| Abstract |
Microthermomemc techniques were applied to samples from mantos and veins in the Hualgayoc District, Peru. Mineralisation in the district is hosted mainly in rocks from the Hualgayoc group (Mesozoic marine sedimentary and volcanic rocks). Primary and secondary inclusions in sphaleriteand gangue minerals were examined petrographically and their homogenisation and freezing temperatures measured. Three stages of sphalerite, with intermittent deposition of quartz, calcite and rhodocrosite are recognized. The results indicate that mineralisation took place at temperatures from about to above 350?C; the lowest values corresponding to vein mineralisation and the highest to the mantos. The highest apparent salinity values were observed in the manto samples (more than 16% NaCl) in contrast tolower salinities (4.3% NaCl) measured in one sphalerite sample from the San Filipe Vein. From the Mantos area to the north and the east, a trend of decreasing temperature and salinity exists. No evidence of boiling was observed in the sphalerite samples; however, boiling may have occurred during deposition of quartz and in the veins. |