西秦岭熊山沟岩体地球化学及构造环境分析  

Geochemistry and tectonic environment of the Xiongshangou intrusion in the West Qinling

作　　者：温志亮[1] 赵仁夫[1] 王文[2] 王锋[3] 郭周平[1] 

机构地区：[1]中国地质调查局西安地质矿产研究所,陕西西安710054 [2]中国地质调查局发展研究中心,北京100037 [3]长安大学,陕西西安710054

出　　处：《中国地质》2008年第4期618-627,共10页Geology in China

基　　金：中国地质调查局地质大调查项目(1212010813050)资助

摘　　要：在区域地质调查及综合研究的基础上,对位于西秦岭天水东南部地区的原百花岩体进行了详细的岩石学、岩石地球化学、岩体接触关系、同位素年龄研究,从中解体出熊山沟岩体,并初步了解了该岩体的岩浆活动规律。熊山沟岩体早期岩石类型为斜长花岗岩,岩石化学成分K2O含量较低,K2O∕Na2O比值为0.33～0.42;晚期岩石类型为二长花岗岩,岩石相对富集K2O,K2O∕Na2O比值为1.01～1.43,岩石属拉斑-钙碱性系列;微量元素富集Th、Hf、Nb、Zr等元素;稀土元素以富集轻稀土,无铕负异常或铕负异常不明显为主要特征;氧同位素值较低(δ18O为+3.32‰),岩石具I型花岗岩的特征,岩浆来源于下地壳物质,形成于大陆弧构造环境。On the basis of regional geological survey and integrated research, the authors conducted detailed studies of the petrology, contact relationships, isotope ages and geochemistry of the original Baihua intrusion in the southeastern part of Tianshui, West Qinling, and through the studies they separated the Xiongshangou intrusion from the Baihua intrusion and gained a preliminary knowledge of the characteristics of magmatic activity of this separated intrusion. The rock type of the early-stage Xiongshangou intrusion is plagiogranite, which is petrochemically.characterized by a low K2O content with K2O/Na2O=0.33-0.42 and A/CNK=1.01- 1.05 ;the rock type formed in the late stage is monzogranite, which is enriched in K2O with K2O / Na2O=l.01- 1.43 and A / CNK=0.86-1.07, and the rock belongs to the tholeiite-calc-alkaline series. Furthermore, the intrusion shows characteristics of enrichment in the trace elements Th, Hf, Nb and Zr and in LREE and no or unpronounced Eu negative anomalies, with δ Eu=0.58-0.87 and low δ^18O （δ^18O=＋3.32%o）. The rock has the features of ＂Ⅰ＂-type granite and the magma was derived from materials of the lower crust and the intrusion formed in a continental arc tectonic environment.

关 键 词：熊山沟岩体 地球化学 构造环境 西秦岭 

分 类 号：P594.1[天文地球—地球化学]