中祁连东段黑龙二长花岗岩地球化学、年代学及其构造意义  

Petrochemistry and Geochronology of the Heilong Monzogranite in the East Section of the Central Qilian Mts.and Their Tectonic Implication

作　　者：徐磊 周伟 胡晓宇 XU Lei;ZHOU Wei;HU Xiao-yu(Geological Survey Co,Ltd.,Sino Shaanxi Nuclear Industry Group,Xi’an 710100)

机构地区：[1]中陕核工业集团地质调查院有限公司,西安710100

出　　处：《四川地质学报》2021年第1期27-32,51,共7页Acta Geologica Sichuan

基　　金：中国地质调查局地质大调查项目(12120113033012)资助。

摘　　要：通过对中祁连东段黑龙二长花岗岩开展详细的年代学、岩石地球化学的分析测试和研究工作。LA-ICP-MS锆石U-Pb测年表明,黑龙二长花岗岩^(206)Pb/^(238)U的加权平均年龄为(481.3±3.7)Ma(MSWD=4.6),属于早奥陶世。岩石地球化学的特征表明,黑龙二长花岗岩属于高碱钙碱性的I型花岗岩,岩石为准铝质-过铝质类型(A/CNK=0.91~1.22)。该二长花岗岩相对富集Rb、Th、U等大离子亲石元素,而相对亏损Nb、Ta、Ti等高场强元素,并且明显亏损P,显示出岛弧岩浆岩的信息。结合区域构造特征,认为黑龙二长花岗岩形成于活动大陆边缘弧的构造环境,同时,也佐证了北祁连洋盆双向俯冲的地质事实。This paper has a discussion on petrochemistry and geochronology of the Heilong monzogranite in the east section of the Central Qilian Mountains.The LA-ICP-MS zircon dating for the Heilong monzogranite yields an average ^(206)Pb/^(238)U age of(481.3±3.7)Ma(MSWD=4.6),belonging to the Early Ordovician.The geochemical features show the Heilong monzogranite belongs to a high-K calc-alkaline of I-type granite,and is characterized by quasi-aluminous to peraluminous series.The monzogranite enriches large ion lithophile element of Rb,Th,U and depletes high field strength element of Nb,Ta,Ti,being obviously P-depleted,which show information of arc-related igneous rocks.Combined with regional geologic structure,this paper considers the Heilong monzogranite may be formed in a continental marginal arc which provides an evidence for bidirectional subduction of the North Qilian ocean basin.

关 键 词：黑龙二长花岗岩 锆石U-PB测年 构造环境 中祁连东 祁连造山带 

分 类 号：P597[天文地球—地球化学]