FFiigguurree 88.. PPhhoottoomiiccrrooggrraapphhss ((rreefflleecctteedd lliigghhtt;; A––FF)) aanndd bbaacckk--ssccaatttteerreedd eelleeccttrroonn iimaaggeess ((G––II)) ooff tteexxttuurraall ffeeaatturreess iin tthee Burrttoon vveeiin iin tthee Ániimaass miinee.. ((A)) Coorrrroodeed pyyrriittee aand aarrsseenoopyyrriittee,, wiitth poorroossiittyy lliineed wiitth ssttaanniittee aand cchaallccopyrriittee.. ((B)) Sttaanniittee aand tteettrraaheedrriittee--grroup miineerraallss fifilllliing iintteerrssttiittiiaall sspace bettween euhedrrall crryssttallss off quarrttz and corrrroded pyrriitte;; ttettrrahedrriitte--grroup miinerrallss hosstt miicrrometterr--siized iincllusiions off challcopyrriitte.. ((C)) Sttanniitte occupyiing iintterrsttiittiiall space among quarrttz,, pyriitte and arsenopyriitte crysttalls.. ((D)) Crusttiiform pyriitte aggregattes wiitth conspiicuous porosiitty and corrosion engulfment,, lined with stannite and tetrahedrite-group minerals.. (E) Stannite,, tetrahedrite and chalcopyrite lining secondary porosity in pyrite and arsenopyrite. (F) Dettaiill off tteettrrahedriitte-group minerals and chalcopyrite inffiilling (location in E); note that chalcopyrite veins tetrahedrite-group minerals. (G) Tetrahedrite-group minerals with inclusions of chalcopyrite and a relict of a cassiterite grain replaced by ssttaanniitte.. ((H)) Dettaiill of stannite, tetrahedrite-group minerals, miargyrite and oscarkempfffifite inffiillings in pyrite cavities. (I)) Detaiill of a stannite, miargyrite and galena inffiilling in pyrite cavities; note tthaatt ggaalleennaa vveeininss sstatannnnitiete. . Keeyy:: apy == arrsenopyrite; cpy = challcopyrite; cst = cassiterite;; gn = galena; mia = miargyrite; osc = oscarkempffiffite;; py = pyrite; qz = quartz; stn = ssttaanniitte;; td = tteettrrahedrriitte--grroup.. TThhee CCoolloorraaddaa vveeiinn sshhoowss maarrkkeedd iinntteerrnnaall bbaannddiinngg tthhaatt iiss ddeeffiinneedd bbyy lliinneeaall aarrrraannggeemeennttss ooff oorree miinneerraallss sseeppaarraatteedd bbyy bbaannddss ooff qquuaarrttzz ((FFiigguurree 99A)).. TThhee maaiinn oorree pphhaasseess aarree ccaassssiitteerriittee,, aarrsseennooppyyrriittee,, aanndd tteettrraahheeddrriittee--ggrroouupp miinneerraallss,, whhiicchh rreepprreesseenntt >>9900% mooddaall aallttooggeetthheerr ooff tthhee oorree.. CCaassssiitteerriittee ffoorrmss aannhheeddrraall ggrraaiinnss,, lelessss ththaann 15105 0μmµm in isnizsei,z me,omstolys tilnyteinrgterorgwronw wnithw qituhaqrtuza arntzd,a tnod a, lteossaerl eesxsteernet,x wteintht, wpyitrhitep yarnidte aarnsdenaorpseynriotep yinri ttehien rtihmesr iomf sthoef tvheeinv. ePiny.riPtey rfiotremfos rmanshaendhraeld graral ignrsa ibnosthb oatsh masamssaesss oesr iosroliasoteldat, eadn,da hnads hbaeesnb peeenrvpaseirvvealsyi vreeplylarceepdl abcye adrsbeynoaprsyernitoep aynrdit eotahnedr soutlhfiedress ualnfidd seus lafonsdalstsu (lfFoigsaulrtes (9FAig–uCr)e. 9CAas–sCit)e. rCitaes saintedr ittheea npdyrtihtee–payrsrietne–oaprysreinteo payssreitme abslasegme balraeg eexaterenseixvteelnys irveepllyacreepdl abcye dstbanynsittaen annitde taentdrahteetdrarihteed-grrioteu-pgr mouinpemrailsn,e wrahlsic,hw ahlsicoh flaolosdoefldo tohdee idnttehrestiitniatel rssptiatciael bseptwaceeebne tthweseee nmtihneesrealms (iFniegruarles (9FBi–gDur,eG9–BJ)–. DL,oGc–aJl) . wLooclfarlawmoiltfer a(minictelu(dininclgu dbiontghb foetrhbfeerribtee raitneda nhdühbünbenrieteri tceocmompopsoistiiotinosn)s )aappppeeaarrss aass ssuubbhheeddrraall aanndd eeuuhheeddrraall ttaabbuullaarr aanndd sshhoorrtt pprriissmaattiicc ccrryyssttaallss uupp ttoo 115500 µμm iinn lleennggtthh tthhaatt oofftteenn ffoorrm parallel aggregates within quartz (Figure 9F); minute inclusions of wolframite are also observed within porosity in pyrite (Figure 9K). The concentration of stannite and, particularly, of tetrahedrite- Minerals 2019, 9, 604 16 of 42 parallel aggregates within quartz (Figure 9F); minute inclusions of wolframite are also observed within porosity in pyrite (Figure 9K). The concentration of stannite and, particularly, of tetrahedrite-group minerals increases towards the vein core, even forming almost monomineralic massive aggregates. Stannite is commonly found isolated within or veined by tetrahedrite-group minerals (Figure 9D), thus indicating a later crystallization of the latter. Chalcopyrite is rare in the Colorada vein and it occurs as scattered inclusions (some tens of µm in diameter) within tetrahedrite-group minerals (Figure 9D). Chalcopyrite is also observed lining porosity within other phase minerals such as quartz and pyrite, and it is locally veined by a second generation of stannite (Figure 9E). Cassiterite and sulfides form garland-like aggregates that draw hexagonal shapes (Figure 9J), in which the central part is occupied by quartz. Porosity and interstitial space among quartz, cassiterite, and the above described sulfides and sulfosalts in the Colorada vein are often lined with oscarkempffite, aramayoite (Figure 9G,J), miargyrite, and terrywallaceite. Pyrite and cassiterite show local replacement by a mineral with the same composition as angelellite [Fe3+ 4(AsO4)2O3] in the form of colloform aggregates (Figure 9K,L). Secondary porosity in pyrite draws pseudo-hexagonal patterns, whereas, in cassiterite, the porosity is mostly irregular. The Rosario vein is mostly composed of pyrite, marcasite, and stannite group minerals, and quartz is the main gangue mineral. Fine-grained marcasite and pyrite (pyrite-I) form slabs of some hundreds of micrometers in length that tend to group into radial aggregates (Figure 10A,B). Aggregates of tabular pyrite and marcasite show myriads of micrometer-sized cavities that distribute in trails parallel to the long axis of the slabs. The fine intergrowths of pyrite–marcasite are in part recrystallized to subhedral and anhedral equant pyrite grains (pyrite-II), between 100 and 300 µm in diameter and a low porosity that results in a more homogeneous aspect when compared to marcasite–pyrite-I aggregates (Figure 10A,B). The pyrite-II grains are not completely homogeneous in color and combine zones with a cream color and an isotropic optical behavior with zones of a clearer (almost white) color and a fair pleochroism that might indicate an incomplete recrystallization of marcasite to pyrite (subtle but visible in Figure 10C). Pyrite (both generations) and marcasite constitute the “skeleton” of the outer sectors of the vein, and the rest of the minerals appear as their replacements or interstitial to them. Cassiterite, which is scarce in the Rosario vein, occurs as micrometer-sized anhedral crystals that form aggregates up to 1 mm across and are locally intergrown with pyrite crystals (Figure 10C). Sphalerite is also scarce and it is only observed as anhedral grains completely surrounded by quartz groundmasses. Pyrite, marcasite and cassiterite are partly replaced by stannite-group minerals along irregular replacement fronts (Figure 10A–C,G). Stannite-group minerals are also common as infillings of porosity within pyrite (±marcasite) and highlight orbicular to polygonal patterns in the distribution of the porosity cavities (Figure 10D,E). The vein grades inwards to a chalcopyrite- and stannite-group minerals-rich assemblage in stark contrast with the abundance of pyrite–marcasite in the vein rims. In the core of the Rosario vein, stannite-group minerals form a massive aggregate that includes famatinite [Cu3SbS4] and stannite. Famatinite is much scarcer than stannite and it occurs as islands that are surrounded and veined by stannite, thus suggesting its earlier formation. Chalcopyrite is found in the form of inclusions within stannite and famatinite and forming thin stringers across them; chalcopyrite might also accumulate along the contacts between pyrite and the massive infilling of stannite-group minerals (Figure 10F). Teallite is particularly abundant in the studied samples of the Rosario vein and it forms subhedral platy crystals that are up to 150 µm in length. Teallite, along with traces of terrywallaceite, occurs lining porosity within pyrite-marcasite, quartz and cassiterite (Figure 10C,H,I). In the same textural position occurs bismuthinite, which is observed to replace and vein terrywallaceite and to host some minute inclusions of native bismuth (Figure 10I). Minerals 2019, 9, 604 17 of 42 Minerals 2019, 9, x FOR PEER REVIEW 17 of 42 FigFuigruere9 .9. BBaacckk--ssccaatttteerreedd eelleecctrtroonn imimagaegse s(A(A,G,G–L–)L a)nadn dphpothoomtoicmroicgrroagprhasp (hrsefl(ercetfleedc tleigdhtl;i gBh–tF; ) Bo–f F) oftetxetxuturarla fleafteuarteusr iens thine CthoelorCadolao vreaidna inv tehien Áinnimthaes mÁinniem. (aAs) Pmairnalel.el b(aAn)dsP oafr qalulaerltzb,a cnadsssiteorfiteq uanadrt z, cassusiltfeidrietse (amnodstslyu lafirdseenso(pmyroistetl yanadr speynroitpe)y. r(iBte) Aanndhepdyrarli tcer)y.st(aBls) oAf nphyerditrea rlepcrlyacsetadl sbyo farpsyenriotpeyrreiptel,a icne d bytuarrnse rneopplaycreidte ,biyn sttuarnnnirteep alancde dtetbryahsetdanrinteit-geraonudp tmetirnaehreadlsr. it(eC-)g Irnotueprstmitiianle rsaplasc.e( Cbe)tIwneteerns tciotirarlosdpeadc e bectrwyesteanls coofr pryordieted ancrdy asrtsaelsnoopfypriyteri ltieneadn wd iathrs setnanonpiyter iatnedl itneetrdahweditrhites-tgarnonuipte mainnderatelst.r (aDh)e Idnrciltue-sgiornosu p mionf ecrhaalslc. op(Dyr)iteIn icnl uas imoansss ooff cshtaanlncoitpe yarnitde tientraahmedarsitse-ogfrosutapn mniitneeraanlsd. (tEe)t rDaheetadilr iotef -ag rcohuaplcompyinrietrea-ls. stannite inclusion within quartz along with an anhedral crystal of pyrite; note stannite stringers across (E) Detail of a chalcopyrite-stannite inclusion within quartz along with an anhedral crystal of pyrite; chalcopyrite. (F) Micrometer-scale euhedral wolframite crystals in a quartz groundmass. (G) note stannite stringers across chalcopyrite. (F) Micrometer-scale euhedral wolframite crystals in a quartz Cassiterite-stannite-pyrite garland; note cassiterite crystals replaced by stannite, both of them hosting groundmass. (G) Cassiterite-stannite-pyrite garland; note cassiterite crystals replaced by stannite, both abundant oscarkempffite and staročeskéite inclusions. (H) Anhedral pyrite crystals conspicuously of them hosting abundant oscarkempffite and staročeskéite inclusions. (H) Anhedral pyrite crystals replaced by arsenopyrite, in turn intensely replaced and veined by tetrahedrite-group minerals. (I) coDnseptaicilu oofu testlyrarheepdlraictee-dgrboyuapr mseinnoepraylrsi rteep, ilnactiunrgn airnsetennospeylyritree;p nloatcee tdhea nmdavrkeeinde zdonbiyngte otrfa ahresednroitpey-grirtoeu. p mi(nJ)e Arablsu.n(dI)anDte otascilaorkfetmetrpafhfieted rliintein-ggr ocauvpitmiesin ienr palysrriteep, laarcsienngoaprysreinteo apnydri tteet;rnaohteedtrhitee-mgraorukpe dmzionnerinalgs.o f ars(Ken) oCpaysrsiittee.ri(tJe) aAnbdu pnydraintet ionstcearrgkreomwpthffis;t neolitne ian gmcianvuittei ews oinlfrpaymriittee, carryssetnaol piny rpioteroasnitdyt, ewtrhaihched isri mte-ogsrtolyu p mifnilelerdal sw. (iKth) Canagsesilteellriittee. a(nLd) pDyertiateil inoft eargnr oinwttehrgs;ronwotteha bmetiwnueteenw poylfrritaem aitnedc rcyasstsailteinritpeo; rcoassistyit,ewrihtei cihs is moansthlyedfirlalel danwdi tshhoawngs eclaevlliittiee.s (lLin) eDde wtaiitlho fanangeilnetlleirtge.r oKweyth: abnegtw = eaenngpelyerliltiteea; napdyc a=s asirtseernitoep;ycraistesi; taerrait e= is anahreadmraayl oainted; schpoyw = scchaavlciotipeysrliitnee; dcswt =it hcaassnigteerlietlel;i toes.cK =e oys:caanrkge=mapnffgiteel;e pllyit e=; paypryit=e; aqrzs e=n qoupayrrtizt;e s;tanr a= = arastmananyioteit;e t;dc p= yte=trachheadlcroitpe-ygrrioteu;pc;s wt =lf c=a wssoitlefrraitme;itoes. c = oscarkempffite; py = pyrite; qz = quartz; stn = stannite; td = tetrahedrite-group; wlf = wolframite. Minerals 2019, 9, 604 18 of 42 Minerals 2019, 9, x FOR PEER REVIEW 18 of 42 Fiigurree 1100.. PPhhoottoomiiccrrooggrraapphhss ((rreefflleecctteedd lliigghhtt;; A––FF)) and bacck--ssccatttteerreed eelleeccttrron iimageess ((G–II)) off ttextturrall ffeatturress iin tthe Rossarriio veiin iin tthe Ániimass miinee.. ((A)) Radiiall aggrregattess off ttabullarr ttwiined marrcasiitte crrysttalls ((whiitte)) afftterr ttabullarr pyrrrrhottiitte parrttlly rrecrrysttalllliized tto pyrriitte ((ccrreamy)) and ssttaanniitte.. ((B)) Pyriitte--marrccaassiittee aaggggrreeggaatetep paartrltylyr erpeplalcaecdedb ybys tsatnaninteit;ei;s iosloaltaetdedg rgarinaisnosf osfp shpahlearlietreitaer earoec colcucdluedeidn qinu qarutazr.tz(C. ()CA) gAggrgergeagtaetoe foaf nahnehderdarlacl acsassistietreirtietec rcyrystsatalslsi nintetergrgrorowwnnw witithhp pyyrriittee--maarrccaassiittee;; porosiity in both minerals lined with stannite. (D) Detail of stannite infifilling in concentrically-arranged porosity in pyrite. ((E)) Porosiitty in pyrite, which is partly lined with stannite, drawing a psseudo-hexagonal pattern.. (F) Chalcopyrriittee vveeiinniinnggs sttaannnnitieteg grroouuppm mininerearlaslsw witihthfa fmamataintiinteitein inth tehve evineinco croer; efa; mfaamtiantitneities pisa rptlayrtrleyp lraecpeldacbeyd sbtayn nstitaen.n(iGte). C(aGs)s iCtearistseitaenridtep yarnidte pyervitaes ipverlvyarseipvlealcye drebpylascteadn nbitye asltoangniitrer eagluolnagr rirerpelgaucelamr ernept lfarocenmtse. n(Ht f)roTenatsll.i t(eHp) lTaetyalclirtyes ptalalstyin crthyestcaolsn itnac tthbee ctwoneteanctp byertiwteeaend pqyuriatret za.n(dI )qCuavrtizty. (iIn) pCyarviitteyl in epdywritieth lisnteadn nwititeh, tsetrarnynwitael,l taecreriytewaanlldacneaiteiv aenbdi snmatuivthe .bKisemyu: tahp. yK=eya: raspeny o=p ayrrsietne;oBpiy=ritnea; tBivi e= bniastmivue thb;isbmisu=thb; isbmis u=t hbinisimte;ucthpiyni=tec; hcaplcyo p= ycrhitael;ccospty=rictea;s scistet r=it ec;afsmsitte=riftae;m famtitn i=te ;famca=tinmitae;r cmasci te=; pmya=rcapsyirteit;e p; yq z= =pyqruitaer;t zq;zs =l =qusaprhtazl; esrli t=e s; psthna=lersittaen; nstinte =; tsetan=ntietea;l ltietea; =tr twea=lliter; rtyrw a=l ltaecreriytwe.allaceite. Minerals 2019, 9, 604 19 of 42 4.3. Chocaya Mine When compared to veins in the Ánimas and Siete Suyos mines, the mineralogy in the Nueva vein in the Chocaya mine is relatively simple, as it consists in base-metal sulfides nearly in its entirety (Figure 11). Sphalerite and marcasite-pyrite intergrowths constitute the 80% (modal) of ore assemblages. Marcasite–pyrite are commonly concentrated towards the rims of the main vein and associated secondary veinlets, close or along the contacts with wall rocks, whereas sphalerite normally occupies the vein cores. The marcasite–pyrite assemblage forms masses of corroded anhedral grains with abundant porosity lined with other sulfides and quartz (Figure 11A–I,L). Grayish white growth zones (somewhat darker than marcasite) with a strong anisotropy in the iron sulfide aggregates might correspond to relicts of an intermediate product after pyrrhotite (see [75,76]). Pyrrhotite relicts between a few µm and some hundreds µm across are commonly observed within the masses of marcasite–pyrite (–intermediate product; Figure 11B,C,K) and suggest that marcasite–pyrite are products of its replacement. The recrystallization of pyrrhotite to form fine-grained marcasite-pyrite(-intermediate product) is further supported by the almost pseudomorphic replacement that resulted in hexagonal patterns (Figure 11J). These probably represent (001) faces of a hexagonal mineral. Porosity in the marcasite–pyrite masses is often oriented along the {100} planes of allegedly replaced pyrrhotite. Detailed observations reveal that pyrrhotite inclusions within marcasite–pyrite (–intermediate product) are often aligned with porosity (Figure 11K). Fine-grained marcasite is partly recrystallized to subhedral pyrite (Figure 11H,I) and therefore a second generation of pyrite (pyrite-II) is considered. Arsenopyrite occurs in minor amounts in the Nueva vein. It forms euhedral and subhedral crystals some tens of micrometers across, which are mostly decorating the contacts between iron sulfide- and sphalerite-rich bands (Figure 11E,F). Sphalerite and galena generally occur as anhedral grains interstitial to pyrrhotite–marcasite–pyrite and arsenopyrite, lining porosity in corroded iron sulfides and forming bands or masses that filled the central portions of the vein and veinlets. Figure 11H shows a veinlet of sphalerite and galena that cuts a mass of marcasite-pyrite; galena concentrates mostly along the rims of this veinlet. It is common that galena and traces of stannite line cavities in sphalerite (Figure 11C), thus suggesting their late crystallization. Bands of sphalerite with contrasting compositions are arranged parallel to the vein banding. Traces of argyrodite [Ag8GeS6] and acanthite form very fine intergrowths that replace galena and that lined interstices between galena and sphalerite. Minerals 2019, 9, 604 20 of 42 Minerals 2019, 9, x FOR PEER REVIEW 20 of 42 FigurFeig1u1r.eP 1h1o. toPmhoitcormogicrraopghrasp(rhesfl (ercetfeledctleigdh lti;gAht–; IA,K–)I,aKn)d abnadc kb-asccka-tstceartetdereedle cetlreocntroimn aimgeasg(eJs, L()J,oLf) teoxf tural featutreexstuinratlh feeaNtuureesv ianv tehien Ninuetvhae vCehino cina ythaem Cihnoec.a(yAa )mFiinnee. -(Aan) dFimnee- dainudm m-gedraiuinme-dgrmainaerdca msiatercraespitlea cing replacing pyrrhotite, partly recrystallized to pByrite. (B) Pyrrhotite relict replaced by a marcasite-pyrite pyrrhotite, partly recrystallized to pyrite. ( ) Pyrrhotite relict replaced by a marcasite-pyrite and and sphalerite assemblage. (C) Massive sphalerite hosting a pyrrhotite relict that is partly replaced by sphalmerairtceasaistes-epmyrbitlea;g peo.ro(Csi)tyM ina scsoirvroedsepdh saplhearileteritheo isst liinngeda wpiythr rghaoletintae. r(eDli)c Btatnhdast oisf sppahratlleyrirtee pwlaitche d by marccaosnittera-pstyinrgit ec;hpemoricoasli tcyominpocsoirtiroond; ethdes ppohraolseitryi ties ilsinleidn ewditwh iptyhrigtea laennda .ga(Dlen)aB. a(En)d Csoorfrosdpehda glerariitnes with controafs tpiynrgitec-hmemarcicaasiltec oamggpreogsaittieosn (p; tsheuedpoomroosrpithysi asfltienr epdyrwrhiothtitpey) srhitoewainndg ograileenntead. (pEo)roCsoitryr olindeedd wgirtahi ns of pyritesp-mhaalerrciates-igtealaengag raengda tceust (bpys aenu darosmenoorppyhristea-sftpehrapleyrirtreh-goatlietnea) svheoinwleitn (gceonrteier-nbtoetdtopmo orof sthitey imlinaegde; with sphalneortiet et-hgaat laernseanaonpdyrictue tisb myoasntlya rdsiestnroibpuyterdit ea-losnpgh athler viteein-g raimlesn, anvde isnplheatle(crieten tceorn-cbeontttroamtes otofwthaerdism age; note tithsa ctoarer)s.e (nF)o Cpoymripteleixs rmepolsatcleymdeinstt roifb tuhete adssaelmonblgagthe emvareciansirtiem–psy, rainted bsyp ahrsaelneoripteyrcitoen, scpehnatrleartietes atnodw ards its cogrea)le. n(Fa.) (CGo) mRpealectxivree prelapclaecmemenetnot fsethqueeanscsee mincblluadgiengm eaarrclays pityer–iptey rreitpelabcyeda rbsye nspohpaylreirtiete, ,s pwhaiclher iinte and galentau.rn( Gis )reRpelaaccetdiv bey rgeaplelnacae. (mHe) nSpt hsaelqeurieten–cgealienncal ustdriinnggere caurtltyinpgy ar mitearrceapsiltaec medassb (yalsmpohsat lceormitep,lewtehlyi ch in turn irsecrreypsltaaclleizdedb ytog aplyernitae.);( Hno)tSe pthhaatl egraitleen–ag acloenncaensttrraintegse arlcoungtt itnhge astmrinagrecra sriitme;m oraisesnt(eadlm poosrtosciotym ipnl etely recrycsotarrlolidzeedd mtoarpcaysriittee-p);ynriotet e(fothllaotwginagle tnhae ccloeanvcaegnetsr aotfe tshea lfoonrmgetrh peysrrthriontgitee)r irsi lmin;edo rwieintht esdphpaolerroitsei ty in and galena. (I) Pervasive replacement of marcasite (mostly recrystallized to pyrite) by sphalerite and corroded marcasite-pyrite (following the cleavages of the former pyrrhotite) is lined with sphalerite galena. (J) Pseudomorphic replacement of marcasite-pyrite and minor amounts of other sulfides of a and gpasleeundao.h(eIx)aPgeornvaal scivryestraelp olaf cpeymrrehnottiotef. m(Ka)r cPaysrititee–(mmaorsctalysitree carsysesmtabllliazgeed wtoithp yorriiteen)tebdy sppyhrrahloetriittee and galenian.cl(uJs)ioPnsse u(idnosemt;o lropchatiiconre pinla Jc)e. m(Le)n tDoeftamil aorfc aas imtea-prcyarsiittee-panyrditem pinsoeurdaommoourpnhts aoffteor thpeyrrrshuoltfiitde es of a pseiundfiolthraetxeda gboyn aspl hcraylesrtiatel oafndp ygrarlheontai t(el.oc(aKti)oPn yirni tJe)–. mKaeyrc: aaspitye =a sasresmenbolpaygreitew; igthn o=r igeanletneda; pmycr r=h otite inclusmioanrcsa(siintes;e pt;ol =o cpaytrirohnoitniteJ;) p. y(L =) pDyertiatei;l qozf =a qmuarctza;s silt e=- pspyhraitlerpitsee; ustdno =m sotarnpnhitaef. ter pyrrhotite infiltrated b y sphalerite and galena (location in J). Key: apy = arsenopyrite; gn = galena; mc = marcasite; po = pyrrhotite; py = pyrite; qz = quartz; sl = sphalerite; stn = stannite. Minerals 2019, 9, 604 21 of 42 5. Ore Mineral Geochemistry 5.1. In-Bearing Minerals Relevant indium contents were found in sphalerite (up to 9.66 wt.% In), wurtzite (up to 1.61 wt.% In), stannite-group minerals (up to 4.11 wt.% In), cassiterite (up to 0.25 wt.% In2O3), and ramdohrite (up to 0.24 wt.% In). Sphalerite shows a relatively wide compositional spectrum in Fe, Cu, In and Cd. Table 1 shows a summary of the compositions of the studied sphalerite grains. Although Fe contents in sphalerite peak at the Ánimas mine, similarly wide compositional ranges were found in the three studied mines: between 7.4 and 27.7 mol. % FeS in the Ánimas mine, between 0.0 and 28.8 mol. % FeS in the Chocaya mine, and between 2.3 and 19.6 mol. % FeS in the Siete Suyos mine (Figure 12A). Despite its variations, the average Cu contents in sphalerite are higher in the Siete Suyos (average = 0.85 wt.%) than in Ánimas (average = 0.62 wt.%) and Chocaya (average = 0.12 wt.%) mines (Figure 12B). The concentration of Cu is particularly high in sphalerite from the Diez vein (up to 5.81 wt.%; average = 1.19 wt.%). The Sn contents in sphalerite (up to 4.90 wt.%) are very erratic in the three mines. Similar to Cu, In contents in sphalerite tend to peak in the Siete Suyos mine (up to 9.76 wt.%, average = 0.83 wt.%) and are lower in the Ánimas (up to 2.37 wt.%, average = 0.21 wt.%) and the Chocaya (up to 1.82 wt.%, average = 0.14 wt.%; Figure 12C) mines. Indium contents in sphalerite are particularly high in the Diez vein (up to 8.62 wt.%). Indium contents in sphalerite increase with depth: in the Siete Suyos mine, the average content in the Chorro vein at the 14 level is of 0.35 wt.% In (up to 0.97 wt.% In), and at the 16 level is 1.10 wt.% (up to 2.47 wt.% In; Figure 12D). In the Arturo vein, the average contents are 0.05 wt.% In at the 19 level, 0.08 wt.% In at the 20 level, and 0.22 wt.% In at the 21 level. This trend is also observed in sphalerite from the Ánimas vein in the eponymous mine, in which the average concentration is 0.20 wt.% In at the 125 level and 0.45 wt.% In at the 175 level, although the maximum values (up to 2.37 wt.%, being identified as an outlier value, and 0.94 wt.%, respectively) obscure such a trend (Figure 12D). The contents in other critical metals, such as Ge, in sphalerite from the three mines are systematically very low, being mostly below their detection limits. The maximum Cd contents in sphalerite are 1.41 wt.% Cd in the Siete Suyos mine, 1.04 wt.% Cd in the Ánimas mine, and 2.82 wt.% Cd in the Chocaya mine, although the average values are around ~0.5 wt.% Cd in the three mines. The measured atomic proportions of Zn and Fe in sphalerite yield a negative correlation and, in the Zn vs. Fe (a.p.f.u.) binary diagram in Figure 13, most compositions lie along the Zn + Fe = 1 (a.p.f.u.) line, thus indicating a dominant substitution between both elements. Nevertheless, a significant number of analyses plot below this line, thus pointing to a deficient occupancy of the cationic position in terms of Zn and Fe alone. In the Fe + Cu + Sn + Cd + In vs. Zn diagram in Figure 13 virtually the entire analyses plot along the Fe + Cu + Sn + Cd + In + Zn = 1 line, which suggests that, besides Fe, coupled substitutions involving other cations also operated (e.g., Zn↔ Fe + Cu + Sn). Indium contents do not show a clear correlation neither with Fe nor with Zn (Figure 13). The In vs. Zn diagram in Figure 13 shows a broad dispersion of data, with enrichment in In below the Zn + In = 1 line and mostly grouped along and below the sphalerite-roquesite tie-line. Although the enrichment in In generally occurs in Fe-rich sphalerite (mostly between 0.05 and 0.20 a.p.f.u.), a trend towards In enrichment in Fe-poor sphalerite occurs in the Chocaya mine (Figure 13). The atomic concentrations of In and Cu yield a positive correlation, so that, in Figure 13, most of the analyses plot along the Cu/In = 1 line, thus suggesting a coupled substitution of Zn by Cu + In. In contrast, Sn and In do not correlate at all. The positive correlation between In and Cu is shown in qualitative compositional images (Figure 14), in which their high and low contents display crustiform micro-bands. In Figure 14, high In and Cu contents correspond to low Zn contents, which thus supports the substitution mechanism above. In contrast, the Fe distribution in Figure 14 does not show any apparent zonal correlation with In, Cu, or Zn. Cd does not correlate with any of the analyzed elements and its contents in sphalerite from the three mines are mostly below 0.010 a.p.f.u., with the exception of peak Cd contents in the Minerals 2019, 9, 604 22 of 42 Chocaya mine (up to 1.25 Cd p.f.u.). The analyses are roughly arranged along the Zn + Cd = 1 line in MFiignuerraels 12031,9t, h9u, xs FsOuRg PgEeEsRti nRgEVpIEuWnc t ual Zn↔ Cd simple substitutions. 22 of 42 Figure 12. Box plot comparison of the Fe (A), Cu (B), and In (C) contents (wt.%) in sphalerite grains from the diiffffeerreennttm minineessa annddo of fI nIn( w(wt.%t.%) f)r ofrmomth tehde iffdeifrfenretnvte ivnesinasn danmdi nmininginlegv elelsve(Dls )(sDtu) dstieudiiendt hine tÁhne iÁmnaism–Cash–oCchayoaca–ySiae–tSeieStuey Sousydois tdricst.riTcth. eThcen cternaltrbaol xboisxi nis tihne thmei dmdilded5l0e %50o%f tohfe thdea tdaa. tTa.h Tehlien leinine itnh ethbeo bxorxe prerpesrensetsntsh tehme medeidanianv avlauleuefo froer aecahchb obxo.x.C Ciricrclelessr reepprreesseenntto ouuttlliieerrss,, whiicch are further than 1.5*(75th percentile/top of box-25th percentile/bottttom off box) and the whiskers are the extreme values that are not outliers. Forr In,, vallues bellow its detectiion limiitt (i..e..,, 0..03 wt..%) have been replaced by 0..015 wt..% to allllow llogariithmiic scalle axiis iin diiagrams (C,)D a)n.d (D). Moosstt oof ftheth setudstieudd iehdomohgoemnoegouens,e opursis,tinpe rissptihnaeleristpeh carlyersittaels cprlyost tawlsithipnl otthe wsipthhainleritthe–e sstpahnanlietrei–tero–qstuaensnitiete p–sreouqduoesteitrenaprsye usydsotetemrn [a2r5y,7s7y],s steimil[a2r5 t,o77 s]p, hsaimleirliater ftroomsp hthaele Hriutearfir oHmuatrhi edeHpuoasriti [H39u]a r(iFdigeuproes i1t5[)3. 9M] (oFsitg usrpeh1al5e)r.iteM oanstalsypsheas lefrriotme atnhael yÁsensimfroasm–CthheocÁaynaim–Saies–teC hSoucyaoysa –dSeipeotesiStsu yaores ddiesptroisbiutsteadr ealdoinstgr itbhuet sepdhaalloenrigtet–hsetasnpnhiatele arnitde– ssptahnanleirteitea–nrdoqsupehsailteer tiitee-–lrinoeqsu iens ittheet iZen-l i+n eFse i+n Cthde +Z Mn n+ vFse. +CuC +d A+gM vns. vSsn. +C uIn+ teArngavrys. dSinag+raImn t (eFringaurrye d1i5a)g. rTahme s(Ftuigduierde 1sp5)h.aTlehreitest suadmiepdlessp choanletariitne uspam top 4le.1s mcoonlt.a %in Cupu2tFoe4S.n1Sm4 (oil..e.%, sColuid2F seoSlnuSti4o(ni. ew.,istohl isdtasnonluitteio) nanwdi tuhps ttaon 9n.i1te m) aonl.d %u pCtuoIn9S.12 m(i.oel.., %solCidu IsnoSlu2 t(iio.en., wsoiltihd rsooqluuteiosnitew).i tAh rsoinqgulees iatne)a.lyAsissi nogfl ea asnpahlaylseirsitoef garsapinh aflreormite tghrea iSnieftreo mSutyhoesS mietieneS upylootstemdi naelopnlgo ttthede saplohnagletrhitees–pchhaallceoriptey–rcithea tliceo-lpinyrei t(eFitgieu-rlien 1e5()F. igure 15). TThhee wuurrttzziittee ccrryyssttaallss weerree aannaallyyzzeedd iinn ssuurrffaaccee ssaampplleess ffrroom tthhee SSiieettee SSuuyyooss miinnee aarreeaa ((ssaamppllee 11339944)).. TThheesseea nanalaylsyessesre vreevael avla rviaabrilaebcloen cceonntcreantitornatsioonf Isn othf aItnr atnhgaet breatnwgeee nbevtawlueeesnb velaolwueist sbdeeltoewct ioitns dlimeteitcatinodn 1li.m61itw atn.%d 1in.61sp whta.l%er iinte sgprhaainlesrwiteit ghrFaeincso wncitehn tFrea tcioonncsetnhtartartiaonngse tbheattw raenenge1 .b2e3twaneden5 .12.923w atn.%d. T5.h2e9 cwotn.%ce.n Ttrhaet icoonnscoefnotrtahteiorncsa toiof nosth, seur cchataiosnCsu, s(u0c.0h4 atso C2.u4 4(0w.0t4.% to) ,2C.4d4 (w0.t6.%5 t)o, C1.d2 6(0w.6t5.% to) ,1S.2n6( 0w.0t.2%t)o, 1S.n8 7(0w.0t2.% to), 1a.n8d7 wAgt.%(b)e, laonwd tAheg d(beeteloctwio nthlei mdeittetoct0io.7n9 lwimt.i%t t)o, a0r.e79a lwsot.v%a)r,i aabrele a. lGsoe rvmarainabiulem. Gcoenrmteanntsiuamre contents are systematically below its detection limit. The current wealth of data is not yet sufficient to draw clear cationic correlations between minor elements within wurtzite. Minerals 2019, 9, 604 23 of 42 systematically below its detection limit. The current wealth of data is not yet sufficient to draw clear cMatinioernalisc 2c0o19r,r 9e,l xa tFiOonR sPEbEeRtw ReEeVnIEmW in or elements within wurtzite. 23 of 42 Figure 13. Correlation between elements in sphalerite from the Ánimas–Chocaya–Siete Suyos district. Figure 13. Correlation between elements in sphalerite from the Ánimas–Chocaya–Siete Suyos district. The chemical composition of sphalerite grains from the Huari Huari deposit is shown for comparison [39]. The chemical composition of sphalerite grains from the Huari Huari deposit is shown for comparison [39]. Minerals 2019, 9, 604 24 of 42 Minerals 2019, 9, x FOR PEER REVIEW 24 of 42 FFiigguurree1 144. .S SEEMM-E-EDDSSq uqualaitliattaivtieveX -Xra-ryaiym iamgaegseosf Ionf (ILnα ()L, αC)u, C(Kuα ()K, Zαn), (ZKnα )(aKnαd) Faend(K Fαe) i(nKsαp)h ianl esrpitheaflreormite MintefhrraeolsmD 20i e1thz9,e v9 e,D xini FeOizn Rvt hPeiEenES Riine Rt eEthVSeIuE ySWioe st em Sinuey.oBs rmigihnte.r Bcorilgohrsteirn dcoiclaotres hinigdhiecratceo nhcigehnetra tcioncseonftrtahteioannsa loyfz et2hd5e o f 42 ealenmalyenzet.dS EelMem-BeSnEt. imSEaMge-Bs SoEf thimeamgaeps poefd tharee amsaaprpeesdh oawrenasin aFrieg ushreow5Bn (lienf tFgigrouurep o5Bf c(olmeftp ogsriotiuopn aolf icmo amgpeso)saitniodnFailg iumraeg5eCs)( aringdh tFgigrouurep 5oCf c(roimghpto gsritoiuonpa olfi mcoamgepso)s. itional images). FiFgiugruer1e5 1.5P. lPoltoot fotfh tehea nanalaylyzezdeds psphhaalelerirtietea anndds statannnnitieteg grraaiinnssf frroom tthhee Ániimas–Chocaya–Siete Suyos didstirsitcrticint itnh tehZe nZ+n +F eF+e +C Cdd+ +M Mnnv vs.s.C Cuu+ + Agg vvss.. Sn + In ternary diagram. The composition of mineral enedn-dm-memembebresrosf oinf tienrteesrteisst ailss oalpsolo tptelodt,teadn,d aindcl uindcelsudcheas lcohpalycroitpey(rciptey )(,cpkëys)t, ekrëitsete(kriëtes) ,(kroëqs)u, ersoitqeu(ersqiste), sp(hrqasle),r istpeh(sal)erainted (stla) nanidte s(tsatnnn).itTe h(setnco).m Tphoes citoimonpaolsvitairoinaatilo vnaorifastaioknu roafi istaek(usraaki)itaen (dsapke) tarundki tpee(tpruekt)ities als(poesth) oisw anls(ob oshldo,wrend (lbionled)., rTehde lcinhe)m. Tichael cohmempoicsailt icoonmopf ospsihtiaolner oitfe sapnhdalsetrainten iatnedg rsatai nsnfirteo mgrathinesH fruoamri Huthaer iHdueaproi sHituiasrsih doewpnosfiot risc sohmopwanr ifsoorn c[o3m9]p. arison [39]. Minerals 2019, 9, 604 25 of 42 Table 1. Summary of element concentrations in sphalerite from the Ánimas–Chocaya–Siete Suyos district (electron probe microanalysis data). Mine Vein Wt.% S Zn Fe Cu Sn Cd Ag In Ge d.l. 0.01 0.03 0.02 0.02 0.04 0.08 0.06 0.03 0.02 MIN 31.70 42.80 0.02 b.d.l. b.d.l. b.d.l. b.d.l. b.d.l. b.d.l. Entire district (n 425) MAX 34.39 67.50 15.99 5.81 4.90 2.82 3.09 9.66 0.07 = Av. 33.04 58.76 5.49 0.56 0.25 0.46 0.04 0.50 0.00 MIN 32.01 47.55 4.30 b.d.l. b.d.l. b.d.l. b.d.l. b.d.l. b.d.l. All samples (n 56) MAX 34.34 61.51 15.81 4.85 4.21 1.04 0.83 2.37 0.04 = Av. 33.20 56.08 8.35 0.62 0.40 0.54 0.05 0.21 0.00 MIN 33.29 49.88 9.40 b.d.l. b.d.l. 0.68 b.d.l. b.d.l. b.d.l. Surface (n 2) MAX 33.61 56.89 13.68 0.10 b.d.l. 0.81 b.d.l. 0.05 b.d.l. = Av. 33.45 53.39 11.54 0.05 - 0.74 - 0.02 - MIN 32.01 47.55 4.30 b.d.l. b.d.l. b.d.l. b.d.l. b.d.l. b.d.l. Ánimas vein MAX 34.34 60.36 15.81 4.85 4.21 1.04 0.83 2.37 0.04 (n = 51) Av. 33.22 55.89 8.43 0.67 0.43 0.54 0.05 0.23 0.00 Ánimas mine Ánimas vein, MIN 32.39 47.55 4.30 b.d.l. b.d.l. b.d.l. b.d.l. b.d.l. b.d.l. level 125 MAX 34.34 60.36 15.81 1.87 0.89 1.04 0.19 2.37 0.04 (n = 42) Av. 33.28 56.33 8.70 0.25 0.11 0.53 0.02 0.20 0.00 Ánimas vein, MIN 32.01 48.15 4.84 0.54 0.24 0.43 b.d.l. 0.16 b.d.l. level 175 MAX 33.47 59.11 9.77 4.85 4.21 0.76 0.83 0.94 b.d.l. (n = 7) Av. 32.87 52.07 7.80 3.12 2.36 0.59 0.25 0.45 - Ánimas vein, MIN 33.09 59.79 4.78 0.79 0.26 0.37 b.d.l. 0.11 b.d.l. level 200 MAX 33.13 60.17 4.79 1.00 0.45 0.60 b.d.l. 0.12 b.d.l. (n = 2) Av. 33.11 59.98 4.79 0.90 0.35 0.48 - 0.11 - Rosario vein, MIN 32.46 60.95 4.69 0.02 0.04 0.30 b.d.l. b.d.l. b.d.l. level 200 MAX 32.74 61.51 5.11 0.10 0.06 0.44 b.d.l. 0.07 b.d.l. (n = 3) Av. 32.63 61.14 4.91 0.06 0.05 0.37 - 0.04 - MIN 31.78 46.34 0.02 b.d.l. b.d.l. b.d.l. b.d.l. b.d.l. b.d.l. All samples (n 149) MAX 34.39 67.50 15.99 2.44 1.87 2.82 0.79 1.82 0.03 = Av. 32.92 61.60 3.02 0.12 0.05 0.48 0.03 0.11 0.00 Chocaya MIN 31.78 53.45 0.02 b.d.l. b.d.l. b.d.l. b.d.l. b.d.l. b.d.l. Surface mine (n 106) MAX 34.39 67.50 12.20 2.44 1.87 2.82 0.79 1.82 0.03 = Av. 32.78 63.31 2.18 0.15 0.06 0.67 0.03 0.14 0.00 Nueva vein, MIN 32.70 46.34 1.03 b.d.l. b.d.l. n.a. b.d.l. b.d.l. n.a. 125 level MAX 33.76 62.05 15.99 0.21 0.27 n.a. 0.28 0.13 n.a. (n = 43) Av. 33.24 57.40 5.08 0.02 0.02 - 0.03 0.03 - MIN 31.70 42.80 1.68 b.d.l. b.d.l. b.d.l. b.d.l. b.d.l. b.d.l. All samples (n 220) MAX 34.32 63.79 11.52 5.81 4.90 1.41 3.09 9.66 0.07 = Av. 33.08 57.51 6.44 0.85 0.34 0.44 0.04 0.83 0.00 MIN 32.04 50.77 4.13 0.19 0.13 0.35 b.d.l. b.d.l. b.d.l. Surface (n 13) MAX 33.31 60.39 8.45 2.84 2.72 1.26 0.26 2.94 0.07 = Av. 32.75 57.22 5.97 1.10 0.66 0.68 0.08 0.67 0.01 MIN 32.34 53.21 2.97 b.d.l. b.d.l. b.d.l. b.d.l. b.d.l. b.d.l. Siete Arturo vein (n 59) MAX 33.91 63.08 10.78 1.96 1.70 0.92 3.09 1.41 b.d.l. Suyos = Av. 33.25 58.38 6.89 0.27 0.15 0.58 0.08 0.13 - mine Arturo vein, MIN 32.46 53.21 4.92 0.18 b.d.l. 0.48 b.d.l. b.d.l. b.d.l. 19 level MAX 33.64 60.62 8.48 0.70 0.62 0.73 3.09 0.33 b.d.l. (n = 16) Av. 33.04 57.96 7.16 0.40 0.28 0.62 0.21 0.05 - Arturo vein, MIN 32.34 54.16 3.07 b.d.l. b.d.l. 0.31 b.d.l. b.d.l. b.d.l. 20 level MAX 33.91 62.58 10.25 0.38 0.25 0.91 0.26 0.23 b.d.l. (n = 16) Av. 33.28 58.53 6.75 0.15 0.09 0.58 0.02 0.08 - Arturo vein, MIN 32.57 54.03 2.97 b.d.l. b.d.l. b.d.l. b.d.l. b.d.l. b.d.l. 21 level MAX 33.80 63.08 10.78 1.96 1.70 0.92 0.43 1.41 b.d.l. (n = 27) Av. 33.35 58.55 6.80 0.27 0.12 0.55 0.03 0.22 - Minerals 2019, 9, 604 26 of 42 Table 1. Cont. Mine Vein Wt.% S Zn Fe Cu Sn Cd Ag In Ge MIN 32.29 52.59 1.68 0.22 0.00 0.43 0.00 0.00 0.00 Chorro vein (n 18) MAX 33.01 63.47 8.95 1.63 1.27 1.26 0.34 2.47 0.00 = Av. 32.69 59.91 4.10 0.78 0.33 0.76 0.06 0.72 0.00 Chorro vein, MIN 32.31 56.78 1.92 0.22 0.05 0.43 0.00 0.00 0.00 14 level MAX 33.01 63.47 6.94 1.45 1.27 1.26 0.12 0.97 0.00 (n = 9) Av. 32.69 61.29 3.44 0.56 0.30 0.68 0.02 0.35 0.00 Siete Suyos Chorro vein, MIN 32.29 52.59 1.68 0.28 0.00 0.57 0.00 0.00 0.00 mine 16 level MAX 32.97 62.65 8.95 1.63 0.98 1.26 0.34 2.47 0.00 (n = 9) Av. 32.69 58.53 4.75 0.99 0.36 0.84 0.10 1.10 0.00 Diez vein, MIN 31.70 45.07 4.40 0.00 0.00 0.25 0.00 0.00 0.00 15 level MAX 33.57 61.39 11.00 5.81 4.90 1.41 0.25 8.62 0.00 (n = 46) Av. 32.79 55.71 7.15 1.19 0.59 0.85 0.04 0.91 0.00 Unknown MIN 31.70 42.80 1.72 0.00 0.00 0.00 0.00 0.00 0.00 vein MAX 34.32 63.79 11.52 5.53 2.20 0.00 0.26 9.66 0.00 (n = 84) Av. 33.24 57.41 6.31 1.06 0.29 0.00 0.01 1.32 0.00 d.l.: detection limit. b.d.l.: below detection limit. n.a.: not analyzed. MIN: minimum value. MAX: maximum value. Av.: average value. Stannite-group minerals were analyzed in samples from the Ánimas, Chocaya and Siete Suyos mines, and a summary of their compositions is shown in Table 2. Only one stannite crystal from the Chocaya mine, in which this mineral occurs in trace amounts, was analyzed. The concentrations of Cu and Sn are relatively homogeneous and adjust to 2 and 1 a.p.f.u., respectively (Figure 16). In contrast, their Fe and Zn contents are variable, with Zn concentrations as high as 3.89 wt.% and Zn/(Fe + Zn) atomic proportions that range between 63.0 and 74.1. Atomic proportions of Fe and Zn yield a negative correlation, and most of the analyses arrange along the Fe + Zn = 1 line in the Zn vs. Fe (a.p.f.u.) diagram (Figure 16), thus pointing to a direct substitution between them (Fe↔ Zn) that is probably framed in the stannite–kësterite solid solution series [78]. Stannite group minerals are up to 3.12 wt.% Ag (average = 0.40 wt.%), 2.16 wt.% Sb and 0.14 wt.% Ge, even though most of the values for Sb and Ge are normally below their respective detection limits. None of these elements yield clear correlations with other cations. Indium, which is up to 4.11 wt.% in stannite, yields no correlation with Fe or Zn, but it shows fair negative correlations with both Cu (at Cu + In = 2 a.p.f.u.) and Sn (at Sn + In = 1 a.p.f.u.; Figure 16). This suggests that the incorporation of In within the structure of stannite group minerals in this study is framed in the stannite-roquesite solid solution (Figure 15). The concentration of In in stannite does not show clear distribution trends, not even at different depths within single veins (Figure 17). The chemical composition of cassiterite was analyzed in the samples from the Siete Suyos and Ánimas mines. FeO contents in cassiterite range between the 0.01 and 3.76 wt.% (average = 0.86 wt.%), SiO2 contents range between below its detection limit and 0.18 wt.% (average = 0.10 wt.%), and MnO contents fall systematically below its detection limit. Ta2O5 and Nb2O5 contents mostly fall below their respective detection limits, except for peak values as high as 0.28 wt.% Ta2O5 and 0.13 wt.% Nb2O5. Indium concentrations are mostly above its detection limit and they are up to 0.25 wt.% In2O3 (average = 0.12 wt.% In2O3). Minerals 2019, 9, 604 27 of 42 Table 2. Summary of element concentrations in stannite from the Ánimas–Chocaya–Siete Suyos district (electron probe microanalysis data). Mine Vein Wt.% S Cu Sn Fe Zn Sb Ag In Ge d.l. 0.01 0.02 0.04 0.02 0.03 0.04 0.06 0.03 0.02 MIN 27.22 26.96 22.64 9.25 b.d.l. b.d.l. b.d.l. b.d.l. b.d.l. Entire district (n 157) MAX 30.15 30.07 28.39 13.91 3.89 2.16 3.12 4.11 0.14 = Av. 29.19 28.61 26.93 11.13 2.13 0.10 0.40 0.59 0.00 MIN 27.22 26.96 22.64 9.25 b.d.l. b.d.l. b.d.l. b.d.l. b.d.l. All samples (n 135) MAX 30.15 30.07 28.26 13.05 3.89 2.16 3.12 4.11 0.14 = Av. 29.16 28.63 26.87 11.14 2.11 0.10 0.38 0.64 0.00 MIN 28.75 28.35 26.60 12.69 0.47 b.d.l. 0.15 b.d.l. b.d.l. Surface (n = 5) MAX 29.62 28.96 27.72 13.05 1.74 b.d.l. 0.33 0.21 b.d.l. Av. 29.27 28.68 27.06 12.86 1.19 - 0.23 0.10 - MIN 27.22 27.34 25.16 9.25 b.d.l. b.d.l. b.d.l. b.d.l. b.d.l. Ánimas vein MAX 30.15 30.07 28.26 12.75 3.05 0.57 1.02 2.31 0.14 (n = 65) Av. 29.17 28.65 27.01 11.42 1.60 0.02 0.25 0.61 0.01 Ánimas vein, MIN 28.58 27.59 25.16 9.25 b.d.l. b.d.l. b.d.l. 0.15 b.d.l. 100 level MAX 29.82 30.07 27.78 12.75 2.99 0.57 1.02 2.31 0.14 (n = 24) Av. 29.33 28.77 26.85 11.08 1.60 0.05 0.23 0.75 0.02 Ánimas vein, Value 29.28 28.19 26.70 11.39 2.45 b.d.l. 0.51 0.71 b.d.l. 125 level (n = 1) Ánimas Ánimas vein, MIN 29.51 28.53 26.91 10.79 1.47 b.d.l. b.d.l. b.d.l. b.d.l. mine 175 level MAX 29.87 29.14 28.26 12.39 2.72 0.16 0.44 0.30 b.d.l. (n = 8) Av. 29.65 28.83 27.72 11.49 1.93 0.03 0.23 0.12 - Ánimas vein, MIN 27.22 27.34 25.33 10.16 b.d.l. b.d.l. b.d.l. 0.06 b.d.l. 200 level MAX 30.15 29.91 28.14 12.59 3.05 0.05 0.56 1.64 b.d.l. (n = 32) Av. 28.92 28.52 26.97 11.66 1.49 0.00 0.27 0.62 - Burton vein, MIN 28.57 27.35 22.64 9.90 1.62 b.d.l. b.d.l. 0.18 b.d.l. 232 level MAX 29.55 29.28 27.66 11.96 3.89 2.16 3.12 4.11 b.d.l. (n = 21) Av. 29.09 28.60 26.60 10.98 2.24 0.25 0.56 0.83 - MIN 28.50 27.51 24.79 9.42 1.67 b.d.l. b.d.l. 0.15 b.d.l. Colorada vein, (n = 33) MAX 30.00 29.35 27.96 12.84 3.88 1.54 2.74 1.81 0.04 Av. 29.21 28.67 26.68 10.25 3.24 0.21 0.52 0.74 - Colorada vein, MIN 28.50 27.51 24.87 9.42 2.79 b.d.l. 0.16 0.36 n.a. 264 level, MAX 29.07 29.35 27.31 10.76 3.56 1.54 2.74 1.81 n.a. (n = 16) Av. 28.89 28.30 26.13 10.15 3.16 0.25 0.75 1.08 - Colorada vein, MIN 28.50 28.44 24.79 9.63 1.67 b.d.l. b.d.l. 0.15 b.d.l. 302 level, MAX 30.00 29.27 27.96 12.84 3.88 0.96 0.76 1.70 0.04 (n = 17) Av. 29.51 29.03 27.19 10.35 3.31 0.17 0.30 0.42 0.00 Rosario vein, MIN 28.79 26.96 25.18 10.65 1.19 b.d.l. 0.31 0.07 b.d.l. 200 level, MAX 29.32 29.13 27.97 12.82 2.62 b.d.l. 0.85 2.10 b.d.l. (n = 11) Av. 29.12 28.51 27.07 11.61 1.91 - 0.49 0.48 - Value 29.70 28.91 27.02 10.32 3.21 0.14 0.67 0.29 b.d.l. Chocaya Surface mine (n = 1) MIN 28.27 26.99 25.41 10.03 b.d.l. b.d.l. b.d.l. b.d.l. b.d.l. All samples (n 21) MAX 29.83 29.05 28.39 13.91 3.73 1.27 2.87 1.73 b.d.l. = Av. 29.36 28.41 27.30 11.16 2.20 0.11 0.53 0.27 b.d.l. Siete MIN 28.67 27.44 25.64 10.03 1.25 b.d.l. b.d.l. b.d.l. 0.00 Suyos Surface (n 19) MAX 29.83 29.05 28.39 11.88 3.73 1.27 2.87 0.73 0.00 mine = Av. 29.41 28.54 27.46 10.97 2.28 0.12 0.53 0.21 0.00 Diez vein, Value 29.48 27.47 26.04 12.00 2.80 b.d.l. 0.44 1.73 b.d.l. level 15 (n = 1) d.l.: detection limit. b.d.l.: below detection limit. n.a.: not analyzed. MIN: minimum value. MAX: maximum value. Av.: average value. Minerals 2019, 9, 604 28 of 42 Minerals 2019, 9, x FOR PEER REVIEW 29 of 42 FFiigguurree 1166.. CCoorrrreellaattiioonn bbeettwweeeenn eelleemmeennttss iinn ssttaannnniittee ffrroomm tthhee ÁÁnniimmaass––CChhooccaayyaa––SSiieettee SSuuyyooss ddiissttrriicctt.. TThhee cchheemmiiccaallc coommppoossitiitoionno of fs tsatnanninteiteg rgarinaisnfsr ofmromth ethHeu HaruiaHriu Harui adreip doespitoissist hios wshnofwornc foomr pcoarmispoanr[is3o9n]. [39]. Minerals 2019, 9, 604 29 of 42 Minerals 2019, 9, x FOR PEER REVIEW 30 of 42 FiFgiugruere1 71.7.B Booxxp plolottc coomppaarriison of In contenttss ((wtt.%. )) inin sstatannnitiet efrformom thteh edidffieffreernetn mt miniense, sv,evinesin asnadn d mminiinninggl elveveelslss tsutuddieieddi inn tthhee Ánniimas–Chocaya––SSiieettee SSuuyyoos sddisitsrtircitc.t T. hTeh ececnetnratrl ablobxo ixs iisn itnheth me imddidled le 505%0%o fotfh theed daatata. .T Thhee lliinnee iin the box representts tthee meeddiaiann vvaaluluee fofor reaecahch bobxo.x T. hTeh oeuotulietlrise rasrea rfeurftuhretrh er thtahnan1 .15.×5×(7(755ththp peerrcceennttiillee//ttoopp ooff bbooxx--2255tthh ppeerrcceennttiillee//bboottttoomm oof fbbooxx) )anandd thteh ewwhihskisekres rasrae rteheth eexetrxetmreem e vavlauleusest hthatata areren nootto ouutltileierrss.. Vallueess beellow tthee deetteeccttioionn lilmimiti t(i(.ie..e, .0, .00.30 3wwt.%t.%) h)ahvaev beebeene rneprelapcleadce bdy by 0.00.10515w wt.t%.%t otoa alllolowwf oforrl ologgaarriitthhmiicc ssccaallee aaxxiiss plloottttiinngg.. 5.52..2O. OththererM Minineerraalsls OOththererm minineerraalsls wwhhoossee miineral chemisttrry waass aannaalylyzzeedd aarere aarsresnenopoypryitreit, ew, wolofrlafmraimtei,t eg,algeanlae,n a, tettertarhahededrirtiete-g-grroouupp mmiinneerralls,, and a variety of other sullffossaallttss iinn mininoorr aammoouunntst,s ,(i(.ei..e .semsesmeysietye,i te, bobuolualnagnegreirteit,ej,a mjaemsoensoitnei,tefr, anfrcakneciktee,itme,i amrgiyarigtey,rpitye,r aprgyyrarirtgey, rainted, orainted,oarriatem, aayroaimtea,ydoiaitpeh, odriatep,hfiozréitley,i te, stfairzoéčlyeistkeé, itset,atreorčreyswkéailtlea, ceteitrer,yowsaclalrakceimtep, ffiostec,aarknedmrpafmfidteo, harnitde) .rIanmadlloohfritthe)e.m I,nt haelilr coof ntcheenmtr,a ttihoenisr in crcitoincacel nmtreattailosnIsn ina ncrditGicealw meertealssy Isnt eamnda tGicea wllyerbee slyoswtetmhaetiircraellsyp beectloivwe tdheetierc rteisopnelcitmiviet sd.etection limits. AArsresnenooppyyrritietew waass aannaallyyzzeedd iinn tthhee vveeiinn ssaampplleess ffrroomm ÁÁnnimimasa sanandd BBurutrotno nvevineisn isni nthteh ÁenÁimniams as mminien.e.A Annaalylyzzeeddg grraaiinnss ffrroom bbootthh vveeiinnss yyiieelldd oovveerrllaappppiningg AAs sccoonntetnentst sthtahta rtarnagneg beebtweteweene 2n92.89 .a8nadn d 313.15.5a ta.%t.%, a, nanddS Sc oconntetennttsst thhaatt rraannggee bbeettwweeeenn 3355..55 aanndd 3355..66 aatt.%.%. .SSbb coconntetnetnst srarnagneg beebtweteweene 0n.704.7 a4nadn d 0.08.989a ta.%t.%, a, nanddN Ni ia annddC Cooc coonntteennttss aarree uupp ttoo 00..0033 aanndd 00..0066 aatt..%%, ,rreessppeecctitviveelyly. . WWolofrlfarmamiteitew awsaasn aalnyazleydzeidn sianm spamlespfleros mfrtohme Áthnei mÁansimmianse .mTinhee. aTnhaley zaendalgyrzaeidn sginracilnusd einfcelrubdeeri te (FfeeOrbbeerittwe e(FeenO1 9b.e3t1waenedn 2129..1321 awntd.% 22a.n12d wMtn.%O abnedt wMeneOn 0b.e5t0waenedn 30..2504 awntd.% 3).2a4n wdtl.e%ss) aanbdu nledsas natbhuünbdnanerti te (FheüObbneetrwitee e(Fne0O.0 b3eatwndee7n. 707.0w3 ta.n%da 7n.7d7 Mwnt.O% banetdw MeennO1 b6e.0tw4 aenend 1262..0943 awndt. %22)..93 wt.%). Galena was analyzed in the samples from the Ánimas vein in the Ánimas mine, from the Chorro Galena was analyzed in the samples from the Ánimas vein in the Ánimas mine, from the Chorro vein and the surface in the Siete Suyos mine, and from the Nueva vein and the surface at the Chocaya vemininaen. dAtnhaelyszuerdfa gcaeliennath geraSiineste ySieulydo esxmtreinmee, layn vdafrrioabmlet hPeb Ncounetvenatvs,e winhainchd rtahnegseu brfeatwceeaetnt 7h5e.4C7h aoncda ya m8in7.e3.9A wnta.%ly. zTehde gPabl ecnoantgernatisn asrye iienlvdeersxetrlye mcoerlryelvaaterdia bwliethP bthcoosne toefn Stsb, (w0.h07ic tho r8a.n70g ewbt.e%tw), eSenn (b7.5d.4.l7. taon d 870..3691)w, Zt.n% (.bT.dh.el. Ptob 4c.o4n6 twent.t%s )a,r aenidn vBeir (sbe.ldy.lc. otorr 6e.l1a7te wdtw.%i)t.h Tthheo sAego cfoSnbte(n0.t0s7 atroe a8l.s7o0 vwatr.i%ab),leS,n bu(bt .dar.le., to 0.i6n1 )g,eZnner(abl.,d h.ilg. htoer4 i.4n6 thwet Á.%n)i,manasd mBiin(eb .(du.pl. ttoo 36..0127 wwtt.%.%)) t.hTahne inA tghceo Snieteten tSsuayroesa (luspo tvoa r0i.a6b9 lwe,tb.%ut) aanred, in geCnheorcaal,yha i(guhpe rtoi n0.t1h1e wÁtn.%im) masinmesin. Teh(ue pGteo c3o.n0t2enwtst .%in) gtahlaennai narteh eupS iteot e0.S1u7y wots.%(u ipn ttohe0 .S6i9etwe tS.%uy)oasn d Cmhoincaey, aup(u tpo 0to.105. 1w1t.w%t .i%n )thme iCnheso.caTyhae mGienec,o anntedn utsp itno g0a.1le7n wata.%re iunp thteo Á0.n1i7mwast .%miinne,t haendS iaevteerSaugye os m0in.1e1, wupt.%to a0t. 1a5 dwistt.r%icti nsctahlee. Chocaya mine, and up to 0.17 wt.% in the Ánimas mine, and average 0.11 wt.% aTteatrdaihsetrdircittes cgarloe.up minerals were analyzed in the samples from the Ánimas and Siete Suyos minTeest.r aThheedyr ibteelgornogu ptom tihnee rtaeltsrawheerderaitnea laynzde dfrienibtheergsiatem sppleesciferso m(FtighuerÁe n1i8m).a sAarnsednSicie tceoSnuteynotss marine es. Thsyeystebmelaotnicgatlloyt vhertye tlroawh,e mdroitsetlyan bdelforweib ietsr gdietetescptieocnie lsim(Fiti gaunrde u1p8) .toA 0r.s7e0n wict.c%on, twenhticsha ressuylsttse imn avteicryal ly velorywl oAws/,(Amso +st lSyb)b realotiwos ibtsetdweetenct i0o nanldim 0i.t04a n(adtoumpicto p0ro.7p0owrtito.%ns,).w Shilivcehr riess uplt stoin 32v.e3r wy tl.o%w, aAnsd/ (iAtss + Sbc)onracteinotsrabteiotwn eise nva0riaanbdle0 i.n0 4an(atloymzeidc gpraoipnos rftriomns b).oSthil vmeirniess;u hpotwoe3v2e.r3, wtet.r%ah,eadnrditeit-sgrcounpc emntinraetriaolns is vainri athbele Siinetaen Saulyozse dmginraei anrsef, rionm gebnoetrhalm, riinchese;rh ino wsielverr ,(atevterraahgeed =r i2te5-.g41ro wutp.%m Ainge)r tahlsanin inth teheS iÁetneimSuays os mminienea r(ea,vienraggeen e=r 1a8l,.6r9ic hwetr.%in Asgil;v Feirg(uarvee r1a8g).e T=he2 5A.4g1/(wAgt. %+ CAug)) rthataion irnantghesÁ bneitmweaesnm 0i.n21e (aanvde r0a.5g6e = 18(.a6t9omwitc.% prAopgo; Frtiigounrse) a1n8)d., TahcceoArdgi/n(Aglgy,+ coCrure)srpaotniodr taon fgreesibbeertgwiteee (nA0g./2(A1 ga n+d C0u.5) 6> (0a.t5o)m anicdp arrogpeonrttiaionn s) antedt,raachceodrrditien g(Flyig, ucorerrse 1s8p oanndd 1to9)f.r Zeiibnecr agnitde F(Ae gsh/(oAwg v+aCriaub)l>e c0o.5n)caenndtraatrigoenns tiina nbotethtr aohf ethder imtei(nFeisg. uIrroesn 18 contents (4.02 to 5.81 wt.%) are systematically higher than Zn contents (below its detection limit to Minerals 2019, 9, 604 30 of 41 2.4M7in ewratls. %20)1,9 ,a 9n, xd F OthRe P EZEnR /R(ZEVnI E+W F e) ratio ranges between 0.00 and 0.34 (atomic proportio3n1s o).f 4T2h e concentrations of In, Ge, and Ga are systematically below their detection limits. 2.47S ewmt.s%ey),i taen, db otuhlea nZgne/r(iZten, a+n Fde )ja rmateisoo nraitneg ewse bre tawneaelny z0e.d00 i na nthde 0S.3ie4t e( aStuomyoics apnrodp Áorntiomnass). mTihnee s. Secmonsceeyni tera itsi ounps toof I0n.1, 4G we, ta.%nd A Gga (arvee sryasgte m= a0t.i0c6a lwlyt b.%el oAwg ;t hne =ir 1d1e)t eacntdio nu pli mtoi t0s..1 3 wt.% Ge (average = Minerals 2019, 9, 604 30 of 42 0.04 wSt.e%m Gseey;i tne ,= b 6o)u. lBaonugelarnitge,e arinted ijsa mupes toon i8t.e3 1w werte. %an Aalgy z(aedv eirna gthee = S 4ie.3te0 Swuty.%os Aangd; nÁ =n i2m6)a sa nmdi nueps. to 0.1S1em wste.%yit Ge ies (uapv etora 0g.e1 4= w0.t0.%3 wAtg. %(a vGeer)a.g He o=w 0.e0v6e wr, ts.%uc Ah gh; ing h= A11g) caonndt uenpt sto a 0s. 1o3f wsotm.%e Goef t(have earnagaley =s es caan0n.d0 b41e 9w s).pt.Z%uir niGoceua;s nn d =uF 6e )ts.o hB omowuixlvaenadrg iearnbiatleely cissoe nuscp oe nft otf ri8na.te3il1oy nw isnti.tn%erb gAortgoh w(oanfv tePhrbeag maen i=nd e 4Ss.3b. 0 Isr uwonltf.oc%so anAltgesn; (tnsse =(e4 2F.06i2)g uatonred5s. 8 u31p–w 5t,ot .7 %–) 1a0r0)e..1 Js1ay mwstte.s%mo naGtiitece a( ialslv yuerphai gtgoeh 0e=.r 20t8.h0 w3a ntw.%Zt.n% Ac gGo,ne e)tv.e Henntos wt(hbeoevuleogrwh, s muitcsohsd the oitgef hctth iAeog na nclioamnlytiestnetsots y 2ai.es4 l7odfw csoto.n%mc)ee, noatfnr atdhtietoh naensZ atlhnya/s(teZ san re+ bFecela)onrw ab tteiho sepr adunergitoeeucstsib odenutw eli emtoei ntm f0io.x0re0 dtha ainsnd aell0ye.ms3e4es( noatft, o faimnnedicl yup pirno ttpeoor 0gr.rt1ioo1wn wns) t.P.%bT haGenedc (o Sanbvc eesrunaltgfroeas t=aio l0tns.0s (4so ewfeI tnF.%i,gG uGer,eesa; n3d –=5 G,2 71a–)a. re sy1s0t)e. mJamatiecsaolnlyiteb eislo uwp ttoh e0i.r28d ewtet.c%ti oAngl, iemvietns. though most of the analyses yield concentrations that are below the detection limit for this element, and up to 0.11 wt.% Ge (average = 0.04 wt.% Ge; n = 21). FFiigguurree 1188. .CCoorrrreelalatitoionn bbeetwtweeenn eelelemmeenntsts inin tetetrtarahheeddrirtiete-g-grorouupp mminineerraalsls (t(etetrtarahheeddrirtiete aanndd frfereibibeergrgitiete) ) frFoimgutrhee 1Á8. nCimoraresl–aCtihoonc baeytaw–eSeient eelSeumyeonstsd iinst treictrta. hedrite-group minerals (tetrahedrite and freibergite) fro the Á ni as–Chocaya–Siete Suyos district. TThhee ddiviveerrggeennccee ooff ssoomee ccoomppoossiittiioonnss ttoo vvaalluueess ooff CCuu +fArogm> th1e Ánimas–Chocaya–Siete Suyos district. The divergence of some compositions to values of Cu + g > 100 aa.p.p.f.f.u.u. .inin ththee AAgg vvss. .CCuu ddiaiaggraramm aanndd oof fFFee ++ ZZnn >> 22 inin ththee ZZnn vvss. .FFee ddiaiaggrraamm isis mmaaininlyly a+tt rAibgu >ta 1b0le at.op.cf.aut.i oinn nthe Ag vs. Cu diagram attributable to cation noorrmaalliizzaattiioonn ttoo SS == 1133 aan.pd. fo.uf .F, ew +h iZchn r>e s2u ilnts tihne aZnno vvse.r eFset idmiagram is a.p.f.u., which results in an overestimaattioionn ooff tt m hheaainly e attoommicic attributable to cation normalization to S = 13 a.p.f.u., which results in an overestimation of the atomic pprproorpopopororttriiotoinon noo fof ftt hthhee eoo otththheeerrr e eelleleemmeeennntttsss iiinn AAgg---rrriiiccchh ttteeetttrrraahheeeddrrriititete aanndd f frfrereibiiberegrgitiet ed dueu et ot oth teh Se S↔ ↔ ex ecxhcahnagneg. e. Minerals 2019, 9, 604 31 of 42 Minerals 2019, 9, x FOR PEER REVIEW 32 of 42 FFiigguurree 1199.. PPlolott ooff tthhee aannaallyyzzeedd tteettrraahheeddrriittee--ggrroouupp mmiinneerraallss aanndd AAgg––CCuu––SSbb ssuullffoossaallttss ffrroomm tthhee ÁÁnniimmaass––CChhooccaayyaa––SSiieettee SSuuyyooss ddiissttrriicctt iinn tthhee AAgg2SS vvss.. CCuu22SS vvss. .SSbb2S23S 3+ +AsA2Ss32 Ste3rtnearrnya rdyiadgiraagmra.m . 6. DiSsceumssseioynit e, boulangerite, and jamesonite were analyzed in the Siete Suyos and Ánimas mines. Semseyite is up to 0.14 wt.% Ag (average = 0.06 wt.% Ag; n = 11) and up to 0.13 wt.% Ge (average = 60..10.4 Pwarta.%genGeeti;cn S=eq6u)e.nBceosu alnadn gEevroiltuetiisonu pof ttohe8 M.31inwerta.%liziAngg F(aluviedrsa ge = 4.30 wt.% Ag; n = 26) and up to 0.11 wt.% Ge (average = 0.03 wt.% Ge). However, such high Ag contents as of some of the analyses can bTehsep murinioeurasl dseuqeuteonmceisx feodr aeancahly ssteusdoiefdfi vneeilny iinn tthereg Srioewten SPuyboasn, dÁnSibmsausl,f aonsadl tCsh(oseceayFai gmuirneess3 a–r5e, dFiigaugrreasm7m–1a0t)ic. aJallmy esshoonwiten isinu pFtiogu0r.2e8s w20t.–%22A. gT, hevee ndethscoruibgehdm toesxttuofreths einandaiclyastee say igelednceoranlcieznedtr aetiaornlys cthryasttaarlelizbaetlioown othf ecadsesitteecrtiitoen alnidm aitrsfoenr othpiysreitlee,m aelonnt,ga wndithu vpatroia0b.1le1 pwrot.p%orGtieon(asv oefr aqguear=tz0, .w04hwicht. %is tGhee; mn =ain2 1a)n. d almost unique gangue mineral in all of the studied veins. Cassiterite is more abundant in the Ánimas mine than in the rest of the district, particularly in the Ánimas and Colorada veins, is o6.nDlyi fsocunssdi oans a minor mineral in the Siete Suyos mine and it is apparently absent in the Nueva vein from the Chocaya mine. Cassiterite is often replaced by sulfides, such as sphalerite and stannite, and s6u.1l.foPsaarlatsg.e nSuetcich Sreeqpuleancceems eanndt iEs vpoolustsiiobnlyo fththee mMaiinne rraelaizsionng fFolru itdhse variable concentrations of cassiterite in thTe hÁe nmiminaesr aalnsdeq uSieentec esSufoyrose amchinsetsu.d Tiehdisv eisi nililnustthreatSeide,t efoSru yinosst,aÁnnceim, bays, athned uCnhuoscuaayla hmiginheesr aabreunddiaagnrcaem omf caatsicsaitlelyritseh ionw snhailnloFwig luevreesls2 i0n– t2h2e. ÁThneimdaess cvreiibne,d wtheexrteuarse sstianndnicitaet eisa fagre mneorrael iazbeudnedaarnlyt tchryanst aclalsizsaitteiorinteo ifnc tahses idteereitpeear nledvaerlss e(nFoigpuyrreit 6e),.a long with variable proportions of quartz, which is the mainPaynridtea dlmisopslat yusn aiq vuaerigeatny goufe temxtinueraral lfeinatualrleos fththaet rsetuqduiiered svpeeicnisa.l Catatessnittieornit.e Tihsem mooresta cboumndmaonnt tinextthueraÁl tnyipmea osfm pyinrietet hina nthien Áthneimreasst, Cofhtohceaydais, tarnicdt ,Spieatret iScuuylaorsl yveiinnsth ceorÁrensipmoansdasn tod aCnohleodraradla shvaepiness, aisnodn lsyecfoonudndarays paomroinsiotry mthinaet rsahl oinwtsh ea SrieecteurSrueynot somrbiniceualanrd tiot ips saepupdaore-hnetlxyagabosneanl tdinistthriebuNtuioenv—a vaenidn ifnrofimllinthges Cohf ohcayypaogmeinnee .(Cquasasrittze,r istpehisaloefrtietne, resptalnacneitde-bgyrosuuplfi dmeisn, esruaclhs aasnsdp hsaulleforistaelatsn; dFsigtaunrneist e3,Ba,nCd, 6suAl,fDos,Kal,t s7.CS,uDc,h 8rAep, 1la0cDem,Ee, n1t1iAs)p oors ssiubplyerthgeenmea mininreearsaolsn (feo.gr .t,h aenvgaerliealbliltee;c oFnigcuenretr 9aKtio).n Isno sfacmaspslietesr fitreomin tthhee ÁAnrtimuraos vaenidn Siine ttehSeu Syioestem Siuneyso.sT mhiisnies, iilnludsitvraidteuda,l fopryirnitset acnrcyes,tablys twheituhn pusseuuadl hoi-ghheexragabounnald ashnacepeosf (cparsisoitre troit ecoinrrsohsaiollno,w wlheivcehl sreinsutlhtes iÁnn einmgauslfvmeienn,tw) ahreer efraesqsutaennnt i(tFeigisufraer 3mBo,Cre). aFbauirnldya anbtutnhdanancta assriet earlistoe pinytrhitee dgereapinesr lienv emlsm(F-siigzuerde g6a).rland-like aggregates along with cassiterite, arsenopyrite and quartz grainPs ytrhiatet ddrisapwla cyirscaulvaarr tioe tpysoefutdeox-thuerxaalgfeoantaulr sehsatpheast wreiqthu iare csepnetrcaial lspatatceen tthioant .isT mheosmtloys ltincoedm wmiothn qteuxaturtrza lotry sppehoaflepryitrei t(eFiinguthreesÁ 3nGim, 9aGs,, C11hJo).c aTyhae, raencdurSrieenteceS uiny ohsevxeaignosncaolr preastpteornnds sbtyo paynrhieted raanlds hoatpheesr manidnesreaclso n(ed.ga.r,y gaploernoas iatnydt hsautlfsohsaolwtss ina Freigcuurrere 4nDt )o irnb ivceuilnasr ftroomps tehued toh-rheeex magionnesa lcadnisntoritb tuhteiroenfo—rea nbde cinofinlsliidnegrsedo fash ya pmoegreen ean(eqcudaorttez., Its psthraolnegriltye ,susgtagnenstiste a-g rreopulpacemminenert atlhsaat nisd eistuhlefro spasletsu;dFoimguorrpeh3iBc ,oCr, dFirgivuerne t6hAro,Dug,Kh, pFairgtiucruela7rC p,lDan, eFsi gouf are fo8rAm,erF imguinreera1l0 wDi,tEh, aFni gourirgein1a1lA h)exoargsounpale orgr epnseeumdion-ehreaxlasg(oen.ga.l, carnygsetalel llsihtea;pFei.g Iunr Beo9lKiv)i.aInn-tsyapmep dleespofrsoitms, tphyerrAhrottuitreo ivs etihne imn othset lSikieetley Smuiynoesraml itnhea,t ifnodrmivisd hueaxlapgyornitael ccrryyssttaallss twhiatth aprese tuod boe- hreepxlaagcoenda blys hoathpeers s(uprlfiiodretso, scionrcreo siti ohna,sw bheeicnh armespullyt sdienscernigbuedlf mtoe cnrty)satraellifzreeq euaernlyt (inFi tghuer em3inBe,Cra).liFzaaitriloyna sbeuqnudenancet ainre daiflsfeorepnytr idteepgorasiitnss (ien.gm. [m33-,s3i9z,e6d2,g6a3r,6la6n])d. -Pliykrerhaogtgitree ghaatse sinadloeendg bweietnh observed in samples from the Nueva vein in the Chocaya mine as anhedral relicts and inclusions in pyrite–marcasite–intermediate product aggregates (Figure 11B,C,K). The presence of intergrown Minerals 2019, 9, 604 32 of 42 cassiterite, arsenopyrite and quartz grains that draw circular to pseudo-hexagonal shapes with a central space that is mostly lined with quartz or sphalerite (Figure 3G, Figure 9G, Figure 11J). The recurrence in hexagonal patterns by pyrite and other minerals (e.g., galena and sulfosalts in Figure 4D) in veins from the three mines cannot therefore be considered as a mere anecdote. It strongly suggests a replacement that is either pseudomorphic or driven through particular planes of a former mineral with an original hexagonal or pseudo-hexagonal crystal shape. In Bolivian-type deposits, pyrrhotite is the most likely mineral that forms hexagonal crystals that are to be replaced by other sulfides, since it has been amply described to crystallize early in the mineralization sequence in different deposits (e.g., [33,39,62,63,66]). Pyrrhotite has indeed been observed in samples from the Nueva vein in the Chocaya mine as anhedral relicts and inclusions in pyrite–marcasite–intermediate product aggregates (Figure 11B,C,K). The presence of intergrown pyrite, marcasite and intermediate product itself, and the generation of secondary porosity are solid arguments for their formation by alteration of pyrrhotite [75,76] by an increase in the state of sulfidation—a combination of temperature and f S2 (e.g., [39]). Of particular interest for Bolivian-type deposits is the benchmark petrographic study of Kelly and Turneaure [66] that describes early hexagonal pyrrhotite, which is partly replaced by monoclinic pyrrhotine along the borders of pyrite–marcasite–siderite veinlets. The occurrence of hexagonal pyrrhotite would point to its crystallization under temperatures above 308 ◦C, which corresponds to the upper limit of formation for monoclinic pyrrhotite [75,79]. Atomic proportions of As in arsenopyrite crystals from the Ánimas and Burton veins indicate temperatures of crystallization, in equilibrium with pyrrhotite, which range between 288◦ and 389 ◦C [80], in good agreement with the crystallization temperatures constrained from the likely occurrence of hexagonal pyrrhotite. The absence of pyrrhotite in the studied veins from the Ánimas and Siete Suyos mines is interpreted, in this context, as the result of its total replacement by pyrite ±marcasite. Such a hypothesis would somehow imply that this replacement did not homogeneously occur throughout the district. Gradients in the degree of replacement of pyrrhotite by marcasite and pyrite along replacement fronts are described in detail in the “Cordilleran” polymetallic deposit of Cerro de Pasco in Peru [81]; similar to our observations and interpretation, these authors describe porous, fine-grained marcasite containing pyrrhotite relicts to mark the beginning of the replacement, which progressively grades to euhedral, nonporous pyrite that is devoid of pyrrhotite relicts. Following this scheme in the Ánimas–Chocaya–Siete Suyos district, the circulation of hydrothermal fluids leading to the replacement of pyrrhotite by pyrite and marcasite would be centered in veins in the NW zone (Siete Suyos mine: pyrite, without marcasite or pyrrhotite), and it was distal to veins in the SE zone (Chocaya mine: pyrite, marcasite, intermediate product, and relicts of pyrrhotite). A complete replacement of pyrrhotite by pyrite along the lifespan of mineralizing systems might lead to the erroneous interpretation that pyrite crystallized early in the sequence in some deposits along with cassiterite, as Ramdohr [75] warned. In general, the crystallization of most of the sphalerite and stannite-group minerals in the Ánimas–Chocaya–Siete Suyos district followed the crystallization of pyrrhotite, cassiterite, and arsenopyrite (Figures 20–22). Iron contents in sphalerite vary broadly at the district scale and within individual veins. The conspicuous enrichment in iron above ~21 mol.% FeS in some sphalerite grains from the Ánimas (up to 27.7 mol.% FeS) and Nueva (up to 28.8 mol.% FeS) veins would point to crystallization in equilibrium with pyrrhotite at temperatures above 250 ◦C [82]. In contrast, the majority of the analyzed sphalerite grains yield FeS concentrations below ~21 mol.% that are compatible with the crystallization of sphalerite along with pyrrhotite + pyrite or with pyrite alone. Accordingly, we consider that Fe-rich (>21 mol.% FeS) sphalerite grains in the Ánimas and Nueva veins were crystallized along with pyrrhotite, and sphalerite crystals with FeS < 21 mol.% in all veins crystallized in equilibrium with pyrite (Figures 20–22). Stannite-group minerals were generally deposited after sphalerite and they are dominated by stannite (±kësterite) compositions. Local famatinite was only observed in one sample from the Rosario vein in the Ánimas mine (Figure 21). Finally, an “invasion” of galena and a wealth of Ag-Pb-Sn sulfosalts, which are characteristic of Bolivian-type deposits in Minerals 2019, 9, 604 33 of 42 general, and of the Ánimas and Chocaya mines in particular [83], occurs late in the sequence in all of thMe isnteuradlsi 2e0d19v, e9,i nx sFO(FRi PgEuErRe sRE2V0I–E2W2 ) . 34 of 42 FiFgiugruer2e0 2.0P. Paraargageneneteitcics eseqquueenncceessd deedduucceedd ffoorr tthhee hhyyppooggeennee miinneerraalliizzaattiioonn iinn tthhee AArrtuturroo, ,CChhoorrroro aanndd DiDezievz evienisnisn inth teheS iSeiteeteS uSuyyoossm mininee. .T Thhee wiiddtthh ooff tthhee bbaarrss aapppprrooxxiimaatteess tthhee rreellaattiivvee aabbuunnddaannccee oof fththe e lisltiesdtedm minienrearlsa.lsL. oLcoactaiotinono fotfh tehme minienrearlapl hpahsaesseos rogr egneenreartaiotinosnys iyeiledlidnigngh ihgihglhiglihgthetdedc ocnocnecnetnrtartaiotinosnso foIfn anIdn thanedm athxeim mumaxicmonucmen tcroanticoennstrfaotriotnhsis fmore tathl iasr eminedtailc aatreed iinndreicdatceodlo rin. Trheedt icmoilnogr. oTfhcery stitmalliinzga tioofn shcorwysntailnlizthateiopna rsahgoewnne tiinc tsheeq upeanracgeeinserteilca steivqeuetoncoeb isse rrevlaattiiovne stom oabdseerovnateiaocnhs vmeaidn,e aonnd etahcehr evfeoinre, adnode s notthnereecfeosrsea driolyesi ndoitc naeteceasbssaorilluyt eintdimicainteg .absolute timing. Minerals 2019, 9, 604 34 of 42 Minerals 2019, 9, x FOR PEER REVIEW 35 of 42 FigFuigreur2e1 .21P. aPraargaegneenteitcics esqequueenncceess ddeedduucceedd ffoorr tthhee hhyyppooggeennee minineeraralilziaztaiotino nini nthteh eÁÁninmimas,a sB,uBrtuornto, n, CoCloorlaodraadaan adndR oRsoasraioriov evienisnsi nint htheeÁ Ánnimimaass mmiinnee.. TThhee wiiddtthh ooff tthhee bbaarsr saapppprorxoixmimataetse tshteh reelraetliavteiv e abuabnudnadnacnecoef othf tehlei sltiestdedm minienrearlasl.s.L Looccaattiioonn ooff tthhee mmiinneerraall pphhaasseess oorr ggeenneeraratitoinosn syiyeiledlidnign ghihghiglihglhigtehdte d conccoenncetrnattriaotniosnos foIfn Ina nadndth tehem maaxximimuumm ccoonncceennttrraattiioonnss ffoorr tthhiiss mmeetatal laarere ininddiciactaetde dini nrerde dcocloorlo. rT.hTeh e timtiimnginogf ocfr ycrsytasltlailzliaztaiotinons hsohwownni nint htheep paarraaggeenneettiicc sseeqquueennccee iiss rreellaattivivee toto oobbsesrevravtaiotinosn ms madaed oeno enaceha ch veivne,iann, dantdh ethreefroerfoerdeo deosens ontont enceecsessasrairliylyi ninddicicaatteea abbssoolluuttee ttiimmiinngg.. Minerals 2019, 9, 604 35 of 42 Minerals 2019, 9, x FOR PEER REVIEW 36 of 42 Fiiggurree 2222.. Paarragenettiic ssequence deduced for tthe hypogene miineralization in tthe Nueva veiin iin tthhee Choccaya miine.. The width of the bars approximates the relative abundance of the listed minerals. Loccattiion off tthhee miinneerraall pphhaasseess oorr ggeenneerraattiioonnss yyiieellddiinngg hhiigghhlliightted ccoonccenttrrattiions off IIn,, aand tthhee maaxxiimum ccoonncceennttrraattiioonn ffoorr tthhiiss meettaall aarreei innddiiccaatteeddi innr reeddc coololor.r. 6.2. ITnhdirueme s: tMagineseroaflomgiicnael rEaxlipzraetsisoionnh aanvde Cboenetnroidlse onnt iIfitse dDiinstrthibeuÁtionni m as–Chocaya–Siete Suyos deposit (Figures 20–22). Assemblages that are typically found in low-sulfidation mineralization characterize stageR1eamnadrkinabcllue dceonccaesnsittreartiitoen, sa rosfe nIno pwyerritee ,chpiyerfrlyh odteittee,catendd ihni gsph-hFaele(rFiteeS and2 1stmanonl.it%e, )asnpdh aallesroi tien. > Swtaugretz2itec,o cmaspsritiesreistet,h aendcr ryasmtadlloizhartiitoen. Sopfhmaleinrietrea, lsstatnynpiitcea al nodf cinatsesritmereidtei aatree- smualfijodra ctoionnstaitsuseenmtsb olafg tehse sourceh maisnepryarliiztea–timona ricna tshitee ,Ásnpihmaales–riCteho(wcaiytha–FSeieSte Su21yoms odli.str%ic)t aanndd tshtaeyn naiptep-efaamr taot ihnoitset .thSet magaejo3rity < is cohfa trhaicst ecrriziteicdabl ymtheteacl riyns ttahlleiz datiisotrnicotf. ATgh-eP bh-iSgnh scuolnfocseanlttsr,awtiohnic hofa rIen tyinp itchaelsoef imntienremraelds iaretep-rseuslefindtast itohne mmiinneerraalliozgaitcioanl e[x8p4–re8s6s]i.oAnc ocof rtdhien ghliyg,ho rceonmciennetrraaltiizoantsio onf iInnt h(uepÁ tnoi m25a1s0– Cphpomc)a yina –wSiheoteleS-uoryeo schdeimstricicatl raengaislytesress a tshhaiftt fwroemre lorwep- otortiendt erbmye dIsiahtieh-asuralfi deta tiaoln. e[n3v7]ir. onInm eunntsd,esrigmroiluarndto tshaamt dpleessc,r ibthede inhiogthheesrt Bcoolnivceianntr-taytpioends eopfo Isni tisn( sep.gh.,a[le3r9i]t)e. aSrime fiolaurntdh riene v-setiangse ferovmolu thtieo nÁonfimthaesm aninde Sraielitzea Stiuoynossy mstienmess,h washebreeeans dtheesc mribaexdiminumpo vraplhuyersy o-rfe Ilna taerde erpeliathtievremlya llobwas ienm spehtaalle(“rCiteo rfdroilmle rtahne- tNyupeev”)a dveepino siint sth(ee. gC.,h[o3c5a,8y1a] m). ine. A similar distribution pattern is shown in the isovalue map for maximum In concentration in 6s.p2h. aInledriiutme :gMraiinnesr ainlo gtihcea lsEuxrpfarecses isoanmanpdleCs osnhtroowlsno ninI tsFiDgiusrtrei b2u3tAio.n Regarding concentrations of In in stannite, the maximum values are found in underground and surface samples in the Ánimas mine, wherRee smtaanrnkiatbe lies cmoonrcee natbruantidoannsto (fFiIgnuwree 2re3Bc)h. iefly detected in sphalerite and stannite, and also in wurtzite, cassiterite, and ramdohrite. Sphalerite, stannite and cassiterite are major constituents of the ore mineralization in the Ánimas–Chocaya–Siete Suyos district and they appear to host the majority of this critical metal in the district. The high concentration of In in these minerals represents the mineralogical expression of the high concentrations of In (up to 2510 ppm) in whole-ore chemical analyses that were reported by Ishihara et al. [37]. In underground samples, the highest concentrations of In in sphalerite are found in veins from the Ánimas and Siete Suyos mines, whereas the maximum values of In are relatively low in sphalerite from the Nueva vein in the Chocaya mine. A similar distribution pattern is shown in the isovalue map for maximum In concentration in sphalerite grains in the surface samples shown in Figure 23A. Regarding concentrations of In in stannite, the maximum values are found in underground and surface samples in the Ánimas mine, where stannite is more abundant (Figure 23B). Figure 23. Isovalue maps for maximum concentrations of indium in sphalerite (A) and stannite (B) grains in surface samples from the Ánimas–Chocaya–Siete Suyos district. Google Earth satellite base image. The incorporation of In in sphalerite and stannite can be contextualized in the sphalerite– stannite–roquesite pseudoternary system (Figure 15) [77,87,88]. In sphalerite grains from the Ánimas–Chocaya–Siete Suyos district, the roquesite component reaches 9.1 mol. %, which is well within the empirically stablished 60 mol. % maximum tetragonal CuInS2 component in solid solution within cubic, sphalerite-type-structure ZnS [87,88]. The correlation that was observed between the Minerals 2019, 9, x FOR PEER REVIEW 36 of 42 Figure 22. Paragenetic sequence deduced for the hypogene mineralization in the Nueva vein in the Chocaya mine. The width of the bars approximates the relative abundance of the listed minerals. Location of the mineral phases or generations yielding highlighted concentrations of In, and the maximum concentration for this metal are indicated in red color. 6.2. Indium: Mineralogical Expression and Controls on Its Distribution Remarkable concentrations of In were chiefly detected in sphalerite and stannite, and also in wurtzite, cassiterite, and ramdohrite. Sphalerite, stannite and cassiterite are major constituents of the ore mineralization in the Ánimas–Chocaya–Siete Suyos district and they appear to host the majority of this critical metal in the district. The high concentration of In in these minerals represents the mineralogical expression of the high concentrations of In (up to 2510 ppm) in whole-ore chemical analyses that were reported by Ishihara et al. [37]. In underground samples, the highest concentrations of In in sphalerite are found in veins from the Ánimas and Siete Suyos mines, whereas the maximum values of In are relatively low in sphalerite from the Nueva vein in the Chocaya mine. A similar distribution pattern is shown in the isovalue map for maximum In concentration in sphalerite grains in the surface samples shown in Figure 23A. Regarding concentrations of In in Msitnaenranlsit2e0,1 9th, 9e, 6m04aximum values are found in underground and surface samples in the Ánimas m36inofe4, 2 where stannite is more abundant (Figure 23B). FFigiguurree 2233.. IIssoovvaalluuee mmaapps sfofor rmmaxaixmimumum cocnocnecnetrnattriaotnios nosf oinfdiinudmiu imn sipnhsaplehraitlee r(iAte) a(And) asntadnnsittaen (nBit) e (Bgr)aginrasi nins siunrsfaucrefa scaemspamlesp flreosmfr othme tÁhneimÁnasim–Cahso–Ccahyoac–aSyieat–eS SieutyeoSsu dyiostsridctis. tGriocot.gGle oEoagrlteh Esaatretlhlistea tbeallsiet e biamseagime. age. TThhee iinnccoorrppoorraattiioonn ofo fIn Iinn sipnhasleprhitael earnitde staanndnites tacannn ibtee ccoanntexbtuealiczoendt eixnt uthalei zsepdhalienriteth–e sspthaanlneirtiet–er–osqtaunensiittee –rposqeuudesoitteerpnsaeryu dsoytsetrenmar y(Fsiygsuterem 1(5F)i g[u7r7e,8175,)88[7].7 ,I8n7 ,8s8p]h. aInlersipteh aglerraiitnesg rfraoinms ftrhoem thÁeniÁmnaism–Cash–oCchayoac–aSyiae–teS iSeuteyoSsu ydoisstrdicist,t rtihcet, rtohqeureosqituee csoitme pcoonmepnot nreeancthreesa c9h.1e sm9o.l1. m%,o lw. h%ic,hw ish iwchelli s wweiltlhwini tthhien etmhepiermicaplilryi csatallbylissthaebdl i6s0h emdo6l.0 %m moal.xi%mummax tiemtruagmonteatl rCaugoInnSa2l cComuIpnoSnecnotm inp soonliedn stoinlustiooln 2 id swoliuthtiionn cuwbiitch, isnphcualbeirci,tes-ptyhpael-esrtirtue-cttyupree -ZstnrSu c[t8u7r,8e8Z]. nTShe[8 c7o,8rr8e]l.atiTohne thcoatr rwelaast ioobnsethrvaetdw baestwoebesne rtvheed b etween the atomic concentrations of In and Cu in sphalerite at Cu/In = 1 (Figure 13) is in good agreement with the well documented incorporation of In in sphalerite following a (Cu+ + In3+) 2+ ↔ 2Zn coupled substitution [11,12,25,39,89,90]. The prevalence (and apparent exclusivity) of this substitution mechanism for the incorporation of In in the structure of sphalerite makes the availability of Cu in the mineralizing system a key factor that controls the distribution and primary concentration of the critical metal. Therefore, it might be anticipated that high concentrations in In across a given deposit or district can only occur if sphalerite crystallized under relatively high activity of Cu. In the studied district, the highest concentrations and average values of In in sphalerite occur in the Siete Suyos mine, which also hosts sphalerite with the highest Cu contents (Figure 12). The occurrence of chalcopyrite disease texture is probably related with the distinctively high activity of Cu during the crystallization of In-rich sphalerite in the Diez vein from the Siete Suyos mine (Figure 5C,D). Such a texture was not observed in the other studied veins. In hydrothermal systems, chalcopyrite disease is mostly attributed to diffusion-controlled replacement of Fe by Cu or to co-crystallization of sphalerite and chalcopyrite [91]. The first case appears to be unlikely in the Diez vein since chalcopyrite disease texture is local and restricted to micro-bands that are not particularly enriched in Fe. X-ray element maps (Figure 14) indicate a compositional zoning in sphalerite characterized by alternating micro-bands enriched in both In and Cu and micro-bands depleted in these elements at relatively constant Fe contents. The crustiform morphologies that are depicted by such bands indicate that they formed as infillings of open spaces, and the alternate superposition of Cu + In-rich and -poor bands suggests the episodic entrainment of fluids enriched in Cu and In during the mineralization. The substitution mechanism that allows for the incorporation of In in stannite is poorly understood. However, our data from the Ánimas–Chocaya–Siete Suyos district suggest that In enrichment is associated with Sn and Cu depletions, at Sn at Sn + In = 1 and Cu + In = 2 (Figure 16; see also [39]). In contrast, a petrukite [(Cu,Zn,Fe)3(In,Sn)S4] component that accounts for the incorporation of In in the studied stannite grains is, in principle, ruled out, since the atomic contents of Cu do not show any correlation with those of Zn or Fe (Figure 16). Minerals 2019, 9, 604 37 of 42 Iron did not play an obvious role in the enrichment of In in the Ánimas–Chocaya–Siete Suyos mineralization, as its atomic concentration in sphalerite does not correlate with that of In, and trends toward In enrichment are observed at any concentration of Fe (Figure 16). However, the Fe contents in sphalerite are indeed useful for the discrimination between sphalerite that crystallized in equilibrium with either pyrrhotite (stage 1) or pyrite (stage 2; Figures 20–22). It is noteworthy that sphalerite with In contents above 1.0 wt.% (54 out of a total 416 EPMA analyses) yielded FeS contents that were below 18 mol. %, thus pointing to crystallization in equilibrium with pyrite and, probably, out of the stability field of pyrrhotite [82]. In contrast, Fe-rich (FeS > 21 mol. %; stage-1) sphalerite yielded much lower In contents (up to 0.35 wt.% In at the Ánimas vein; Figure 21). In consequence, we deduce that the main incorporation of In in the Ánimas–Chocaya–Siete Suyos mineralization occurred during the crystallization of sphalerite and stannite in an intermediate-sulfidation stage of mineralization (stage 2 in Figures 20–22). In addition, the modest In enrichment in cassiterite and high-Fe sphalerite took place during an earlier low-sulfidation stage of mineralization (stage 1). Finally, ramdohrite, which crystallized late in the paragenetic sequence during an intermediate-sulfidation and sulfosalt-rich mineralization stage (stage 3), also accounts for some minor In contents. 7. Conclusions Detailed textural observations in ore mineralization from the Ánimas–Chocaya–Siete Suyos district revealed a relatively complex mineralogy that can be associated with a three-stage mineralization sequence. In general terms, a first stage rich in cassiterite + arsenopyrite + pyrrhotite ± Fe-rich sphalerite was followed by a second stage rich in pyrite + sphalerite + stannite ± famatinite and a third stage rich in galena and Ag-Pb-Sn sulfosalts. The mineralogy records a shift from the low- to intermediate-sulfidation stages of mineralization. Intermediate-sulfidation assemblages are dominant in vein mineralization in the Ánimas and Siete Suyos mines, in the SE sector of the district. Indium occurs in exceptionally high concentrations in sphalerite (up to 9.66 wt.% In) and stannite (up to 4.11 wt.% In) from the Ánimas and Siete Suyos mines, and in lower, although still anomalous, amount in wurtzite (up to 1.61 wt.% In), cassiterite (up to 0.25 wt.% In2O3), and ramdohrite (up to 0.24 wt.% In). In sphalerite, the atomic concentrations of In and Cu yield positive correlations at Cu/In = 1 thus pointing to a (Cu+ + In3+)↔ 2Zn2+ coupled substitution. In stannite, the atomic concentrations of In, Cu, and Sn yield negative correlations at In + Cu = 2 and In + Sn = 1. The incorporation of In in the structure of these two minerals can be contextualized in the sphalerite–stannite–roquesite pseudoternary system. The availability of Cu during the crystallization of sphalerite is necessary for In enrichment in sphalerite. In this study, the highest values of In in sphalerite were found in the Diez vein in the Siete Suyos mine; the sphalerite richest in In occurs as micrometer-sized crustiform micro-bands that are also enriched in Cu, and that contain local chalcopyrite disease texture that is suggestive of a high activity of Cu in the mineralizing fluids. Our analytical results point to the identification of intermediate-sulfidation state assemblages with abundant sphalerite and stannite as the chief host for In in the Ánimas–Chocaya–Siete Suyos district and probably in other similar, dome-hosted Bolivian-type deposits. Supplementary Materials: Available online at http://www.mdpi.com/2075-163X/9/10/604/s1. Table S1: List of samples. Table S2: Representative EMPA analyses. Author Contributions: Conceptualization, L.T., J.C.M., P.A. and O.R.A.-B.; fieldwork, L.T., M.C. (Malena Cazorla), J.C.M., L.G., D.A., B.T., Á.M., D.M.; methodology, L.T., M.C. (Malena Cazorla), J.C.M., M.T., M.C. (Marc Campeny); writing—original draft preparation, L.T., M.C. (Malena Cazorla); writing—review and editing, A.C., J.C.M., P.A., O.R.A.-B. Funding: This study benefitted from the Peruvian CONCYTEC-FONDECYT-World Bank project 107-2018-FONDECYT-BM-IADT-AV, the budged granted by the Generalitat de Catalunya (Autonomous Government of Catalonia) to the Consolidated Research Group SGR 444 and the AECID project A3/042750/11. Minerals 2019, 9, 604 38 of 42 Acknowledgments: The help and hospitality extended by the miners from the Ánimas and Siete Suyos cooperatives during sampling and field work are most gratefully acknowledged. We appreciate the technical support by Xavier Llovet (Centres Científics i Tecnològics, Universidad de Barcelona, CCiT-UB) during the acquisition of EPMA data. We appreciate constructive comments from two anonymous reviewers, which have helped us to improve the manuscript. Conflicts of Interest: The authors declare no conflict of interest. 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