Mineralogical characterization of Sn deposits from the Santa Fe District, Bolivia

The Sn-Zn-Pb-Ag Japo-Santa Fe-Morococala ore deposit is located in the Central Andean Belt province. The ore mineralization is hosted in a Paleozoic metasedimentary sequence and porphyritic Oligocene-Miocene igneous rocks. Ore minerals occur in veins and disseminations. Two types of ore mineralization are distinghished: (1) An early Sn mineralization and (2) a late Sn and Zn-Pb-Ag mineralization. Mineral association consists mainly of quartz, pyrite, cassiterite, other sulfides and sulfosalts. Cassiterite, up to 0.25 wt% In, constitutes the earliest mineralization. Galena and sphalerite are the main sulphide minerals. Sphalerite shows up 0.24 wt% In. Stannite group is represented by stannoidite, kësterite, and sulfides of the Sn-Cu-Zn-Fe-S system. Sulfosalts include sakuraiite, potosiite, franckeite, freibergite, tetrahedrite, myargyrite, boulangerite, jamesonite, zinckenite, cylindrite and andorite. In this deposit, after an epigenetic magmatic stage, a long greisen-hydrothermal event took place with several episodes of metal deposition.Peer ReviewedPostprint (published version

Mineral chemistry of In-bearing minerals in the Santa Fe mining district, Bolivia

The Santa Fe mining district is located in the Central Andean tin belt of Bolivia and contains several SnZn-Pb-Ag deposits. From the economic point of view, the most important deposits of the district are Japo, Santa Fe and Morococala. Beyond the traditional metal commodities, the Central Andean Tin Belt could become an exploration target for indium, owing to the potential of the ore-bearing paragenesis with high concentrations of this technology-critical element. In the Santa Fe mining district, the ore occurs as two main types: (a) Sn-rich cassiterite-quartz veins, and (b) Zn-Pb-Ag veins with sphalerite, galena and stannite mineral phases. The In content in igneous rocks is between 1.5 and 2.5 ppm, whereas in the ore concentrate it attains up to 200 ppm. The 1,000×In/Zn ratio in concentrate ranges from 25 up to 4,000. Exceptionally high In values were found in sakuraiite from Morococala deposit (2.03 wt%). Sakuraiite in this deposit shows evidences for a link between stannite and kësterite trend of solid solutions. There is a noteworthy exploration potential for strategic metals in this district and even in similar deposits elsewhere in the Central Andean tin belt.Peer ReviewedPostprint (published version

Mineral chemistry of In-bearing minerals in the Santa Fe mining district, Bolivia

[eng] The Santa Fe mining district is located in the Central Andean tin belt of Bolivia and contains several Sn-Zn-Pb-Ag deposits. From the economic point of view, the most important deposits of the district are Japo, Santa Fe and Morococala. Beyond the traditional metal commodities, the Central Andean Tin Belt could become an exploration target for indium, owing to the potential of the ore-bearing paragenesis with high concentrations of this technology-critical element. In the Santa Fe mining district, the ore occurs as two main types: (a) Sn-rich cassiterite-quartz veins, and (b) Zn-Pb-Ag veins with sphalerite, galena and stannite mineral phases. The In content in igneous rocks is between 1.5 and 2.5 ppm, whereas in the ore concentrate it attains up to 200 ppm. The 1,000×In/Zn ratio in concentrate ranges from 25 up to 4,000. Exceptionally high In values were found in sakuraiite from Morococala deposit (2.03 wt%). Sakuraiite in this deposit shows evidences for a link between stannite and kësterite trend of solid solutions. There is a noteworthy exploration potential for strategic metals in this district and even in similar deposits elsewhere in the Central Andean tin belt.[spa] El distrito minero Santa Fe se encuentra ubicado en la Faja Estannífera de la cordillera Central Andina de Bolivia, que aloja diversos depósitos de Sn-Zn-Pb-Ag. Desde el punto de vista económico, los depósitos más importantes en este distrito son los de Japo, Santa Fe y Morococala. Más allá de los productos metálicos tradicionales, la Faja Estannífera podría convertirse en un blanco de exploración para elementos como el indio, por el potencial de su paragénesis mineral con altas concentraciones de este elemento, crítico para el desarrollo de tecnología. Los yacimientos minerales del distrito de Santa Fe se presentan en dos tipos principales: (a) depósitos ricos en Sn, constituidos por vetas de cuarzo con casiterita, y (b) depósitos diseminados de Zn-Pb-Ag, con esfalerita, galena y estannita. El contenido de In en las rocas ígneas del distrito, varía entre 1,5 y 2,5 ppm, mientras que en el concentrado de los minerales de mena alcanza hasta 200 ppm de In. Asimismo, la razón 1.000×In/Zn en concentrados de mineral oscila entre 25 y 4.000. Fases de sakuraiíta del yacimiento de Morococala contienen valores excepcionales de In (hasta 2.03% en peso). La sakuraiíta en el distrito minero de Santa Fe muestra evidencia de ser el vínculo mineralógico entre la tendencia general de las soluciones sólidas de estannita y kësterita. Existe un potencial de exploración obvio para metales estratégicos en este distrito e incluso en depósitos similares en otras zonas de la Faja Estannífera en la cordillera Central Andina

Mineralogía del depósito de Sn del distrito de Santa Fe, Bolivia

El depósito de Sn-Zn-Pb-Ag de Japo-Santa Fe-Morococala se encuentra en la provincia metalogenética del cinturón Central Andino. La mineralización se encuentra encajada en una secuencia metasedimentaria paleozoica y rocas ígneas porfídicas del Oligoceno-Mioceno. Las menas se encuentran en vetas y diseminaciones. Se distinguen dos tipos de mineralización: (1) una mineralización temprana de Sn y (2) una mineralización tardía de Sn y Zn-Pb-Ag. La asociación mineral consiste principalmente en cuarzo, pirita, casiterita, sulfuros y sulfosales. La casiterita, hasta 0,25% en peso de In, constituye la mineralización más temprana. La galena y la esfalerita son los principales sulfuros. La esfalerita presenta 0,24% de In. Los minerales del grupo de la estannita están representados por estannoidita, kersterita y sulfuros del sistema Sn-Cu-ZnFe-S. Las sulfosales incluyen sakuraiita, potosiita, franckeita, freibergita, tetrahedrita, myargyrita, boulangerita, jamesonita, zinckenita, cylindrita y andorita. En este depósito, después de una etapa magmática epigenética, se produjo un largo evento greisen-hidrotermal con varios episodios de deposición de metales.Peer ReviewedPostprint (published version

El sistema skarn-epitermal de Zn–(Pb–Cu) de Velardeña, Durango (México): nuevos datos fisicoquímicos de los procesos de mineralización

The Velardeña mining district is economically the most important of Durango state. The ore deposits occur in different skarn zones developed within the intrusive contact between Mesozoic limestones and Eocene granitic stocks and dikes. The most important ore deposits are related to the Santa María dike and Reyna de Cobre porphyritic stock (separated from each other by 10 km). They occur as irregularly shaped replacement masses developed near the intrusive contact and have a skarn paragenesis dominated by calc-silicates and sulfides. The mineral assemblages show replacement textures and are dominated by calcic clinopyroxene (Di97-53Hd42-02Jh04-01) and garnet (Ad100-57Grs43-00) in the exoskarn, with wollastonite particularly abundant in the endoskarn. Hydrous silicates are actinolite, epidote, and chlorite, whereas sulfides include pyrite, sphalerite, pyrrhotite, galena, chalcopyrite, and sulfosalts. Scheelite, hematite, quartz, and calcite are also present. According to sphalerite geobarometry, the skarns formed at hypabyssal depths (~3–4 km). They developed by a succession of replacive mineralizing events, including (a) a prograde stage at temperatures from =470 to 335 °C in conditions of low f(CO2), followed by (b) a retrograde stage from 335 to 220 °C. There was a general increase in f(O2), accompanying the temperature decline during the formation of the system, which accounts for a process of mixing with cooler, oxidizing, and dilute water. During the retrograde stage, wollastonite calcic garnet and clinopyroxene formed. On the other hand, hydrous silicates, sulfides, sulfosalts, scheelite, and hematite crystallized during the retrograde stage. Skarn mineralization is crosscut by veins of calcite, fluorite, adularia, and sphalerite. The vein mineralization formed at temperatures below 200 °C. The different ore deposits of Velardeña constitute a telescoped skarn–epithermal mineral system.This project was sponsored by Industrias Peñoles, S.A. de C.V., and the stable isotope measurements were supported by the Catalan project 2014-SGR-1661. The SEM-EDS and WDS analyses and BSE images were obtained with the assistance of Carlos Linares. Teresa Pi Puig is thanked for the XRD analyses. We thank Thomas Bissig, Bernd Lehmann, Teresa Ubide and Lisard Torró i Abat and for helpful comments on the manuscript. We also thank the anonymous reviewers for constructive comments.Peer ReviewedPostprint (published version

El sistema skarn-epitermal de Zn–(Pb–Cu) de Velardeña, Durango (México): Nuevos datos fisicoquímicos de los procesos de mineralización

[eng] The Velardeña mining district is economically the most important of Durango state. The ore deposits occur in different skarn zones developed within the intrusive contact between Mesozoic limestones and Eocene granitic stocks and dikes. The most important ore deposits are related to the Santa María dike and Reyna de Cobre porphyritic stock (separated from each other by 10 km). They occur as irregularly shaped replacement masses developed near the intrusive contact and have a skarn paragenesis dominated by calc-silicates and sulfides. The mineral assemblages show replacement textures and are dominated by calcic clinopyroxene (Di97-53Hd42-02Jh04-01) and garnet (Ad100-57Grs43-00) in the exoskarn, with wollastonite particularly abundant in the endoskarn. Hydrous silicates are actinolite, epidote, and chlorite, whereas sulfides include pyrite, sphalerite, pyrrhotite, galena, chalcopyrite, and sulfosalts. Scheelite, hematite, quartz, and calcite are also present. According to sphalerite geobarometry, the skarns formed at hypabyssal depths (~3-4 km). They developed by a succession of replacive mineralizing events, including (a) a prograde stage at temperatures from ≥470 to 335 °C in conditions of low f (CO2), followed by (b) a retrograde stage from 335 to 220 °C. There was a general increase in f (O2), accompanying the temperature decline during the formation of the system, which accounts for a process of mixing with cooler, oxidizing, and dilute water. During the retrograde stage, wollastonite, calcic garnet and clinopyroxene formed. On the other hand, hydrous silicates, sulfides, sulfosalts, scheelite, and hematite crystallized during the retrograde stage. Skarn mineralization is crosscut by veins of calcite, fluorite, adularia, and sphalerite. The vein mineralization formed at temperatures below 200 °C. The different ore deposits of Velardeña constitute a telescoped skarn-epithermal mineral system.[spa]El distrito minero Velardeña es económicamente el más importante del estado de Durango. En él, las mineralizaciones comprenden diferentes zonas de skarn, desarrolladas entre el contacto de calizas mesozoicas, stocks y diques del Eoceno. Los depósitos de Velardeña más importantes están relacionados al dique Santa María, y el stock porfídico Reyna de Cobre (separados entre sí ~10 km). La mineralización ocurre como reemplazamiento, formando cuerpos irregulares cerca del contacto con los intrusivos, caracterizados por una paragénesis típica de skarn (calcisilicatos y sulfuros). Las asociaciones minerales muestran texturas de reemplazo dominados por clinopiroxeno cálcico (Di53Hd42-02Jh04-01) y granate (Ad100-57Grs43-00) en el exoskarn, y wollastonita particularmente abundante en el endoskarn. Los hidrosilicatos son actinolita, epidota y clorita; los sulfuros incluyen pirita, esfalerita, pirro tita, galena, calcopirita y sulfosales. Scheelita, hematita, cuarzo y calcita también están presentes. El geobarómetro de esfalerita estima que las mineralizacionestipo skarn de Velardeña se formaron a profundidades hipabisales (~ 3-4 km). La mineralización metálica se desarrolló por una sucesión de eventos de reemplazamiento, que incluyen (a) una etapa prógrada a ≥470 a 335 °C y baja f(CO ), seguida por (b) la etapa retrógrada de 335 a 2202°C. Hubo un aumento general de f(O ), durante el descenso de temperatura en laformación del yacimiento, debido a la mezcla de fluidos mineralizantes con agua más fría, oxidante y diluida. Durante la etapa retrógrada, se formaron wollastonita, granate cálcico y clinopiroxeno. La etapa prógrada dio lugar a la formación de hidrosilicatos, sulfuros (inclu- yendo sulfosales), scheelita y hematita. Además de las mineralizaciones tipo skarn en Velardeña, hay vetas epitermales de calcita, fluorita, adularia y esfalerita, cortando los calcosilicatos. La mineralización en estas vetas se estima que se formó a <200 °C. Por ello, es plausible proponer que los depósitos minerales que conforman el distrito minero Velardeña constituyen un sistema skarn-epitermal telescópeado

Nanoscale Structure of Zoned Laurites from the Ojén Ultramafic Massif, Southern Spain

We report the first results of a combined focused ion beam and high-resolution transmission electron microscopy (FIB/HRTEM) investigation of zoned laurite (RuS2)-erlichmanite (OS2) in mantle-hosted chromitites. These platinum-group minerals form isolated inclusions (<50 um across) within larger crystals of unaltered chromite form the Ojén ultramafic massif (southern Spain). High-magnification electron microscopy (HMEM), high angle-annular dark field (HAADF) and precession electron diffraction (PED) data revealed that microscale normal zoning in laurite consisting of Os-poor core and Os-rich rims observed by conventional micro-analytical techniques like field emission scanning electron microscope and electron microprobe analysis (FE-SEM and EPMA) exist at the nanoscale approach in single laurite crystals. At the nanoscale, Os poor cores consist of relatively homogenous pure laurite (RuS2) lacking defects in the crystal lattice, whereas the Os-richer rim consists of homogenous laurite matrix hosting fringes (10–20 nm thickness) of almost pure erlichmanite (OsS2). Core-to-rim microscale zoning in laurite reflects a nonequilibrium during laurite crystal growth, which hampered the intra-crystalline diffusion of Os. The origin of zoning in laurite is related to the formation of the chromitites in the Earth’s upper mantle but fast cooling of the chromite-laurite magmatic system associated to fast exhumation of the rocks would prevent the effective dissolution of Os in the laurite even at high temperatures (~1200 ºC), allowing the formation/preservation of nanoscale domains of erlichmanite in laurite. Our observation highlights for the first time the importance of nanoscale studies for a better understanding of the genesis of platinum-group minerals in magmatic ore-forming systems.This research was supported by Spanish projects: RTI2018-099157-A-I00 and CGL2015-65824-P granted by the “Ministerio de Ciencia, Innovación y Universidades” and Ministerio de Economía y Competitividad” (MINECO) respectively. Additional funding was provided by the Ramón y Cajal Fellowship RYC-2015-17596 granted by the Spanish MINECO to JMGJ. A. Jiménez-Franco is supported with a postdoctoral grant (CVU 350809) from the National Council on Science and Technology (CONACYT) of Mexico

Experiences of mining engineering students in cooperation for development

Future engineers, in addition to technical knowledge, should incorporate in their academic curricula aspects that contribute to make mining a sustainable activity. This will contribute to changing the concept that society has about mining and to be a socially accepted activity. In the mining engineering studies at the Universitat Politècnica de Catalunya (UPC), students have the opportunity to develop cooperation projects together with professors and other staff members. They all collaborate with artisanal miners from different underdeveloped countries, mainly from Latin America, and contribute to making mining more environmentally friendly. Moreover, they have the opportunity to acquire a social sensitivity that can be of great importance during the development of their professional career. This study presents some experiences of undergraduate, master, and doctoral students in cooperation activities in mining. The projects were developed as a collaboration between UPC and universities or NOGs in Latin America. The activities have been carried out in underdeveloped areas where mining is practiced with a high environmental impact and poor use of resources. A survey among the participants in the projects shows the students' favourable perception of this activity.This work has been carried out with the support of the Centre de Cooperació per al Desenvolupament (CCD-UPC), which financed the Cooperation projects. We thank the NGO Mineria per al Desenvolupament for its contribution to the development of the projects

Desarrollos metodológicos para el estudio de nanominerales y nanopartículas de elementos de alto valor tecnológico en yacimientos minerales

Hasta hace aproximadamente una década, las nanopartículas y nanominerales eran unos auténticos desconocidos en el ámbito de los yacimientos minerales. Sin embargo, el progresivo desarrollo de técnicas analíticas más potentes ha permitido caracterizar partículas cada vez de menor tamaño, lo cual ha llevado aparejado una verdadera explosión de la nanociencia y sus posibles aplicaciones directas en los procesos tecnológicos o nanotecnología

The Poopó Polymetallic Epithermal Deposit, Bolivia: Mineralogy, Genetic Constraints, and Distribution of Critical Elements

The tin-rich polymetallic epithermal deposit of Poopó, of plausible Late Miocene age, is part of the Bolivian Tin Belt. As an epithermal low sulfidation mineralisation, it represents a typological end-member within the "family" of Bolivian tin deposits. The emplacement of the mineralisation was controlled by the regional fault zone that constitutes the geological border between the Bolivian Altiplano and the Eastern Andes Cordillera. In addition to Sn and Ag, its economic interest resides in its potential in critical elements as In, Ga and Ge. This paper provides the first systematic characterisation of the complex mineralogy and mineral chemistry of the Poopó deposit with the twofold aim of identifying the mineral carriers of critical elements and endeavouring to ascertain plausible metallogenic processes for the formation of this deposit, by means of a multi-methodological approach. The poor development of hydrothermal alteration assemblage, the abundance of sulphosalts and the replacement of löllingite and pyrrhotite by arsenopyrite and pyrite, respectively, indicate that this deposit is ascribed to the low-sulphidation subtype of epithermal deposits, with excursions into higher states of sulphidation. Additionally, the occurrence of pyrophyllite and topaz has been interpreted as the result of discrete pulses of high-sulphidation magmatic fluids. The δ34SVCDT range in sulphides (−5.9 to −2.8 ) is compatible either with: (i) hybrid sulphur sources (i.e., magmatic and sedimentary or metasedimentary); or (ii) a sole magmatic source involving magmas that derived from partial melting of sedimentary rocks or underwent crustal assimilation. In their overall contents in critical elements (In, Ga and Ge), the key minerals in the Poopó deposit, based on their abundance in the deposit and compositions, are rhodostannite, franckeite, cassiterite, stannite and, less importantly, teallite, sphalerite and jamesonite