西藏山南比马组安山岩形成时代及意义

金属矿山 ›› 2014, Vol. 43 ›› Issue (08): 91-94.

西藏山南比马组安山岩形成时代及意义

闫国强¹，丁俊²，黄勇²，王欣欣^1,3，张凯⁴

1.成都理工大学地球科学学院，四川成都 610059；2.中国地质调查局成都地质调查中心，四川成都 610081；3.山西地勘局217地质队，山西大同 037008；4.中国冶金地质总局第二地质勘查院，福建甫田 351111

出版日期:2014-08-15 发布日期:2015-03-31
基金资助:
* 西藏大型矿床成矿专属性研究项目（编号：1212011221073），青藏高原南部矿床勘查模型与定位预测技术项目（编号：2011CB403105），西藏米拉山铜矿整装勘查区关键基础地质研究项目（编号12120114050501）。

Geochronology and Significances of Bima Formation Andesite of Shannan,Tibet

Yan Guoqiang¹，Ding Jun²，Huang Yong²，Wang Xinxin^1,3，Zhang Kai⁴

1.Academy of Earth Science,Chengdu University of Technology,Chengdu 610059,China；2.Chengdu Center of China Geological Survey,Chengdu 610081,China；3.The 217 Geological Team of Bureau of Geology and Investigation of Shanxi,Datong 037008,China； 4.The No.2 Geological Exploration Institute of CMGB,Putian 351111,China

Online:2014-08-15 Published:2015-03-31

摘要/Abstract

摘要： 通过对西藏山南努日矿区南矿段出露的白垩系下统比马组地层顶部岩性段采集的安山岩，运用野外宏观描述、锆石阴极发光、锆石微区LA-ICP-MS的方法，对安山岩产状、安山岩中锆石形态、地球化学、同位素年代学进行了详细分析，结果显示：比马组安山岩与下伏麻木下组火山岩呈整合接触关系，锆石的阴极发光图像显示其具有较好的晶形、清晰的振荡环带和w(Th)/w(U)值大于0.1的特点，为典型的岩浆成因锆石，锆石U-Pb谐和年龄为92.04±0.71 Ma（MSWD=0.74），属晚白垩世。这一年龄代表了比马组安山岩的形成时间，也代表了桑日群火山岩喷发持续时间从晚侏罗世一直持续到晚白垩世，精确的锆石U-Pb年代学证据，很好地约束了桑日群弧火山岩的活动时限，同时也暗示了努日矿床自晚侏罗世开始即有大规模的、持续的岩浆活动。

关键词: 桑日群, 安山岩, 比马组, 锆石U-Pb定年

Abstract: The occurrences,morphology of zircon,geochemistry and geochronology of andesite sampled from the upper section of cretaceous Bima formation emerged in Nuri mining area of Shannan,Tibet were analyzed in detail through the field macroscopic description,cathodoluminescence images of zircon and LA-ICP-MS to zircon.The results showed that Bima formation andesite has a comformable contact with underlying Mamuxia formation volcanic rock.The cathodoluminescence images of zircons showed that the zircon have better crystal form and clearer oscillatory band with ratio of w(Th)/w(U) greater than 0.1,which indicated that the zircon is a typical magmatic origin rock.Zircon with the U-Pb concordant age of 92.04±0.71 Ma（MSWD=0.74）belongs to the late Cretaceous epoch which represents the ore-forming time of Bima formation andesite,also represents that the eruptions of Sangri Group volcanic rock lasts from late Jurassic epoch to the late Cretaceous epoch.The accurate zircon U-Pb chronology evidence greatly constraints the activity time of Sangri Group arc volcanic rocks.Meanwhile,it implies that the Nuri deposit suffer from many large-scale and sustaining magmatic activities since the late Jurassic epoch.

Key words: Sangri group, Andesite, Bima formation, Zircon U-Pb dating

闫国强, 丁俊, 黄勇, 王欣欣, 张凯. 西藏山南比马组安山岩形成时代及意义[J]. 金属矿山, 2014, 43(08): 91-94.

YAN Guo-Qiang, DING Jun, HUANG Yong, WANG Xin-Xin, ZHANG Kai. Geochronology and Significances of Bima Formation Andesite of Shannan,Tibet[J]. Metal Mine, 2014, 43(08): 91-94.

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