Summary:
Catalina Huanca is a medium-sized carbonate-replacement (Zn-Pb-Ag) deposit located in the Andean Cordillera of southern Peru. The Catalina Huanca mineralization is located at the base of a major Tertiary eastward thrust and consists of veins and replacement bodies. It is controlled by a NE trending horsetail fault structure cutting the foreland Tertiary red beds (previously attributed to the Permo-triassic Mitu Group; Davila et al., 2012) and the overthrusted Pucara Group limestones. Spacially associated pre-ore igneous rocks include rhyolitic and trachytic dikes.
Mineralization at Catalina Huanca comprises seven stages with contrasting mineralogy. Stage I corresponds to the hightemperature skarn replacement, with biotite and subordinate diopside, pyroxmangite, andradite, and ilvaite. It is followed by stage II, with high-temperature hematite replaced and overgrown by magnetite (mushketovite). Stage III consists of adularia, and abundant euhedral pyrite and quartz with minor arsenopyrite, while stage IV is dominated by Fe-rich sphalerite with chalcopyrite disease in part replacing the early pyrite. Stage V is characterized by early fluorite associated with hematite, quartz, Fe-poor sphalerite, fahlore, enargite, chalcopyrite, and galena. Stage VI corresponds to the epithermal evolution of the system, with abundant siderite-rhodochrosite as replacement and open space fillings, followed by kaolinite. Finally, stage VII is characterized by the presence of carbonates (subhedral or muddy facies) and minor apatite.
The goal of the present study is to characterize the mineralizing fluids and their evolution. A large number of samples (>50) has been used to define the paragenetic sequence of the mineralization. Of these, about fifteen key mineralized samples were selected from Stages III and IV for fluid inclusion analyses in ore and gangue minerals, combining traditional microscopy with near-infrared (NIR) microscopy and microthermometry. This approach allows tracing the hydrothermal fluid evolution and the P-T-X conditions of ore formation.
Abundant primary and secondary L-V inclusions are found in sphalerite (early and late), but only secondary inclusions in fluorite. First results on fluorite show Th ranging from 150° to 250°C and salinities from 8 to 11 wt% NaCl eq. Further studies will include microthermometry measurements on sphalerite-hosted inclusions, cathodoluminescence petrography, electron microprobe analyses of sphalerite, Raman spectroscopy and LAICP-MS analyses of individual fluid inclusions in gangue and ore minerals.