Characteristics Comparison Of The Gold-bearing Quartz Veins Of Typical Gold Deposits In Dadu River Gold Mineralization Belt

DaduRiver gold mineralization belt is located in the west margin of Yangtze Block and on the both sides of the DaduRiver in Kangding district.According to its tectonic position,DaduRiver gold mineralization belt lies in the zone of transition among the Songpan-Garze orogen,the Sichuan-Yunnan meridional structural belt and Southwest Sanjiang orogenic belt.The geological exploration work shows that gold deposits can be divided intotwo different ore-bearing layers which consist of sedimentary coverand basement.Gold deposits in this district are mainly quartz-vein type.In order to figure out the similarities and differences in gold-bearing quartz veins of different ore-bearing layers in DaduRiver,author introduceing deposit geological features among different ore-bearing layers and comparing symbiotic combination,mineralogy characteristics,geochemical characteristics and formation age of the gold-bearing quartz veins.The similarities and differences of thegold-bearing quartz veins are found,it provides relevant evidence for the genesis of gold deposits in this area.The master's thesis achieves the following main results and understanding:(1)The ore mineral compositions are quite simple in the basement and sedimentary cover.The basement's ore mineralsare mainly quartz with less sulfide,while the sedimentary cover's ore mineralsare mainly sulfide with less quartz.In the case of the same deposit,there are pyrite-quartz combination in the upper layers and polymetallic sulfide-quartz combination in the deep layers.(2)The gold-bearing quartz veins of gold deposits in Dadu River arevein,lenticular and a few centimeters to tens of centimeters thick.The mineralogy characteristics ofgold-bearing quartz veinsin different ore-bearing layers are similar.Quartz is gray and white.There is some smoke greyquartz in the basement.Quartz mainly has xenomorphic granular texture.Quartz in the basement is larger than the quartz in sedimentary cover.Quartzis wavy extinction.(3)The micro elements content trends of quartz in different ore-bearing layers are similar.The quartz of deposits in basement contains more micro elements.In terms of a single deposit,the content of micro elements in quartzof the lower ore body is richerthan the upper part,showing a vertical element enrichment regularity.The REE distribution patterns of quartz are quite similar to each other in different ore-bearing layers.It showsthat the gold depositsof Dadu River have the same source and property of metallogenic fluid.Through research of hydrogen and oxygen isotopes in quartz,found that the source of the water may be composed of meteoric water,metamorphic water and magmatic water mixture of two or more.The homogenization temperature ranges of the quartz inclusion in the period of gold metallogenic are similar among different ore-bearing layers,distributed in 160 ~ 280?.Combining previous research shows that the metallogenic fluid belongs to low temperature,low salinity,weak alkaline hydrothermal fluid,the metallogenic depth of deposits in basement is greater than the sedimentary cover deposits(4)Experimental data by testing the quartz with the method of ESR shows the approximate mineralogenetic epoch among the different ore-bearing layers.Generally,metallogenic ages center on 10~24Ma,while individual metallogenic ages are concentrated in4~8Ma,36~40Ma and 48~50Ma.Obviously,it is the characteristics of the multiphase and multi-stage.Because of the coincidence that 10~24Ma equals to Tibet Plateau post-collision(0~25Ma)periods and the cainozoic intracontinental orogenycaused the ductile-brittle shear zone mineralization,so DaduRiver gold deposits are the orogenic gold deposits formed by shear action in the post-collision period..(5)By comparing the symbiotic combination,mineralogy characteristics,geochemical characteristics and formation age of the gold-bearing quartz veins shows that the DaduRiver gold deposits have the same genesis,and belong to the same metallogenic series of orogenic gold deposit.