Detrital Zircon Of Host Strata In Kuhai-Saishitang Area,Qinghai Province,and Its Geological Significance

The Saishitang-Kuhai is one of constituting the Ela Mountain metallogenic Belt in the northern part of Tibetan Plateau.In recent years,there was much controversy between Permian and Triassic the host strata ages of copper deposit for a long time.Choosing the continuous,thick layer and typical sedimentary rocks as study objects,uses LA-ICP-MS zircon U-Pb age isotope chronology to study detrital zircon age distribution and discuss strata age and material source in Tong Yugou copper deposit and Kuhai.Some scholar support Permian of strata age of Tong Yugou copper deposit and other insist of Triassic.The strata of rock formations are mainly clastic rocks of neritic facies and some marble.The zircon age spectrum of Tongyugou copper deposit can divided into five groups: 228 ~ 323 Ma,372~542Ma,647 ~ 965Ma?1187Ma ~ 1591 Ma and 1738 ~ 2496 Ma.The group of 228~323Ma,the peak age is 285 Ma.The group of 372~542 showing the most powerful peak age is 414 Ma and show strong magmatic thermal events of source.Peak age is 760 Ma of neoproterozoic.Researcher think that the strata age of Kuhai is same as Tongyugou.The upper part of strata is shallow water carbonate deposition and the lower part is abyssal-bathyal shale phyllite or argillaceous slate.The zircon age spectrum of Kuhai can also divided into five groups: 277 ~ 335 Ma,403 ~ 565 Ma,717 ~ 995Ma?1154 ~ 1766 Ma and 1827 ~ 3128 Ma.The group of 277 ~ 335 Ma,403 ~ 565 Ma,1827 ~ 3128 Ma,the peak age is respectively 330 Ma,437Ma,2494 Ma.The primary difference is only Tongyugou copper deposit existing peak age of neoproterozoic and only Kuhai existing peak age of Palaeoproterozoic.Comparing with tectonic thermal event of around,Eastern Kunlun region was mainly providing material source for Kuhai and the Western Qinling area provide for Tongyugou.The results show that youngest zircon U-Pb age is 228Ma?245Ma?277Ma.This show that the upper limit of strata age is early-middle Triassic in Tongyugou copper deposit.But the youngest zircon U-Pb age of Kuhai is 277Ma?290Ma?295Ma that showing the strata age is middle Permian.Combining of magma age and paleontological data considering the host strata age is early-middle Triassic to middle Permian.The thesis systematic summarized predecessor's research results.We can conclude that structural setting of this area is back-arc basin formed by A'nimaqing Ocean subduction.Researcher think that the basement strata age is Lower Proterozoic.The zircon age of metamorphic siltstone of Tadong are mainly distributed in 711 ~799Ma.This show that the stract age is less than 711 Ma and maximum deposition age is Neoproterzoic.This also indicate that the study area has lower Proterozoic basement.