西藏铁格隆南超大型铜(金)矿床绢云母矿物学特征及地质意义
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1.中国地质科学院矿产资源研究所;2.山东省地质科学研究院;3.中国地质科学院;4.成都理工大学;5.中国地质大学(北京),地球科学与资源学院

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中国地质科学院矿产资源研究所基本业务费项目(编号KK1921,KK2116,KJ2102)和国家自然科学基金项目(编号41902097,42102116)


Mineralogical characteristics and implications of sericite from the Tiegelongnan super-large copper (gold) deposit in Tibet
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1.MNR Key Laboratory of Metallogeny and Mineral Assessment, Institute of Mineral Resources, Chinese Academy of Geological Sciences;2.Shandong Geological Science Institute;3.Chinese Academy of Geological Sciences;4.College of Earth Sciences, Chengdu University of Technology;5.School of Earth Sciences and Resources, China University of Geosciences(Beijing))

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    摘要:

    铁格隆南矿床产出了西藏班公湖-怒江成矿带多龙矿集区最大的斑岩-高硫型铜(金银)成矿系统。由于高硫型矿化与蚀变对斑岩型矿化和蚀变的广泛叠加,导致其成矿系统结构和成矿作用机制变得十分复杂,一定程度阻碍了其精细成矿模型的构建。本文基于铁格隆南矿床现有的勘查和研究成果,从矿物学的角度,以绢云母为典型蚀变矿物,通过详细的镜下鉴定、扫描电镜和电子探针分析,详细揭示不同空间位置、不同产状绢云母的矿物学特征和成因,探究其对铁格隆南矿床成矿机制的指示意义。结果显示,铁格隆南矿床绢云母主要由白云母端元、伊利石端元、绿鳞石端元以及少量钠云母端元组成。矿体中绢云母与铜矿物具有成因联系。在深部的早期水岩反应中,绢云母主要与黄铜矿伴生,热液蚀变斑岩形成的绢云母呈现高Si低Al的特征,而热液蚀变砂岩呈高Al低Si的特征。随着流体向浅部继续运移,绢云母共生的金属矿化转换为斑铜矿和铜蓝,多形成高Al低Si的绢云母。相对于在侵入岩中产出的绢云母,在砂岩中形成的绢云母的Fetot、Fe3+、Na+含量更高。侵入岩中形成富Fe2+绢云母,指示热液还原性较强;砂岩中形成富Fe3+的绢云母,指示热液偏氧化。此外,在黄铁绢英岩化带较中-浅部产出的绢云母常与较多高岭石和铜蓝、斑铜矿伴生,指示了热液中的SO2发生聚集、温度降低、酸性增强并导致水岩反应增强和矿质沉淀的过程。综上,绢云母与不同矿物组合及其地球化学特征,对成矿流体环境及勘查评价有良好的指示意义。

    Abstract:

    The Tiegelongnan deposit yields the largest porphyry-high sulfidation Cu (Au, Ag) mineralization system in the Bangong-Nujiang metallogenic belt of Tibet. For the advanced argillic alteration was widely imposed on the phyllic zone, which results in a complex mineralization process and metallogenic system that impedes the construction of an accurate metallogenic model. Based on the previous exploration and research works of the Tiegelongnan deposit, we mainly focus on the typical alteration mineral (sericite) to study its mineralogical characteristics by scanning electron microscope and electron microscope, and uncover the mineralogical characteristics and genesis of sericite which produced in different conditions and locations, which aimed to study the metallogenic mechanism of the Tiegelongnan deposit. Finally the significance of the mineralization mechanism was discussed through all the geochemical analyses. It is proved that the sericite of the Tiegelongnan deposit are composed of muscovite, illite and celadonite endmembers as well as minor paragonite endmembers. In the ore-body sericite and copper minerals have a close paragenetic link. In the early-stage water-rock interactions in deep levels, high Si and low Al sericite-chalcopyrite was produced in porphyries, while high Al and low Si sericite-chalcopyrite was yielded in sandstone. With the progression of hydrothermal evolution towards shallower levels, the sulfides graded to bornite and covellite and the sericite with high Al and low Si content was produced. Besides, sericites from the altered sandstones are also enriched in Fetot, Fe3+, Na+ compared to those present in intrusions. Fe2+-rich sericite in porphyries indicates a reduced hydrothermal condition, while Fe3+-rich sericite in sandstone implies a relative oxidized hydrothermal condition. In the mediate-shallow level of the phyllic alteration zone of the Tiegelongnan deposit, sericites frequently occurring with a certain amount of kaolinite as well as bornite and covellite, which reflects that the SO2 enrichment, temperature decreasing and acid increasing resulted in a stronger water-rock interaction and copper precipitation. All in all, different mineral assemblages concerning with sericite and the distinct sericite geochemical characteristics have some important implications for the hydrothermal conditions and the exploration prospecting.

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  • 收稿日期:2021-12-29
  • 最后修改日期:2022-02-16
  • 录用日期:2022-02-16
  • 在线发布日期: 2022-12-29
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