minerals Article Mineralogy and Distribution of Critical Elements in the Sn–W–Pb–Ag–Zn Huanuni Deposit, Bolivia Andreu Cacho 1, Joan-Carles Melgarejo 1 , Antoni Camprubí 2,*, Lisard Torró 3 , Montgarri Castillo-Oliver 4, Belén Torres 1, David Artiaga 5, Esperança Tauler 1 , Álvaro Martínez 6, Marc Campeny 1,7, Pura Alfonso 8 and Osvaldo R. Arce-Burgoa 9,10 1 Departament de Mineralogia, Petrologia i Prospecció Geològica, Facultat de Ciències de la Terra, Universitat de Barcelona, Carrer de Martí i Franquès s/n, 08028 Barcelona, Spain; acachoamgeo@gmail.com (A.C.); joan.carles.melgarejo.draper@ub.edu (J.-C.M.); belentcgeo@gmail.com (B.T.); esperancatauler@ub.edu (E.T.); mcampenyc@bcn.cat (M.C.) 2 Instituto de Geología, Universidad Nacional Autónoma de México, Ciudad Universitaria, Coyoacán, 04510, CDMX, Mexico 3 Geological Engineering Program, Faculty of Sciences and Engineering, Pontifical Catholic University of Peru (PUCP), Av. Universitaria 1801, San Miguel, Lima 15088, Peru; lisardtorro@hotmail.com 4 ARC Centre of Excellence for Core to Crust Fluid Systems (CCFS) and GEMOC, Department of Earth and Planetary Sciences, Macquarie University, North Ryde, NSW 2109, Australia; montgarri.castillo-oliver@mq.edu.au 5 Centres Científics i Tecnològics, Universitat de Barcelona, Carrer de Martí i Franquès s/n, 08028 Barcelona, Spain; artiaga@ccit.ub.edu 6 Departement des Sciences de la Terre, Université de Genève, Rue des Maraîchers 13, 1205 Genève, Switzerland; alvaro@bizkaia.eu 7 Departament de Mineralogia, Museu de Ciències Naturals de Barcelona, Passeig Picasso s/n, 08003 Barcelona, Spain 8 Departament d’Enginyeria Minera, Industrial i TIC, Escola Tècnica Superior d’Enginyeria de Mines de Manresa, Universitat Politècnica de Catalunya, Avinguda de les Bases de Manresa 61–73, 08242 Manresa, Spain; maria.pura.alfonso@upc.edu 9 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; info@osvaldoarce.com 10 Eloro Resources Ltd. Av. La Floresta 497, Of. 101, San Borja, Lima 15037, Peru * Correspondence: camprubitaga@gmail.com or camprubi@comunidad.unam.mx; Tel.: +52-555-622-4310 (ext. 128)  Received: 28 August 2019; Accepted: 28 November 2019; Published: 4 December 2019  Abstract: The polymetallic Huanuni deposit, a world-class tin deposit, is part of the Bolivian tin belt. As a likely case for a “mesothermal” or transitional deposit between epithermal and porphyry Sn types (or shallow porphyry Sn), it represents a case that contributes significantly to the systematic study of the distribution of critical elements within the “family” of Bolivian tin deposits. In addition to Sn, Zn and Ag, further economic interest in the area resides in its potential in critical elements such as In, Ga and Ge. This paper provides the first systematic characterisation of the complex mineralogy and mineral chemistry of the Huanuni deposit with the twofold aim of identifying the mineral carriers of critical elements and endeavouring plausible metallogenic processes for the formation of this deposit, by means of a multi-methodological approach. With In concentrations consistently over 2000 ppm, the highest potential for relevant concentrations in this metal resides in widespread tin minerals (cassiterite and stannite) and sphalerite. Hypogene alteration assemblages are hardly developed due to the metasedimentary nature of host rocks, but the occurrence of potassium feldspar, schorl, pyrophyllite and dickite as vein material stand for potassic to phyllic or advanced argillic alteration assemblages and relatively high-temperature (and low pH) mineralising fluids. District-scale mineralogical zonation suggests a thermal zonation with decreasing temperatures from the central to the peripheral areas. A district-scale zonation has been also determined for δ34SVCDT values, which range −7.2% to 0.2% (mostly −7% to −5%) in the central area and −4.2% to 1.0% Minerals 2019, 9, 753; doi:10.3390/min9120753 www.mdpi.com/journal/minerals Minerals 2019, 9, 753 2 of 26 (mainly constrained between −2% and 1%) in peripheral areas. Such values stand for magmatic and metasedimentary sources for sulfur, and their spatial zoning may be related to differential reactivity between mineralising fluids and host rocks, outwardly decreasing from the central to the peripheral areas. Keywords: critical elements; indium; gallium; germanium; tin; silver; cerium; hydrothermal; bolivian tin belt 1. Introduction The Huanuni Sn–W–Pb–Ag–Zn deposit is the largest tin producer in Bolivia and, alongside the San Rafael deposit in Peru, spearheads the tin production in the world. The 2017 production was 8415 tonnes of tin and, despite a fall in production below 7000 tons in 2018, the tin production in Huanuni still accounts for over a half of the total production of Bolivia. These deposits belong to the Bolivian Tin (Sn–W–Ag–Sb–Bi) Belt (Figure 1) that has significant critical metal resources (In, Ge and Ga [1–10]). Increasing international demand is envisaged for In, Ge and Ga, particularly in emerging technologies such as the production of photovoltaic cells (In and Ga), optical fibre and infrared optical technologies (Ge). In addition, these metals are listed as Critical Raw Materials for the European Union [11], which attests to their strategic importance due to the large share in their supply by China—By far, the largest global producer of In, Ga and Ge. The Andean cordillera contains four metallogenic belts from west to east, these are the Fe, porphyry Cu–Mo(–Au), Cu–Pb–Zn–Ag, and Sn–(W–Ag–Sb–Bi) belts [3], the last of which is commonly referred as the “Tin Belt”. The Tin Belt extends between southeast Peru and the northernmost tip of Argentina, and most of it sits on western Bolivia (Figure 1). The Oruro region in southwest Bolivia is located on the central part of the Tin Belt, at the hinge between the northerly NW–SE part of the belt and the southerly N–S part (Figure 1). This region contains some of the most outstanding tin deposits in the world, which correspond to various types or models of formation. Despite its major economic importance, only a few studies are available on the Huanuni deposit [12–17]. Early studies [12–14] determined the essential characteristics of this deposit, including its general features, structural configuration, mineralogy, and ore distribution. To the extent of the existing literature, the formation of the Huanuni deposit is not clearly ascribed to any existing model of formation or type of deposits. The Bolivian Tin Belt is constituted by Upper Triassic to Lower Jurassic, and Miocene to Pliocene major epochs in association with subalkaline peraluminous S-type magmatism [18–20]), and the possible association of the Huanuni deposits with Miocene intrusive rocks is not addressed in this paper. The present study aims at the determination of the distribution of critical metals in the Huanuni deposit in the light of the time and space distribution of the minerals that bear them. This includes the determination of its paragenetic sequence and differences in the mineralogy of central to distal portions of the deposit. This one corresponds to a group of papers of various Bolivian tin deposits with the same collective aim. Minerals 2019, 9, 753 3 of 26 FFiigguurree 11.. RReeggioionnaal lggeeoolologigciacla ml mapa pshsohwoiwngin tgheth loeclaotcioanti oonf tohfet shteudstyu adryeaa r(Heau(aHnuunain duenpiodseitp: owshiti:tew bhoixte). bInosxe)t. sIhnoswets sthhoew loscathtieonlo ocfa ttihoen moafpth weimthainp twhei tEhainstethrne CEaosrtdeirlnlerCao (rAdnildleeraan( mAnordpehaontemctoornpihc outnecittso narice uafntietrs aArercaef-tBeur rAgrocae -[B2u1r]g oaand[2 1th] ea nddisthtreibduistitorinb uotfi otnhoe f BthoeliBvioalniv iTaninT iBneBlte lits isaaftfetre rMMllyynnaarrcczzyykk aanndd Wiilllliiaammss--JJoonneess [[33]])).. 2.. Geollogy The Huanunii diisttriictt ((Oruro departtmentt,, Panttalleón Dallence proviince)) iis llocatted 275 km SE off La Paz,, iin tthe centtrall partt off tthee EEaasstteerrn Coorrdiilllleerra ooff tthhee BBoolliivviiaann Annddeess ((FFiigguurree 11)).. The Easttern Cordiillllera iis composed off Ordoviiciian tto Crettaceous sediimenttary sequences,, compriisiing tthiick bllack shalles,, siillttsttones,, lliimesttones,, sandsttones,, sllattes and quarttziittes ((Fiigures 1 and 2;; [[2222]])).. These were regiionalllly aafffefcetcetdedb ybNy NNWN–WSS–ESSstEr iksitnrgikfianugl t faanudlt foalndds yfsoteldm ss[y2s3te],mpso ss[2ib3l]y, dpuoesstiobltyh edFuame attoi nitahne oFraomgaetninyian dorroegaectniyv aatned dreuarcitnigvattheed Adnudrienagn .thTe hAensdeedainm. eTnhtaer ysepdaimckeangtaeriys paaffcekcategde bisy alfofewc-tgedra dbye rloegwi-ognraldme erteagmioonrapl hmisemtamreolartpehdistmo t hrelaFtaemd atoti nthiaen Foarmogaetinnyi.anIn otruosgieonnys. oInf tMruiosicoennse oafc iMd isotcoecnkes acnid dstoomckess aoncdcu droinmtehse occecnutrr ainl ptharet coefntthraelE paasrtte ronf Cthoer dEialsleterarn, a Cnodrdthilelyerar,e apnadr ttlhyecyo avreer epdarbtylyi gconvimerberdit besy, wighniicmhbarrietelsa,t we Mhiicohc eanre liantea gMei[o2c2e,n24e– i2n7 a].ge [22,24–27]. The miineralliisatiion iin the Huanunii deposiit iis llargelly hosted by quartziites,, shalles and siilltstones of the Palleozoiic Lllallllagua,, Uncíía and Cancañiirii formatiions and,, to a llesser extent,, by the pyrocllastiic and llava sseerriieess oof fththe eMMioicoecneen eMMororcoccoacla lFaoFrmoramtiaotnio [n28[]2, 8a]r,oaurnodu nthde tPhoezPokoozonki ohnilil (hFiilgl u(Freig 2u)r. eTh2)e. TChaencCaañnircia ñFiorrimFoartmioant i(oAns(hAgsilhl)g icllo)ncsoinstssi sotsf olaf mlaimnainteadte didaimamicitciteitse, ss, asnanddstsotonnese saanndd mudssttoness that attaiin about 1500 m iin thiickness and are a product of gllaciiall-flfluviiall formatiion wiithiin an extensiionall regime [29,30]. The Llallagua Formation consists of sandstones and quartzites with intercalated mudstones and limolites that attain about 1500 m in thickness and underlies the Uncía Formation [31]. The early Uncía Formation (Wenlock to Ludlow) consists of laminated shales that were deposited during a marine transgression. The polymetallic deposits are found dominantly on the eastern flank and the nucleus of the locally overturned (towards the SW) Pozokoni anticline and are hosted by rocks of the Llallagua aMninde raUlsn2c0í1a9 , 9fo, 7r5m3ations [31]. Miocene porphyric dikes, approximately N-S striking, crop east o4f otfh2e6 Pozokoni anticline and extend for over 2 km (Figure 2). These are inferred as the most likely source for the hydrothermal polymetallic deposits [21]. A similar dike also occurs at the Dolores mine, on trhege iwmeest[e2r9n,3 s0i]d. e Tohf ethLel amllianginuga dFiosrtmricatt, isotnrikcionngs iWstsSWof–sEaNnEd satnodne osvaenr d50q0u mar tlzointegs, awnidth a isnmtearlclearla otende omnu dthsteo nneosrathnedrnli mpoalritt eosft htahtea tdtaisitnriacbt.o uAtll1 5t0h0esme idniktheisc koncecsusr anpderuipnhdeerrallileys tthoe tUhen cmíaiFnoerramliasteido na[r3e1a].. TNheeveerathrleyleUssn, ctíhaeF oocrcmuarrteionnce( Wofe na lobclikndto inLturudsloiown) bceolnoswis tCseorfrola Pmoiznoakteodnis h(Halueasntuhnati wmeinree;d Feipgousriet e2d) wduitrhining tahme caorrine eotfr tahnes ghroemssoionny.mous anticline is inferred [21]. FFiigguurree 22.. LLooccaall ggeeoollooggiiccaall mmaapp ooff tthhee oorree ddeeppoossiittss aatt HHuuaannuunnii,, iinn wwhhiicchh mmiinneerraalliisseedd bbooddiieess aarree iinnddiiccaatteedd uuppoonn aaeerriiaall pphhoottoo iinntteerrpprreettaattiioonn ooff tthhiiss aarreeaa.. MMooddiififieedd ffrroomm CCaacchhoo eett aall.. [[3322]].. The pHoulyamnuentai lldicepdoespiot scitosnasrisetsfo oufn dsedvoemrailn taenntsly oof nvtehinese asntder nbrfleacncikasa nwditth enno upcrleufesreonf ttihael olorcieanlltyatoiovne r[t1u2r]n beudt (htoawvianrgd srotuhgehSlyW c)oPnoczenoktroicn ianandt ircaldiniael apnadttearrnesh, othsutesd rebsyemrobclkinsgo fa trhaediLala nlleasgtueda arnrdanUgnecmíaenfot r(mFiagtuioren s2)[.3 1H].owMeivoecre,n we ep omrpahy ytreinctdatiikveesl,ya spoprrto txhiem vaeteinlys Nin-tSo stthrrikeein mg,acirno pfameaisliteos:f (tAhe) 1P1o0z°o k(eo.ngi.,a nVteictali nGeraande,x tOenridenfoter,o Nveure2vka,m C(hFuigaullraen2i) .oTr hPersoegarreesoin fveerirnesd),a s(Bt)h e16m0o° s(tel.igk.e, lyNsooruterñcea for Cthreuhzeyrdar ovtehiner),m aanldp o(Cly)m betawlleiecnd e0p45o°s iatsnd[2 10]8.0A° (sei.mg.i,l aErspdeikraenazlsao aoncdc uArms aatritlhlae Dveoilnosr)e. sInm tihnies, ostnudthye, wes tgeronuspid ethoef tvheeinms ininintog dthirsetrei cmt, satirni kdinogmWaiSnWs, –aE NceEntarnadl odvoemra5i0n0 amroluongd, athned Ha sumanaullneri omnienoen atnhde Pnozrtohkeorni phairltl,o afnthde tdwisot rpicetr. iAphlletrhael soerd dikiestsaol cdcuormpaeinrisp hnearmalelyd toBothneanmzian earnadli sLeda aSrueear.teN e(svoeurthe laensds, the occurrence of a blind intrusion below Cerro Pozokoni (Huanuni mine; Figure 2) within the core of the homonymous anticline is inferred [21]. The Huanuni deposit consists of several tens of veins and breccias with no preferential orientation [12] but having roughly concentric and radial patterns, thus resembling a radial nested arrangement (Figure 2). However, we may tentatively sort the veins into three main families: (A) 110◦ Minerals 2019, 9, 753 5 of 26 (e.g., Veta Grande, Oriente, Nueva, Chuallani or Progreso veins), (B) 160◦ (e.g., Norteña or Cruzera vein), and (C) between 045◦ and 080◦ (e.g., Esperanza and Amarilla veins). In this study, we group the veins into three main domains, a central domain around the Huanuni mine and Pozokoni hill, and two peripheral or distal domains named Bonanza and La Suerte (south and southeast of the central domain, respectively). The peripheral zones are richer in Zn relative to the central. The veins are normally less than 1 m thick, e.g., the Veta Grande vein is up to 50 cm thick, veins in the La Suerte area are 10 cm to 70 cm thick, and about 25 cm thick in the Bonanza area. The mineralised areas extend across a ~10 hm2 quadrangle (Figure 2). Most veins do not crop out but their tops are found between 100 m and 350 m below the Pozokoni hill summit, and some of them occur even deeper (480 m below the summit height). This attests to some potential of undiscovered mineralised structures [21]. The mineralised structures are crudely banded and include early quartz and tourmaline followed by cassiterite, and then by various generations of ore associations [13]. The available data from fluid inclusions in this deposit indicate the occurrence of saline brines up to 26 wt.% NaCl equiv., homogenisation temperatures up to 425 ◦C, and many metals dissolved in inclusion fluids, including Sn and Ge [15,17,31]. 3. Methodology A total of 42 in situ surface and gallery samples were obtained, including 31 samples from the Huanuni mine, six from the La Suerte Mine and five from the Bonanza mine. Samples were studied in thin (n = 3) and thick (n = 19) polished sections by means of transmitted- and reflected-light petrography, X-ray diffraction (XRD), Raman microspectroscopy, scanning electron microscopy with energy analyser (SEM-EDS), electron probe microanalysis (EPMA), and laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS). Except for the ICP-MS analyses, the rest were carried out at the Centres Científics i Tecnològics of the Universitat de Barcelona. The XRD equipment was a PANalytical XPert PRO MPD (Almelo, The Netherlands/Malvern, UK) alpha1 diffractometre with a focaliser primary monochromator and an Xcelerator detector. The radiation used was Ko1 Cu (λ = 1.5406 Å) at 45 kV and 40 mA. Spectra were interpreted by means of the PANalytical XPert JCPDS. A dispersive spectroscope Horiba Jobin Yvon LabRam 800 (Horiba, Tokyo, Japan) was used for mineral identification by means of Raman microspectroscopy. A laser with a wavelength of 532 nm and a beam diameter of 2 µm was used; the acquisition time for each analysis was 10 s. The SEM-EDS equipment was an ESEM Quanta 200 FEI XTE 325/D8395 (Hitachi, Tokyo, Japan) electron microscope with an INCA Energy 250 EDS detector attached. The equipment was operated at 20-25 keV, 1 nA and at a working distance of 10 mm. The EPMA equipment was a Cameca SX-50 (Cameca, Gennevilliers, France) with four WDS spectrometres and EDS at 20 keV and beam current of 15 nA. The analytical programs and standards were pyrite (S, PET, Kα), FeS2 (Fe, LIF, Kα), Co (Co, LIF, Kα), NiO (Ni, LIF, Kα), GaAs (As, TAP, Lα), and InSb (Sb, PET, Lα) for analyses on arsenopyrite; rutile (Ti, PET, Kα), Fe2O3 (Fe, LIF, Kα), Nb (Nb, PET, Lα), InSb (In, PET, Lα), cassiterite (Sn, PET, Lα), and Ta (Ta, LIF, Lα) for analyses on cassiterite; sphalerite (S, PET, Kα), FeS2 (Fe, LIF, Kα), sphalerite (Zn, LIF, Kα), CdS (Cd, PET, Lα), and InSb (In, PET, Lα) for analyses on sphalerite; FeS2 (S, PET, Kα), FeS2 (Fe, LIF, Kα), chalcopyrite (Cu, LIF, Kα), sphalerite (Zn, LIF, Kα), Ge (Ge, LIF, Kα), GaAs (As, TAP, Lα), Ag2S (Ag, PET, Lα), CdS (Cd, PET, Lα), InSb (In, PET, Lα), cassiterite (Sn, PET, Lα), InSb (Sb, PET, Lα), PbS (Pb, PET, Mα), and Bi2S3 (Bi, LIF, Lα) for analyses on sulphosalts. LA-ICP-MS analyses were carried out with a Photon-Machines Excite 193 nm excimer laser system coupled to an Agilent 7700x (Agilent Technologies, Santa Clara, CA, USA) ICP-MS mass spectrometer at Macquarie University Geochemical Analysis Unit (GAU) (Australia). Calibration of the instrument was done using a NIST610 standard and the values of Cu and Bi of minerals that were previously analysed by EPMA [33]. Each analysis of stannite and arsenopyrite was normalised to the S contents determined by the electron microprobe, whereas cassiterite analyses were normalised against Sn. The counting time for each analysis was 90 s, including 30 s of background and 60 s of Minerals 2019, 9, 753 6 of 26 sample acquisition. In all analysis, the repetition rate of the laser beam was 10 Hz, and its energy density, 70% (6.5 J/cm2). To monitor the accuracy of the measurements, the BCR-2 standard was also analysed as a secondary standard. The samples were analysed in runs of 15 analyses, comprising 10 analysis of unknowns, bracketed by two analyses of the NIST610 at the beginning and the end of each run, as well as one analysis of the BCR external standard after the first set of NIST610. The detection limits for REE, Ba, Rb, Th, U, Nb, Ta, Pb, Sr, Zr, Hf, Ti, Y and Ga span 10 ppb to 20 ppb, for Sc and V 100 ppb, and for Ni 2 ppm. The accuracy for each analysis ranges between 1 and 10 wt.%, and the spot diameter ranged between 14 µm and 40 µm. Data reduction was carried out online by using the GLITTER software [34,35]. The data are displayed in Table S2 (the full extent of analysed elements). The absolute values for trace elements presented in this manuscript should be taken with caution, given the different nature of the standards and the samples. However, previous works have shown that good accuracy and precision can be obtained during the analysis of sulphides by LA-ICP-MS using the NIST610 standard [36]. Their research included repeated LA-ICP-MS analysis of a PS-1 (sulphide standard) and obtained values comparable (<5% error) to those resulting from solution [37]. Sulphur isotopes analyses were carried out in situ in 30 single grains of sulphide minerals. Pyrite, pyrrhotite, sphalerite and galena grains were separated by careful hand picking under a binocular microscope. Samples were analysed with a continuous flow mass spectrometer Delta C Finnigan MAT coupled with an elemental analyser TC-EA Carlo Erba 1108, at the Centres Científics i Tecnològics of the Universitat de Barcelona. The results are expressed in the delta notation as per mil deviations of the Vienna-Canyon Diablo Troilite (VCDT) standard and the standard deviation is determined to be 0.2%. The results were calibrated by using the IAEA S1, IAEA S2, IAEA S3 and NBS-123 international reference standards. 4. Mineralogy 4.1. Alteration and Gangue Minerals Hydrothermal alteration assemblages are poorly developed in host rocks (mainly quartzites, sandstones and shales) due to the low reactivity between them and hydrothermal fluids. Therefore, their spatial distribution cannot be clearly determined from the currently available surface and underground exposures, although indicated widespread silicification and quartz-sericite alteration, with less consistent argillic alteration, pyritization and tourmalinization [38]. Quartz, schorl, potassium feldspar (not adularia), “sericite” (essentially fine-grained muscovite), chlorite (chamosite), epidote, calcite, and kaolinite are more conspicuous as vein material than as alteration minerals in host rocks (Figure 3). Alunite, dickite, halloysite and nacrite, although not found in this study, have been also reported [16,39]. Monazite-(Ce) is strongly associated with “sericite”, and stetindite with chlorite. The occurrence of potassium feldspar as vein material may stand for potassic alteration assemblages. Pyrophyllite has been identified by XRD in the central sector in our study and indicates the occurrence of advanced argillic alteration. Kaolinite also occurs as a late alteration mineral, possibly as part of argillic alteration assemblages. “Sericite” is commonly observed in association with quartz and sulphides (Figure 3A), and may occur replacing previously formed hydrothermal potassium feldspar (Figure 3B). The latter is suggestive of phyllic alteration developed on earlier potassic alteration. Chlorite, epidote and calcite are closely associated and constitute propylitic alteration assemblages that may also include montmorillonite. Propylitic assemblages may also develop on earlier potassic assemblages (Figure 3C,D). All alteration and ore-bearing assemblages are susceptible to experiencing fracturing and non-hydrothermal brecciation (Figure 3E,F), thus favouring the emplacement of later associations in all the mineralised areas in the Huanuni district. Minerals 2019, 9, 753 7 of 26 FFiigguurree 33.. PPhhotootmomicircorgorgarpahpsh sofo afltaelrtaetriaotnio mn imneinraelrsa alsnda nmdicmroicfrraocftruacritnugri ning thine tHhueaHnuunani udnepi odseitp. o(sAit). P(Aer)vPaesrivvaes ipvheypllhicy lalilctearlatteiroanti oanssaoscsioatceiadt ewdiwthi tshpshpahlearlietrei tieni nthteh eLaL aSSuueretrete aarreeaa; ;ttrraannssmiitttteedd ppoollaarriisseedd lliigghhtt,, ccrroosssseedd ppoollaarrss ((XXPPLL)).. ((BB)) Hyyddrrootthheerrmaall ppoottaassssiiuum ffeellddssppaarr ((ppoottaassssiicc aalltteerraattiioonn)) rreeppllaacceedd bbyy ppeerrvvaassiivvee pphhyylllilcica lateltreartaiotinonm imneinraelrsailns tihne tLhae SLuear tSeuaerretae; XarPeLa.; (CX)PHL.y d(Cro) thHeyrmdraoltphoetramssailu mpoftealsdssiupmar f(eplodtsapsasirc (paolttearsasticio anlt)eraastsioocni)a atessdocwiaittehd swpihtha lseprihtael,ebrirtee,c cbiraetcecdiataendd anpdo sptodsattdeadtebdy byp rporpopylyiltiitcica alltteerraattiioonn miinneerraallss iinn tthhee Boonnaannzzaa aarreeaa;; ttrraannssmiitttteed ppllaannee ppoollaarriisseedd lliigghhtt ((TPPPPLL)). .((D)) SSaamee aass ((C)),, XPPL.. ((E)) Twoo sseettss ooff miiccrrooffrraacctturriing,, tthee ffiirrsstt oonee aaffffeeccttiing ssttaagee--11 pyrriittee aand aassssoocciiaatteed wiitth ssttaagee--22 cchaallccoopyrriittee,, aand tthee sseeccoonnddo noenwe itwhiinthsitna gest2a,gien t2h,e Cine ntthrael aCreean;trreafll ecatreeda;p orleafrliescetdedli ghpto(lRarPisPeLd) . (lFig) hMt ic(rRoPfrPaLct)u. ri(nFg) Mthaictraofffreaccttsusrtiangge -t2hastt aanfnfeictetsa sntdageea-r2l isetraanrnsietne oapnydr ietearalniedr parysreitneoipnytrhiteeC aenndt rpayl rairtea i;nR tPhPe LC.entral area; R PPL. 4.2. Ore Minerals 4.2. OBrees Midiensertahles silicates mentioned above, the minerals that constitute hypogene ore associations in thBeedsiedpeoss tithea rseilidcoamtesin manetnlytiosnueldp haibdoevsea, nthdes mulipnheoraslasl ttsh,aot xciodnesst,itwutoel fhraympoagteesn,ep ohroes pashsaotceisa,tiaonnds icna rtbhoen adteepso(sFiitg aurree sd4o–m6)i.naTnhtleys esuarlpehciodnessi gannedd sinulaplhpohsaabltest,i coaxlidoreds,e rwfoolrfreaamchatoefs,t hpehogsrpouhaptsesa,b aonvde. cSaurlbpohnidateess a(rFeigaucraenst h4i–t6e).[ ATgh2eSs]e, aarres ecnoonpsyigrniteed[ FineA aslSp]h,abbiestmicuatl hoinrditeer [fBoir2 Se3a]c,hč eorfn týhitee g[rCouu2pCsd aSbnoSv4e]., Schualplchoidpeysr itaere[C aucFaenSt2h]i,tec ob[Aalgt2iSte], [CarosAensSop],ygraitlee n[aFe[PAbsSS]],, gbeirssmduorthffiinteite[N [iBAi2sSS3]],, mčearrncýasitiet e [[CFeuS2C],dpSynrSi4t]e, c[FheaSlc2o],ppyyrrirthe o[tCitueF[FeeS12−],x cSo],brahlotidteo s[tCanonAisteS][,C gua2lFeenSan [3PSb8]S,]s,p ghearlsedriotrefafintde w[NuirAtzsiSte],[ mZnaSr]c,asstiatnen [iFtee–Sk],ë pstyerriittee [FeS2], pyrrhotite [Fe1−xS], rhodostannite [Cu2FeSn3S8], sphalerite and wurtzite [ZnS], stannite–kësterite [Cu2FeSnS4–Cu2ZnSnS4], and teallite [PbSnS2]. Sulphosalts are cervelleite [Ag4TeS], freibergite [Ag6(Cu4Fe2)Sb4S13−x], matildite [AgBiS2], proustite–pyrargyrite [Ag3AsS3–Ag3SbS3] and treasurite Minerals 2019, 9, 753 8 of 26 [Cu2FeSnS4–Cu2ZnSnS4], and teallite [PbSnS2]. Sulphosalts are cervelleite [Ag4TeS], freibergite [Ag6(Cu4Fe2)Sb4S13−x], matildite [AgBiS2], proustite–pyrargyrite [Ag3AsS3–Ag3SbS3] and treasurite [Ag7Pb6Bi15S32]. Oxides are cassiterite [SnO2], hematite [Fe2O3], and rutile [TiO2]. Wolframates are the endmembers of wolframite, ferberite [FeWO4] and hübnerite [MnWO4]. Phosphates are fluorapatite [Ca5(PO4)3F], and monazite-(Ce) [(Ce,La,Nd,Th)PO4]. Carbonates are calcite [CaCO3], siderite [FeCO3], and otavite [CdCO3]. There is also fluorite [CaF2], native bismuth [Bi], and stetindite [Ce4+SiO4], a considerably rare mineral. Other minerals, reported in earlier publications [39,40] are boulangerite [Pb5Sb4S11], bournonite [PbCuSbS3], cylindrite [Pb3Sn4FeSb2S14], franckeite [(Pb,Sn) Fe2+ 6 Sn2Sb2S14], freieslebenite [AgPbSbS3], greenockite [CdS], herzenbergite [SnS], jamesonite [Pb4FeSb6S14], owyheeite [Pb7Ag2(Sb,Bi)8S20], pavonite [(Ag,Cu)(Bi,Pb)3S5], plagionite [Pb5Sb8S17], semseyite [Pb9Sb8S21], and stibnite [Sb2S3]. Supergene associations comprise a broad number of phosphates, sulphates, silicates, and carbonates. Sulphates are anglesite [PbSO4], and szomolnokite [FeSO4·H2O]. Phosphates are drugmanite [Pb 3+ 2(Fe ,Al)H(PO4)2(OH)2], plumbogummite [PbAl3(PO4)2(OH)5·H2O], and pyromorphite [Pb5(PO4)3Cl]. The sole carbonate found as a supergene mineral in this study is an indium carbonate with no known stoichiometric formula, and that may constitute a new mineral species. Other supergene minerals, reported in earlier publications [39,40] are aheylite [(Fe2+,Zn)Al6(PO4)4(OH)8·4H2O], chalcanthite [CuSO4·5H2O], chalcosiderite [CuFe3+ 6(PO4)4(OH)8·4H2O], crandallite [CaAl3(PO4)2(OH)5·H2O], cronstedtite [Fe2+ Fe3+(SiFe3+ 2 )O5(OH)4], faustite [(Zn,Cu)Al6(PO4)4(OH)8·4H2O], fibroferrite [Fe3+(SO4)(OH)·5H2O], hisingerite [Fe3+ 2Si2O5(OH)4·2H2O], hydrowoodwardite [Cu0.5Al0.5(OH)2(SO4)0.25·0.75H2O], hydrozincite [Zn (CO ) (OH) ], jarosite [KFe3+ 5 3 2 6 3(SO4)2(OH)6], linarite [PbCu(SO4)(OH)2], ludlamite [(Fe2+,Mg,Mn)3(PO4)2·4H2O], montetrisaite [Cu6(SO4)(OH)10·H2O], nikischerite [NaFe2+ 6Al3(SO4)2(OH)18·12H2O], perhamite [Ca3Al7(SiO4)3(PO4)4(OH)3·16.5H2O], redgillite [Cu6(OH)10(SO4)·H2O], scorodite [Fe3+(AsO4)·2H2O], valentinite [Sb2O3], variscite [AlPO4·2H2O], vivianite [Fe2+ 3(PO4)2·8H2O], and wavellite [Al3(PO4)2(OH,F)3·5H2O]. 4.3. Petrography Pyrite is one of the most abundant metallic minerals in either mineralised area of this deposit and its aggregates may form several types of textures (Figure 4), including “bird’s eyes” along with marcasite or other textures that resulted from pyrrhotite replacement through an increase in sulphidation. However, pyrite can be replaced by sphalerite (Figure 4A), arsenopyrite or hematite. Pyrrhotite is an abundant mineral in the Central area but nearly absent in the peripheral areas of the deposit. Besides being commonly replaced by pyrite and by fine intergrowths of pyrite-marcasite (intermediate product), it can be replaced by stannite, galena and sphalerite. Arsenopyrite is a major metallic mineral in the Central and La Suerte areas, although it is relatively scarce in the Bonanza area. It generally occurs as euhedral and subhedral crystals partially replaced by chalcopyrite or pyrrhotite through microfractures. Sphalerite is observed interstitial to arsenopyrite crystals (Figure 4B) pointing to a later crystallization. Sphalerite also occurs after pyrite, either reactively (Figure 4A,D) or passively (Figure 4C). Sphalerite, chalcopyrite and galena are conspicuous minerals in the Bonanza and La Suerte areas, although they are relatively scarce in the Central area. Chalcopyrite occurs generally replacing sphalerite as chalcopyrite disease textures (Figure 4A) or in microfractures (Figure 3E). Sphalerite can be also replaced by galena and late sulphosalts, and may also present exsolutions of rare černýite (Figure 4B). Sphalerite is one of the main indium-bearing minerals in the deposit, as attested by an unidentified indium carbonate that forms in close association with sphalerite as its supergene alteration product (Figure 6F). Besides sphalerite, galena may also replace pyrite and hematite and, in turn, it is replaced by late sulphosalts. Zn- and Sn-rich assemblages are often spatially associated with apatite (Figure 4D) and potassium feldspar (Figure 4F), at least in the Central area, which suggests that such assemblages are associated Minerals 2019, 9, 753 9 of 26 with potassic assemblages. Rutile is a characteristic mineral of the peripheral areas of the mineralisation, replaced by quartz and wurtzite (Figure 4E). Fiigurree4 .4P. hPoht omtoimcriocgroragprhaps hofs Zonf- riZchn-braicshe mbeatsael amssoetcaial tiaosnssoicniatthieonHsu ain utnhied eHpousaint.u(nAi) Cdheaplocsoipt.y r(iAte) dCisheaalsceopteyxrtiutere dsiisneaspseh atelexrtiutereths aint r sephlaaclereiaterl itehrapt yrreiptelaicnet heaerBlioenr apnyzraitaer eina; tRhPeP BLo.n(Ban) zSata agree-a2;b RasPePmL.e (tBal) sSutalpghei-d2 ebsawseit hmextasol lsvueldphčeidrnesý iwteitfhro mexsoplhvaelde rčiteerninýitthee fLroamS useprhtealaerreiate; binac kth-sec aLtat eSreuderetlee catreoan; (bBaScEk)- ismcatgte.re(Cd )eSlteacgtreo-2nb (aBsSeEm) eitmalasguelp. h(Cid)e sSitnagthe-e2B bonasaen zma eatraela ;snuolptihceidthese pina stshivee Bporencainpzita tiaorneao;f nspohtiaclee rtihtee apfatesrsipvyer ipter;eBciSpEitiamtiaogne .o(fD s)pShtagler-i2teb aasfetemr eptaylrsituel;p hBiSdEe siminaagseso. c(iDat)i oSntawgieth-2p bhaysllei c-malettearla tsiounlpmhidnesra lisn ianssthoceiaLtaioSnu weriteh aprheya;llnico-atilctertahtieorne amcitniveeraplsr eicni pthitea tLioa nSuoefrstpe haarleear;i tneoatifcte rthpey rietaecatinvde pthrecoipccituartrioen coef osfpahpalaetrititee; BafStEeri mpyargitee. a(En)dS tthaeg eo-c2cruurtrielnecaes soofc aiaptaetditew; iBthSEq uimaratzgea. n(dE)w Sutartgzei-t2e rinuttihlee aLsasoScuiaetretde awreitah; BqSuEaritmz agned. w(Fu)rStztaitgee -i2n bthaese Lma eStuael-rrtiec haraesas;o BciSaEti oimnawgiet.h (Fsp) hSatalegrei-t2e bpasretl ymreetpala-rciecdh basysochciaaltciopny wriitteh, csapshsiatleerriittee, apnadrtsltya gre-p3lastcaendn ibtey ricmhamlcinopgyproittea,s sciausmsitferlditsep, aarn(dp osttaasgsiec-3a ssetamnbnliateg er)iimnmthiengC epnotrtalssairuema; BfeSlEdsimpaarg (ep.otassic assemblage) in the Central area; BSE image. Arsenopyrite is a major metallic mineral in the Central and La Suerte areas, although it is relatively scarce in the Bonanza area. It generally occurs as euhedral and subhedral crystals partially replaced by chalcopyrite or pyrrhotite through microfractures. Sphalerite is observed interstitial to arsenopyrite crystals (Figure 4B) pointing to a later crystallization. Sphalerite also occurs after pyrite, either reactively (Figure 4A,D) or passively (Figure 4C). Sphalerite, chalcopyrite and galena are conspicuous minerals in the Bonanza and La Suerte areas, although they are relatively scarce in the Central area. Chalcopyrite occurs generally replacing sphalerite as chalcopyrite disease textures (Figure 4A) or in microfractures (Figure 3E). Minerals 2019, 9, 753 10 of 26 FigurFeig5u.reP h5.o Ptohmotiocmroicgrroagprahpshos fotfi nti-nr-ircihcha assssoocciiaattiioonnss iinn tthhee HHuuanaunnuin diedpeopsiot.s i(tA. )( ASt)agSet-a2g ceh-2alccohpaylcriotep yrite and sapnhd aslpehriatlee,riaten, dansdta sgtea-g3e-s3t asntannintietea annddc chhaallccooppyyrriittee rreepplalcaicnign gstasgtae-g1e p-1yrprhyorrtihteo tainted aqnudarqtzu ianr ttzhei n the Central area; RPPL. (B) Stage-1 arsenopyrite replaced by stage-2 pyrrhotite, schorl and chalcopyrite, Central area; RPPL. (B) Stage-1 arsenopyrite replaced by stage-2 pyrrhotite, schorl and chalcopyrite, then by stage-3 stannite in the Central area; RPPL. (C–E) Similar sequence to that in B including stage-1 then by stage-3 stannite in the Central area; RPPL. (C–E) Similar sequence to that in B including pyrite and cassiterite, stage-2 chlorite (chamosite) and stage-3 bismuthinite in the Central area; back- stages-c1atpteyrreidte ealnecdtrcoans s(iBtSeEri)t eim, satgaegse. -2(Fc) hSlotargitee-2( cahsasomcioastiioten) baentdwesetang esi-d3ebriitsem auntdh icnaistseitienritteh ereCpelanctirnagl area; back-esacralitetre rpeydrrehloetcitter,o annd(B cSaEss)itiemriateg beesi.n(gF )reSptlaagceed-2 bays sstoacgiea-t3i ostnanbneittwe iene tnhes iCdeenrtirtael aanreda;c BaSssEi tiemraitgee.r e(Gpl)a cing earlieSrtapgye-r2r hcaostsiittee,riaten dancda ssiditeerritiet,e abnedi nsgtagre-p3l asctaendnibtey asntadg bei-s3msuttahninitiete rienpltahciengC enartlriearl paryeriat;e BinS Ethiem age. (G) SCtaegnetr-a2l caaresas;i teBrSiEte imanadges. id(He)r itSeta,gaen-2d wstoalgfrea-m3 isteta anndi tecaasnsidterbities mcruotshsciunti taenrde prleapclaincegde abyrl isetragpey-3r ite in the Csetanntnraitle,a qreuar; tBz SaEndi mpyargite. in(H th)eS Lta gSeu-e2rtwe aorlefar;a BmSEit eimaangde.c assiterite crosscut and replaced by stage-3 stannite, quartz and pyrite in the La Suerte area; BSE image. Minerals 2019, 9, 753 11 of 26 FigurFeig6u.reP h6.o Ptohmotoicmroicgrroagprahpshos folfa ltaetem minineerraall aassssoocciiaatitoionns sanadn drarrae rme imneirnaelsr ainls tihne tHhueaHnuunain duenpiosdite.p osit. (A,B)(ASi,Blv) eSri-lrviecrh-riacshs oascsioactiiaotnioon fosft astgaege3 3i nint htheeB Boonnaannzzaa aarreeaa; ;nnootitciec efrferiebiebrgeirtge,i tme,amtiladtitield ainted acnerdveclelerivtee lleite replacing galena but not cassiterite. (C) Stage-1 pyrrhotite replaced by stage-2 sphalerite and rare replacing galena but not cassiterite. (C) Stage-1 pyrrhotite replaced by stage-2 sphalerite and rare gersdorffite in the Central area. (D) Stage-2 native bismuth replaced by stage-3 bismuthinite in the gersdorffite in the Central area. (D) Stage-2 native bismuth replaced by stage-3 bismuthinite in the Central area. (E) Stage-2 siderite intergrown with otavite in the Central area. (F) Stage-2 indium-bearing Centrsaplhaarleerai.te( Ere)pSltaacgeed- 2bys iad esuripteerignetnereg urnokwnnowwnit hinodtiuavmi tceairnbothneatCe esnpetrcaielsa irne at.he(F B)oSntaangzea-2 airnead.i uAmll -abree aring sphablearcikte-screatptelarecde delbecytraons u(BpSeEr)g iemnaeguesn. known indium carbonate species in the Bonanza area. All are back-scattered electron (BSE) images. 4.4. Paragenetic Sequences Cassiterite and stannite are the most abundant Sn minerals in the deposit (Figure 5). Cassiterite All mineralised areas recorded paragenetic sequences that can be simplified into three is relatively abundant in the Central area, generally as passively precipitated vein material along hypogene stages of mineralisation, and correlated among the three mineralised areas despite their withdqiuffaerretnzcaesn dinp myrinrheroatliotgeyo (rFaigruserenso 7p yarnidte 8()h. eSntacgee, a1n ceoanrslisytsm oifn bearasel-(mFeigtaul rseu5lpCh,iFd,eHs )a)nads meuahye dral to sucbohnetadirna lcacsrsyitsetraitles oanr,dl eascsanfrtheiqteu.e Snttalgye, i2n ias saslosoc iabatisoen mwetiathl-rpicyhr iatnedo irs stthaen mniatein( Fcaigrruierre o5fC s,cDho,Grl), . It is commcaosnsiltyerriteep laancde dinbdyiusmta-nbenairtien(gw sipthaolerrwitei thino uthtes cdheoprols(iFt;i gthuer eo5cBcu–rDre,nFc–eHs )o).f Ccaosbsailte, rnitieckiesl raenladt ively scarcceeirniupme rmipihneralls abrelaosnog fttoh tehdise sptaogseit ,aws wherlle. iSttasyges t3e mcoantsicisatlsl yofp sousltpdhaotseaslte-arirclhy aZsnso-rciicahtioanss oacnidat iso ns as anhedthrea lmcaryins tcaalrsrrieerp olafc seidlv,eirn mtuinrner,ablsy, lpaatertricsuulalprlhyi dine sthaen dpesruiplhpehroals aalrtesa.sS oidf etrhiet ediespaolssiot. cSoumpemrgoennei n the Central area, in association with cassiterite (Figure 5F,G), intergrown with rare otavite (Figure 6E), due to the alteration of pyrrhotite, and is a scarce mineral in the peripheral zones of the deposit. Minerals 2019, 9, 753 12 of 26 Stannite–kësterite is a common mineral in the Central area of the deposit, normally as replacements after pre-existing sulphides (Figures 4F and 5), and can be found in close association with schorl (Figure 5B–E) and “sericite”. It was also found in the La Suerte area. Sn-rich assemblages in the Huanuni deposit are systematically postdated by Ag-rich assemblages (Figure 6A,B). The latter are associated with “sericite” both in the Central and peripheral zones. Freibergite is possibly the most abundant silver mineral in the deposit and is common in the Bonanza area, in close association with matildite, galena, cervelleite and teallite (Figure 6A,B). Galena forms symplectitic textures along with matildite and/or proustite-pyrargyrite in the latest hypogene assemblages of the deposit (Figure 6A). Acanthite, argentopyrite, apatite, bismuthinite, cervelleite, cobaltite, ferberite and hübnerite (wolframite), gersdorffite, monazite-(Ce), rhodostannite, rutile, treasurite, wurtzite and stetindite are scarce minerals. Despite their scarcity and the inherent difficulty in determining their occurrence or abundance, nickel, cobalt and tungsten minerals (gersdorffite, cobaltite and wolframite) are seemingly confined to the Central area of the deposit. Cobaltite and gersdorffite occur in association with sphalerite (Figure 6C). Bismuthinite occurs late in the hypogene assemblages as replacements of earlier native bismuth (Figure 6D). 4.4. Paragenetic Sequences Aaslslomciaintieornasl iasreed daormeaisnarteecdo rbdye dphpoasrpahgaetnese, tiscuslpehqauteens,c eosxithhyadtrcoaxnidbees, saimrsepnliafiteesd, icnatrobotnharteees,h eytpc.o, gene stagepsaorftimcuilnarelrya wlisitaht iiornon, ,a cnodppcoerr,r aenladt eledada maso mngajothr ecatthiorenes (me.ign.,e draruligsmedanairteea).s despite their differences in Drusy quartz occurs in all stages in the three mineralised areas. Stage 1 in the Central area (Figure mineralogy (Figures 7 and 8). Stage 1 consists of base-metal sulphides and may contain cassiterite and 7) is characterised by open-space lining with quartz, cassiterite, arsenopyrite (essentially euhedral) and acantphyitrer.hoSttiateg e(a2si sgarolsuonbdamsaesmsees)t.a lD-ruicrihnagn sdtaigset h2e imn atihne cCarerniterralo fasrecah,o prly,rciates saitnedr itaersaenndopinydriitue mw-ebreea ring sphaldeerpitoesiitnedt hine dasespoocisaitti;otnh ewoitchc ugerrrsednocrefsfitoef acnodb acoltb,anltiictke.e lTahnesde cmeriniuermalsm winereer afolsllboweleodn gbyt oa tshuibs-stage as westlal.geS twagithe 3schcornl,s icshtasmoofssitue lpanhdo ssaidlte-rritiec,h aansds othceiant iboyn snaatinvde bisistmhuethm, awinolfcramrriiter aonfd stihlve esrecmoninde rals, particguelnaerrlaytiionnt ohfe cpaessritpehrietera, loacraelalys ocrfytshtealdliezpinogs iats. tShuep neeregdelnee tians svoacriaetyio. nSstaagree 3d oinm thinea Cteedntbrayl pahreoas pish ates, sulphcahtaersa,cotexriihzeyd rboyx itdhee sp,raercsipeintaattieosn, ocfa rsbtaonnnaittee, ss,pehtacl.e, rpitaer t(wiciuthla crhlyalwcoiptyhriitreo ndi,sceoaspep teerx,taunreds)l, eaandd atshem ajor cationthsir(de .gge.,nderrautigomn oafn pityer)r.hotite lining micro-fractures; the final association consists of “sericite”, acanthite and bismuthinite, frequently replacing native bismuth. FigurFeig7u.reP a7r. aPgaerangeetnicetsice qsueqeunecnecein int htheeC Ceennttrrall area ooff tthhee HHuaunaunnui ndiedpoespiotss, iotsr, PoorzPokooznoik Hoinlli aHreiall. area. MineMrailnsehraiglsh hliigghhltiegdhtiend riend readr earteh tohsoesew witihths isgignniifificcaanntt ccoonncceenntrtaratitoinosn isni nInI, nG,eG, Ge,aG, Na,bN anbda Tnad. Ta. Stage 1 in the La Suerte peripheral area (Figure 8) consists of the first generation of pyrite and acanthite, followed by the crystallisation of euhedral arsenopyrite and sphalerite with chalcopyrite disease textures. Stage 2 in the La Suerte peripheral area consists of the second generation of pyrite, rutile and a first generation of cassiterite, followed by a second generation of arsenopyrite that partly replaced pyrite, galena, “sericite”, and sphalerite. Stage 3 in the La Suerte peripheral area consists of stannite–kësterite and the second generation of cassiterite, followed by silver sulphosalts such as matildite, freibergite and proustite–pyrargyrite. Minerals 2019, 9, 753 13 of 26 FFiigguurree 88.. TThhee ppaarraaggeenneettiicc sseeqquueennccee iinn tthhee ppeerriipphheerraall aarreeaass ooff tthhee HHuuaannuunnii ddeeppoossiittss ((BBoonnaannzzaa aanndd LLaa SSuueerrttee aarreeaass)).. MMiinneerraallss hhiigghhlliigghhtteedd iinn rreedd aarree tthhoossee wwiitthh ssiiggnniifificcaanntt ccoonncceennttrraattiioonnss iinn IInn,, GGee aanndd GGaa,, aanndd CCee--bbeeaarriinngg mmiinneerraallss iinn bblluuee.. 5. MDinreursayl Cqhueamrtzisotrcyc urs in all stages in the three mineralised areas. Stage 1 in the Central area (FiguSreph7a)leisritceh farroamct etrhies etdhrbeey mopineenr-aslpisaecde alrienaisn gwwasi tahnaqluysaerdtz ,byc amsseiatenrsi toef, EarPsMenAo.p Iytsr imtea(xeismseunmti airlolyn ecuohnetednrtasl )oacncudrp iynr rthhoe tCiteen(atrsagl raoruean:d umpa tsos e1s1). wDtu.%ri nFge s(taavgeera2gien 6th.6e2C went.t%ra Fl ae)r eian, tphyer iBteonanandzaar saerneao,p uypri tteo w11e.r9e7 dwetp.%o sFitee (davineraagsseo 9c.i2a6t iwont.%w Fiteh) igne rthsde oLraffi Stueeratned arceoab, aalntdit eu.pT tho e2s1e.8m wint.%er aFles (waveerreagfoel l9o.5w wedt.%b yFea) siun bt-hseta Cgeenwtriathl asrcehao r(lT,acbhlaem 1o asnitde aTnadblsei dSe1r)i. tMe, oasntd inthdeiunmby cnonattievnetsb iinsm suphtha,lewriotelf r(aFmigiuterea n9,d Ttahbeles e1c oanndd gTeanbeler aSt1io) naroe fbcealosswit ethriet ed,eltoeccatilolyn clrimysitta, lbliuzti nsogmaes gthreainnse eadrele utpin tov a0r.8ie8t yw. t.S%ta Igne (3avienrathgee 0C.e2n4 twratl.%ar Iena) iisnc thhaer aCcetenrtirzaeld abreyat, huepp troe c0ip.8i2ta wtiot.n%o fIns t(aanvneirtaeg, esp 0h.2a lwerti.t%e (wIni)t hinc hthaelc oBpoynraintezad iasreeaas,e atnedxt uurpe st)o, a0n.1d7 twhet.%th iIrnd (gaevneeraragtei o0n.0o2 fwpty.%rr hIont)i tien ltihnein Lgam Siucerrot-ef raarcetau.r eTsh;etrheefofirne,a lthaes shoicgihaetisotn incdoinusmis tcsoonfc“esnetrriactiitoen”s, aoccacnutrh iinte satnagdeb-2i ssmphuathleirniittee i,nf rtehqeu Cenentltyrarle apnladc iBnognnanaztiav earbeiassm. Cuathd.mium contents in sphalerite are up to 0.7 wStt.%ag eCd1 iinn tthhee LCaenSturearl taerepae rbiupth aerttaalinar tehae( Fhiigguherest8 a)vceornasgies tvsaoluf eths einfi rthste gBeonnearnatziao naroefa p(0y.r4i3te watn.%d aCcdan).t hite, followed by the crystallisation of euhedral arsenopyrite and sphalerite with chalcopyrite As of EPMA analyses (Table S1), in the cassiterite samples from the Central area were recorded (by means of EPMA) concentrations up to 1.42 wt.% TiO2 (average 0.15 wt.% TiO2), up to 1.21 wt.% FeO (average 0.66 wt.%), up to 0.37 wt.% Ta2O5 (average 0.05 wt.% Ta2O5), and up to 0.23 wt.% Nb2O5 Minerals 2019, 9, 753 14 of 26 disease textures. Stage 2 in the La Suerte peripheral area consists of the second generation of pyrite, rutile and a first generation of cassiterite, followed by a second generation of arsenopyrite that partly replaced pyrite, galena, “sericite”, and sphalerite. Stage 3 in the La Suerte peripheral area consists of stannite–kësterite and the second generation of cassiterite, followed by silver sulphosalts such as matildite, freibergite and proustite–pyrargyrite. 5. Mineral Chemistry Sphalerite from the three mineralised areas was analysed by means of EPMA. Its maximum iron contents occur in the Central area: up to 11 wt.% Fe (average 6.62 wt.% Fe) in the Bonanza area, up to 11.97 wt.% Fe (average 9.26 wt.% Fe) in the La Suerte area, and up to 21.8 wt.% Fe (average 9.5 wt.% Fe) in the Central area (Table 1 and Table S1). Most indium contents in sphalerite (Figure 9, Table 1 and Table S1) are below the detection limit, but some grains are up to 0.88 wt.% In (average 0.24 wt.% In) in (avertahgeeC 0e.n0t4ra wl atr.%ea ,Nupb2tOo50).,8 a2ltwhto.%ugIhn (iatsv eNrabg ean0d.2 Twat .%coInnt)einntsth aerBe omnaonsztlaya brealo, awn dthuep dtoet0e.c1t7iownt .l%imInits for these( aevlermageent0s..0 2Inwdti.u%mI no)cicnutrhse bLealoSwu eirttse daerteeac.tiTohne rleimfoirte ,inth me ohsigt hoefs thine dciausmsitceornitcee nantraltyiosnes.o LcAcu-rICinP-MS analystsaegse -i2ns pchaaslseirtietreitine t(hFeigCuenretrsa l9a nadnBdo n1a0n, zTa abrelaes .SC2a) damlsiuom ycieolndtendt slionwsp hvalleureitse ainre ucrpittioca0l.7 ewlet.m%ents, clustCerdining tahreoCuenndt r0a.l2a wreta.%bu Itna2tOta3i)n. the highest average values in the Bonanza area (0.43 wt.% Cd). FiguFreig u9r. eI9n.dIinudmiu mcocnoncecenntrtraattiioonnss iinns pshpahlearlietrei(toer a(nograe)n,gstea)n, nsittaen(gnrieteen )(garnedecna)s saitnedri teca(bssluitee)r, ibtye m(belaunes), by meanosf EPoMf AEPanMdAL Aa-InCdP -MLAS.-BICoxPe-sMreSp.r eBseonxtetsh erseppanreosfesntat ndthaerd sdpevaina tioonf s,swtainthdaanrdin ddiceavtiioantioofnasv, erwagiteh an values (horizontal line), and black lines represent the span of the total variation of analytical values. indication of average values (horizontal line), and black lines represent the span of the total variaAtisonof oEf PaMnaAlytaincaall yvsaelsue(Ts.a ble S1), in the cassiterite samples from the Central area were recorded (by means of EPMA) concentrations up to 1.42 wt.% TiO2 (average 0.15 wt.% TiO2), up to 1.21 wt.% FSetOan(naviteer–akgeës0t.e66riwtet .%fr)o, ump ttoh0e.3 7Cwent.%traTla 2aOr5e(aa vsehraogwe s0 .0s5ewvte.r%alT ae2Ole5m),eanntdaul pstuob0s.2ti3tuwtti.o%nsN, b2rOan5 ging betw(eaevner a0g.1e w0.0t.4%w at.n%dN 6b.321O 5w),ta.%lth Zoung, hupit stoN b0.a2n9d wTta.%co nAtegn, tuspa rteom 0o.1s3tl ywbte.%low Gteh, eadnedt euctpio tno l0im.3i2ts wfotr.% In (averthaegsee 0el.e1m2 ewnts.%. I nIdni;u EmPoMccAur; sTbaeblolwe Sit1s)d. eLteAct-iIoCnPl-imMiSt inanmaolystseosf tihne csatassnitneirtiete–kanësatlyesreitse. L(FAi-gICuPre-Ms S9 and 10, Taanballey sSe2s)i nyicealsdseitder sitiem(Filiagru rveasl9uaensd to1 0t,hToasbele oSb2t)aailnsoedy ibelyd eEdPlMowAv (aTluaebslein Sc2ri)t.i cal elements, clustering around 0.2 wt.% In2O3). Minerals 2019, 9, 753 15 of 26 Table 1. Summary of compositions of significant elements in key minerals of the Huanuni deposits (see full dataset in Tables S1 and S2). Mineral Area Element Type of Value wt.% n Method Fe Average 9.50 23 EPMA Std.dev. 5.43 Maximum 21.80 Central Minimum 0.27 In Average 0.24 23 EPMA Std.dev. 0.21 Maximum 0.88 Minimum b.d.l. Fe Average 6.62 11 EPMA Std.dev. 4.04 Maximum 11.00 Bonanza Minimum 0.48 In Average 0.20 11 EPMA Std.dev. 0.23 Maximum 0.82 sphalerite Minimum b.d.l. Fe Average 9.26 19 EPMA Std.dev. 2.67 Maximum 11.97 La Suerte Minimum 2.86 In Average 0.02 19 EPMA Std.dev. 0.05 Maximum 0.17 Minimum b.d.l. Fe Average 8.82 53 EPMA Std.dev. 4.40 Maximum 21.80 All areas Minimum 0.27 In Average 0.15 53 EPMA Std.dev. 0.20 Maximum 0.88 Minimum b.d.l. In Average 0.12 19 EPMA Std.dev. 0.09 Maximum 0.32 Minimum b.d.l. In Average 0.28 7 LAICPMS Std.dev. 0.03 Maximum 0.33 stannite Central Minimum 0.23 Ge Average - 19 EPMA Std.dev. - Maximum 0.13 Minimum b.d.l. Ga Average 63 ppm 7 LAICPMS Std.dev. 40 ppm Maximum 123 ppm Minimum 8 ppm (average 0.04 wt.% Nb2O5), although its Nb and Ta contents are mostly below the detection limits for these elements. Indium occurs below its detection limit in most of the cassiterite analyses. LA-ICP-MS analyses in cassiterite (Figures 9 and 10, Table S2) also yielded low values in critical elements, clustering around 0.2 wt.% In2O3). Minerals 2019, 9, 753 16 of 26 Table 1. Cont. Mineral Area Element Type of Value wt.% n Method In2O3 Average 0.01 50 EPMA Std.dev. 0.01 Maximum 0.08 Minimum b.d.l. In Average 0.22 3 LAICPMS Std.dev. 0.01 Maximum 0.22 Figurec a9s.s iItnerdiituem conCc enttrratlions in sphalerite (oMrainngime)u, mstannite (gre0e.n2)1 and cassiterite (blue), by Nb2O5 Average 0.04 50 EPMA means of EPMA and LA-ICP-MS. Boxes represent the span of standard deviations, with an Std.dev. 0.06 indication of average values (horizontal line), Manadx imbluacmk lines rep0r.e2s1ent the span of the total variation of analytical values. Minimum b.d.l. Ta2O5 Average 0.05 50 EPMA Stannite–kësterite from the Central area sShtodw.dse v.several ele0m.08ental substitutions, ranging between 0.1 wt.% and 6.31 wt.% Zn, up to 0.29 wtM.%ax Aimgu, mup to 0.13 w0.t3.7% Ge, and up to 0.32 wt.% In Minimum b.d.l. (average 0.12 wt.% In; EPMA; Table S1). LA-ICP-MS analyses in stannite–kësterite (Figures 9 and 10, Table S2) yielded sKimeyi:lba.rd .vl.a=luvealsu teos btehloowset hoebdteatiencteiodn bliym iEt,PnM=Anu (mTbaebr loef aSn2a)l.y ses. Figure 10. Trace and major element contents in stannite and cassiterite of the Huanuni deposit as per LA-ICP-MS determinations. Stannite–kësterite from the Central area shows several elemental substitutions, ranging between 0.1 wt.% and 6.31 wt.% Zn, up to 0.29 wt.% Ag, up to 0.13 wt.% Ge, and up to 0.32 wt.% In (average 0.12 wt.% In; EPMA; Table S1). LA-ICP-MS analyses in stannite–kësterite (Figures 9 and 10, Table S2) yielded similar values to those obtained by EPMA (Table S2). In summary, the specific analyses to determining the occurrence and contents in critical elements allow indicating that In is consistently present in stannite, cassiterite and, particularly, sphalerite. Ga yielded low contents in stannite, and other critical elements like Nb or Ta occur in low contents in cassiterite. Minerals 2019, 9, 753 17 of 26 6. Sulphur Isotopes Sulphur isotope determinations were carried out on 30 sulphide (sphalerite, galena, pyrrhotite and pyrite) samples from the three mineralised areas of the Huanuni deposit (Table 2 and Figure 11). δ34S values range between −7.5% and −0.2% in galena, between −4.2% and 0.2% in sphalerite, between −6.3% and 1.0% in pyrite, and between 34 −6.2% and −5.3% in pyrrhotite. δ S values altogether are grouped around 0% in the peripheral Bonanza and La Suerte areas (−4.2% to 1.0%) but skewed toward lower values in the Central area (−7.2% to 0.2%). However, pyrite samples from the Central area yielded a broad variation in δ34S values, ranging between −6.3% and 0.2%. δ34S values for the entire deposit range between −7.5% and 1.0% altogether and describe a nearly bimodal distribution that can be narrowed down between −7% and −5%, and between −2% and 1%; such data distribution corresponds to the majority of samples from the Central and peripheral areas, respectively. Table 2. Sulphur isotope compositions of sulphides in the Huanuni deposit. Area Mine Sample Mineral δ34SVCDT (%) galena −7.5 HUA-240 pyrite −2.0 HUA-240-1 pyrrhotite −5.8 HUA-240-2 pyrrhotite −5.9 pyrite 0.2 Central Huanuni HUA-MU-2 pyrrhotite −5.3 HUA-MU-3 pyrite −6.3 HUA-MU-4 pyrite −4.5 HUA-MU-5 pyrite −5.3 pyrite −5.9 HUA-MU-6 pyrite −6.1 HUA-MU-7 pyrite −0.1 HUA-MU-8 pyrrhotite −6.2 HUA-BO-1 pyrite −0.8 Bonanza HUA-BO-2 pyrite 0.5 HUA-BO-3 sphalerite −1.1 HUA-BO-4 pyrite −1.3 sphalerite −4.2 HUA-SU-1 sphalerite −1.7 Peripheral pyrite −0.9 HUA-SU-2 sphalerite 0.2 pyrite −1.8 La Suerte pyrite 1.0 HUA-SU-3 sphalerite −1.0 galena −0.2 pyrite −1.3 HUA-SU-4 galena −1.7 HUA-SU-5 pyrite 0.8 pyrite 0.5 HUA-SU-6 sphalerite −3.3 Minerals 2019, 9, 753 18 of 26 FFiigguurree 1111.. HHiissttooggrraamm ooff ssuullpphhuurr iissoottooppiicc ccoommppoossiittiioonn ((δ3 344SS)) ooff ssuullpphhiiddee mmiinneerraallss iinn tthhee HHuuaannuunnii ddeeppoossiitt,, rreellaattiivvee ttoo tthhee VVCCDDTT ssttaannddaarrdd.. 7.. Diiscussiion 77..11.. PPaarraaggeenneettiicc CCoonnssttrraaiinnttss oonn tthhee GGeenneessiiss ooff tthhee DDeeppoossiitt TThhee tthhrreeee hhyyppooggeennee ssttaaggeess ooff mmiinneerraalliissaattiioonn tthhaatt aarree cchhaarraacctteerriisseedd iinn aallll tthhee ssttuuddiieedd aarreeaass ooff tthhee HHuuaannuunnii ddeeppoossiitt aarree iinn aaccccoorrddaannccee wwiitthh tthhee bbaassiicc sscchheemmee ooff mmiinneerraalliissaattiioonn tthhaatt wwaass aallrreeaaddyy ddeedduucceedd uuppoonn tthhee ssyysstteemmaattiicc rreeccoonnnnaaiissssaannccee ooff BBoolliivviiaann ttiinn ddeeppoossiittss [[88,1,122––1144]].. TThhiiss iimmpplliieess ttwwoo iinniittiiaall ssttaaggeess ooff mmiinneerraalliissaattiioonn rriicchh iinn ccaassssiitteerriittee aanndd bbaassee--mmeettaall ssuullpphhiiddeess,, aanndd aa llaattee ssttaaggee tthhaatt iiss cchhaarraacctteerriisseedd bbyy tthhee ooccccuurrrreennccee ooff ssttaannnniittee––kkëësstteerriittee aanndd ssuulplphhoossaallttss.. AAmmoonngg tthhee aavvaaiillaabbllee flfluuiidd iinncclluussiioonn ssttuuddiieess iinn tthhiiss ddeeppoossiitt [[1155––1177]],, tthhee cclloosseesstt ttoo aa ssyysstteemmaattiicc aatttteemmpptt rreelliieess iinn ddaattaa ffrroomm tthhee KKeelllleerr aannddB Baannddyyv eviening rgoruopuipnginsgtso wtoawrdartdh ethpee rpipehreiprahlezraoln ezsonoefst hoef mthinee mrailniseerdalaisreead [a1r6e].a T[h16e]l.a Ttthere s ◦ ◦ latuttdeyr sretupdoyrt eredptoermtepde rtaemtupreesraotfuhreosm oof gheonmisaotgieonnisuaptioton 4u2p5 toC 4(2m5o °sCtl y(matoastbloyu att 3a6b0ouCt )3a6n0d °Clo)w antod mloowd etroa tmeosadleinraittiee ss(aulipnittoie1s1 .(6uwp tt.o% 1N1.a6C wl etq.%u iNv.)a,Callt heqouuigvh.),s aallitnheoubrgihn essaulinpet ob2ri6nwest .u%pN toa C2l6e wqut.i%v. NhaavCel aelqsuoivb.e ehnavreep aolrstoe db[e1e7n] . rHepoowrteevde r[,1p7a]r. aHgeonweetivcesre, qpuaernacgeesntehtaict asreeqsuimeniclaers ttohtahto asered estiemrmilairn etdo inthtohsee Hdeutaenrmunini edde pions itthhea Hveubaeneunndi edsecpriobseidt htoavoec cbuereans aderescsrpiobnedse ttoo aocgceunre raasl ias erdesdpeocnresaes etoi nat egmenpeerraaltiusered odfemcrienaesrea ilnis itnemg flpueridatsuirne ootfh merindeerpaolissiitnsgo ffltuhiedBs oinli voitahnert idnebpeolsti[t8s, 1o4f ]t.he Bolivian tin belt [8,14]. TThhee ooccccuurrrreennccee ooff sscchhoorrll aanndd ppoottaassssiiuumm ffeellddssppaarr iinn ssttaaggee 22 iinn tthhee cceennttrraall ppaarrtt ooff tthhee ddeeppoossiittss ((PPoozzookkoonnii aarreeaa)) ssuuggggeessttss tthhaatt ((AA)) ssuucchh aarreeaa rreeccoorrddeedd tthhee iinnflfluuxx ooff flfluuiiddss wwiitthh hhiigghheerr tteemmppeerraattuurreess tthhaann iinn tthhee ppeerriipphheerraall ppoorrttiioonnss ooff tthhee ddeeppoossiitt,, aanndd ((BB)) ssttaaggee 22 rreepprreesseennttss aann iinnccrreeaassee iinn tteemmppeerraattuurree ooff mmiinneerraalliissiinngg flfluuiiddss wwiitthh rreessppeecctt ttoo ssttaaggee 11,, aass aallrreeaaddyy ssuuggggeesstteedd iinn rreeffeerreennccee [[1144]].. IInn ssppiittee ooff tthhee ssccaarrccee ggeeooththeerrmmoommeetrtricicd deteetremrmininataitoinosnsa vaavialailbalbelfeo rfotrh itshdise pdoespito,stiht,e tahses oacsisaoticoinatbioentw beeetnwsecehno rslcahnodrl raenladt irveellaytihvieglyh theimghp etreamtupreersaotufrmesi noefr amliisninergahliysidnrgo thhyedrmroatlhflerumidasl ifslusuidsst aiisn esdusetmainpeirdic aemllypiinricsaelvlyer ainl tsyepveesraolf tmypinees roafl mdeipneorsaitl sd[e4p1o–s4i6ts]. [I4n1–t4h6e]s.e Inty tpheesseo ftydpeepso osift sd,ewpohsiicths, iwnchliucdhe inpcolrupdhey pryo-rtpyhpyerya-ntdypSen a–nWd dSenp–Wos itdse, pscohsoitrsl,- bsecharoirnl-gbmeairninerga lmaisnseorcaial taiossnoscfioartimonesd fgoernmereadl lygeantetreamllyp earta ttuermesptehraatturraensg tehbaet twraenegne >b3 ◦ ◦ e0tw0 eCena >n3d0<0 5°0C0 anCd. S