This is anopenaccess article undertheCCBY-NC-SAThis Universidad NacionalAutónoma de México. Peer Reviewing under the responsibility of 6,2019 Manuscript September accepted: Corrected manuscript received: August 30,2019 Manuscript received: February 22,2019 org/10.18268/BSGM2020v72n3a270719 Geológica processes:ore-forming Boletín delaSociedad Mexico: newphysical-chemical constraintson deposits, central-northern Cu) skarn-epithermal Velardeña Velardeña Zn–(Pb–Cu) The Zn–(Pb– Partida, E., Rajabi, A., Escalante, E.,2020,The Jiménez-Franco,Canet, C.,Alfonso A., P., González- How tocitethisarticle: [email protected] * Corresponding author:(A.Jiménez-Franco) Col. Metalurgica, 27370,Torreón, Coahuila, Mexico. 8 Tehran, 16thAzarSt.,EnghelabSq.,Tehran, Iran. 8 Santiago deQuerétaro, Mexico. Autónoma de México, CampusJuriquilla, 76230, 7 Manresa 61-73,08242Manresa, Barcelona, Spain. versitat Politècnica deCatalunya, Av. delesBases 6 Coyoacán, 04510,CDMX,Mexico. al Autónoma deMéxico, CiudadUniversitaria, 5 ia, Coyoacán, 04510,CDMX,Mexico. Nacional Autónoma de México, Ciudad Universitar 4 Coyoacán, 04510,CDMX,Mexico. cional Autónoma deMéxico, CiudadUniversitaria, 3 Diagonal 645,08028Barcelona, Catalunya, Spain. Facultat de Química, Universitat de 8 Barcelona, Av. 2 s/n, 08028,Barcelona, Catalunya, Spain. UniversitatAplicada, deBarcelona, MartiiFranquès 1 Abdorrahman Abigail fisicoquímicos delosprocesosmineralización El sistemaskarn-epitermaldeZn–(Pb–Cu)Velardeña,Durango(México):Nuevosdatos New physical-chemicalconstraintsonore-formingprocesses The VelardeñaZn–(Pb–Cu)skarn-epithermaldeposits,central-northernMexico: license(https://creativecommons.org/licenses/by-nc-sa/4.0/) colo Gooy olg f cec,Uiest f Science, Geology, University of College of School of Departament deMineralogia,PetrologiaDepartament iGeologia Posgrado Universidad en Ciencias de la Tierra, Na Dept. d’EnginyeriaDept. Minera, Industrial i TIC, Uni Institut de Nanociència i Nanotecnologia, IN2UB Centro de Ciencias de la Atmósfera, Universidad Industrias Peñoles, prolongación Comonfort s/n, Centro deGeociencias, UniversidadNacional Instituto Instituto Universidadde Geofísica, Nacion

Mexicana, 72(3), A270719. http://dx.doi. Jiménez-Franco Rajabi 8 , Edgar , Edgar 1,2,3* , Carles Boletín de la Sociedad Geológica Mexicana Geológica Sociedad la de Boletín Escalante - - - - retrogradefromstage was There °C. 220 to 335 °C 335 to low in conditions of ≥470 from temperatures at stage mineralizing events, including(a) aprograde replacive They developed by a succession of at hypabyssal formed skarns (~3–4 km). depths According to sphalerite geobarometry, the hematite, quartz, andcalcite are alsopresent. chalcopyrite,galena, andsulfosalts. Scheelite, sulfides include pyrite, sphalerite, pyrrhotite, are actinolite, epidote, andchlorite, whereas Hydrousabundant inthe endoskarn. silicates in the exoskarn, with wollastonite particularly chemical modeling, massive sulfides. etry, telescoping, geo epitermal–skarn Keywords: paragenesis, geothermom mineral system. ermal of deposits ore Velardeña constitute a telescoped skarn–epith different The °C. 200 below vein at temperatures mineralization formed calcite, fluorite, adularia, andsphalerite. The of stage. mineralization iscrosscut Skarn by veins and hematite crystallized duringthe retrograde hydrous silicates, sulfides, sulfosalts, scheelite, and clinopyroxene Onthe other hand, formed. the retrograde stage, wollastonite, calcicgarnet with cooler, oxidizing, anddilute water. During mixing system, which accounts for aprocess of the temperature of decline during the formation a general increase in (Di and are dominated byclinopyroxene calcic mineral assemblages show replacement textures dominated by calc-silicates andsulfides. The intrusive contact and have paragenesis a skarn shaped replacement masses developed near the other by 10km).They occurasirregularly Cobre porphyritic (separated stock from each related to the Santa María dike andReyna de and dikes. most important ore are The deposits Mesozoic stocks limestones and Eocene granitic developed within the intrusive contact between zones ore occurindifferent skarn deposits Durangostate. The the most important of VelardeñaThe mining district iseconomically ABSTRACT Canet 97-53 Hd 9 42-02 4,5 Jh , Pura 04-01 ) and garnet (Ad ) andgarnet f Alfonso f (CO (O 2 ), accompanying the 2 ), followed by (b)a 6 , Eduardo 100-57 Grs 43-00 - - - ) González-Partida /72(3)A270719/2020 stocks y diques del Eoceno. de Velardeña Los depósitos entre elcontacto de calizas mesozoicas,desarrolladas ralizaciones comprenden diferentes zonas deskarn, importante del estado de Durango. En él, las mine El distrito minero Velardeña es económicamente el más RESUMEN ros masivos. mal, modelización geoquímica, sulfu mometría, telescopeo skarn-epiter Palabras clave: paragénesis, geoter telescópeado. sistema skarn-epitermal eldistrito minero Velardeñaconforman constituyen un es plausible minerales proponer que que los depósitos a <200 °C. Por ello, se estima que se formó vetas cortando los calcosilicatos. La mineralización en estas de calcita, fluorita, adularia y esfalerita, epitermales Velardeña, en mineralizaciones tipo skarn hay vetas yendo sulfosales), scheelita y hematita. Además de las de hidrosilicatos,lugar a la formación sulfuros (inclu cálcico y clinopiroxeno.granate dio prógrada La etapa wollastonita, Durantese formaron retrógrada, la etapa más fría, oxidantemineralizantes y diluida. con agua del yacimiento,formación debido a la mezcla de fluidos ral de f(O aumento gene de 335a220°C.Huboun retrógrada a 335 °C y baja f(CO ≥470 a prógrada etapa una incluyen(a) que miento, de reemplaza por una sucesión de eventos se desarrolló hipabisales (~ 3-4km).La mineralización metálica deVelardeñatipo skarn aprofundidades seformaron barómetro deesfalerita estima que las mineralizaciones tita, cuarzo ycalcita también están presentes. Elgeo tita, galena, calcopirita y sulfosales. Scheelita, hema y clorita; los sulfuros incluyenpirita, esfalerita, pirro Los hidrosilicatos son actinolita, epidota el endoskarn. abundante en y wollastonita particularmente exoskarn, 53 reemplazo dominados por clinopiroxeno cálcico (Di Las asociaciones minerales muestran texturas de (calcisilicatos y sulfuros). típica de skarn paragénesis del contacto con los intrusivos, caracterizados por una cerca reemplazamiento, cuerpos irregulares formando como entre sí ~10 km). La mineralización ocurre deCobreMaría, y elstock (separados porfídico Reyna más importantes están relacionados al dique Santa Hd4

2-02 Jh 2 ), durante el descenso de temperatura en la 04-01 ) y granate (Ad y granate ) 7 , 2 ), seguida por (b) la etapa por (b) la etapa ), seguida 100-57 Grs 43-00 1 ) en el en ) 97------

The Velardeña Zn–(Pb–Cu) skarn-epithermal deposits, central-northern Mexico ABSTRACT The Velardeña Zn–(Pb–Cu) skarn-epithermal deposits, central-northern Mexico INTRODUCTION 1. Introduction provinces ofcentral-northern Mexico (Key:SMO=Sierra CP =CentralPlateau). MadreOriental; SMOc=Sierra MadreOccidental; shown inFigure 2.Thetopmapshows thelocationofVelardeñain relationtothethreemain geological mining district oftheSanta María (fromLa Industriasections toSantaMaría) and San Lorenzo (fromSanMateotoReynadelCobre) ranges are Isabel,columncross- and (right)isbasedstratigraphic onSGM (1997). Geologicalschematic (6)Guardarraya.Theschematic María and ReynadeCobre.Minor oreoccurrencesare(1)LaIndustria, (2)LaEsperanza, (3)Antares, (4)SanMateo,(5)Santa Figure 1 2 2 Eocene age. Asa result, numerous deposits skarn plutonic and hypabyssalto intermediate rocksof and inmanyplaces they were intruded byfelsic Mexico, and eastern throughout central-northern Mesozoic carbonate rocksare widelydistributed poration, 2016). (1460000 t/yr ROM Copper Cor ore; Southern in San Luis PotosíZn–Cu (–Ag–Pb) deposit state 2016), bothinZacatecas state, andthe Charcas (2200000 t/yr ROM ore; Industrias Peñoles, the FranciscoI. Madero Zn–Cu–Pb(–Ag) deposit (936000t/yrROMdeposit ore; SGM, 2014)and del Oro2016), the Concepción Cu(–Pb–Zn–Au) run-of-mine (ROM) ore Industrias Peñoles,yr of Chihuahua state (processingcapacity: 690,000t/ as the Naica Zn–Pb(–Cu–Au–Ag) in deposit are giant base-metal deposits, suchthese skarns metallogenic stages (Camprubí, 2009). Some of throughwere acomplex formed of succession / / Location and detailed geologicalmap of theVelardeña miningshowing district, thetwomain Santa ore deposits: Boletín de la Sociedad Geológica Mexicana Geológica Sociedad la de Boletín Boletín de la Sociedad Geológica Mexicana Geológica Sociedad la de Boletín http://dx.doi.org/10.18268/BSGM2020v72n3a270719 /72(3)A270719/2020 - /72(3)A2707192020 and Garrey, 1908;Levich, 1973;Gilmer mine, notably the metallogenic evolution (Spurr the Santa María mineralization of on the skarn logical interest, several workshave been focused exploration in2006.Due to its economicandgeo mining activities, Industrias Peñoles resumed of the 1970s and,after a three-decade interruption the only productive one inthe entire district in the Santa María mine (Figuremine was 1). This the mineralized areas inVelardeña,only oneof ore reserves for 24Mtof calculated a total of Durangostate. Felder (1979) important district of Mexico,central-northern economically the most the Velardeñadistrict in Pb–Zn(–Cu) mining thistype is that of Another large ore of deposit Reyna deCobre (Figure 1). the district, mainly at potential in the northwest of ried out in 2006 revealed new areas with economic perspectives (PinetandTremblay,geology 2009). 1986, 1988;Gilmer, 1987a,1987b)andstructural However, exploration car thereactivation of et al ., - - occurrences. Thelocationofbothprofiles isshown inFigure 1. mining withthelocationofmainore and deposits district, Figure 2 mineralized areas isanalyzed andre-interpreted. tion between Reynade Cobre and Santa María and processes, such astemperature, pressure, physical-chemical variables associated with these the Velardeña mining district and to constrain the in skarns processes of that led to the formation thisworkto elucidateis the aimof district. The (sulfur isotopes)data from theVelardeña mining fluid chemistry), andgeochemical (microthermometry), inclusion mineral and (paragenesis ical and Tremblay, 2009). sediments (Pinet volcanic andQuaternary deposits dissected by a ~3 km wide graben filled by Eocene two2). These rangesare NW-trending anticlines and SanLorenzo (to the east), respectively (Figure Santa María (to the west) km, lying in the ranges of ized areas are separated from each other by ~10 Santa MaríaandReynaThe deCobre mineral Schematic geological sections oftheVelardeña Schematicgeologicalsections This contributionThis presents new mineralog f (O 2 ). Inaddition,the metallogenic connec Boletín de la Sociedad Geológica Mexicana Mexicana Mexicana Geológica Geológica Sociedad Sociedad la la de de Boletín Boletín http://dx.doi.org/10.18268/BSGM2020v72n3a270719 f (CO 2 ), - - - 2. Geologicalsetting 2.1. REGIONAL FRAMEWORK ( the Velardeña mining district, namely of skarns intrusive bodies show a spatial association with the and dikes. stocks and the TwoEocene granitic intrusive contact between the Mesozoic limestones (Figures 1and2).Allare developed along the the southwest and San Lorenzo to the northeast bounded by two mountainranges: Santa María to Cuencamé valley (Valle de Cuencamé), which is 4 km wide, known NW–SE trending as graben, Torreón.a 3to miningdistrict encompasses The the city of Durango state, ~60 km southwest of VelardeñaThe miningdistrict is located in Clark preciousand basemetals(Damon of are richly endowed with ore deposits, particularly maniego to the south by the E–W ElBajío Fault (Nieto-Sa and east by the SMO, to the west by the SMOc, and about 2000 m,bounded to the north altitude of ceous toEocene( ignimbrites, withagesrangingfrom Upper Creta volcanic rocks, mostlyandesites, rhyolites,of and athicksequence of North America, andit consists Farallon theformer plate beneath of subduction the SMOc isa silicic volcanic arc resulting from the luz-De-Antuñano Laramide orogenesislatein Eocene times(Egui Mesozoic rocks sedimentary by the mation of fold-and-thrust belt that resulted from the defor Central Plateau, CP) (Figurea SMOis 1).The Occidental (SMOc), and( Madre Oriental (SMO), ( physiographic provinces(Figure 1): ( three studyareaThe situated is at the junction of San Lorenzo range(Figure 2b). ( located in the Santa María range (Figure 2a);and a b ) the Antares dike(strike direction: NW–SE), ) theReynade Cobre the in porphyritic stock, The CP is anelevatedThe plateau, with an average et al. et al , 1982;Camprubí, 2009). According to /72(3)A270719/2020 ., 2005).Boththe SMOc andthe CP / 72(3)A270719/2020 e.g., et al Ferrari ., 2000).Onthe other hand, c ) theMesaCentral (or b et al. ) the Sierra Madre) the Sierra ,2005). a ) the Sierra ) the Sierra et al. , 1981; 3 3 - - - -

INTRODUCTION/ The Velardeña Zn–(Pb–Cu) skarn-epithermal deposits, central-northern Mexico GEOLOGICAL SETTING The Velardeña Zn–(Pb–Cu) skarn-epithermal deposits, central-northern Mexico GEOLOGICAL SETTING 2.2. GEOLOGY OFTHESTUDY AREA 4 4 mlcmn fvolcanic andhypabyssal rocks. emplacement of with major fault systems, which also control the from the CP areand initsvicinities associated Nieto-Samaniego m thick succession that fills the Cuencamé graben Cuencamé the thatfills succession thick m lavas (SGM, 1997). The basaltic rhyolitic tuffs form and a ~160 andesitic by followed tuffs rhyolitic continued through the Miocene, producing welded sequence (Rogers and clastscomingfrom the underlying Cretaceous continental conglomerates withcarbonate cement ~450 m, andwhichof consists age of thickness the Ahuichila Formation (Eocene), with anaver overlain beds.unconformably sequence is This by mudstone and organic-matter-rich lutite nation of rhythmic alter flysch a thickness, in m ~80 nian), and lutite; and ( interbedded limestone in thickness, consistingof Cura Formation (Albian–Cenomanian), ~300 m limestones rich inchert nodules; ( thin-layered 300–400m,composedof of thicness 1997), ( tions: from the baseto the top (Kelly, 1936; SGM represented in the study area by three forma America (Barboza-Gudiño North the Lower Jurassic marginat of the western volcanicarc, developed fromthe UpperTriassic to Formation theNazas represent acontinental of position (Barboza-Gudiño basaltic to andesitic com is crosscutby dikesof it and metamorphism, low-grade by affected and beds red with associated lavas and tuffs silicic to intermediate crop outinthe studyarea, of consists (SGM, 1997) (Figure unit,which 1). This doesnot Formation, Upper Triassic to Lower Jurassic inage onthe meta-volcanosedimentary Nazas formably Mexico. uncon sequence was deposited This of the Gulf ceous sequence related to the opening of a predominantly carbonate transgressive Creta thestudyarea to correspond mainly rocksThe of / / Boletín de la Sociedad Geológica Mexicana Geológica Sociedad la de Boletín Boletín de la Sociedad Geológica Mexicana Geológica Sociedad la de Boletín Magmatic activity started in the Oligocene and CretaceousThe transgressive sequence is a ) the Aurora Formation (Albian), with a c ) the Indidura Formation (Turo et al. et al. , 1961). (2005), mineral deposits (2005), mineral deposits et al. et al. , 2004). The rocks, 2004).The , 1998). http://dx.doi.org/10.18268/BSGM2020v72n3a270719 b ) the Cuesta del /72(3)A270719/2020 ------/72(3)A2707192020 2.3. SKARNSINTHEVELARDEÑAMININGDISTRICT mineralization in the Velardeña mining district the hypabyssal rocksassociated with the ore of for magmatic biotite determined was boundary) 33.4±1.7 Ma (ca.Eocene–Oligocene K-Ar age of and labeled and trachytes.them as“alaskites” A hypabyssal rocks intheVelardeña miningdistrict. noticed the relationship between ore mineralization and first (1908) Garrey and Spurr 2). and 1 and the Eocene Ahuichila conglomerates (Figures dikes that crosscut the entire Mesozoic sequence dioritic) hypabyssaland NW–SE-trendingstocks to (granitic also produced felsictointermediate alluvial sediments (Figure 1). Eocene magmatism Quaternary and are covered by upto 300 mof ically classified as monzogranites with porphyritic with monzogranites as classified ically Velardeña districthave mining been petrograph sequence.–quartz) veins placedintheskarn (–adularia, calcite–fluorite–sphalerite high-grade ( and sulfides, and bycalc-silicates dominated shaped replacement with a paragenesis masses the calcareous strata ( and, occurs with dikesand stocks ated with intrusive contact of surface. Inbothareas, the mineralizationassoci is copper mineralsthat the on occur secondary green in Spanish), which comesfrom the striking blue- eralization, despite its name (“Copper Queen” Pb-Zn min with mainly de Cobrealso askarn is Levich, 1973;Gilmer andGarrey, (Spurr deposits 1908;Ambriz,1979; Zn–Pbskarn asanotableeral authors example of Santa María mine has been studied byThe sev caldera”volcanic a“graben-type center. rence of Aguirre-Díaz facts), mulated (among other in the Cuencamé graben 1988). Duetothepyroclasticthick accu deposits (Levich, 1973;Gilmer magmatism andthe Basin andRange extension resulted theSMOcarc fromthe overlapping of asalarge volcano-plutonicinterpreted complex that byFelder a whole, (1979).As been district has this These authors described the intrusive authors These bodies h r eoi-eae geu ok fthe oreThe deposit-related igneous rocksof et al. (2008)occur the suggested et al. et al. , 1986,1988).Reyna , 1986;Gilmer a ) asirregularly et al., b ) as ------

abundant pyrite and pyrrhotite, andoccur( sphalerite variety), and chalcopyrite, galena (marmatite are principally with sulfides The sulfides. bole, chlorite, calcite and quartz with associated calcicamphi panied bya later assemblage of being themost abundant, andare accom garnet clinopyroxene (plus subordinate wollastonite), The mineralization. and predominant calc-silicates are calcic garnet sulfide higher metrically texture,inequigranular andcontainsthe volu assemblage, variable size, in grain with replacive, a calc-silicate-rich ness, upto of 50 m;it consists disseminated pyrite, chalcopyrite andsphalerite. with wollastonite, epidote, chlorite and calcite, and silicification pervasive showing bodies, intrusive ate zone rock,developed is an endoskarn on the awaymeters from the contact withthe carbon partly altered usually appears tosericite. Afew subordinate plagioclase and biotite. K-feldspar quartz and K-feldspar with length, of consisting contain subhedral phenocrysts, upto 4 mmin texturesto granular (Jiménez-Franco, 2012). They de Cuencamé (Figure 2A). betweenboundary the Antares dikeandthe Valle one isacalcite vein-faultbiggest located on the the Basin andRange extension (Oligocene). The faults relatedcut by to NW–SE-striking normal fault controlled. mineralized The structures are origin andare in (2009), these veins are epithermal chalcopyrite. According to Pinet and Tremblay arsenopyritepyrite, and and galena withminor minerals contain sphalerite (Fe-poor, pale variety), with subordinate ore adularia and quartz. The fluorite and calcite of assemblage an by acterized in brecciation intrusive rocks. Theyare char the proximity suffered of them of Some km. eral 20mandextend for sev maximumof thickness diptothe NE; theyNW–SE and steeply have a hosted inthe carbonate sequence, generally strike district are notexposed at the surface, theyare the exoskarn. gates, ( massive, centimeter-sized, aggre coarse-grained The exoskarnirregular is in shapeandthick The oto theveins inthe VelardeñaMost of mining b ) disseminated; and ( Boletín de la Sociedad Geológica Mexicana Mexicana Mexicana Geológica Geológica Sociedad Sociedad la la de de Boletín Boletín c ) within veinlets in http://dx.doi.org/10.18268/BSGM2020v72n3a270719 a ) as ------3. Samplingandmethods Ore mineralization wasfound onlyindrill cores types. rock and assemblages mineral of sification the essential minerals and a preliminary clas of sample, which allowed a preliminary identification Cobre area). from Santa María area and 5from Reyna del del Cobre mine), and 13 in surface outcrops (8 (28 from Santa María mine and19from Reyna theunderground mine Cobre area), 47 infront of (139 fromSanta Maríaarea and48fromReyna de the Velardeña miningdistrict:187from drill cores For thisstudy, 247rocksamples were collected in lα, paeie ZK) n imnt (TiKα, ( MnKα); ilmenite and (ZnKα) sphalerite ClKα), (FKα, obsidian (CrKα), (NaKα, diopside SiKα), kaersutite CaKα, (CaKα), plagioclase KKα), chlorite (AlKα) and albite (AlKα), sanidine (BaLα, MnKα, KKα, TiKα, MgKα) and pyrope (MgKα), SiKα, FeKα, (for biotite were used we standards 1 μm, and diameter 30 a of s; counting the time of ( conditions: (WDS) analyses were out in the following carried UNAM versity UNAM ( probe (EMP)JEOLJXA-8900XR,at the Uni analyses were obtained with an electron micro persive X-rayspectrometry (EDS). Quantitative semi-quantitative chemicalby analyses dis energy obtain back-scattered electron(BSE) images and de México, UNAM Mexico ( versity of ( de Recursos Naturales the Natural Resources ( Department table-top electronscanning microscope (SEM), at sections were analyzed with a Hitachi TM-1000 microscopy. Additionally, all the polished thin standardished thinsectionsusing petrographic ples; Table 1). most samplesfor further (totaling analysis 47 sam or underground mine, from which were selected Instituto de Geofísica arsoi ecito a aeo each Macroscopic descriptionwasmade of Mineral assemblages were studied in 31pol ). Wavelength dispersive spectrometry b ) for carbonates: 15KeV, 10nA,beam a /72(3)A270719/2020 / 72(3)A270719/2020 ) for silicates: 20 keV, 20nA, beam Laboratorio Universitario de Petrología, ). This equipment allowed). This us to ), National Autonomous Uni fthe GeophysicalInstitute ) of Universidad Nacional Autónoma Departamento Departamento 5 5 ------

GEOLOGICAL SETTING/ The Velardeña Zn–(Pb–Cu) skarn-epithermal deposits, central-northern Mexico SAMPLING AND METHODS The Velardeña Zn–(Pb–Cu) skarn-epithermal deposits, central-northern Mexico SAMPLING AND METHODS Table 1.Sampledescriptionfrom theVelardeñadistrict. siderite; Sph— sphalerite; Wo—Wollastonite;Zrn —Zircon. — Ca-garnet;Hemhematite;— marcasite; Po—pyrrhotite;Grt KF—K-feldspar;— scheelite; Sd— Mc Py—pyrite;Qtzquartz; Sch galena; — fluorite;Gn — Fl Ca-clinopyroxene;epidote;chalcopyrite; Ep chlorite; Cpx — — Cpy — chalcopyrite; Chl— Cpy— chabazite; *Mineralogy complemented byX-ray Key:Amp—Ca-amphibole; diffraction. Apy—arsenopyrite; Brt —barite; Cal —calcite;Cha, 6 6 / / Boletín de la Sociedad Geológica Mexicana Geológica Sociedad la de Boletín Boletín de la Sociedad Geológica Mexicana Geológica Sociedad la de Boletín http://dx.doi.org/10.18268/BSGM2020v72n3a270719 /72(3)A270719/2020 /72(3)A2707192020 erated atwereScans 40kVand20mA. recorded randomly oriented sample. X-radiationgen was a towards nm) 0.15405 = (λ radiation Kα1,2 Cu source. anodetube also directs The the collimated equipped withaCuanodetube is as the X-ray tute ( Insti Geology the at located diffractometer 1400 aPhilips using (XRD), diffraction X-ray by ples 67. 49;pyrite,13; galena, 63;pyrrhotite, 2;sphalerite, clinopyroxene,garnet, calcite,22; fluorite, 14; 32; analyzed points was:adularia, 24; amphibole, 6; of number The (PbMα). crocoite and (AgLα) Ag (SbLα), stibnite (SKα), marcasite (CuKα), cuprite SnLα), (ZnKα, sphalerite CoKα), FeKα, (NiKα, AsKα, skutterudite were standards time the counting s; 30 a and of μm, 1 of diameter beam ( and BaLα); (for plagioclase and ZnKα) (for sphalerite CaKa), (for dolomite SrLa, (forFeKa),MgKa), MnKa, calcite NaKa, KKα, (for kaersutite were standards s; 30 the of time counting a and μm, 1 of diameter 600 heating-freezing stage at theGeosciences studies wereTHMSG- out onaLinkam carried Bodnarand Vityk (1994). Microthermometric of H values andisochores were calculatedan assuming and Van-den-Kerkhof and Hein (2001). Salinity Bodnar the recommendationsof following rejected, were suspected were fications FI where leakage, decrepitation, orother modi tures were measured in afewrelevant FI. Those additionally, halite and clathrate melting tempera clinopyroxenecite, quartz, garnet, and sphalerite; cal in hosted (FI) inclusions fluid from obtained and thenhomogenization temperatures (T (Tm),first, temperatures melting Ice crystals. ene calcite, and clinopyrox sphalerite, quartz, garnet Roedder 1984) were analyzed in to thecriteria of studied inthiswork. rocks of suite the of classifications mineralogical s/step. Table 1summarizes samplelocationsand from 4° 0.02° to and 70° 2 (2θ) with a step-scan of 2 –alsse,uigteeutoso state the equationsO–NaCl using system, of Bulk mineralogy was determined for 27sam determined was Bulk mineralogy Fluid inclusions of primary origin (according primary of inclusions Fluid Instituto de Geología, UNAM c fr ufds 2 KV 20nA, 20 KeV, sulfides: for ) Boletín de la Sociedad Geológica Mexicana Mexicana Mexicana Geológica Geológica Sociedad Sociedad la la de de Boletín Boletín http://dx.doi.org/10.18268/BSGM2020v72n3a270719 ). This instrument ). This et al. (1985) H ) were ------4.1. PARAGENETIC SEQUENCE 4. Results are given as δ as given are Tecnològics Universitat de Barcelona the Barcelona University ( of ters analyzer, and Scientific the at Cen Technological spectrometer interfaced to aTC-EAt elemental Finnigan MAT continuous flow isotope-ratio mass analyzed byspectrometrymass a Delta using C a microdrill under a binocular microscope. Samples were using separated were sulfides pure chalcopyrite, 4;sphalerite, 5). Nearly 7andgalena, pyrite, analyses: 5; mineral separates (number of °C for Tm andto±2°Cfor T showruns that measurements are accurate to ±0.2 Center ( gene stage. ( can be distinguished (Figure 6): ( paragenetic stages linkedtohydrothermal activity the textural microscopicanalysis, three of basis a complex, multistage hydrothermal event. On the by caused 5) and 4, 3, (figures deposition mineral textures sequential that an epigenetic, suggest are rich incalc-silicates and show replacement VelardeñaOre-bearing mineral assemblages of Zn-Pb mieralization. with adularia) and fluorite (± breccia and veins chlorite, ( Zn-Pb-Cu, ( ( with disseminated Zn-Cu-Pb mineralization, mineralization isdividedas( granitoids, marble, limestone and chert. Likewise, Velardeñadistrict: altered mining porphyry, rocks host the in occur Five broad typesof within ±0.1‰at 1σ. blo Troilite) standard. analytical precision The is relative to the V-CDT (Vienna-Canyon del Dia b ii ) retrograde skarn, ( ) retrograde skarn, asv rsm-asv ieaiaino ) massive orsemi-massive mineralization of Sulfur isotope data were obtained from 21 Centro de Geociencias, UNAM iv ) endoskarn, and( ) endoskarn, iii /72(3)A270719/2020 / 72(3)A270719/2020 34 ) retrograde skarn of epidote and epidote of ) retrograde skarn S‰ values, i.e. permildeviations c ) vein filling, and ( and filling, vein ) v ), calcite and quartz H , i . ) prograde skarn, ) prograde skarn, a Spain ) prograde skarn, ) prograde skarn, Centres Científics i Científics Centres ). Calibration ). The results). The d ) super 7 7 - - -

SAMPLING AND METHODS/ The Velardeña Zn–(Pb–Cu) skarn-epithermal deposits, central-northern Mexico RESULTS The Velardeña Zn–(Pb–Cu) skarn-epithermal deposits, central-northern Mexico RESULTS galena; Grt:garnet (andradite);KF:K-feldspar (adularia); Llt: lillianite;Po:pyrrhotite; Py:pyrite;Sch:scheelite; Sph: sphalerite. Apy:arsenopyrite; Cal:calcite;Chl:chlorite; Clz:clinozoisite;(actinolite); Cpx:clinopyroxene (diopside); Cpy:chalcopyrite;Gn: (Sp-2) withcalcite,fromlate veinmineralization (sample V-129-G,transmittedlight). Mineral abbreviations:Amp: amphibole sphalerite Zoned,Fe-poor ofsubhedral(I) crystals light). plane polarized light, transmitted VW-158-AB, (sample skarn assemblages poor sphalerite(Sp-2)withchalcopyrite disease(sampleVE-60-V,reflected light).(H)Scheelite and clinozoisite fromtheretrograde Fe- Crystals ofreflected (G) (sample C-05-C, light). inclusions withinchalcopyrite prismatic (F) Lillianite C-04-F, reflected light). of(E) Sulfideparagenesis(Sp-1) (sampleV-20-D,reflected galena, light). sphalerite sphalerite, pyrite, and arsenopyrite(sample transmitted light,planepolarized light).(D)Sulfideassemblageof pyrite,arsenopyrite, pyrrhotite, chalcopyrite,and minor Fe-rich transmitted light,planepolarized adularia,and light). (C)Retrogradeskarnassemblagewithactinolite, calcite(sampleV-26-B, C-05-C, (sample cryptocrystalline assemblage calcite-chlorite a to replacement showingandpartial anomalousanisotropy crystals zoning,with concentric clinopyroxene inclusions,and(sample C-23-N,transmittedlight). (B)Euhedral interstitial calcite andradite Figure 3 8 8 / / Petrographicimagesof mineral assemblage representative of theVelardeña (A)Euhedral oredeposits. andradite crystals Boletín de la Sociedad Geológica Mexicana Geológica Sociedad la de Boletín Boletín de la Sociedad Geológica Mexicana Geológica Sociedad la de Boletín http://dx.doi.org/10.18268/BSGM2020v72n3a270719 /72(3)A270719/2020 /72(3)A2707192020 is located in fractures and grains boundaries (sample C-04-F). Mineral abbreviations: Amp: amphibole (actinolite); Apy: arsenopyrite;Cal: Apy: (actinolite); amphibole Amp: Mineralabbreviations: boundariesC-04-F). andgrains (sample in fractures located is paragenesis of galena,pyrite,arsenopyrite, and marcasite,(sample C-04-F).(F)Assemblageof pyrite, arsenopyrite, and galenacrystals; Sulfide (E) V-88-J). (sample assemblage (supergene),siderite–marcasite replacivelate a by followed paragenesis Pyrite–arsenopyrite(D) replaced acicularcrystalswithin asphaleriteassemblage (sample V-122-F).(C)Actinolite byaquartz-calcitegroundmass (sampleV-26-B). (A) Euhedral andradite crystalswithconcentric zoning, clinopyroxene inclusions, and interstitial calcite(sample C-23-N). (B)Relicandradite Figure 4 calcite; Cpx:clinopyroxene (diopside); Gn: galena;Grt:garnet (andradite); Mc:marcasite;Py:pyrite;Qz:quartz; Sd:siderite; Sph:sphalerite. SEM-BSE(secondary electronmicroscopy inbackscattering electronsimage)of mineral assemblagesoftheVelardeña oredeposits. Boletín de la Sociedad Geológica Mexicana Mexicana Mexicana Geológica Geológica Sociedad Sociedad la la de de Boletín Boletín http://dx.doi.org/10.18268/BSGM2020v72n3a270719 /72(3)A270719/2020 / 72(3)A270719/2020 9 9

The Velardeña Zn–(Pb–Cu) skarn-epithermal deposits, central-northern Mexico RESULTS The Velardeña Zn–(Pb–Cu) skarn-epithermal deposits, central-northern Mexico RESULTS Photomicrograph ofthesphalerite crystals incalcitevein(sampleV-129-G, transmittedlight,planepolarized light).Cal: calcite;Sph:sphalerite. (C) exhibited. wheregenerationsare growthofmine, several Maria Santa Epithermalvein inside the (B) AB). (sample VW-158 deposit Maria Figure 5 10 10 (Figure 4a). Garnet crystals are crystals euhedral with (Figure 4a). Garnet relatively formed later than clinopyroxenegarnet that implies which 4a), and 3b, 3a, (figures María crystals, bothinReynade Cobre andinSanta in poikiliticgarnet as inclusions usually occurs in the exoskarn; clinopyroxene formed and garnet During the prograde stage calcic clinopyroxene ited (figures 3c to 3h). Such assemblages occur Such assemblages to 3h). 3c (figures ited scheelite, hematite, quartz and calcite were depos Pb pyrite, andpyrrhotite) and sulfosalts (lillianite, (pyrite, arsenopyrite, sphalerite, chalco galena, sulfides chlorite), and epidote amphibole, (calcic withquartzandcalcite.occurs after plagioclase,and pseudomorphs andalso abundant in the endoskarn, occurs as veinlet infills particularly is which Wollastonite, length. in μm roxenes occur asshort prismatic crystals, up to 300 rarely exceeddiameter,in 3mm whereas clinopy concentric zoninganisotropy,and anomalous and / / (A)Coresampleshowing epithermal and(white) veinoffluorite calcite (purple theskarnassemblagefrom gray)cutting theSanta Boletín de la Sociedad Geológica Mexicana Geológica Sociedad la de Boletín Boletín de la Sociedad Geológica Mexicana Geológica Sociedad la de Boletín 3 During theretrograde stage hydroussilicates Bi 2 S 6 ; andboulangerite, Pb 5 Sb http://dx.doi.org/10.18268/BSGM2020v72n3a270719 4 S 11 ), as well as /72(3)A270719/2020 - - - /72(3)A2707192020 occurs throughoccurs all the mineralized zones. Inveins, and Sphalerite sulfides. abundant Sphalerite most the are galena 3b). (Figure veinlets filling and garnets calcic replacing diameter, in μm ~50 to Chlorite isfound asradial aggregates, up skarn. in the endo exoskarn andplagioclase phenocrysts in the replaces3h) and commonly calcic garnets (Figure long μm 700 to up prisms forms Epidote radial aggregates. crystals,4c), assingle or forming (Figure grains included insphalerite and galena crystals,length,in which upto1mm are generally latter (Figure 4b). replace the and may pseudomorphically garnet with respectinterstitially to clinopyroxene and chalcopyrite, which as a coge canbe interpreted intergrowths pyrrhotite,with galena, pyrite and and aggregates mosaic mineralization itforms boundaries.grain Inthe massive or semimasive across,centimeters withcurvilinear equilibrium sphalerite develops anhedral crystals, upto a few Calcic amphibole occurs mostly asacicular Calcic amphiboleoccurs - - Figure 6 symbols arerelated totemperatures inFigures 10and 12.Blackbarsthickness corresponds torelativeabundance of minerals. Cobre deposit. Symbols: quartz:circles; calcite: squares; amphibole:triangles; garnet: hexagon; sphalerite: diamond. All colored l engnrtosadi ait fstructures ple vein generations andinavariety of events, which resulted in multi of asuccession of mineralization is alsocomplex, being the product paragenesis (Figurelate previous 5b). This skarn vein andbreccia mineralization that crosscutthe (Figureafter plagioclasephenocrysts 4d). pyrite aspseudomorphs In the endoskarn occurs (Figuressphalerite and minor galena 3d and 3e). chlorite and quartz in cogenetic association with calcite,with interstitial euhedral crystals gates of aggre exoskarn, pyrite ascoarse-grained occurs to 0.5 mm,while pyrrhotite is upto 200 µm.Inthe pyriteup is sizes. sizetures of andgrain grain The tex massive ores, inalarge occurring variety of pyrite andpyrrhotite. veinletsgalena crosscutpyrite, sphalerite, chalco all the mineralized zones. Atthe microscopiclevel, has boulangerite intergrowths. in Galena occurs generally associated with sphalerite and commonly netic association (Gilmer Comparative paragenetic tables oftheVelardeña skarnparagenetic and Comparative Left: vein deposits. SantaMariadeposit. Right: Reyna del The final hydrothermal stage produced the produced stage hydrothermal final The Pyrite and pyrrhotite are widespread in the Boletín de la Sociedad Geológica Mexicana Mexicana Mexicana Geológica Geológica Sociedad Sociedad la la de de Boletín Boletín et al. http://dx.doi.org/10.18268/BSGM2020v72n3a270719 , 1988).Galena is - - - - locaatrsi fvein mineralization and also characteristic of sphalerite is quartz. Apale, Fe-poor variety of with alternating as monomineralic bands occurs ite, chlorite andchabazite (Figure 3c). porphyritic rocks show alteration halos withseric aggregates, associated with quartz. Veins hostedin across, disseminated and occurs within the calcite laria develops rhomb-shapedcrystals, upto 1 mm aggregates.mosaic Adu forms calcite commonly and as chalcedony,anhedral aggregates whereas (Figure both as microcrystalline 5a). Quartz occurs abundant also adularia and fluorite and with quartz, calcite by filled mostly are Veins banding. crustiform and texture open-filling brecciation, as chalcopyrite. marcasite, inaddition to subordinate and galena in veins andbreccias are arsenopyrite, pyrite and aggregates. Other ore minerals that are present concentric zoning (Figure 3i), and ( 5c): ( (Figure textures open-filling different two forms Some of the veins are rich in fluorite, which fluorite, in rich are veins the of Some a ) subhedralcrystals, upto1cmacrosswith /72(3)A270719/2020 / 72(3)A270719/2020 b ) botryoidal 11 11 - -

The Velardeña Zn–(Pb–Cu) skarn-epithermal deposits, central-northern Mexico RESULTS The Velardeña Zn–(Pb–Cu) skarn-epithermal deposits, central-northern Mexico RESULTS 4.2.2. CALCIC CLINOPYROXENE AMPHIBOLE CALCIC 4.2.1. CHEMISTRY MINERAL 4.2. to ReynadeCobre samples, whileempty diamonds correspond toSantaMaríasamples; apfu: atomsper formula unit. et al.(2005). (f) K-feldspar (adularia)plotted onorthoclase–albite–anorthite triangular diagram.Blackdiamonds correspond Meinertworldwide by compiledcomposition range Zn skarndeposits forthe indicates dashedarea diagram; triangular (Ad) diopside (Di)–hedenbergite (Hd)triangular diagram. (e)Calcicgarnetsplottedonapyralspite (Pyr)–grossular (Gr)–andradite Fe+Mn correlation Mgvs. in calcicclinopyroxenes.al. (2012).(c) (d)Calcicclinopyroxenes plottedon johannsenite (Jh)– of Leakeetal.(2004).(b)Magnesium-iron-manganese amphibolesclassification ofcalcium amphibolesof Hawthorne et Figure 7 12 12 while Mg varies between 4.048 and 4.072 apfu 0.844 to 0.745atoms unit(apfu), per formula FeThe contentinthe amphiboles rangesfrom between 0.019 and0.431apfu,Mgfrom 0.544to clinopyroxeneThe have crystals Fe contents 2 andFigure 7b). (0.04 to 0.055 apfu; Table in manganese depleted are they because fields, actinolite and mingtonite et al. Hawthorne the amphibolegroup of clature of actinolite (Figure 7a). et al. Leake of classification (Tablethe to According 2). / / Composition diagrams of silicates (electron-microprobe data)fromtheVelardeña Compositiondiagramsof skarns.(a)Amphiboleplot silicates Boletín de la Sociedad Geológica Mexicana Geológica Sociedad la de Boletín Boletín de la Sociedad Geológica Mexicana Geológica Sociedad la de Boletín Additionally, according to the latest nomen (2004), all the analyzed correspond to crystals (2012), the crystals plot between (2012), the crystals the cum http://dx.doi.org/10.18268/BSGM2020v72n3a270719 /72(3)A270719/2020 - - /72(3)A2707192020 4.2.4. K-FELDSPAR K-FELDSPAR 4.2.4. GARNET CALCIC 4.2.3. are classified as diopside (cf. Morimoto bergite series (Di Figure 7c).Theybelong tothediopside–heden 0.978 apfu,andMnupto 0.045 apfu (Table 3; 3). (Meinert skarns Zn up to 2.3 mol %. All plotted crystals in the field of spite” component(Mg+Mn+Fe the “pyral zoning, concentric their in reflected variabletheir is composition (Ad are andradite,Although all the analyzed garnets crystallized from hydrothermal fluids; Dal-Negro fluids; hydrothermal from crystallized order between orthoclaseandmicrocline, usually adularia variety ( K-feldspar correspond to the of crystals The i.e., 97-53 cytl ihsm ereo of withsomedegree crystals et al., Hd 42-02 2005) (Figure 7e;Table Jh 04-01 2 +) being very low, ; Figure 7d)and 100-57 et al. Grs 43-00 , 1988). ), as - - 4.2.4. SULFIDES 4.2.4. SULFIDES (figures 3e, 4e, and4f). ver contentsrangingbetween 0.40and0.21wt.% PbS,galena, revealed althoughtheanalyses a sil As. 32.6 to33.4atom %of pure arsenopyrite, FeA of ideal formula crystals. Chemically, approximate thecrystals the al. pyrrhotite (cf. Lusk polytypeof the monoclinic S). Suchto corresponds composition atom %of position closeto Fe (figures 3,4d,and4e). arsenopyrite, pyrrhotite, andBi- and Sb-sulfosalts sphalerite, chalcopyrite, galena, pyrite,of consists Velardeña oreThe essentially assemblage of exceeding ~0.50wt.%(Table 3). as Or et al. variations between thetwo sphalerite types. significant show not do and concentrations low in Mn) are (0.136–2.219atomand manganese %of Cd) elements such ascadmium(<0.223 atom % of ies that were optically identified. In contrast, other % FeS), which with the two isinagreement variet sphalerite from veins ( ( skarns is associated with garnet (16–22 mol %FeS) correspond to sphalerite that 12.61 wt.%Fe),that so thehighestconcentrations variation(from the crystals in 2.69 to range of contents (Figure 8b; Table 4). Iron showsa wide between differences significant are Chemically,there ture. and galena, variety. Inbothcases, sphalerite is intergrown with veins and breccias, corresponding to the pale tite (dark) variety; and ( with calc-silicates,to themarma corresponding can be recognized (Figure 8): ( mineralization, the of stages different to sponding , 1993). w oe f curneo sphalerite, corre occurrence of Two modes of pure matches composition galena The that of up to 0.5 mmlongeuhedral Arsenopyrite forms yield achemicalEMP analyses Pyrrhotite com 17) Cmoiinly te ae classified are they Compositionally, 1978). , 96-92 Ab Sp-1 08-04 Sp-2 and An has“chalcopyrite disease” tex 7 00 S Sp-2 9 (Figure 7f), with barium not (a 44ao fFe; 55.6 (ca. 44.4 atom % of Sp-2 b , particularly inthe iron ) Boletín de la Sociedad Geológica Mexicana Mexicana Mexicana Geológica Geológica Sociedad Sociedad la la de de Boletín Boletín Sp-2 ) isiron-poor (4–6mol http://dx.doi.org/10.18268/BSGM2020v72n3a270719 , in calcite–fluorite in , a ) Sp-1 Sp-1 , associated ), whereas s S, with et ------4.2.6. CARBONATES CARBONATES 4.2.6. 22 O,2OH. Apfu

Table 1). amphiboles (sampleV-26-B, fromtheVelardeñaskarndeposits Table 2.Chemical compositionand structural formulas of calcic : atomsper formula unit.H stitial position with respect to silicates and sulfides and silicates to respect with position stitial Carbonate minerals occur inveins and in inter km. ~3–4 0.8–0.9 kbar, of corresponding to a depth is obtained thus pressure The 3e). and 3d (figures found inparagenesis with pyrite and pyrrhotite because they correspond to Table 4) that were selected (#10, 11, and12of Scott (1981) has been applied to three analyses Hutchinsonand sphalerite geobarometerThe of

Cr Al H Na MgO MnO Total Mn TiO SiO CaO K NiO FeO Fe Mg Na Ca Cr Ni Al Ti Si 2 K 2 2 2 . O 2

O O 2+ O 2+

O

2 * 2

3 3

apfu wt. % ......

/72(3)A270719/2020 / 72(3)A270719/2020 101. 19. 13. 57. 0 0 6 0 0 0 0 0 0 0 4 0 0 0 0 2 0 0 7 2 #1 ...... 00 00 81 47 14 15 03 71 00 00 05 79 05 02 04 05 00 12 92 17 70 90 48 54 2 O based onstructuralformula 102. 20. 13. 58. 0 0 6 0 0 0 0 0 0 0 4 0 0 0 0 1 0 0 8 2 #2 ...... Sp-1 00 00 54 45 12 17 02 80 00 00 07 75 05 02 04 90 00 13 00 20 05 02 72 08 crystals andwherecrystals 102. 19. 13. 57. 0 0 7 0 0 0 0 0 0 0 4 0 0 0 0 1 0 0 7 2 #3 ...... 00 01 37 38 17 17 00 95 00 00 05 84 04 03 04 91 00 15 94 19 82 03 96 04 13 13 -

The Velardeña Zn–(Pb–Cu) skarn-epithermal deposits, central-northern Mexico RESULTS The Velardeña Zn–(Pb–Cu) skarn-epithermal deposits, central-northern Mexico RESULTS

#2 to#3fromVW-158-AB,#4#7C-23-N; #9from C-02-E;#10to#12fromV-26-B,Table1). Table 3.Chemical compositionand structural (#1fromsampleC-04-F; fromtheVelardeñaskarndeposits formulas ofselectedsilicates based on6O);diopside. Kfs:Kfeldspars (structuralformula based on8O);adularia.n.a.:notanalyzed. Apfu 14 14 Cr Fe Al Na MgO MnO Total Mn TiO SiO BaO CaO K NiO FeO Fe Fe Mg Na Ba Ca Cr Ni Al Ti Si K : atomsperformulaunit.Grt:Ca garnets(structural formula based on12O);andradite. Px:Caclinopyroxenes (structural formula 2 2 2 2 . . 2

O O O 3+ 2+ O / 2+

/ O

2 2

3 3 3

Boletín de la Sociedad Geológica Mexicana Geológica Sociedad la de Boletín Boletín de la Sociedad Geológica Mexicana Geológica Sociedad la de Boletín

apfu wt. % ......

99. 16. 17. 65. 0 0 0 0 0 3 0 0 0 0 0 0 0 0 0 0 0 Kfs n.a. n.a. n.a. #1 ...... - - - 96 05 00 00 93 03 00 57 04 24 51 00 00 00 02 00 00 80 17 03 24

100. 15. 17. 65. 0 0 0 0 0 3 0 0 0 0 0 0 0 0 0 0 0 Kfs n.a. n.a. n.a. #2 ...... - - - 92 07 00 00 95 04 00 01 00 46 78 00 00 00 00 00 01 61 55 99

40

100. 12. 24. 53. 0 0 0 0 0 1 0 0 9 0 0 0 0 0 0 0 0 0 0 n. n.a. Px #3 ...... - - 00 02 98 00 04 98 00 00 54 52 00 22 01 85 00 00 67 30 02 http://dx.doi.org/10.18268/BSGM2020v72n3a270719 a. 06 56 16

92

100. 25. 54. 17. 0 0 0 0 0 0 0 0 0 0 0 1 0 0 1 0 0 1 0 n.a. n.a. Px #4 ...... - - 00 00 00 31 00 00 95 05 01 00 00 01 00 01 9 00 00 62 20 97 97 54

61 9

100. 26. 54. 17. 0 0 0 0 0 0 0 0 0 0 0 1 0 0 1 0 0 0 0 n.a. n.a. /72(3)A270719/2020 /72(3)A2707192020 Px #5 ...... - - 00 00 00 41 00 00 97 02 01 00 00 01 00 02 98 00 02 82 30 06 92 99

51

100. 25. 54. 18. 0 0 0 0 0 0 0 0 0 0 0 1 0 0 1 0 0 0 0 n.a. n.a. P #6 ...... - - 00 00 01 26 00 00 98 03 01 00 00 00 00 01 98 01 03 85 31 x 89 83 14

32

100. 26. 55. 18. 0 0 0 0 0 0 0 0 0 0 0 1 0 0 1 0 0 0 0 n.a. n.a. Px #7 ...... - - 00 00 00 29 00 0 97 02 01 00 00 01 00 01 99 00 01 63 39 08 28 03

71 0

33. 32. 98. 31. 0 0 0 0 0 2 0 3 0 0 2 0 0 0 0 n.a. n.a. n.a. n.a. Grt #8 ...... - - - - 00 25 00 00 02 06 01 07 00 02 81 00 01 16 17 23 52 10 77

34. 34. 97. 17. 1 8 0 0 0 2 0 3 0 0 2 0 0 0 0 n.a. n.a. n.a. n.a. Grt #9 ...... - - - - 58 69 00 00 02 06 01 07 00 02 81 14 16 33 43 37 35 96 91

100. 32. 35. 32. 0 0 0 0 0 2 0 2 0 0 2 0 0 0 0 # n.a. n.a. n.a. n.a. Grt ...... 10 - - - - 01 05 00 00 00 05 01 97 00 01 97 00 00 00 13 96 31 35

82

100. 33. 34. 32. 0 0 0 0 0 2 0 2 0 0 2 0 0 0 0 # n.a. n.a. n.a. n.a. Grt ...... 11 - - - - 00 00 00 00 00 05 01 99 00 00 95 00 00 00 14 07 97 36

54

99. 31. 33. 34. 0 0 0 2 0 2 0 0 2 0 0 0 0 0 0 #12 n.a. n.a. n.a. n.a. Grt ...... - - - - 00 00 00 01 01 99 00 04 94 00 01 03 14 05 41 98 51 05 78

to #2from sampleV-39-A;#3to#6from V-18-E;#7to#9from V-129-G;10to12from VE-02-AD,Table1). Table 4.Chemical compositionand structural formulas of selectedsphalerite (#1 fromtheVelardeñaskarnand veindeposits Total Mn Mn Ag Ag Cd Cu Cd Cu As As Zn Zn Pb Sb Sn Pb Sb Sn Fe Fe Bi Bi

S S .

wt. % atom % ......

53. 38. 10. 50. 99. 12. 0 33. Sp- 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 . #1 019 ...... 00 ...... 081 03 00 01 00 65 01 00 00 08 02 00 75 00 00 00 00 65 30 34 93 08 89 1

53. 38. 10. 50. 99. 12. 0 33. Sp- 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 . #2 002 ...... 00 ...... Boletín de la Sociedad Geológica Mexicana Mexicana Mexicana Geológica Geológica Sociedad Sociedad la la de de Boletín Boletín 242 00 00 00 00 01 00 00 02 63 00 00 00 04 00 02 72 93 32 09 66 06 58 1

http://dx.doi.org/10.18268/BSGM2020v72n3a270719 39. 50. 99. 11. 33. Sp- 0 9 0 0 0 0 0 0 0 0 54. 0 0 0 0 0 0 0 0 0 #3 ...... 00 ...... 03 78 00 03 01 21 00 00 00 06 00 05 02 24 00 00 00 00 60 34 81 43 79 2 1

39. 50. 99. 11. 33. Sp- 0 9 0 0 0 0 0 0 0 0 53. 0 0 0 0 0 0 0 0 0 #4 ...... 00 ...... 04 97 00 00 05 19 05 00 00 00 09 00 07 21 01 00 00 00 39 36 75 65 78 9 1

11. 33. 99. Sp- 53. 0 0 0 0 0 0 0 0 0 39. 0 0 0 0 0 50. 0 0 0 0 #5 10 ...... 00 .00 .00 ...... 03 02 03 07 21 02 01 01 02 05 18 09 00 00 00 68 62 65 9 5 2 1

11. 33. 39. 50. 99. Sp- 54. 0 0 0 0 0 0 0 0 0 0 9 0 0 0 0 0 0 0 0 #6 ...... 00 03 02 02 18 01 00 00 01 00 92 01 01 01 15 06 00 00 02 59 61 75 11 92 4 1

100. 61. 33. 45. 49. 0 Sp- 0 2 0 0 0 2 0 0 0 0 0 2 0 0 0 2 0 0 0 . #7 . . . .00 ...... 017 52 77 00 00 46 00 00 00 02 22 40 00 00 00 17 00 00 06 16 05 28 90 03 2

100. 33. 46. 50. Sp- 62. 0 3 0 0 0 0 0 0 0 0 0 2 0 0 0 0 0 0 0 0 #8 . . . .00 ...... 00 . . . 23 16 00 06 49 00 00 00 02 10 73 00 00 04 43 00 00 04 60 16 53 16 6 2 /72(3)A270719/2020

/ 72(3)A270719/2020

100. 62. 33. 46. 50. Sp- 0 3 0 0 0 0 0 0 0 0 0 2 0 0 0 0 0 0 0 0 #9 . . . .00 ...... 00 . . . 33 08 07 05 56 0 00 00 04 14 66 02 00 04 49 00 00 09 47 62 06 57 26 0 2

54. 100. 11. 33. 39. 50. Sp- 0 0 0 0 0 0 0 0 0 0 9 0 0 0 0 0 0 0 0 #10 . . .00 ...... 00 . . . 239 14 00 01 44 00 01 00 00 06 71 00 00 00 38 02 00 00 40 92 47 36 17 1

54. 11. 33. 39. 50. 99. Sp- 0 0 0 0 0 0 0 0 0 0 9 0 0 0 0 0 0 0 0 #11 . . .00 ...... 00 . . . 06 14 00 39 00 01 00 00 02 71 03 00 00 34 03 00 00 31 30 47 82 06 69 1

11. 33. 39. 50. 99. Sp- 54. 0 0 0 0 0 0 0 0 0 0 9 0 0 0 0 0 0 0 0 #12 ...... 00 . . . 01 00 01 02 38 00 00 00 00 00 76 00 01 01 33 01 00 00 41 78 57 31 82 2 1

15 15

The Velardeña Zn–(Pb–Cu) skarn-epithermal deposits, central-northern Mexico RESULTS The Velardeña Zn–(Pb–Cu) skarn-epithermal deposits, central-northern Mexico RESULTS

Table 5.Summaryoffluidinclusionsmicrothermometricdatafrom theVelardeñaskarndeposits. +samples forFI studyinReynade Cobre(undermine) from levels1,2,3,5,7,8amd9. clinopyroxenes; Grt—Cagarnets;Qtzquartz; Sp—Sphalerite. melting. #=number of analyzed inclusions,min.=minimum value,max.=maximum value.Abbreviations:Cal — calcite;CpxCa Key: Th=temperature of homogenization, Tm=temperature oficemelting (freezing pointdepression), *clathratemelting, **halite 16 16 + + VW / + + + + + + / VE- V RC- RC- V + + + + + C C RC- RC- RC- RC- RC- RC- S C C C C C V V V Boletín de la Sociedad Geológica Mexicana Geológica Sociedad la de Boletín Boletín de la Sociedad Geológica Mexicana Geológica Sociedad la de Boletín - - - ample RC #7 RC #3 RC #2 RC RC #1 RC - - 02- - 129------158- 07- 07- 36- 04- 04- 02- 02- 02- 81- 81- 200- N9 # 5 # N9 5 # N9 N8#6 N5#2 N5#1 N5#5 N5#5 N7#4 AD #2 M M C F F E E E S S G AB

T

Reyna de Cobre de Reyna Santa María L ocation ......

retrograde retrograde retrograde retrograde retrograde retrograde prograde prograde prograde prograde prograde prograde prograde prograde prograde prograde prograde prograde prograde prograde prograde prograde S vein vein vein vein vein tage http://dx.doi.org/10.18268/BSGM2020v72n3a270719

M Sp- Sp- Cpx Qtz Qtz Qtz Qtz Cal Cal Cal Cal Cal Cal Cal Cal Cal Cal Cal Cal Cal Cal Cal Cal Cal Cal Cal ineral Grt 1 2

15 28 13 18 11 16 17 18 15 20 12 21 11 11 32 10 20 23 18 16 /72(3)A270719/2020 /72(3)A2707192020 3 9 # 7 4 8 9 8

FIA b b d b b b b b b b b b b b c c c c a a a a c c a

- -

min 295/297/300 260/370/480 395/376/400 230/250/268 289/343/420 365/ 400/413/458 120/148/184 130/134/138 1 100/120/148 259/269/295 220/229/244 232/ 296/318/334 236/260/286 310/345/390 240/249/256 337/352/376 288/324/346 170/186/196 284/370/388 375/455/4 294/386/396 234/315/353 295/299/306 290/340/390 44/156/179 ./mean/max. Th(°C) 413/468 269/297 75

- - - - 22.0/ 18.0/ 21.0/ 23.2/ ------max./mean/min. - - 14.5/ 13.0/ 11.0/ 18.0/ 14.0/ 12.0/ 17.7/ 10.8/ 12.0/ 13.0/ 13.0/ 16.8/ 17.0/ 14.7/ - 7.0/ 4.2/ - - - - 8.0/ 8.1/7.2/6.1* 5.0/3.3/1.3* 8.7/ 4.5/ 6.9/ 1.0 / 1.0 Tm (°C) Tm ------27.5/ 20.0/ 23.4/ 24.8/ ------12.4/ 10.2/ - - - 14.5/ 14.4/ 13.5/ 19.5/ 14.0/ 12.0/ 19.9/ 12.5/ 13.1/ 13.7/ 14.9/ 17.6/ 18.9/ 14.7/ 9.9/ - 8.7/ 5.2/ 6.9/ - 6.7 ------35.0** 23.0** 26.0** * 29.2 13.3 ------7.0 15.5 14.7 8.7 9.5 6.9 14.5 19.8 16.0 21.0 14.0 12.0 21.0 14.0 14. 14.9 18.0 21.0 20.0 14.7

0 *

min./mean/max. Salinity (wt.% NaCl eq.) 16/16/16 21/22/23 15/16/18 16/17/18 17/18/19 17/19/21 20/21/23 20/21/22 13/13/13 18/18/18 10/10/10 31/34/35 33/34/36 12/14/17 13/13/13 32/35/40 18/18/18 11/16/19 17/18/21 15/17/19 30/32/33 21/22/23 18/18/18 9/11/14 7/14/18 7/8/13 4/5/7

4.3.1. REYNA DE COBRE FLUID INCLUSIONS INCLUSIONS FLUID COBRE DE REYNA 4.3.1. INCLUSIONS FLUID 4.3. In the Reyna de Cobre samples, it was possible shown inFigure 10. in Table 5andplot on aT Hedenquist andHenley, 1985). which impliesthat isabove thisgas 3.7 wt.%(cf. clathrates, in the veins, through of the formation and 9d).CO 9b,(figures 9c, halite always being solid the solid), calcite,areFI some poly-phased(liquid+vapor + phases (liquid + vapor) (Figure 9a). In late vein assemblages,skarn the FI are aqueous with two the In μm. 25 to 5 from size in ranging isolated, crystals, or tributed following growth zonesof FIhaveThe andare dis regular morphologies calcite, withupto3.3mol%MnCO3. atesbetween vary near pure calcite to manganoan Chemically, carbon 3i). these and 3g, 3a, (figures eq. (Figure 10;Table 5). NaCl wt.% 32–38 and 234–353°C, salinity,with wt.% NaCl eq.; 2–23 and °C, 220–390 salinity,with high to low 9–14 wt.%NaCleq.;( and °C, 100–148 salinity,with intermediate and data that partly overlap those above: ( of clusters three define which FI, calcite-hosted by T variation of range of widest The eq. NaCl wt.% ~10 salinity and °C salinity ~18 wt.% NaCl eq., and ( 21–23 wt.% NaCl eq., ( ( (FIA): assemblages FI different three to respond in the T wt.% NaCleq.(Figure 10a;Table 5). T possible crystals, to obtain results with from garnet also 18wt.%NaCleq.Itwas valuesand salinity of which yield the highestT to measure FI hostedby clinopyroxene crystals, a ) T H from 337 to 376 °C and salinity from 17 to 21 to from17 salinity and °C 376 to from337 The microthermometric data are microthermometric summarizedThe Microthermometry data fromMicrothermometry quartzdistribute H bten26ad~3 Cadslnt fof salinity and °C ~335 and 296 between H –salinity spaceinthreethat clusters cor 2 was detected particularly was FI, in some and ( b c ) high T ) medium to high T ) mediumtohigh H b ) T andsalinityisdisplayed Boletín de la Sociedad Geológica Mexicana Mexicana Mexicana Geológica Geológica Sociedad Sociedad la la de de Boletín Boletín H H versus salinity diagram versussalinity diagram , from 375 to 475 °C, 475 to 375 from , H of 395–400 °C and °C 395–400 of http://dx.doi.org/10.18268/BSGM2020v72n3a270719 H c ) T and very high H o 294–396 of a ) low T H and H - - - 4.3.2. SANTA MARIA FLUID INCLUSIONS FLUID MARIA SANTA 4.3.2. types are plotted. (b) Histogram of iron contents, in X%FeS. types areplotted.(b)Histogramof ironcontents, and Fe+CdMnplot,where veins.(a)Zn vs. 2sphalerite = 67,electronmicroprobedata)from theVelardeña skarns Figure 8 aiiy wt 1419 C ad – w. NaCl wt.% 4–7 and °C, 144–179 with salinity, plot (Figure 10b, Table 5): ( data are defined clusters inof a T 18wt.% NaCl eq.for As calcite, four salinity of T samples, witharange of analyzable quartz-hosted FI exclusively invein In the Santa María mineralized area, we found wt.% NaCleq. Sp-2 16–18 wt.% NaCl eq., and ( ºC and salinityof ures 3g and 10a; Table 5): ( (fig types sphalerite two the with correspondence revealed thein T Compositiondiagramsof allsphalerite crystals(n Two different populations of sphalerite FI are FI sphalerite of populations Twodifferent : T H f 1016 C n slnt o 20–22 of salinity and °C 170–196 of /72(3)A270719/2020 / 72(3)A270719/2020 H versusplot, havingsalinity a a H ) of 130–138 °C and °C 130–138 of Sp-1 a ) low T H : T –salinity binary –salinity binary H o 310–390 of H andlow 17 17 b - )

The Velardeña Zn–(Pb–Cu) skarn-epithermal deposits, central-northern Mexico RESULTS The Velardeña Zn–(Pb–Cu) skarn-epithermal deposits, central-northern Mexico RESULTS/ DISCUSSION

Key: Cpy,chalcopyrite;Gn,galena; Py,pyrite;Sph,sphalerite. 4.3.3. SULFUR ISOTOPES SULFUR 4.3.3. Table 6.Sulfur isotopedata, 18 18 V UASM VE- V VE- S C C C C sml AM2 fTable(sample VASM-22 6). of the Santa María mineralized area from avein of thelate generation ( to sphalerite sponds of -3.9‰that corre +2.6‰, except one value of are distributeda shortrange, in between -1.1and pre δ All 6. Table is and 11 Figure sulfides in sented of composition isotopic Sulfur deposit). the Reyna de Cobre eq., (equivalent to FIA (c) of NaCl wt.% 30–33 and °C, salinity,400–458 with wt.% NaCl eq.; and( 10–21 and °C, 230–468 with salinity, high and and 22–23wt.%NaCl eq.; ( eq.; ( V V V V V V V V V V - / V / - ample 122------129- - O2 O4 O4 O4 20- 20- 78- 75- 75- 39- 39- 39- 26- 18- Boletín de la Sociedad Geológica Mexicana Geológica Sociedad la de Boletín 88- Boletín de la Sociedad Geológica Mexicana Geológica Sociedad la de Boletín 200T 60------AC D D P R R A A A B E b D J F F F 22 G V

) low T

Reyna de Cobre de Reyna H and high salinity, with 120–184 °C, Santa María L ocation ...... δ

34 S (‰), for sulfideS minerals from theVelardeñaskarndeposits. d ) highT

c ) mediumtohighT retrograde retrograde retrograde http://dx.doi.org/10.18268/BSGM2020v72n3a270719 prograde prograde prograde prograde prograde prograde prograde prograde prograde prograde prograde prograde H andveryhigh vein vein vein vein vein S tage

34

S values Sp-2 Massivemineralization Massivemineralization Zn- with skarn Prograde Massive Massivemineralization Calcite vein Zn- with skarn Prograde Zn- with skarn Prograde Prograde Zn- with skarn Prograde Massiv Calcite vein Calci Endoskarn Massivemineralization Endoskarn Zn with skarn e Prograd Zn- with skarn Prograde Calcite vein Massivemineralization ), H /72(3)A270719/2020 - - /72(3)A2707192020

te vein te mineralization e

mineralization Classification skarn with Zn with skarn 5.1. TYPEOFDEPOSIT 5. Discussion

ntrso structure and mineral composition. In of in terms (Santa María and Reyna de Cobre) are very similar Velardeña occurrencesof twoThe studied skarn 346±25°C. result of OhmotoandRye (1979), with a themometer of mineral pair was calculated with the isotopic geo this respectively. of formation temperature The of isotopically analyzed, with δ have been and 4f) and 4e, 3e, (figures paragenesis Table 6), pyrite occur apparently andgalena in In one sample from Reyna de Cobre (C-04-F of

- - Cu Cu Cu Cu Cu Cu Cu ------Pb Pb Pb Pb Pb Pb Pb

Cpy - 1.0 0.8 0. 0.

9 7

- - - 0.9 0.9 Gn 34 0.9 0.0 0. δ

34 f+2.6and0.0‰, S of 5

S

(CTD)

- - - Sph 0.7 1.3 1.8 0. 1. 3. 0

.9 6 1 9

- 0.7 1.0 2.6 2.2 Py 0.5

- Figure 9 + solid (S) (halite) (sample V-81-S). (D) Fluid inclusion in calcite with liquid + vapor + solid (halite) (sample RC-N9 # 5); Qz: quartz. Qz: 5); # RC-N9 (sample (halite) solid + vapor + with liquid inclusion incalcite Fluid (D) V-81-S). (sample (halite) (S) solid + (sample C-07-M). (B)FIA (fluid inclusionassociation) insampleRC-N9 #5;(C)Fluid inclusionincalcitewithliquid (L)+vapor(V) Hutchinsonand Scott (1981), 0.8–0.9 kbar, con of usingthe sphalerite geothermometer skarns 1981). (Einaudi deposits imal, dike-related skarn mineralization canalsobe characterized as prox aureoles around the intrusive contact, the studied oritic composition), and ( porphyritic texture; to granodi granitic of stocks the precursormagmatism (dikes and the nature of et al allow(Einaudi usto categorize them skarns as zinc These characteristics sulfides.by (Cu) nied Zn–Pb largely accompa bycomposed andradite garnet betweenand limestonesare (anddikes) stocks both areas, occuralong the intrusive contact skarns Photomicrographs of fluid inclusions from the Velardeña skarns and veins. (A) liquid + vapor fluid inclusions in quartz inclusions fluid vapor + liquid (A) veins. and skarns Velardeña the from inclusions fluid of Photomicrographs The calculatedThe pressure for the Velardeña ., 1981; Meinert et al ., 2005). Considering ( b Boletín de la Sociedad Geológica Mexicana Mexicana Mexicana Geológica Geológica Sociedad Sociedad la la de de Boletín Boletín ) that skarns develop) that skarns as http://dx.doi.org/10.18268/BSGM2020v72n3a270719 et al a ., - - - - ) 5.2. PROCESSES ANDCONDITIONSOFFORMATION ucsino replacive mineralizingevents of a succession by form metasomatism, deposits through Skarn marized by Meinert occurrences, Zn skarn depositsin sum the field of spite”–andradite–grossular) fall, for bothstudied (“pyral diagram plotted in a ternary garnets of kbar) are generallyCu-rich (Shimazaki,1975). Velardeña,(1–3 whereas the skarns case of deeper (<1 kbar) are typically Zn- and Pb-rich, thisbeing crust (i.e.,Moreover, lessthan5km). shallow skarns that theyat firms formed hypabyssal inthe depths triggered by amagmatic-hydrothermal system, On the other hand, the chemical composition /72(3)A270719/2020 / 72(3)A270719/2020 et al . (2005)(Figure 7e). 19 19 - -

The Velardeña Zn–(Pb–Cu) skarn-epithermal deposits, central-northern Mexico DISCUSSION The Velardeña Zn–(Pb–Cu) skarn-epithermal deposits, central-northern Mexico DISCUSSION 20 20 Canet and clinopyroxenecalcic garnet ( produce hightemperature minerals, typically stage is dominated by progressive reactions that ture) stage ( stage and asubsequentretrograde (lower tempera generally including a prograde (high temperature) nta fhedenbergite (Figure 7d). instead of the clinopyroxene crystals,they so are diopside assemblages); and/or ( hematiteity (presentfield in of the studied mineral enhanced paragenesis, although this canbeexplained by ( magnetite in the studied reaction is the absence of this only drawback The of the prograde skarn. reaction (2) better foraccounts the evolution of in low below the temperature range for reaction (1), even T the and °C, ~375 at place temperature,taking of opyroxene byimplies a significant decrease garnet 10). (Figure clin 1998) According to our FIdata, the replacement of (Bowman, °C 335 to down mum temperature at which it can take place drops on temperaturegreater dependence and the mini (Figure 12).Ontheother hand, reactiona (2)has low in °C ~390–490 to shift may which °C, ~450–525 of temperatures, high it takesplacewithinarelatively narrowrange of + 9 hedenbergite + 2 O 9 quartz +CO 2 hedenbergite +calcite + 0.5O quartz thecalc-silicates involved, are (Figure 12): of the chemical variability regardless of formation, ( 4a). Two3a and possible reactionsleading garnet after clinopyroxene formed that garnet (Figures which indicates within poikiliticgarnet, inclusions clinopyroxene has arelict character as and occurs affected by CO ity but on temperaturelittle is dependent andis / / H Boletín de la Sociedad Geológica Mexicana Geológica Sociedad la de Boletín Boletín de la Sociedad Geológica Mexicana Geológica Sociedad la de Boletín range obtained in garnet (337–376 °C) is well is °C) (337–376 garnet in obtained range Reaction (1) impliesanincrease in O et al. f (CO f , 2009, 2011a). In the Velardeña skarns, (O e.g., 2 2 ) conditions (Figure) conditions 12a).Therefore, ( 2 Einaudi ) conditions, fallinguptothestabil 2 fugacity (Bowman, fugacity 1998). Besides, 2

b → ) thelowFe et al. 3 andradite + magnetite , 1981). The prograde , 1981). The f (CO http://dx.doi.org/10.18268/BSGM2020v72n3a270719 e.g., 2

→ 2+ Logan, 2000; Logan, /Mg ratio in 2 andradite + ) conditions 2 fugac 2 1 ) ) a /72(3)A270719/2020 - - - - - /72(3)A2707192020 ) mineralsis shown toskarnformation stages inFigures 6and 12. from SantaMariaDeposit. Theassignment oftheanalyzed (Table 2).(A)FIAsfrom TheReyna deCobredeposit. (B)FIAs inclusions analyzed intheVelardeña skarn and veindeposits homogenization temperatures (TH)of theindividual fluid Figure 10 ate rocks, through areaction that involves calcite into thecarbon magmas granitic of the intrusion having during orshortlyafter the skarn, formed of phase mineral first-appearing the been have may ditions (Bowman, 1998). Therefore, wollastonite f atpartial pressure,least 540 °C being with of high CO on crystallization stronglydepends ture of andinthe exoskarn. Itstempera the endoskarn the Velardeña bothin occurring skarns, stage of the prograde Wollastonite is another mineral of (CO Diagramshowing salinity(wt.%NaCleq.) vs. 2 ) or about 475 °C low at low at low °C 475 about or ) f (CO 2 ) con - - - 2 samples. Py:pyrite,Sp:sphalerite; Cpy:chalcopyrite;Gn:galena. from ReynadeCobresamples.(Bottom)Valuesfrom SantaMaría Values (Top) 6). (Table vein deposits and skarns Velardeña the from Figure 11 (Bowman, 1998;Figure 12a): and quartz and that from is independent ation of garnet. garnet. ation of scheelite, andrevealingalter the pseudomorphic forretrogradethe stage, hematite also finding and Velardeña theskarns confirmed above mineralogy the petrography2011a). The andSEMstudy of ( sulfides panied by quartz and calcite, andby base metal epidote, calcicamphiboles, and chlorite) accom hydrous silicates(commonly of essentially consist during theprograde stage(Table 5;Figure 10). at high temperature (T (Figureditions 12b).Besidescalcite, quartzformed reaction (3) at low univariant line of T values as high as ~470 °C (Table with 5), just below the FIAs), different to therefore, temperature conditions (corresponding, range of Velardeña in awide calcite formed of in the skarns calcite +quartz Retrograde deposits assemblagesskarn Zn in analysisrevealedOur microthermometry that Histograms showingHistograms e.g., Einaudi → wollastonite +CO et al. δ H 34 : 390–400 °C), therefore °C), 390–400 : SCDT (in ‰) values of sulfidesof values (in ‰) SCDT 1981; Canet Boletín de la Sociedad Geológica Mexicana Mexicana Mexicana Geológica Geológica Sociedad Sociedad la la de de Boletín Boletín http://dx.doi.org/10.18268/BSGM2020v72n3a270719 f 2 (CO H et al. ( reaching , 2009, 2 ) con f 3 (O ) 2 - - - ) that most T noteworthy is It 12). and 10 (figures °C ~335 at between prograde andretrograde be stages should and, therefore,garnets the temperature boundary later conditions accountfor the replacement of at temperaturesformed (T inVelardeñaing intoaccountthat calcic garnets and low takes place at 390 °C and high hematite andradite + 3 CO ( the following reaction (Figure 12): mineral replacement could be explainedThis by mation that are contrasting with those of skarns, skarns, mation that are contrasting with those of for 2007) andshowand Albinson, of conditions Camprubí (cf. deposits epithermal low-sulfidation structures are similar to the typical Mexican de Cobre mineralized areas. mineralized These laria are foundSanta both in María andReyna al. quist andHenley, 1985;Wilkinson,2001; Canet e with cooler, oxidizing and dilute water (cf. Heden changes12). These canbe explained by mixing stages), there is a general increase in retrograde and prograde the (whichcomprises °C ~220 to °C 475 over from Velardeña skarns, the the paragenesis of involved intheevolution of (Figure 10). obtained from calcite other than that from veins (Figure 12d),according to thelowest T °C 220 around be could stage retrograde the of °C. 346 isotopic (sulfur) equilibrium temperatures of 345 °C; Table 5), as well as galena and pyrite, with limit, according tothe T ( sphalerite iron-rich sulfides, the Regarding 10). the temperature dropped below thislimit (Figure in largethese minerals were amounts when formed thatindicating °C, 335 lowerthan are quartz and Sp-1 , 2011b). hsrato sidpneto the reaction of This isindependent Veins rich in calcite, fluorite, quartz and adu and quartz fluorite, calcite, in Veinsrich Accompanying the temperature decline the otherthe lowerOn hand, temperature limit ) was deposited around) wasdeposited thistemperature f (CO H /72(3)A270719/2020 / 72(3)A270719/2020 values obtained from FIincalcite 2 ) (Bowman, 1998;Figure 12c); tak 2

→ 3 quartz + 3 calcite + H measurements (average: H ) down to 337 °C, the °C, 337 to down ) f (CO 2 4 ) or at 335 °C f (O ) f (O 2 H ) (Figure values 2 ) and 21 21 - - - - t

The Velardeña Zn–(Pb–Cu) skarn-epithermal deposits, central-northern Mexico DISCUSSION The Velardeña Zn–(Pb–Cu) skarn-epithermal deposits, central-northern Mexico DISCUSSION (diopside); Grt: garnet (andradite); Hem:hematite; Hd: hedenbergite; Mag: magnetite;Qz:quartz;Sph: sphalerite; Wo:wollastonite. (CO paths forprograde(A,B,and C)and retrograde (D)stagesof formation of theVelardeña skarns.Dashed at lines:univariantcurves Figure 12 22 22 2 ) of at 1.5MPa;solid lines:univariantcurves eCbe,aogwt h curneo adularia de Cobre), alongwiththeoccurrence of salinity (FIA“ NaCl eq. (figures 9b, 9c, and 9d).This variation in strong variations insalinity(inFI),from 7to 23% FI;and( clathrates during the freezing of of ( remarkably ( roughly overlapping theresults inthisstudy. values from -3.5‰ to 2.5‰ from Santa María, and Rye, 1979).Gilmer indicates a magmatic origin for sulfur (Ohmoto between -1.1 and+2.6‰(Table 6), unequivocally δ of variation of eralizations were found too. general range The sulfur, and min vein differences between skarn of al (cf. deposition Canet (Figuresystem 10), probablycontrolling metal hydrothermal the affected boiling that indicates / / b ., 2016).With respect to the isotopic composition ) high CO Boletín de la Sociedad Geológica Mexicana Geológica Sociedad la de Boletín Boletín de la Sociedad Geológica Mexicana Geológica Sociedad la de Boletín Temperature vs. O2fugacity diagram(Ca–Fe–Si–C–O–Hsystemat500kbar; after Temperaturevs. Bowman 1998)showing suggested general 2 a pressure, revealed by the formation ) temperatures (T d ” in Santa ” Maria and“ 34 S in sulfides from the skarns, the from sulfides in S et al et al. ., 2011b;Cruz-Pérez (1988) reported δ reported (1988) H http://dx.doi.org/10.18268/BSGM2020v72n3a270719 blw 0 °C; 200 below ) f (CO c ” in Reyna” 2 ) of 6MPa.Mineral abbreviations: Ad:andradite; Cal:calcite;Cpx:clinopyroxene 34 c et S /72(3)A270719/2020 - /72(3)A2707192020 ) in the vein mineralizing fluid (which sulfate–sul (which fluid mineralizing vein the in source (cf. OhmotoandRye, 1979). would correspond, inboth cases, to a magmatic an equal total whichsulfur isotopiccomposition, from starting even significant) is fractionation fide sulfides may account for higher for account may sulfides -3.9‰. This of δ lowest the us gave that María) Santa (fromcorresponds to analysis a sphalerite grain mineralization. among stagesof differences of effects the reflecting likely 11), ure δ distributionthe of in analyses ismuch higher, no regularity is observed Rye, 1979). In Santa María, where the number of between these minerals and H different the with agrees pyrite (Figure > sphalerite > galena 11), which δ Cobre, de Reyna In n h ohr ad te ny en sulfide vein only the hand, other the On 34 S depletion relativeS depletion to the skarn 34 34 S values follow the order S values per mineral (Fig 34 S fractionation factors 2 f S (Ohmoto and (O 2 ) conditions 34 S value, - - f 6. Concludingremarks Santa María, are very similarin( occurrences, two ReynaThe skarn de Cobre and whether they are stackedortelescoped. ores,are and/orporphyry-type overprinting skarn typically polymetallic and/or Ag-rich, andsome this, inthe Mexican telescoped deposits context are (Ixtacamaxtitlán, Puebla).deposits According to Cosalá, Sinaloa), but alsoinother epithermal metallogenetic history,( notonlyfor skarns several other telescoping processes inthe Mexican toe, 1994). Moreover, Camprubí (2013) mentioned resulting in atelescoped (cf.mineral system Silli to overprint deposits, and earlier the deeper skarn have allowed at veins highcrustal levels formed an overprinting process. faulting should Normal veins suggest stages) and the epithermal grade and T ticularly insphalerite (Fe content, isotopic values par characteristics, ore in differences Significant stage produced actinolite, clinozoisite and chlorite low in conditionsof °C, 335 to °C ≥470 from temperatures at place stage took with calcite and minorquartz. This wollastonite, andradite and diopside, along of prograde stagecharacterized is by the formation stage and asubsequentretrograde stage. The cive mineralizing events, includingaprograde composition. togranodioritic granitic of ceous limestonesandOligocene and dikes stocks km 3–4 to along the intrusivedepth) contact between Creta equivalent kbar; 0.8–0.9 = (P crust at hypabyssal formed skarns, zinc the in depths most productive Mexico. incentral-northern the María mine, whichone of historically was economicpotential with Santa of well in terms Reyna couldbe comparable as de Cobre skarns and ( fluids; mineralizing of evolution and conditions the orebodies; ( composition andparagenesis of hs krsfre yasceso frepla by formed of asuccession skarns These Velardeña are occurrencesof twoThe skarn c oreo sulfur. Therefore,) source of the prospective H ) between the skarn (prograde and retro) between the skarn f (CO Boletín de la Sociedad Geológica Mexicana Mexicana Mexicana Geológica Geológica Sociedad Sociedad la la de de Boletín Boletín 2 http://dx.doi.org/10.18268/BSGM2020v72n3a270719 ). The retrograde). The a ) structure, e.g b ., - - - - - ) References Acknowledgements constitute on the whole a telescoped skarn–epi they the skarns; that are contrasting with those of inboth formation study areas, showing conditionsof are found adularia and quartz fluorite, mixing withcooler, oxidizing anddilutewater. increase in there the skarns, a general is of in theformation °C. 220 Accompanying to the temperature decline involved dropped temperature until °C 335 stage took place fromite and boulangerite). This chalcopyrite andpyrrhotite), and sulfosalts (lillian galena, sphalerite, arsenopyrite, (pyrite, sulfides along withsubordinate hematite, scheelite and accompanied by abundant quartz and calcite, Aguirre-Díaz, G. J., G., Labarthe-Hernández, tive comments. also thank the anonymousreviewers for construc and foron the helpful manuscript.comments We Lehmann, Teresa Ubideand Lisard Torró iAbat XRD analyses. WeBissig, thank Thomas Bernd Carlos Linares. Teresathanked for PiPuig is the BSE images were obtained with the assistance of SEM-EDS and WDS analyses and 1661. The were supportedbythe Catalan project 2014-SGR- S.A. de C.V., andthe stable isotope measurements project This was sponsored by IndustriasPeñoles, mineralization. purely andepithermal magmatic for both skarn sulfuris sourceThe mineralsystem. of thermal Epithermal veins with calcite,Epithermal sphalerite, in Volcanology10: Amsterdam, Elsevier, Modelling and Response, Developments Martí, J. (eds.), Caldera Volcanism:Analysis, Madre Occidental, Mexico,Gottsmann, J., in the Sierra of and graben-calderas Flare-up Gutiérrez-Palomares, I.,2008,Ignimbrite Tristán-González, M., Nieto-Obregón, J., f (O /72(3)A270719/2020 / 72(3)A270719/2020 2 ,wihacut o rcs f), which accountsfor aprocessof 23 23 - - -

CONCLUDING REMARKS/ The Velardeña Zn–(Pb–Cu) skarn-epithermal deposits, central-northern Mexico ACKNOWLEDGEMENTS/REFERENCES The Velardeña Zn–(Pb–Cu) skarn-epithermal deposits, central-northern Mexico REFERENCES 24 24 Ambriz, M. D.,Ambriz, 1979, Geología yacimientosy Camprubí, A., Albinson, T.,Camprubí, A.,Albinson, 2007, Epithermal Camprubí, A., 2013,Tectonic andMetallogenietic 2009, Majormetallogenic Camprubí, A., provinces Bowman,J. R.,1998,Basicaspectsand Bodnar, R.J., Vityk, M.O., 1994,Interpretation Bodnar, J., Reynolds, J., Kuehn, 1985, Fluid C.A., Barboza-Gudiño, J. R.,Hoppe,Gómez- M., Barboza-Gudiño, J. R.,Tristán-González, / / Boletín de la Sociedad Geológica Mexicana Geológica Sociedad la de Boletín Boletín de la Sociedad Geológica Mexicana Geológica Sociedad la de Boletín de Ingenieros de Minas, Metalurgistas y Convención Nacional de la Asociación en Velardeña, Dgo. 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