Geochemical And Chronological-characteristics And Its Tectonic Significance Of Intermediate-acid Intrusive Rocks In Delingha,Qinghai

The Qinghai Delingha area is located in the western part of the Qilian Mountains,and is the part of the South Qilian tectonic magmatic belt.The intermediate-acid intrusive rocks are more developed such as granulite,quartz amphibole,and amphibole in the area,but the research work is relatively weak.This work was jointly supported by the Regional Geological Mineral Survey Project of the four 1: 50000 geological maps(J47E010003,J47E010004,J47E011003,J47E011004)in Yeniuji area,Delinha district,Qinghai Province(Project No.1212011221152).The 3 intrusive bodies include Kepumengke diorite,Habeidawu granite and Yeniujishan granite.These rocks were analyzed by petrochemical,chronological and isotopes method so that discussing the magma activity and tectonic environment in the area.The main results obtained from the above studies are as follows:1.the LA-ICP-MS zircon U-Pb isotope dating was performed on the three rock masses of Kepumengke diorite,Habeidawu granite and Yeniujishan granite,with the ages being 446 ± 5Ma,441 ± 5Ma and 440 ± 7Ma,respectively.These intrusive bodies ages were established.2.Detailed analysis of these bodies was done.The lithology of the Kepumengke diorite was mainly granodiorite,diorite,and dioritic porphyrite,and belong to the characteristics of type I granite;Habeidawu granite is a quasi-aluminumsuperaluminum granite with the characteristics of S-type granite;Yeniujishan granite is mainly I type granite,and also has the characteristics of S-type granite.3.In terms of its forming environment,the Kepumengke diorite was formed at the end of the subduction phase of the middle-late Ordovician and Silurian oceanic basin.The Yeniujishan granite and the Habeidawu granite were formed during the syn-collision stage after the end of the the subduction phase of the middle-late Ordovician and Silurian oceanic basin.