Geology, geochemistry, fluid inclusions and O–H stable isotope constraints on genesis of the Lake Siah Fe-oxide ± apatite deposit,NE Bafq, Central Iran

The Lake Siah iron ± apatite deposit is situated in the Bafq Mining District(BMD),Central Iran.The iron ± apatite orebodies are hosted by a succession of rhyolite,rhyolitic tuff,trachyandesite,and andesite of Lower Cambrian age.The host rock has undergone widespread alteration and mineralization stages including Na(albite-quartz),followed by Na-Ca(albite-calcite-amphibole-magnetite ± quartz ± epidote),magnetite-apatite,K(biotite ± K-feldspar),hydrolytic(sericite-quartz),and argillic(kaolinite-montmorillonite ± dickite),respectively.Electron microprobe analyses(EPMA) from magnetite and hematite show significant variations of trace elements.Based on Ni/Cr+Mn and Ca+A1+Mn versus Ti+V diagrams,the majority of magnetite samples belong to Kiruna-type deposits.At least,three generations of fluid inclusions,including solid-bearing(L+V+S)(Type Ⅰ),liquid-rich(L+V)(Type Ⅱ-A),vapor-rich(L+V)(Type Ⅱ-B),and liquid or vapor mono-phase(Type Ⅲ),are recognized in quartz and apatite.The solidbearing fluid inclusions in quartz completely homogenized at temperatures of 150 to> 530℃ with salinities of 30-58 wt% NaCl equiv.Liquid-rich fluid inclusions in apatite homogenized to a liquid phase at 175-210℃,whereas the vapor-rich fluid inclusions homogenized to a vapor at 335-350℃.Oxygen isotope analysis was carried out on quartz and magnetite.The hydrogen and oxygen isotopic compositions of quartz(δOvalues of 7.57-11.04‰) show that with progress in time the oreforming solutions gradually evolved from a magmatic to meteoric-dominated source.