内蒙古西乌旗巴布盖诺尔地区早二叠世花岗斑岩U-Pb年龄、地球化学特征及其地质意义  

Zircon U-Pb Age and Geochemical Characteristics of the Granite Porphyry in the Babugainuoer Area,West Ujimqin Banner,Inner Mongolia and Their Geological Implications

作　　者：王承洋 陈伟[1] 齐路晶 俞嘉嘉 孙珍军 黄静宜 杨乐 齐松 WANG Chengyang;CHEN Wei;QI Lujing;YU Jiajia;SUN Zhenjun;HUANG Jingyi;YANG Le;QI Song(MNR Key Laboratory of Metallogeny and Mineral Assessment,Institute of Mineral Resources,Chinese Academy of Geological Sciences,Beijing 100037;College of Earth Sciences,Institute of Disaster Prevention,Sanhe,Hebei 065201;Inner Mongolia Shandong Gold Geological Mineral Survey Co.,Ltd,Chifeng,Inner Mongolia 024005)

机构地区：[1]中国地质科学院矿产资源研究所,自然资源部成矿作用与资源评价重点实验室,北京100037 [2]防灾科技学院地球科学学院,河北三河065201 [3]内蒙古山金地质矿产勘查有限公司,内蒙古赤峰024005

出　　处：《地球学报》2025年第2期283-297,共15页Acta Geoscientica Sinica

基　　金：防灾科技学院中央高校基本科研业务费专题项目(编号:ZY20215134);国家自然科学基金青年科学基金项目(编号:42002093)联合资助。

摘　　要：内蒙古西乌珠穆沁旗巴布盖诺尔地区位于大兴安岭南段西坡,本文对该区出露的花岗斑岩进行了锆石U-Pb年代学、Hf同位素及全岩地球化学研究,以揭示其形成时代、成因特征和构造意义。结果显示,SBLY-2样品12个测点的^(206)Pb/^(238)U年龄为(269±3)~(279±3)Ma,加权平均值为(274±3)Ma(MSWD=1.7)。SBLY-3号样品12个测点的^(206)Pb/^(238)U年龄为(269±3)~(282±4)Ma,加权平均值为(275±3)Ma(MSWD=1.6)。表明巴布盖诺尔地区花岗斑岩是早二叠世晚期岩浆作用的产物,而并非前人认为的白垩纪。岩石高硅、低铝、低镁、高碱,且富集Rb、Th、U、K等元素,相对亏损Nb、Ta、Ti等元素,具有A型花岗岩的特征。本次研究的花岗质岩石样品的锆石εHf(t)=8.2~11.1,二阶段Hf模式年龄(TDM2)为588~789 Ma,表明其成岩物质主要来源于新元古代期间新增生的年轻下地壳。综合研究认为,巴布盖诺尔地区早二叠世花岗斑岩形成于造山后伸展环境,暗示古亚洲洋至少在早二叠世之前已经闭合。The Babuganuoer area,West Ujimqin Banner,Inner Mongolia,is located at the western slope of southern Great Xing’an Range.For the purpose of revealing its formation age,petrogenesis and tectonic significance,we conducted a comprehensive study of zircon U-Pb chronology,Hf isotope and whole-rock geochemistry for granite porphyry exposed in this area.The 206Pb/238U ages of 12 spots of zircons from Sample SBLY-2 are between(269±3)–(279±3)Ma,with a weighted mean ^(206)Pb/^(238)U age of(274±3)Ma(MSWD=1.7).The 206Pb/238U ages of 12 spots of zircons from Sample SBLY-3 are between(269±3)–(282±4)Ma,with a weighted mean ^(206)Pb/^(238)U age of(275±3)Ma(MSWD=1.6).The above results reveal that they were magmatic products of the Late Early Permian,rather than the previously believed Cretaceous.These rocks show characteristics of high silicon,low aluminum,low magnesium,high alkali,rich potassium and low sodium.These samples are enriched in Rb,Th,U,K elements and depleted in Nb,Ta,Ti elements,indicating a genesis of aluminous A-type granites.Zircons of these rocks haveεHf(t)values of 8.2–11.1,and the two-stage Hf model ages(TDM2)of 588–789 Ma,suggesting that the Early Permian granitic rocks in the Babugainuoer area mainly derived from the newly accreted lower crust during the Neoproterozoic period.We comprehensively conclude that the Early Permian granitic rocks in the Babugainuoer area were formed in a post-collisional extensional setting and the Paleo-Asian Ocean was closed no later than the Late Permian.

关 键 词：巴布盖诺尔 花岗斑岩 岩石地球化学 LA-ICP-MS 锆石U-Pb年龄 HF同位素 

分 类 号：P595[天文地球—地球化学] P597.3[天文地球—地质学]