内蒙古西乌旗巴布盖诺尔地区早二叠世花岗斑岩年代学、地球化学特征及其地质意义
投稿时间:2024-01-09  修订日期:2024-03-17  点此下载全文
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王承洋* 防灾科技学院 101601
基金项目:本文受国家自然科学基金青年科学(42002093)和防灾科技学院中央高校基本科研业务费专题项目(ZY20215134)联合资助。[通讯
中文摘要: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、Hf同位素,以及全岩地球化学的综合研究,以揭示其形成时代、成因特征和构造意义。LA-ICP-MS 锆石 U-Pb 定年结果显示,巴布盖诺尔地区花岗斑岩形成于273~274 Ma左右,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。
中文关键词:巴布盖诺尔  花岗斑岩  岩石地球化学  锆石U-Pb年龄  Hf同位素
 
Geochemistry, zircon U-Pb age and Hf isotope of the granite porphyry in the Babugainuoer area, West Ujimqin Banner, Inner Mongolia and their geological implications
Abstract:The Babuganuoer area, West Ujimqin Banner, Inner Mongolia, is located at the westen 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. Zircon U-Pb dating results indicate that these granitic rocks formed at 273 Ma~274 Ma, revealing 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 have εHf(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 s formed in a post-collisional extensional setting and the Paleo-Asian Ocean was closed no later than the late Permian.
keywords:Babugainuoer  granite porphyry  petrogeochemistry  zircon U-Pb age  Hf isotopes
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