地学前缘 ›› 2010, Vol. 17 ›› Issue (1): 1-10.

• 论文 •    下一篇

大别山北缘金刚台火山岩SHRIMP锆石U-Pb年龄及构造意义

  

  1. 1中国地质大学(北京) 地质过程与矿产资源国家重点实验室, 北京 100083
    2中国地质大学(北京) 地球科学与资源学院, 北京100083
    3河南省国土资源科学研究院, 河南 郑州 450053
  • 收稿日期:2009-08-17 修回日期:2010-01-09 出版日期:2010-01-28 发布日期:2010-01-28
  • 通讯作者: 罗照华(1956—),男,教授,博士生导师,矿物学、岩石学、矿床学专业。Email:luozh@cugb.edu.cn
  • 作者简介:黄丹峰(1985—),男,硕士研究生,矿物学、岩石学、矿床学专业。Email:huangdanfeng0216@163.com
  • 基金资助:

    河南省地质矿产重大科技攻关计划项目(26417);国家自然科学基金项目(90814007, 4091112007940673046, 40434010)

Zircon SHRIMP UPb age and tectonic implications of Jingangtai volcanic rocks in north margin of Dabie Mountains.

 HUANG  Dan-Feng, LUO  Zhao-Hua, LEI  Xin-Xiang   

  1. 1State Key Laboratory of Geological Processes and Mineral Resources, China University of Geosciences(Beijing), Beijing 100083, China
    2School of Earth Sciences and Resources, China University of Geosciences(Beijing), Beijing 100083, China
    3Henan Academy of Land and Resources Sciences, Zhengzhou 450053, China
  • Received:2009-08-17 Revised:2010-01-09 Online:2010-01-28 Published:2010-01-28

摘要:

位于大别山造山带北淮阳火山岩带中段的金刚台火山岩的形成时代一直存在争议。新的地质观察表明,其不整合于早白垩世商城岩体之上,不应当归属为侏罗纪。对金刚台火山岩3个样品进行了SHRIMP锆石UPb定年,其中喷出相的黑云母粗面岩(B09)年龄为(1284±36) Ma,次火山相的闪长玢岩(B21)年龄为(1291±22) Ma,靠近火山岩层底部的粗安岩(B26)年龄为(129±2) Ma。样品B09的测年数据误差较大,B21和B26则非常一致,表明金刚台火山岩形成于129 Ma,火山喷发持续时间较短。金刚台火山岩是大别造山带早白垩世巨量岩浆爆发事件的产物。结合前人的研究成果,区域火山地质特征和商城岩体剥露机制的综合分析表明:(1)金刚台火山岩形成之前,区域发生了强烈的挤压隆升;(2)金刚台火山岩是造山带岩石圈拆沉作用的产物;(3)火山岩形成后区域进入长时间的岩石圈伸展阶段,因而129 Ma是大别山地区构造转换的分界时间。

关键词: 大别山;金刚台火山岩, SHRIMP锆石U-Pb年龄;早白垩世;构造转换

Abstract:

The age of the Jingangtai volcanic rocks, which spread over the central part of North Huaiyang volcanic rock belt, has been in controversy for a long time. New observations indicate that Jingangtai volcanic rocks unconformably overlie the early Cretaceous Shangcheng Pluton, hence they must have not  formed in the Jurassic. A SHRIMP UPb dating on individual zircons from three representative samples of Jingangtai volcanic rocks shows that the age of extrusive biotite trachyte (B09) is (1284±36) Ma, the age of subvolcanic diorite porphyrite (B21) is (1291±22) Ma and the age of trachyandesite (B26) representing the lower part of volcanic rock series is (129±2) Ma. The dating error for sample B09 is relatively large, however, the age of sample B21 is consistent with B26, which suggests that Jingangtai volcanic rocks formed at 129 Ma, and the duration of volcanic eruption was short. Jingangtai volcanic rocks are the products of largescale magmatism in Dabie Orogen in the Early Cretaceous. Combined with the foregoing research works, the regional geological features and the denudation mechanism of Shangcheng Pluton show: that (1) before the forming of Jingangtai volcanic rocks, the region had undergone intensively compressional uplift; that (2) Jingangtai volcanic rocks are the products of lithosphere delamination; that (3) after the forming of Jingangtai volcanic rocks, the regional lithosphere had been extended for a long time, thus 129 Ma is the boundary of tectonic transition for Dabie Orogen.

Key words: Dabie Mountains, Jingangtai volcanic rocks, SHRIMP zircon U-Pb dating, Early Cretaceous, tectonic transition

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