地学前缘 ›› 2016, Vol. 23 ›› Issue (5): 291-300.DOI: 10.13745/j.esf.2016.05.028

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东天山白山斑岩钼矿床深部斑岩体锆石SIMS U-Pb定年、Hf同位素组成及其地质意义

 刘彬, 王学求   

  1. 1. 中国地质科学院 地球物理地球化学勘查研究所, 河北 廊坊 065000
    2. 国土资源部 地球化学探测技术重点实验室, 河北 廊坊 065000
  • 收稿日期:2015-12-13 修回日期:2016-01-13 出版日期:2016-09-15 发布日期:2016-09-15
  • 作者简介:刘彬(1990—),男,博士研究生,主要从事勘查地球化学研究。
  • 基金资助:

    国土资源部公益性行业科研专项“北方沉积盆地化探技术研究与扫描示范”(201511034);中国地质调查局地质矿产资源调查评价专项(1212011220923);国家重点基础研究发展计划“973”项目(2012CB416600);国家自然科学基金面上项目(4127106)

SIMS U-Pb dating and Hf isotope of zircons from the deep granite porphyry in Baishan Mo deposit, eastern Tianshan, Northwest China, and their geological significance.

 LIU  Ban, WANG  Hua-Qiu   

  1. 1. Institute of Geophysical and Geochemical Exploration, Chinese Academy of Geological Sciences, Langfang 065000, China
    2. Key Laboratory of Geochemical Exploration, Ministry of Land and Resources, Langfang 065000, China
  • Received:2015-12-13 Revised:2016-01-13 Online:2016-09-15 Published:2016-09-15

摘要:

白山钼矿位于东天山康古尔—黄山韧性剪切带三岔口—白山斑岩铜钼矿带中,为典型的斑岩型钼矿。本文以白山钼矿床深部花岗斑岩体为研究对象,对其进行了精确的锆石SIMS U-Pb定年以及锆石原位Hf同位素分析,旨在确定白山钼矿床深部斑岩体的形成时代以及岩石成因,进而分析其形成时的动力学背景。本文获得的白山钼矿床深部斑岩体锆石SIMS U-Pb年龄为(229.7±3.2) Ma,这一结果与前人获得的辉钼矿Re-Os等时线年龄225~229 Ma基本一致,因此可以代表成矿岩体的形成年龄为晚三叠世。锆石原位Hf同位素组成特征显示,εHf(t)均显示正值,为+8.3~+12,地壳模式年龄(TCDM)为556~758 Ma。结合前人研究成果及区域地质演化历史,可以确定白山钼矿床深部斑岩体形成于晚三叠世陆内伸展环境,由新生下地壳部分熔融形成。

关键词: 白山斑岩型钼矿, 锆石SIMS U-Pb定年, 锆石Hf同位素

Abstract:

The Baishan porphyry Mo deposit is located in the SanchakouBaishan porphyry coppermolybednum belt, which is hosted in the eastern part of KangguerHuangshan ductile shear zone in eastern Tianshan, NW China. In this paper, SIMS U-Pb dating and in situ Hf isotope of zircons from the deep granite porphyry in Baishan deposit were systematically determined, so that we can constrain the petrogenesis and formation age of the granite porphyry emplaced in Baishan, and can reveal the geodynamical setting of the rockforming process of Baishan porphyry Mo deposit. Zircon SIMS U-Pb dating indicates that the magmatic activities in Baishan occurred at 229.7±3.2 Ma. Combined with the molybdenite ReOs isochron age (225229 Ma) reported by previous researchers, it is concluded that mineralization of the Baishan porphyry Mo deposit occurred in Triassic which is the same period as that of the rock formation. In situ Hf isotopic analyses of zircons that had previously been dated by SIMS yielded positive εHf(t) values ranging from +8.3 to +12 and the crustal model age ranging from 556 Ma to 758 Ma. Combined with the regional geological evolutionary history and isotopic data in this paper, we propose that the deep granite porphyry in Baishan deposit was formed in an intracontinental extension setting in the Late Triassic and the magma might be originated by partial melting of a juvenile lower crust.

Key words: Baishan porphyry Mo deposit, zircon SIMS U-Pb dating, zircon Hf isotope

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