北山造山带南部芦草沟地区早三叠世酸性脉岩成因  

Petrogenesis of Early Triassic Felsic Dikes in the Lucaogou Area of Southern Beishan Orogenic Belt

作　　者：过磊[1] 王国强[1] 郭琳[1] 卜涛 GUO Lei;WANG Guo-qiang;GUO Lin;BU Tao(Research Center for Orogenic Geology,Geological Survey of China,Key Laboratory for the Study of Focused Magmatism and Giant Ore Deposits,Ministry of Land and Resources,Xi＇ an Center of Geological Survey,Geological Survey of China,Xi＇an 710054,China)

机构地区：[1]中国地质调查局西安地质调查中心中国地质调查局造山带地质研究中心国土资源部岩浆作用成矿与找矿重点实验室

出　　处：《矿物岩石地球化学通报》2018年第3期502-512,共11页Bulletin of Mineralogy, Petrology and Geochemistry

基　　金：国家自然科学基金项目(41502061);中国地质调查局地质调查项目(DD20160012)

摘　　要：位于中亚造山带南缘的北山造山带芦草沟地区发育多条酸性岩脉,对其开展系统的岩石学、岩石地球化学和锆石UPb年代学研究,对再造区域地质演化具有重要意义。研究结果显示,芦草沟地区酸性脉岩的U-Pb年龄为（248.8±1.8）Ma,即早三叠世;具有高Si低Mg的地球化学特征;富集大离子亲石元素Rb、Ba、Th、U、K等,亏损高场强元素Nb、Ta、Ti、P,Eu异常不明显;具低的Y、Yb含量,高的Sr/Y、La/Yb值和较低的Na_2O/K_2O值,与中国东部燕山期类埃达克岩的地球化学特征相似。岩石成因研究显示其具较低的MgO、Cr、Ni含量,并强烈亏损Nb、Ta,其残留相可能由辉石＋石榴子石＋金红石±角闪石组成,是在后碰撞背景下加厚下地壳部分熔融的产物。There are many felsic dikes in the Lucaogou area of Beishan orogenic belt in the southernmost Central Asian Orogenic Belt（ CAOB）. In order to understand the regional geological evolution rebuilding,petrology,geochronology and geochemistry analyses of the Lucaogou felsic dikes were performed. The results showed that these dikes have zircon U-Pb age of（ 248. 1±1. 8） Ma,indicative of the product of Early Triassic magmatism. The dikes have relatively high SiO_2 and low MgO. They also are enriched in LILE（ Rb,Ba,Th,U,K） and depleted in HFSE（ Nb,Ta,Ti,P）,with an significant negative Eu anomaly. These rocks have low Y,Yb contents,with high Sr/Y,La/Yb and relatively low Na_2O/K_2O ratios,which are similar to the geochemical characteristics of the Yanshanian adakitic rocks from Eastern China,indicating that the felsic dikes are likely to be derived from the partial melting of the thickened lower crust in the post-collisional setting,with pyroxene ＋ garnet ＋ rutile ± amphibole as residual phases.

关 键 词：酸性脉岩 岩石成因 埃达克岩 北山造山带 

分 类 号：P581[天文地球—岩石学]