Geochemical Characteristics And Discussion On The Mineralization Of The Saishitang Cu Deposit,Qinghai

The SaiShitang Cu deposit is located in the convergence zone between East Kunlun and West Qinling,southeast region of Ela Mountain structural belt,the eastern margin of Kuhai-Saishitang tectonic melange belt.The SaiShitang Cu deposit belongs to SaiShitang-RiLonggou metallogenic belt of Ela polymetallic metallogenic belt.Combining with achievements done by former scientists and the detailed results of field geological survey,geological features of ore deposit,fluid inclusion and isotope geochemical characteristics of this very deposit have been further studied,meanwhile the properties of metallogenic rock bodythe,source of ore-forming materials and mineralization process in this ore deposit have been revealed in this paper as well.At last the genesis of this ore deposit has been discussed while the metallogenic model has also been initially established on account of specifically regional tectonic evolution and geochronological data.The ore bodies of SaiShitang Cu deposit which are stratiform-like,lenticular,cystic occurred in the skarn contact zone and surrounding rock.The ore-bearing wall rocks are marble and metamorphic siltstone.Structure is controlled by detachment fault,slip fault and the skarn contact zone.Metallic minerals are chalcopyrite,pyrite,magnetite,pyrrhotite,galena,sphalerite,arsenopyrite;nonmetallic minerals are dominated by garnet,diopside,calcite,sericite and so on.The ores are mostly massive,disseminated,stratiform-like and thin vein in structure,while some of them are idiomorphic-subhedral,structural residual,interstitial structures.The mineralization process can be divided into three stages:the skarn stage,retrogressive metamorphism-oxide stage and sulfide stage.The intrusive rocks in mining Area are mainly quartz diorite.The time of the intrusive rocks is about 220Ma.The magma was intruded during the medium-later Indo-Chinese.The magmatic complex is from comagmatic evolution.Major element show that the geochemical characteristics of the intrusive rock is high-K calc-alkaline and meta-aluminous.Composition of trace element and rare earth elements exhibits its typical skarn deposit characteristics.The fluid inclusions homogenization temperature shows that ore-forming fluids translate from early high temperature and high salinity to late low temperature and low salinity.The ore-forming fluids belongs to NaCl-H2O system.The ore-forming fluid occurred the boiling event in fluid evolution.S and C isotopic studies have suggested that the sulfur source and the carbon resource are derived from deep magmatic.Characteristics of orogenic belt Pb isotopic suggest that its source is controlled by magmatic and surrounding rock.The medium Indo-Chinese,SaiShitang-Ela region is activity effected by East Kunlun and West Qinling,where occurred large range the tectonic magmatic activity.the formation of magma enter into surrounding rock.The magmatic which is rich in metallogenic material occurred contact metasomatism in contact zone with carbonate rock.The boiling action and other effects break physico-chemical equilibrium,Precipitation and enrichment of metal sulfides formate formate copper deposit.