地质论评2017，Vol.63Issue(4)：1079-1101,23.DOI:10.16509/j.georeview.2017.04.017
青海南山构造带西段黑马河花岗杂岩体锆石U-Pb年代学、地球化学特征及其地质意义
LA-ICP-MS Zircon U-Pb Dating, Geochemistry and Its Geological Significance of the Heimahe Granitic Pluton in the Western Segment of the Qinghai'nanshan Tectonic Belt
摘要
Abstract
Objectives:As a granitic pluton in the west part of the Qinghai'nanshan tectonic belt,the Heimahe granitic pluton are mainly composed of granodiorite,quartz diorite,diorite and gabbro.The formation age and geochemical affinity of those rocks play a key role for investigating the transitional relation between the west Qinling and the Qilian orogenic belts in Paleozoic Tethys evolution stage.Methods:In this paper,a detailed study of LA-ICP-MS zircon U-Pb dating,petrology and geochemistry characteristics was carried out for quartz diorite,granodiorite and mafic microgranular enclaves from the Heimahe granitic pluton.Results:The LA-ICP-MS zircon U-Pb ages of the granodiorite and MMEs are 244.4 ± 1.1 Ma and 243.0 ± 1.2 Ma,respectively,indicating that the Heimahe granitic pluton formed in early Middle Triassic.The whole rock geochemical data show that quartz diorite and granodiorite belong to the metaluminous high-K calc-alkaline series and MMEs are high-K calc-alkatine to alkaline series.The REE patterns display rightward incline and weak negative Eu anomalies (δEu =0.65 ～ 0.83).The trace element geochemistry is evidently characterized by positive anomaly of LILEs (e.g.Cs,Rb,Th,K) and Pb,negative anomaly of HFSE (e.g.Nb,Ta,Ti) and P,Ba.Conclusions:The petrographic and geochemical characteristics of the Heimahe granitic pluton imply a closely subduction-related origin at active continental margin arcs,with crust—mantle mixing characteristics.The maric magma was derived from partial melting of the mantle wedge which was metasomatized bv hydrous fluids from subduction slab dehydration.Then the quartz diorite originated from crystallization differentiation of mantle source magma,and the granodiorite originated from crust sourced magma mixing somne mantle sourced magma.Connecting with the predecessors research results,it can be supposed that the petrogenesis of the Heimahe granitic pluton may be related to the southward subduetion of Zongwulong Oceanic crust during the early Middle Triassic.关键词
青海南山/黑马河花岗杂岩体/锆石U-Pb年龄/岩石成因/构造环境Key words
Qinghai'nanshan tectonic belt/Heimahe granitic pluton/LA-ICP-MS zircon U-Pb dating/petrogensis/tectonic setting引用本文复制引用
张永明,裴先治,李佐臣,李瑞保,刘成军,裴磊,陈有炘,陈国超,王盟..青海南山构造带西段黑马河花岗杂岩体锆石U-Pb年代学、地球化学特征及其地质意义[J].地质论评,2017,63(4):1079-1101,23.基金项目
本文为国家自然科学基金资助项目(编号:41472191、41502191、41172186)、中国地质调查局地质调查项目(编号:12120114041201、12120114018219)、中央高校基本科研业务费专项资金项目(编号:CHD2011TD020、2013G1271091、2013G1271092)的成果.This study was supported financially by the National Nature Sciences Foundation of China (No.41472191,41502191,41172186),the Regional Geological Survey Projects of China Geological Survey (No.12120114041201,12120114018219) and the Fundamental Research Funds for the Central Universities (No.CHD2011TD020,2013G1271091,2013G1271092). （编号:41472191、41502191、41172186）
