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现代地质 ›› 2021, Vol. 35 ›› Issue (05): 1206-1217.DOI: 10.19657/j.geoscience.1000-8527.2021.036

• 岩石学 • 上一篇    下一篇

西昆仑上其木干花岗岩锆石饱和温度和Ti温度的地质意义

陈海云1(), 孙晓东2, 张志3()   

  1. 1.中国电建集团西北勘测设计研究院有限公司,陕西 西安 710065
    2.内蒙古自治区第九地质矿产勘查开发院, 内蒙古 锡林浩特 026000
    3.中国地质大学(武汉)地球物理与空间信息学院,湖北 武汉 430074
  • 收稿日期:2019-04-16 修回日期:2020-12-01 出版日期:2021-10-10 发布日期:2021-11-04
  • 通讯作者: 张志
  • 作者简介:张 志,男,博士,教授,1964年出生,遥感地质专业,从事地质、遥感地质学研究工作。Email: 171560655@qq.com
    陈海云,男,硕士研究生,工程师,1989年出生,地质学专业,主要从事岩石学与遥感地质、地质工程方面工作。Email: 851134447@qq.com
  • 基金资助:
    青海省青藏高原北部地质过程与矿产资源重点实验室专项基金项目(2019-kz-01);青海省科技厅创新平台建设专项项目(2019-ZJ-T04);中国地质调查局项目“西昆仑成矿带矿产资源遥感地质调查”(1212011120889)

Zircon Saturation Temperature and Titanium Temperature and Geological Significance of Granites in Shangqimugan, West Kunlun Orogen

CHEN Haiyun1(), SUN Xiaodong2, ZHANG Zhi3()   

  1. 1. Northwest Engineering Co. Ltd., Xi’an, Shaanxi 710065, China
    2. No.9 Institute of Geology and Mineral Resources Development of Inner Mongolia, Xilin Hot, Inner Mongolia 026000, China
    3. Institute of Geophysics & Geomatics, China University of Geosciences, Wuhan, Hubei 430074, China
  • Received:2019-04-16 Revised:2020-12-01 Online:2021-10-10 Published:2021-11-04
  • Contact: ZHANG Zhi

摘要:

通过对上其木干花岗岩进行锆石微量元素和全岩主量元素分析,借助锆石饱和温度和Ti地质温度,反演岩浆源区的温度,进一步分析花岗岩的形成环境。锆石具有典型岩浆岩锆石向左倾斜的稀土元素配分模式,即轻稀土元素明显亏损、重稀土元素明显富集,具有显著的Ce正异常和Eu负异常。锆石饱和温度计算结果表明,上其木干花岗岩的锆石饱和温度介于772~829 ℃之间,平均值为800 ℃,属于高温花岗岩。锆石Ti地质温度的平均最低温度为614 ℃,平均最高温度为634 ℃,花岗岩中锆石形成的温度在614~634 ℃之间。结合锆石微量元素特征、锆石饱和温度和Ti温度与Th/U、10000/Hf的关系,可以判断上其木干花岗岩可能形成于西昆仑造山带增厚的岩石圈下部发生拆沉作用所导致的幔源岩浆底侵,岩浆结晶分异过程中发生了锆石的重结晶或存在多期岩浆(熔体-流体)注入事件。岩浆形成热源可能与羌塘地块沿着康西瓦大断裂和塔里木地块碰撞拼贴结束后,于后碰撞板内伸展体制下导致的软流圈上涌、幔源岩浆的底侵作用有关。

关键词: 微量元素, 锆石饱和温度, Ti温度, 西昆仑上其木干

Abstract:

In this study, we conducted zircon trace element and whole-rock major element analyses on the Shangqimugan granites, and calculated the zircon saturation temperatures and titanium temperatures, which can unravel the temperatures of the source magma, and the formation environment of granite is further analyzed. Our zircon samples present typical igneous zircon REE left-inclining patterns. Besides, LREEs are obviously depleted and HREEs enriched. The samples have distinct negative Eu anomalies and positive Ce anomalies. The results indicate that the zircon saturation temperatures for the Shangqimugan granites are at 772-829 ℃ (average 800 ℃), which belong to high-temperature granite. The minimum Ti-in-zircon average temperature is 614 ℃, the maximum average temperature is 634 ℃, and the zircons were formed at 614-634 ℃ in the granites. Combining with zircon trace elements characteristics, the zircon saturation temperatures and the correlation between titanium temperature with Th/U and 10000/Hf, we suggested that the Shangqimugan granites were formed by delamination of the thickened lower lithosphere led by mantle underplating in the West Kunlun Orogen. During the magma fractionation, zircon has recrystallized and multiphase magma (melts-fluids) replenishment may have occurred. The heat source of magma was probably related to the asthenospheric upwelling (mantle underplating), which occurred during the post-collision intraplate extension at the end of Qiangtang-Tarim plate convergence along the Kangxiwar fault.

Key words: trace element, zircon saturation temperature, titanium temperature, Shangqimugan of WestKunlun

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