The formation of (Ni-Co-Sb)-Ag-As ore shoots in hydrothermal galena-sphalerite-fluorite veins

Abstract Unusual hydrothermal native As-sulfide ± Ag arsenide antimonide sulfosalt ore shoots and their co-genetic sulfide-fluorite-barite-quartz host veins, which are common in the region whole Central Europe, were investigated at three localities Schwarzwald, SW Germany, to understand physico-chemical processes governing change from a normal (= common) an exceptional shoot regime. Based on fluid inclusions, formation of gangue minerals is result binary mixing between NaCl-rich brine CaCl 2 -rich (both ~ 20 wt% NaCl aq.). This correlation, major minor composition, temperature (~ 150 °C), ? 34 S signature identical (within error) veins. Thermodynamic modeling indicates that must have resulted redox conditions by local influx volumetrically reducing agent, probably hydrocarbons. The elemental content mineralogy each locality (Ag-As-rich: Münstertal; Ag–Ni-As-rich: Urberg; Ag–Ni-As-Sb-rich: Wieden) reflect metal mixed fluid, while mineral textures, successions, assemblages thermodynamically and, regarding sulfur, kinetically controlled. vein sulfides requires addition sulfide, most sulfide-bearing rocks, because thermodynamic kinetic reasons suggest two vein-forming metal-bearing fluids not source sulfur. final textures influenced later remobilization As Ag. results number sulfosalts, mostly proustite-pyrargyrite. Interestingly, greater stability Sb-endmember sulfosalts enables them form even As-dominated systems.