地学前缘 ›› 2021, Vol. 28 ›› Issue (3): 355-378.DOI: 10.13745/j.esf.sf.2021.1.9

• 成矿模式与定量找矿模型 • 上一篇    下一篇

新疆尾亚—天湖地区花岗岩类剥蚀程度估算及对区域找矿的启示

李季霖1,2(), 陈正乐1,3,*(), 周涛发2, 韩凤彬1, 张文高1, 霍海龙1, 刘博1,2, 赵同阳4, 韩琼4, 李平4, 郑加行4, 陈贵民5   

  1. 1.中国地质科学院 地质力学研究所 国土资源部古地磁与古构造重建重点实验室, 北京 100081
    2.合肥工业大学 资源与环境工程学院, 安徽 合肥 230009
    3.东华理工大学 核资源与环境国家重点实验室, 江西 南昌 330013
    4.新疆维吾尔自治区地质调查院, 新疆 乌鲁木齐 830000
    5.新疆维吾尔自治区地质矿产勘查开发局第六地质大队, 新疆 哈密 839000
  • 收稿日期:2021-01-20 修回日期:2021-02-18 出版日期:2021-05-20 发布日期:2021-05-23
  • 通信作者: 陈正乐
  • 作者简介:李季霖(1991—),男,博士研究生,矿田构造学专业。E-mail: 741161098@qq.com
  • 基金资助:
    国家科技支撑计划项目(2018YFC0604005);中国地质调查局项目(DD20190161);国家自然科学基金项目(41902214);中国地质调查局基本科研业务费项目(JYYWF20183702);中国地质调查局基本科研业务费项目(JYYWF20180602)

Estimation of the extend of granitoid exhumation in the Weiya-Tianhu area: Insight into ore prospecting in the Central Tianshan region, Xinjiang

LI Jilin1,2(), CHEN Zhengle1,3,*(), ZHOU Taofa2, HAN Fengbin1, ZHANG Wengao1, HUO Hailong1, LIU Bo1,2, ZHAO Tongyang4, HAN Qiong4, LI Ping4, ZHENG Jiaxing4, CHEN Guimin5   

  1. 1. Ministry of Land and Resources Key Laboratory of Paleomagnetism and Tectonic Reconstruction, Institute of Geomechanics, Chinese Academy of Geological Sciences, Beijing 100081, China
    2. School of Resources and Environmental Engineering, Hefei University of Technology, Hefei 230009, China
    3. State Key Laboratory of Nuclear Resources and Environment, East China University of Technology, Nanchang 330013, China
    4. Xinjiang Institute of Geological Survey, Ürümqi 830000, China
    5. No.6 Geological Survey Team, Bureau of Xinjiang Geology and Mineral Resources Development, Hami 839000, China
  • Received:2021-01-20 Revised:2021-02-18 Online:2021-05-20 Published:2021-05-23
  • Contact: CHEN Zhengle

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摘要：

尾亚—天湖地区位于新疆中亚造山带东南部的中天山地块内,晚古生代—中生代岩浆活动强烈,产出了战略性关键矿产尾亚钒铁磁铁矿。在详细岩相学观察的基础上,对尾亚、天湖和沙泉子南岩体中的角闪石和黑云母进行了电子探针(EMPA)测试分析,限定了3个岩体结晶的温压条件、氧逸度、含水量和含铁指数等要素,为解析中天山地块的岩浆-成矿物化条件及其区域找矿勘查工作提供参考。测试结果表明,该区花岗岩类中的角闪石富镁、钙、钠,贫钾,属于钙角闪石族;黑云母有高镁、钛、铝、钾和低硅、钠的特征为镁质黑云母。角闪石和黑云母的化学成分揭示其寄主岩浆为钙碱性造山带岩系,具有壳幔混源的特征,推测可能是板块俯冲背景下由地幔楔与大陆地壳物质混熔形成。根据角闪石-黑云母矿物温压计,估算出沙泉子南石英闪长岩的结晶温度为651~753 ℃,压力为31~79 MPa,尾亚二长花岗岩和钾长花岗岩的结晶温度为762~833 ℃,压力为85~215 MPa,天湖花岗闪长岩的结晶温度为668~812 ℃,压力为31~117 MPa。3个岩体岩浆结晶时的氧逸度lgf(O2)范围为-15.7~-9.4,而且在角闪石结晶时岩浆具有较高的含水量。综合分析,认为该区的花岗岩类具有高温、低压、高氧逸度、富水和高含铁指数的特点,有利于Fe等成矿元素在流体中富集,具有良好的铁矿成矿条件。进一步利用角闪石-黑云母压力计,计算了花岗岩类岩体的侵位深度,从而估算出岩体的剥蚀程度处于2.2~5.5 km,且区域的隆升剥蚀量差异明显;结合现有的矿产地表展布特征,推测天湖岩体一带深部仍具有较好的铁矿找矿潜力。

关键词: 矿物学特征, 物理化学条件, 角闪石-黑云母温压计, 隆升-剥蚀程度, 中天山地块尾亚—天湖地区

Abstract:

The Weiya-Tianhu granitoid area is located on the Central Tianshan Terrane, Xinjiang, southeast of the Central Asian Orogenic Belt (CAOB), where Late Paleozoic-Early Mesozoic magmatic activities were widespread and the strategic key mineral Weiya V-Ti magnetite is produced. This paper reports the detailed petrographic observations of the region. Based on these observations, the compositions of amphiboles and biotites from the Weiya, Tianhu, and Shaquanzinan granitoids were obtained by electron microprobe analysis (EMPA) to constrain the crystallization controlling factors for the three granitoids. The constrained controlling factors such as temperature, pressure, oxygen fugacity, water content and Fe provide references for analyzing the physicochemical conditions of magmatic mineralization and ore prospecting in the region. The EMPA data show that the amphiboles are rich in Mg, Ca and Na, poor in K, and belong to calcic amphiboles. The biotites have the characteristics of high Mg, Ti, Al and K contents and low Si and Na contents, which suggests a magnesia origin. The chemical compositions of amphiboles and biotites revealed their host magma to be the calc-alkaline orogenic rock series from a hybrid crustal-mantle source, attributed probably to partial melting of mantle wedge and continental crust under the tectonic setting of plate subduction. The crystallization temperature and pressure of the Shaquanzinan quartz diorite, Weiya monzonitic granites and moyites, and Tianhu granodiorites, calculated by geothermometric method, were 651-753 ℃ and 31-79 MPa, 762-833 ℃ and 85-215 MPa, 668-812 ℃ and 31-117 MPa, respectively. The magmatic oxygen fugacity lgf(O2) in the three granitoids at crystallization varied from -15.7 to -9.4, with high water content in the melt during amphibole crystallization. Therefore, it is suggested that the granitoids in the region have the characteristics of high temperature, low pressure, high oxygen fugacity, water-rich and high Fe index, which are beneficial to elemental enrichment in ore-forming fluid and hence favoring Fe mineralization. The intrusive depth of these granitoids was further assessed by Al-in-hornblende barometry. The results show that the extend of granitoid exhumation is between 2.2-5.5 kilometers in the region, where the rates of uplifting and exhumation differ significantly. Together with the known ore distribution on land surface, it is proposed that Fe prospectivity is highly favorable at depth in the Tianhu granodiorite area.

Key words: mineralogical characteristics, physicochemical conditions, Al-in-hornblende barometry, uplifting-exhumation extend, Weiya-Tianhu area in the Central Tianshan Terrane

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