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Geoscience ›› 2023, Vol. 37 ›› Issue (03): 645-661.DOI: 10.19657/j.geoscience.1000-8527.2023.003

• Ore Deposits and Geochemical Prospecting • Previous Articles     Next Articles

Geochronology and Tectonic Setting of the Lamasu Cu Deposit in Northern Xinjiang: Evidence from In-situ LA-ICP-MS Garnet U-Pb Dating

WANG Xiaotong1,2(), LIU Jun1(), YANG Yan3, HE Juncheng2   

  1. 1. MNR Key Laboratory of Metallogeny and Mineral Assessment, Institute of Mineral Resources, Chinese Academy of Geological Sciences, Beijing 100037, China
    2. China University of Geosciences (Beijing), Beijing 100083, China
    3. Development Research Center of Chinese Geological Survey, Beijing 100037, China
  • Received:2022-05-13 Revised:2023-04-17 Online:2023-06-10 Published:2023-07-20

Abstract:

Garnet, as a typical altered mineral in skarn deposits, is suggested to be an important mineral for obtaining accurate ore-forming age. There are abundant skarn Cu deposits in the Chinese Western Tianshan, yet the actual skarn Cu ore-forming ages remain controversial. This limits sufficient understanding of skarn Cu ore genesis and metallogenic dynamic background in the Chinese Western Tianshan. To obtain accurate metallogenic age of skarn Cu deposits in the Chinese Western Tianshan, we selected garnet from the Lamasu Cu deposit for systematic geochemical and geochronological study by Electron Probe X-ray Micro-Analyzer (EPMA) and LA-ICP-MS U-Pb dating. According to the hand-specimen and petrographic characteristics of the garnet minerals, the Lamasu deposit has three types of garnets, including red-brown, light-brown and yellow-green garnets. These garnets belong to the andradite-grossularite series, and occur as andradite (56.96%-85.09%) with minor grossularite (14.33%-43.85%). Three types of garnets yielded LA-ICP-MS U-Pb weighted average ages of (389.1±2.0) to (387.0±2.3) Ma, indicating that the Lamasu Cu mineralization occurred during the Middle Devonian subduction of the northern Tianshan oceanic crust.

Key words: LA-ICP-MS U-Pb dating, garnet, skarn, Lamasu, Xinjiang

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