PROXIMAL TO DISTAL GEOCHEMICAL SIGNATURES OF HYDROTHERMAL MINERALIZATION IN THE CANDELARIA CU-AU DISTRICT, CHILE
Vein and wallrock geochemistry show high Cu concentrations (>1000 ppm) closest to ore (<100 m), then Zn (>600 ppm), Pb (>100 ppm), and Mn maxima increasingly farther away. The Mn maximum (>10,000 ppm) occurs 1-3 km from ores; farther along faults. The Mn concentrations return to background (~1,300 ppm) at distances of ~5-6 km. Calcite composition shows a similar trend, but without Zn and Pb. The Sr isotope composition of near ore vein calcite is close to primitive magmatic signature (~0.704) and increases to be similar to that of the carbonate wallrocks (~0.707; open ocean carbonate signature) at ~4.5 km distance. Wallrock 87Sr/86Sr ratios decreases towards ores, likely due to the addition of hydrothermal calcite closer to ores. O isotope compositions of water in equilibrium with the vein calcite are higher (~13.0-2.5‰) near ores, due to contributions from magmatic and meteoric waters and dissolved wallrock carbonates. It decreases away from ores, down to ~-10‰ at ~5 km, then remains at such values 5-8 km away from ores, indicating more meteoric water component and less dissolved wallrock carbonate. The water C signature is dominated by wallrock carbonates near ores (~1.4 to -2‰) and decreases away to -8 to -4‰ at ~5 km, then remains at such values at 5-8 km distances, probably due to less wallrock contribution and more organic components.