Phosphates from the La Argentina and La Rosario veins (Mina Capillitas), Catamarca

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Pablo A. Yaciuk
Fernando Colombo
Karina L. Lecomte


Mina Capillitas (Catamarca, Argentina) is a high to intermediate sulfidation epithermal deposit (Cu - Zn - Pb ± As - Sb - Au - Ag). Phosphates are scarce at the deposit. Studies with SEM-BSE and electron microprobe (WDS mode) confirmed the presence of aluminum phosphate-sulphates (APS), pyromorphite and fluorapatite. APS occurs as rhombohedral (pseudocubic) crystals with strong compositional zoning, showing substitution between Sr and Ca, and S and P. They are part of a solid solution dominated by svanbergite SrAl3(SO4)(PO4) (OH)6 and crandallite CaAl3(PO4)(PO3OH)(OH)6. Crystal cores are enriched in P and Ca; their concentrations decrease rimwards, associated to an increase in Sr and S. APS are associated to hübnerite, tennantite-(Zn), pyrite, chalcopyrite, enargite, galena, sphalerite and roquesite. Pyromorphite Pb5(PO4)3Cl occurs as long prismatic crystals showing steep bipyramids, or filling microscopic veinlets. Its occurrence within algal mats hanging from the gallery roofs at the Santa Rita Mine is remarkable. Pyromorphite shows partial substitution of Pb by Ca (up to 3.32 wt.% CaO) and minor amounts of Mn, Fe and Zn. Elements in tetrahedral coordination other than P are present in negligible amounts. Fluorapatite is magmatic and is an accessory in the granite that hosts the mineralized veins. It forms subhedral to anhedral crystals that are F-rich (~3.5 wt.%). Textural relations and mineralogical associations suggest a hypogenic origin for the APS minerals, related to an early stage of the high sulfidation mineralization. Pyromorphite has a supergenic origin, probably enhanced by microbial activity in some occurrences.

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Yaciuk, P. A. ., Colombo, F., & Lecomte, K. L. (2021). Phosphates from the La Argentina and La Rosario veins (Mina Capillitas), Catamarca. Revista De La Asociación Geológica Argentina, 78(3), 375-389. Retrieved from

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