Origin and evolution of ore-forming fluids of the Machangqing Cu-Mo polymetallic deposit in western Yunnan: Constraints from the in-situ trace elements and H-O isotopic composition of garnet

被引：0
|
作者：
Ji Y. [1 ,2 ]
Du L. [1 ,2 ,3 ]
Chen J. [1 ,2 ]
Huang Z. [3 ]
Li B. [4 ]
Li X. [1 ,2 ]
Liu L. [1 ,2 ]
Yang Z. [1 ,2 ]
机构：
[1] College of Resources and Environmental Engineering, Guizhou University, Guizhou, Guiyang
[2] Key Laboratory of Karst Georesources and Environment, Guizhou University, Ministry of Education, Guizhou, Guiyang
[3] State Key Laboratory of Ore Deposit Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guizhou, Guiyang
[4] Faculty of Land and Resource Engineering, Kunming University of Science and Technology, Yunnan, Kunming
来源：
Dizhi Xuebao/Acta Geologica Sinica | 2023年 / 97卷 / 04期
关键词：
garnet; H-O isotopes; Machangqing Cu-Mo polymetallic deposit; ore-forming fluids; trace elements;
D O I：
10.19762/j.cnki.dizhixuebao.2023105
中图分类号：
学科分类号：
摘要：
The Machangqing Cu-Mo deposit, located in the Sanjiang Tethyan metallogenic belt, is a polymetallic deposit related to the intrusion of alkaline porphyry in the Himalayan period. Previous studies have shown that the Machangqing Cu-Mo polymetallic deposit was formed in a porphyry-skarn metallogenic system. However, due to the lack of systematic mineralogical research, a mineralization process and metallogenic effects of skarn are still unclear, limiting a comprehensive understanding of the mineralization process of this deposit. Herein, this paper considers garnet in skarn mineralization in Machangqing deposit as the research object, and uses H-O isotope, electron probe (EPMA) and LATCP-MS in-situ microregion technology to carry out isotope and composition analysis to define the source of ore-forming fluids and invert the evolution process of ore-forming fluids. The garnets can be divided into early euhedral garnets (Grt I) and late anhedral type (Grt II). The Grt I, coexisting with the pyroxene, pyrite and chalcopyritc, belongs to the grossular-andradite garnet solid solution (And 49.37~99.58 Gro 0~49.79). The Grt II has elevated Fe compared to Grt I, and mainly consists of andraditc (And 67.5~99.85 Gro 0_31.84). Both the types of garnets arc enriched in Th, U, LREEs and Nd, depleted in Ba, Sr, Hf and Nb. Based on the chemical compositions of garnet, the Grt I may have formed under mildly acidic, oxidized and low W/R conditions, whereas the Grt II may have formed under acidic, oxidation, and high W/R conditions. In addition, the SDV.SM0W values and § On„id values of these garnets range from-122. 6%o to-98. 6%o and 5. 95%o to 8. 25%o, respectively, implying that the hydrothcrmal ore-forming fluid originated from magma-derived fluid. A comprehensive consideration of data indicated that the oxygen fugacity and temperature of the ore-forming fluid presented a decreasing trend during the skarn mineralization process, and the pH of the fluid gradually changes from acid to weak acid neutral. This process may have been the main mechanism to trigger the precipitation of skarn type mineralized copper molybdenum sulfide in the Machangqing deposit. © 2023 Geological Society of China. All rights reserved.
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页码：1140 / 1156
页数：16
相关论文
共 99 条
  • [1] Bau M., Rare-earth element mobility during hydrothermal and metamorphic fluid-rock interaction and the significance of the oxidation state of europium, Chemical Geology, 93, 3-4, pp. 219-230, (1991)
  • [2] Bau M., Controls on the fractionation of isovalent trace elements in magmatic and aqueous systems: Evidence from Y/ Ho, Zr/Hf, and lanthanide tetrad effect, Contrib. Journalof Mineralogical and Penological Sciences, 123, pp. 323-333, (1996)
  • [3] Bau M, Dulski P., Anthropogenic origin of positive gadolinium anomalies in river waters, Earth and Planetary Science Letters, 143, pp. 245-255, (1996)
  • [4] Bau M, Dulski P., comparing yttrium and rare earths in hydrothermal fluids from the Mid-Atlantic Ridge: Implications for Y and REE behaviour during near-vent mixing and for the Y/Ho ratio of Proterozoic seawater, Chemical Geology, 155, pp. 77-90, (1999)
  • [5] Xianwu Bi, Ruizhong Hu, Zaojun Ye, Shuxun Shao, A study on the relationship between A-type granites and copper mineralization taking Machangqing copper mine as an example, Science in China (Series D: Earth Science), 6, pp. 489-495, (1999)
  • [6] Bi Xianwu, Hu Ruizhong, Peng Jiantang, Wu Kaixing, Su Wenchao, Zhan Xinzhi, Geochemical characteristics of the Yao'an and Machangqing alkaline-rich intrusions, Acta Petrologica Sinica, 21, 1, pp. 113-124, (2005)
  • [7] Bian Xiaolong, Zhang Jing, Wang Jialin, In situ analysis of garnets from the Hongshan skarn copper deposit in Northwest Yunnan Province and its geological implications, Acta Petrologica Sinica, 35, 5, pp. 1463-1477, (2019)
  • [8] Calagari A A, Hosseinzadeh G., The mineralogy of copper-bearing skarn to the east of the Sungun-Chay river, East-Azarbaidjan, Iran, Journal of Asian Earth Sciences, 28, 4-6, pp. 423-438, (2006)
  • [9] Chen Lu, Liu Yongsheng, Hu Zhaochu, Gao Shan, Zong Keqing, Chen Haihong, Accurate determinations of fifty-four major and trace elements in carbonate by LA-ICP-MS using normalization strategy of bulk components as 100%, Chemical Geology, 284, 3-4, pp. 283-295, (2011)
  • [10] Clayton R N, Mayeda T K., The use of bromine pentafluoride in the extraction of oxygen from oxides and silicates for isotopic analysis, Geochimicaet Cosmochimica Acta, 27, 1, pp. 43-52, (1963)
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