Microthermometry of enargite-hosted fluid inclusions from the Lepanto, Philippines, high-sulfidation CuAu deposit
1995; Elsevier BV; Volume: 59; Issue: 19 Linguagem: Inglês
10.1016/0016-7037(95)00282-5
ISSN1872-9533
AutoresD.P. Mancano, Andrew R. Campbell,
Tópico(s)Geochemistry and Geologic Mapping
ResumoThe spatial relation between porphyry and high-sulfidation epithermal deposits is particularly well revealed in the Mankayan mineral district of northern Luzon, Philippines, where the Lepanto high-sulfidation CuAu deposit lies over and adjacent to the Far Southeast (FSE) porphyry CuAu deposit. Consequently, a study was undertaken to characterize the fluids responsible for epithermal mineralization in this environment. The ore stage at Lepanto consists of enargite-luzonite (Cu3AsS4), pyrite, tennantite-tetrahedrite, and chalcopyrite. Infrared petrography of the enargite reveals variable transparency, with growth banding and twinning visible in euhedral specimens. Two phase (liquid > vapor) fluid inclusions occur as primary and secondary types ranging from vapor) fluid inclusion. This inclusion yielded a salinity of 1.2 eq. wt% NaCl. There is a large discrepancy in Th and apparent salinities between the enargite mineralization and the subjacent porphyry deposit despite contemporaneous formation, suggesting that the hot, (>500°C) hypersaline, magmatic brines associated with porphyry mineralization did not directly ascend to the elevation of the enargite deposit. However, absorbtion of magmatic vapors into overlying meteoric water may have created the mineralizing fluid of the Lepanto deposit. As this liquid moved to the northwest along the Lepanto fault, it was cooled and diluted by mixing with groundwater, resulting in enargite deposition.
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