Geology and fluid inclusion of Wadi Sharis Neoproterozoic orogenic gold deposits in northwestern Yemen

The Wadi Sharis orogenic gold deposit in northwestern Yemen is related to the fault and shear zones vein at medium depth in the crust in the Neoproterozoic meta-sedimentary and meta-volcanosedimentary succession of greenschist to amphibolite facies metamorphism． Three distinct fluid inclusion types have been identified in the gold-bearing quartz sulphide veins of the deposit: ( 1) type I: vapour-liquid two-phase ( VH2O － LH2O ) ， ( 2) type II: three-phase CO2 ( VCO2 － LH2O － LCO2 ) and ( 3) type III: vapour-rich ( LCO2 － VCO2 ) inclusions． Six analysis of individual fluid inclusion indicate the fluid inclusions comprise mainly of H2O and CO2 ． Formation P-T conditions recorded by fluid inclusions in quartz crystals correspond to 180℃-380℃ and up to 130 MPa，as indicated by high-density CO2 bubbles ( up to 0. 98 g /cm3 ) observed in some inclusions． The estimated crystallization pressures correspond to approximately 4-10 km of overburden，assuming a lithostatic load． The salinity ranges from 0 to 22 wt%． The deposit holds at 0. 2-5 g /t Au and contains low-moderate salinity．