Zircon Ce4+/Ce3+ ratios and ages for Yulong ore-bearing porphyries in eastern Tibet |
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| Authors: | Hua-Ying Liang Ian H Campbell Charlotte Allen Wei-Dong Sun Cong-Qiang Liu Heng-Xiang Yu Ying-Wen Xie Yu-Qiang Zhang |
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| Institution: | (1) Key Laboratory for Metallogenic Dynamics, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou, 510640, China;(2) Research School of Earth Sciences, Australian National University, Canberra, ACT 0200, Australia;(3) Key Laboratory of Isotope Geochronology and Geochemistry, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou, 510640, China;(4) Institute of Geochemistry, Chinese Academy of Sciences, Guiyang, 550002, China;(5) Guilin Institute of Technology, Guilin, 541004, China |
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| Abstract: | Yulong ore-bearing porphyries, along the northwestern extension of the Red River–Ailao Shan fault system in eastern Tibet, consist of five porphyry deposits, containing a total of more than 8 million tons of copper resources. U–Th–Pb laser inductively coupled plasma mass spectrometry dating of zircon shows that the porphyries were emplaced in Early Tertiary (41.2–36.9 Ma), covering a period of ∼4.3 Ma, with formation ages decreasing systematically from northwest to southeast. The start of porphyry magmatism coincided with the onset of transpressional movement along the Red River–Ailao Shan fault system, implying a close link between these two events. Age sequence in intrusions can be plausibly explained by assuming that a region of melting in the lower northwestern plate moved southeasternward along the Tuoba–Mangkang fault relative to the upper plate. Zircon grains from the Yulong ore-bearing porphyries have higher Ce4+/Ce3+ than those from barren porphyries in the region. This suggests that the ore-bearing porphyries crystallized from a relatively oxidized magma, which has important implications for future ore exploration in the region and other Cu deposits in convergent margin environments in general. |
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| Keywords: | Porphyry copper deposits Geochronology Zircon Laser ablation ICP-MS Continental subduction Tibet |
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