地质学报2018，Vol.92Issue(5)：964-978,15.
青海东昆仑东段加当橄榄辉长岩锆石U-Pb年代学、地球化学及地质意义
Zircon U-Pb Dating and Geochemistry of the Jiadang Olivine Gabbro in the Eastern Section of East Kunlun, Qinghai Province and Their Geological Significance
摘要
Abstract
The mafic-ultramafic rocks in Paleo-Tethys domain of East Kunlun are poorly documented.Study of petrography,geochronology and geochemistry of the Jiadang olivine gabbro from the Eastern Section of East Kunlun,Qinghai Province can provide new constraints for the Late Paleozoic-Early Mesozoic tectonomagmatic evolution in East Kunlun.LA-ICP-MS zircon U-Pb dating yielded a weighted mean age of 249.7 ±3.0 Ma (n=21,MSWD=0.105) for olivine gabbro,indicating that the rock formed in the Early Triassic.Detailed lithogeochemical studies show that the olivine gabbro is characterized by high content of Al2O3(14.71％～18.60％),low content of TiO2 (0.07％～0.19％),P2O5 (0.02％),alkali (K2O+Na2O=1.65％～2.01％),and Na2O＞K2O,suggesting that the olivine gabbro belongs to sub-alkaline gabbro series.This suite of rocks is enriched in LILE (such as Rb,Sr,Ba,Th,K) and Pb,relatively depleted in HFSE (such as Nb,Ta,P,Zr,Ti),low REE contents,slightly enriched in LREE with obviously positive Eu anomaly (ΣREE=9.79× 10-6～12.55×10-6,(La/Yb)N=5.61～28.51,δEu=1.64～2.48).The geochemical characteristics and trace element discrimination diagrams show that the parental magma of olivine gabbro derived probably from the mantle influenced by the subducton,with the parental magma experiencing assimilation contamination by the upper crustal material and a certain extent of crystallization differentiation during the magma evolution.In combination with evolutionary characteristics of regional structures in East Kunlun,the authors consider that the olivine gabbro was formed during AnyemaqenPaleo-Tethys ocean subduction in Early Triassic.关键词
地球化学/LA-ICP-MS锆石U-Pb测年/橄榄辉长岩/加当/东昆仑Key words
geochemistry/LA-ICP-MS zircon U-Pb dating/olivine gabbro/Jiadang/East Kunlun引用本文复制引用
孔会磊,李金超,栗亚芝,贾群子,国显正,张斌..青海东昆仑东段加当橄榄辉长岩锆石U-Pb年代学、地球化学及地质意义[J].地质学报,2018,92(5):964-978,15.基金项目
本文为中国地质调查局地质大调查项目(编号DD20160013,12120115022101,12120113029000)资助的成果. （编号DD20160013,12120115022101,12120113029000）
