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现代地质 ›› 2023, Vol. 37 ›› Issue (06): 1509-1523.DOI: 10.19657/j.geoscience.1000-8527.2023.033

• 矿床学与区域成矿学 • 上一篇    下一篇

三江特提斯马厂箐斑岩铜钼矿床成矿时间尺度探讨:来自石英中Ti-Al扩散年代学的约束

张靓1(), 陈奇1,2(), 高添1, 李雯1, 钱金龙1,2, 刘俐君1,2, 王长明1,2   

  1. 1.中国地质大学(北京)地球科学与资源学院,北京 100083
    2.中国地质大学地质过程与矿产资源国家重点实验室,北京 100083
  • 收稿日期:2022-08-27 修回日期:2023-03-15 出版日期:2023-12-10 发布日期:2024-01-24
  • 通讯作者: 陈奇,男,博士研究生,1994年出生,矿物学、岩石学、矿床学专业,主要从事矿床学与矿床地球化学研究。Email: cq94@foxmail.com
  • 作者简介:张靓,女,本科生,2001年出生,地质学专业,主要从事矿床学与矿床地球化学研究。Email: 2080905262@qq.com
  • 基金资助:
    国家重点研发计划项目(2020YFA0714802);国家自然科学基金重大研究计划项目(92162101)

Delicate Timescale of the Machangqing Porphyry Copper-Molybdenum Deposit in Sanjiang Tethyan Domain, SW China: Constraints from the Diffusion Chronology of Ti and Al in Quartz

ZHANG Liang1(), CHEN Qi1,2(), GAO Tian1, LI Wen1, QIAN Jinlong1,2, LIU Lijun1,2, WANG Changming1,2   

  1. 1. School of Earth Science and Resources, China University of Geosciences (Beijing), Beijing 100083, China
    2. State Key Laboratory of Geological Processes and Mineral Resources, China University of Geosciences (Beijing), Beijing 100083, China
  • Received:2022-08-27 Revised:2023-03-15 Online:2023-12-10 Published:2024-01-24

摘要:

近年来,斑岩矿床成矿时间尺度的研究趋向精细化和多样化。利用高精度同位素测年、元素扩散年代学以及热力学数值模拟等方法,斑岩矿床的成矿时间尺度被精确限定在几十年到几十万年之间。石英作为一种在各个成矿阶段脉体中稳定存在的矿物,成为精细研究热液脉冲过程的良好对象。本文以三江特提斯马厂箐斑岩铜钼矿床为研究对象,基于对各阶段脉体关系和矿物组合精细梳理,利用石英中Ti和Al的扩散年代学方法,在限定成矿时间尺度同时也对扩散年代学的适用性提出几点思考。马厂箐矿床的脉体具有多阶段活动特征,据其脉体穿插关系和矿物组成划分出多个热液脉冲阶段。选取样品中可以分别代表两个成矿阶段的A2脉和B3脉石英进行元素扩散模拟。结果显示,早阶段石英CL强度和Ti元素关联度更高,使用Ti扩散模型限定的成矿时间尺度为10.5~57.5 ka;而主成矿阶段CL强度和Al元素关联度更高,使用Al扩散模型限定的成矿时间尺度为522.3 ka。综合分析认为,使用元素扩散年代学限定斑岩成矿的时间尺度可能会受到温压条件、模拟位置、元素测试分辨率和精度等因素的影响,因而需要结合成矿条件和矿物生长特征合理构建扩散模型。

关键词: 成矿时间尺度, 扩散年代学, 石英, 斑岩矿床, 马厂箐, 三江特提斯

Abstract:

In recent years, studies on the porphyry metallogenic timescale have become more refined and diversified.By using high-precision isotope dating, element diffusion chronology and thermodynamic numerical simulation, the porphyry metallogenic timescale are precisely defined to be between tens to hundreds of thousands of years.Quartz is a chemically stable mineral in various mineralization stages, which can be utilized as an ideal object to explore episodic hydrothermal processes.Taking the Machangqing porphyry Cu-Mo deposit in the Sanjiang Tethyan Domain as the case study, and basing on the fine arrangement of the vein relationship and mineral assemblage at each stage, we used the diffusion chronology method of Ti and Al in quartz to constrain the timescale, and discussed the practical application of diffusion chronology.The Machangqing deposit contains multi-stage hydrothermal veins, which can be divided into multiple hydrothermal stages based on their crosscutting relationship and mineral composition.For the quartz in the early-ore A2 and main-ore B3 veins, our finding shows that the early-ore quartz samples have higher correlation between the CL intensity and Ti element, and its timescale defined by the Ti diffusion is 10.5-57.5 ka; for the main ore stage, the quartz CL intensity has a higher correlation with the Al element, and its timescale defined by the Al diffusion is 522.3 ka.Overall, we consider that using element diffusion chronology to constrain the porphyry metallogenic timescale may be affected by the temperature-pressure conditions, simulation location, analytical precision and accuracy.Therefore, it is necessary to construct a reasonable diffusion model based on the metallogenic conditions and mineral growth characteristics.

Key words: timescale, diffusion chronology, quartz, porphyry deposit, Machangqing, Sanjiang Tethan domain

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