Geochronology And Petrochemistry Study On Intermediate-acid Intrusive Rocks, Nawucuo, Tibet

The Bangong-Nujiang combine zone is a large-scale melange zone. It has long been widespread concern in the geological community, because this combine zone with an complex tectonic evolution. Currently, the predecessors of the Bangong-Nujiang combine zone has made many research on the Ophiolite suite of this melange zone, but the study of island arc magmatism in the process of subduction is not a lot. The rock samples from the intermediate-acid intrusive rocks collected from Southern Nawucuo, are firstly investigated in this study, in which the subjects of U-Pb isotope chronology, petrology, and elemental geochemistry are involved.The6representative samples method of Zircon U-Pb dating reports we got and13representative samples method of elemental geochemistry. The report show that the age of quartz monzodiorite114.7+11.0/-6.0Ma, monzonitic granite112.4+3.5/-6.1Ma, granodiorite105.2+3.8/-4.5Ma, granite porphyry105.0+2.0/-2.5Ma, diorite porphyries104.5+1.91-94Ma, granite93.4+2.5/-3.0Ma.The Granitoids from The Southern of Nawucuo has the high vaules of SiO2which is about64.56%～74.18%and the the vaules of K2O which is about2.65%～4.65%. In Neutral intrusive rocks the value of SiO2is52.54%63.19%and the value of K2O is52.54%～63.19%.The A/CNK of Granitoids is1.38～1.52, Corundum molecules and No diopside are appeared in CIPW. According to the diagrammatize of A/CK-A/CNK and the results of CIPW,we can judge the intermediate-acid intrusive rocks which discussed in this article should belong to the stone of high-K calc-alkaline and Weakly peraluminous.When the Bangong-Nujiang lithosphere dived to the south,the slabs of the oceanic crust were subjected to breaking off during this subduction,which caused the materials from the asthenosphere to uplift.With the liquation of lithospheric mantle, the intermediate-basic magma was formed,then it shaped intrusive rock and volcanics.The upper crust molten acidic magma were baked by Mantle source material, after mixing together they appeared fractional crystallization.And the Southern of Nawucuo granite were formed.