地学前缘 ›› 2024, Vol. 31 ›› Issue (2): 299-312.DOI: 10.13745/j.esf.sf.2023.2.85

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岩浆热液白钨矿氧同位素组成研究:对流体源区与演化过程的示踪

吴锟言1,2(), 刘飚1,2,*(), 吴堑虹1,2, 李欢1,2   

  1. 1.中南大学 有色金属成矿预测与地质环境监测教育部重点实验室, 湖南 长沙, 410083
    2.中南大学 地球科学与信息物理学院, 湖南 长沙, 410083
  • 收稿日期:2022-09-08 修回日期:2023-03-14 出版日期:2024-03-25 发布日期:2024-04-18
  • 通讯作者: *刘 飚(1989—),男,博士,硕士生导师,主要从事矿床学方面研究。E-mail: biaoliu@csu.edu.cn
  • 作者简介:吴锟言(1998—),女,硕士研究生,主要从事矿物地球化学研究。E-mail: wukunyan@csu.edu.cn
  • 基金资助:
    国家重点研发计划项目“钦杭成矿带湘南段铜锡多金属矿产深部探测技术示范”(2018YFC0603902);湖南省自然科学青年基金项目“不同类型钨矿床中白钨矿的稀土配分型式及其替代机理研究”(2021JJ40722)

Oxygen isotope composition of scheelite in magmatic-hydrothermal W deposits: Tracing fluid source and evolution process

WU Kunyan1,2(), LIU Biao1,2,*(), WU Qianhong1,2, LI Huan1,2   

  1. 1. MOE Key Laboratory of Metallogenic Prediction of Nonferrous Metals and Geological Environment Monitoring, Central South University, Changsha 410083, China
    2. School of Geosciences and Info-Physics, Central South University, Changsha 410083, China
  • Received:2022-09-08 Revised:2023-03-14 Online:2024-03-25 Published:2024-04-18

摘要:

南岭地区中生代发育大量岩浆热液型钨矿床,但是成矿岩体类型、侵位深度以及围岩性质存在差异,且成矿过程中受多期流体活动与大气降水的影响,流体源区与演化过程复杂。本文对不同类型钨矿床中多阶段白钨矿进行了氧同位素组成分析,研究结果显示与S型花岗岩侵入相关的白钨矿氧同位素值最高(5.7‰~7.8‰),A型花岗岩侵入相关的最低(2.9‰~4.5‰),I型花岗岩侵入相关的落在二者之间(5.6‰)。不同类型钨成矿早期流体均主要为岩浆水,后期成矿过程中外来流体贡献不同,其中大气降水对夕卡岩和云英岩型钨矿化影响较小,而石英脉型矿化存在较大比例的大气降水的加入。此外,单颗粒石英脉型白钨矿的氧同位素组成也存在较大的不均一性,核部到边部逐渐降低的趋势反映了多期次的流体活动。综合分析认为,早期结晶的白钨矿尽管经历岩浆分异、流体出溶与热液沉淀,仍保留岩浆熔体的部分氧同位素特征,而早—晚阶段白钨矿氧同位素组成的变化详细记录了流体源区特征与演化过程。夕卡岩与云英岩型白钨矿形成主要与强烈的水岩反应相关,而石英脉中白钨矿沉淀主要与大量的大气降水加入有关。

关键词: 岩浆热液, 白钨矿, 氧同位素, 流体源区, 南岭地区

Abstract:

A large number of magmatic hydrothermal tungsten deposits were formed in Nanling area in the Mesozoic with complex fluid source and evolution process. The ore deposits differ in the ore-forming granite type, intrusion depth and surrounding rock, and formed under influences of multi-stage fluid activities and meteoric water mixing. In this study the oxygen isotope composition of scheelites from different types of tungsten deposits are analyzed. The results show that scheelite related to S-type granite intrusion had the highest δ18O values (5.7‰-7.8‰), and those to A- and I-type granites had the lowest (2.9‰-4.5‰) and in-between (5.6‰) δ18O values, respectively. The ore-forming fluids in the early stage were mainly magmatic water, while the contribution of meteoric water in the late stage varied, where the addition of meteoric water, which had little effect on skarnization and greisenization, had large impact on quartz vein mineralization. The δ18O values in single quartz vein scheelite grain showed high spatial heterogeneity, with a decreasing trend from core to edge, reflecting multi-stage fluid activity. The study concludes based on the δ18O data that although scheelite of the early stage had undergone magmatic differentiation, fluid exsolution and hydrothermal precipitation, it still retains some characteristics of magmatic melt; while scheelite of early-late stage can reveal the fluid source and evolution in detail. The mineralization of skarn and greisen scheelite is mainly related to intense fluid-rock interactions, while scheelite precipitation in quartz vein is mainly related to the addition of large amounts of meteoric water.

Key words: magmatic-hydrothermal, scheelite, oxygen isotope, fluid source, Nanling

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