西秦岭白马山“C”型埃达克岩成因:地球化学、Sr-Nd-Pb同位素制约  

Petrogenesis of the Baimashan C-type adakite in Western Qinling:Constraints from their geochemistry and Sr-Nd-Pb isotopic compositions

作　　者：王建中[1,2] 钱壮志[2] 徐刚[2] 姜超[2] 

机构地区：[1]中国人民武装警察部队黄金第五支队,西安710100 [2]长安大学西部矿产资源与地质工程教育部重点实验室,西安710054

出　　处：《华东地质》2016年第3期174-181,共8页East China Geology

基　　金：国家自然科学基金"新疆喀拉通克铜镍硫化物矿床成矿作用与深部地质过程"(项目编号:41372101)

摘　　要：白马山小岩体位于西秦岭白马山金矿区内,与矿床具有密切的空间关系。通过研究白马山岩体主量、微量及稀土元素地球化学特征及Sr-Nd-Pd同位素组成特征,探讨其岩石成因。白马山石英闪长岩属高钾钙碱性系列岩石,具有与"C"型埃达克岩相似的地球化学特征。Sr-Nd-Pb同位素组成特征显示,该小岩体富放射性成因Pb,初始(^(87)Sr/^(86)Sr)t比值为0.70637,_εNd_(t)=-6.75,具有较高的T_(DM)值(1.53Ga),说明岩浆主要来自于大陆下地壳,且与耀岭河群的基性火山岩相似,这些"C"型埃达克质岩浆可能源于加厚基性下地壳的部分熔融,其残留相为(角闪)榴辉岩。The Baimashan small rock body, related to gold deposit in space, is located in the Baimashan gold mining field, western Qinling metallogenic belt. This study conducted geochemical characteristics analysis of main elements, trace elements and rare earth elements, and Sr-Nd-Pd isotopic composition so as to understand its petrogensis. The results indicate that these rocks belong to high K calcalkalic series and have geochemical compositions similar to the C-type adakite. Sr-Nd-Pb isotopic compositions show that the rock body is characterized by enrichment of radiogenic P b , with initial （^87Sr/^86S r）t of 0. 706, negative εNd（ t） of -6. 75, and TDM of 1. 53Ga, implying that the magmas should derive from lower continental crust and geochemically similar to the mafic rocks of the Yaolinghe Group. It can be concluded that the rock might result from partial melting of thickened mafic lower crust, with residual phase being amphibole eclogite.

关 键 词：地球化学 Sr、Nd、Pb同位素组成 “C”型埃达克岩 岩石成因 西秦岭 

分 类 号：P597[天文地球—地球化学]