Dehydration of hot oceanic slab at depth 30–50 km: KEY to formation of Irankuh-Emarat Pb Zn MVT belt, Central Iran

摘要: Abstract Irankuh-Emarat is an important district of Pb Zn MVT-type deposits in Iran. The are hosted by Lower and Upper Cretaceous dolostone which several stages mineralization were identified. deposition sulfide minerals occurred spatially within or close to shale-siltstone units with replacement open space filling textures. Field observations, mineralogical petrographic studies show different degrees alteration related mineralization. Dolomite, particularly Fe-rich dolomite, ankerite, bitumen silicified rocks associated the principal Hydrothermal fluids at Irankuh had low sulfidation form dolomite ankerite pyrite shale formations. Chemical analysis representative samples belt that sphalerite, Fe content varies between 0.3 5.2%, Cd 150–2000 ppm. In galena, Ag 150–1200 ppm Sb 140–1200 ppm. Fluid inclusion study shows homogenization temperatures (Th) 150–260 °C fluid salinities 9–21% (NaCl, wt% equiv). observations showed high ore was deposited as member favourable for chemical reaction. this paper, we present a conceptual model formation MVT district. We suggest hydrothermal originated from dehydration oceanic subduction slab, liberated Pb, Zn, other metals, may have removed metals organic material continental crust. down dip thermal gradient slab about 18 °C/km (hot slab). More than 90% all water released depth zone forearc region (depth 30 50 km). isotopic compositions 206Pb/204Pb 18.42 18.45; 208Pb/204Pb 38.53 38.62 207Pb/204Pb 15.63 15.65. Very radiogenic Pb-isotopes indicate source slightly contaminated basement rocks. Deep-seated thrust faults formed during early subduction, (Late Cretaceous?) played role upward migration shallow depths.