Petrography and petrology of listwaenitesin the east of Khoosf

The studied area is situated in southwestern Birjand (South Khorasan). Lithologic units which are studied contains part of the late Cretaceous coloured melange, Cretaceous and Paleogen flysh sediments, Neogen congolmerate and Tertiary volcanic rocks. The listwaenite of this area often appears along fault zone, boundary of units, bedding planes and schistiosity as yellow and brownish vein. The effect of CO2 bearing hydrotermal solutions on mentioned units, in suitable physico - chemical and termodynamic conditions, caused Listwaenitization reactions. Field and microscopic' studies revealed that alteration process comprises pre-sta~e reactions (specially serpentine and talc forming reactions in ultrabasic rocks) and main reactions of listwaenitization which in primary mineral paragenesis is changed to silisic - carbonate assemblages listwaenite). Abundance and type of minerals is depended on composition of primary rock, PH, Eh, T, PCOl and PH)o' Microscopic studies and XRD analysis show presence of magnesite, breunerite, dolomite, calcite, smithsonite, quartz, clinochlore, talc, muscovite, chromite, pyrite and magnetite. Also SEM analysis and polyshed section studies represents Fe, Ni, Fe-Ni-Co sulphur that must be considered as pathfinder minerals for prospecting of Au, Ag, Hg, ....