Ore-forming Fluid Characteristics And Research On Metallogenic Mechanism Of The Hutouya Lead-zinc Polymetallic Deposit,Qinghai Province,China

The Qimantage region is located in the Southwestern Margin in the Qaidam Basin and the eastern section of Eastern Kunlun Orogenic Belt.It consists of North Qimantage magmatic arc,Qimantage ophiolitic tectonic melange belt and North Kunlun magmatic arc and etc.Hutouya lead-zinc polymetallic ore district is located in the Early Paleozoic magmatic arc of the eastern section of Eastern Kunlun Qimantage.Based on studying and analyzing the previous results and having finely field geological work,through geological characteristics,fluid inclusions and isotope geochemical characteristics in-depth study,we can determine the mineralization geological body,ore-forming material sources and mineralization processes.Finally,the author discussed the metallogenetic mechanism combined with the metallogenic chronology and regional tectonic evolution background.Hutouya orebodies were controled by the northwest-striking fault and contact zone of the rock body and formation,hosted in the adamellite and surrounding rock contact zone and nearby marble mainly assume lenticular,stratiform-like vein.The ore-hosting rocks are marble,dolomite and limestone.Ore minerals include magnetite,sphalerite,chalcopyrite,pyrite,galena and hematite;gangue minerals comprise garnet,diopside,epidote,calcite,mica,quartz,fluorite and feldspar.The main structure of the ore mining include massive structure,disseminated structure,brecciated structure and banded structure;ore texture comprise automorphic granular texture,hypidiomorphic granular texture,metasomatic texture,cataclastic texture,radial texture and oolitic texture.The mineralization process is divided into skarn stage,retrograde alteration stage and quartz-sulfide stage.Sulfur and lead isotope studies have shown that metallogenic materials of Hutouya deposit mainly come from the magma,partly from the surrounding rock that the ore-forming fluid through it.Hydrogen and oxygen isotopic researches indicate that the of metallogenic hydrothermal fluid mainly contained magmatic hydrothermal and mixed into the meteoric water and increasing gradually with mineralizationprocess.The results of fluid inclusions suggest that metallogenic hydrothermal fluid is medium-high temperature,medium-low salinity,medium density.The two characteristics of exsolving fluid in skarn stage are a medium-high temperature,low salinity and medium-high temperature,high salinity and there are massive fluid boiling in this stage,as the mineralization process,the temperature and salinity of the ore-bearing hydrothermal fluid were gradually decreased.During the early uartz-sulfide stages when the main ore minerals were precipitated,the ore-forming fluids had gone through an immiscible process(boiling)that may have caused the precipitation and concentration of Pb,Zn,Fe and Sn.