Isotopic constraints on fluid/rock ratios in carbonate rocks: Barite-sulfide mineralization in the Schwaz Dolomite, Tyrol (Eastern Alps, Austria)

摘要: Abstract The significance of isotopic data on constraining the physical conditions fluid-rock interaction and mineralization processes in carbonate rocks is discussed, based example barite-tetrahedrite Lower Devonian platform carbonates Western Greywacke Zone (Tyrol, Austria). Available strontium, oxygen, carbon sulfur are complemented with oxygen for barite. Barites homogeneous δ18OV-SMOW δ34SCDT values ∼ + 15.4 23.5‰ , respectively. Their 87 Sr 86 ratios vary between 0.7128 0.7113 first generation 0.7117 0.7123 younger remobilization. dolomitic host rock shows a significant variation Sr, O C composition non-mineralized mineralized zones: 0.7076 0.7133, δ18OV-SMOW-values +28.11 +20.65‰, δ13CPDB-values −1.15 3.06‰. Fluid/rock volume order 1.3–3.2 calculated open-system behaviour by modelling shifting capacities. isotope combined other geological evidence support following genetic model: Subsequent to synsedimentary sulfide during an Early rifting stage, collision tectonics Carboniferous time led expulsion Ba- Sr-rich orogenic brines, which evolved from metamorphic fluids consisting essentially H2O some CH4, into external sedimentary fold-and-thrust belt. brines remobilized sulfides, mixed meteoric waters carbonates, reacted evaporitic horizons finally caused recrystallization dolomite precipitation barite structurally weak zones at 70–130°C. During later Alpine orogeny supergene oxidation products were formed, sulfates, sulfides further late faults fractures.