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Geoscience ›› 2020, Vol. 34 ›› Issue (02): 233-243.DOI: 10.19657/j.geoscience.1000-8527.2020.02.02

• Ore Deposits • Previous Articles     Next Articles

Geochemisty and SHRIMP Zircon U-Pb Chronology of Ore-bearing Rocks from Graphite Deposit in Beizhen County, Liaoning Province

YANG Peiqi1,2(), LIU Jingdang1, ZHANG Yangfei4, LIANG Shuai3, LIU Shumei4   

  1. 1. School of Mining, Liaoning Technical University, Fuxin, Liaoning 123000,China
    2. No. 104 Exploration Team of Non-ferrous Geology of Liaoning Co.Ltd.,Yinkou,Liaoning 115007,China
    3. Shenyang Geological Survey, CGS,Shenyang,Liaoning 110031,China
    4. Chemical Geological Exploration Institute of Liaoning Co.Ltd,Jinzhou, Liaoning 121007,China )
  • Received:2019-07-04 Revised:2020-02-26 Online:2020-05-25 Published:2020-05-25

Abstract:

Dutun graphite deposit in Beizhen County of Liaoning Province occurs in the Middle Proterozoic Gaoyuzhuang Formation. This study carried out systematic analyses on geochemical characteristics of ore-bearing rocks and SHRIMP U-Pb dating for detrital zircons to understand the forming age and tectonic setting of graphite deposit in this area. The geochemical results show that the ore-bearing rocks are characterized by high contents of REEs and enrichment of LILE (such as Rb, Ba, K and Sr), suggesting that the source rocks derived mainly from terrigenous clastic materials mixed with minor amount of marine materials and deposited in an anoxic environment. SHRIMP U-Pb dating yields an average surface age of (2535.64±25.59) Ma for detrital zircons, indicating that upper limit of deposition of ore-bearing source rocks was later than the early Early Proterozoic; the surface ages of (1216.75±12.33) to (1675.70±17.46) Ma for recrystallized zircons, representing that low limit of deposition of the ore-bearing sequence was not later than the late Mesoproterozoic; and an average surface age of (212.53 ± 3.69) Ma for authigenic zircons, revealing that late Triassic magmatic-tectonic thermal events played an important ore-controlling role in recrystallization, enrichment and mineralization of crystalline graphite. Therefore, it can be concluded that black organic-rich rock series deposited in the Mesoproterozoic neritic environment was transformed into epimetamorphic graphite deposit through carbonaceous recrystallization, driven by late-stage metamorphism and late Triassic magmatic activity.

Key words: crystalline graphite, zircon SHRIMP U-Pb geochronology, geochemical features, Gaoyuzhuang Formation, Beizhen County,Liaoning Province

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