Age,Petrogenesis and Tectonic Implications of High-Mg Diorite in Chayong Region,Yushu,Qinghai
Wang Jian
Sun Fengyue
Jiang Hefang
Yu Lu
Wang Fei
Ning Chuanqi
Zhang Wanhui
Abstract：This paper presents petrography,electron microprobe results,zircon U-Pb dating and geochemistry of diorites at Chayong, Yushu,Qinghai Province,with the aim of constraining its petrogenesis and geodynamic significance.The dating results indicate that the diorite formed in the Late Triassic(230±2 Ma).Electronic Probe analysis results show that plagioclase has a band structure with by-townite and calciclase in the centre,andesine and labradorite on the edge.Biotite belongs to magnesia biotite,which crystallized at tem-perature of 647―688 ℃,at depth of 14.2―15.5 km.Hornblende belongs to calcic amphibole and has the characteristics of crust-mantle mixing origin of the magma.The diorites contain high SiO2,MgO,Mg#values,Cr and Ni,enriched in large ion lithophile elements (LILEs)and light rare earth elements(LREEs),depleted in the high field strength elements(HFSE),which is similar with high-Mg diorite.TheεHf(t)values of zircons from the diorites vary from ―10.4 to ―10.3 and from ―6.4 to ―4.0,and their Hf one-stage model ages vary from 1 021 to 1 311 Ma.They are likely formed from mantle peridotites by reacting with Si-rich melts released from subducted oceanic slab.Combined with regional tectonic evolution,it is suggested that the diorites might have been resulted from the subduction of Jinshajiang Ocean in the Late Triassic.
Keywords：high-Mg dioritezircon U-Pb geochronologygeochiemistrycrystal chemistryQinghaiYushu
Publication Date：2018-01-01
Online Publishing Date：2025-08-15(First online date of this platform, not the publication date of the document)
Pages：20( 733-752 )