Geochronology, Geochemistry and Sr-Nd-Pb-Hf Isotopes of No. I
Complex from the Shitoukengde Ni–Cu Sulfide Deposit in the
Eastern Kunlun Orogen, Western China: Implications for
the Magmatic Source, Geodynamic Setting and Genesis |
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作者姓名: | LI Liang SUN Fengyue LI Bile LI Shijin CHEN Guangjun WANG Wei YAN Jiaming ZHAO Tuofei DONG Jun ZHANG Dexin |
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摘 要: | The Shitoukengde Ni-Cu deposit, located in the Eastern Kunlun Orogen, comprises three mafic–ultramafic complexes, with the No. I complex hosting six Ni-Cu orebodies found recently. The deposit is hosted in the small ultramafic bodies intruding Proterozoic metamorphic rocks. Complexes at Shitoukengde contain all kinds of mafic-ultramafic rocks, and olivine websterite and pyroxene peridotite are the most important Ni-Cu-hosted rocks. Zircon U-Pb dating suggests that the Shitoukengde Ni-Cu deposit formed in late Silurian(426–422 Ma), and their zircons have εHf(t) values of-9.4 to 5.9 with the older T_(DM1) ages(0.80–1.42 Ga). Mafic-ultramafic rocks from the No. I complex show the similar rare earth and trace element patterns, which are enriched in light rare earth elements and large ion lithophile elements(e.g., K, Rb, Th) and depleted in heavy rare earth elements and high field strength elements(e.g., Ta, Nb, Zr, Ti). Sulfides from the deposit have the slightly higher δ~(34)S values of 1.9–4.3‰ than the mantle(0 ± 2‰). The major and trace element characteristics, and Sr-Nd-Pb and Hf, S isotopes indicate that their parental magmas originated from a metasomatised, asthenospheric mantle source which had previously been modified by subduction-related fluids, and experienced significant crustal contamination both in the magma chamber and during ascent triggering S oversaturation by addition of S and Si, that resulted in the deposition and enrichment of sulfides. Combined with the tectonic evolution, we suggest that the Shitoukengde Ni-Cu deposit formed in the post-collisional, extensional regime related to the subducted oceanic slab break-off after the Wanbaogou oceanic basalt plateau collaged northward to the Qaidam Block in late Silurian.
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收稿时间: | 2016/12/2 0:00:00 |
修稿时间: | 2008/5/17 0:00:00 |
Geochronology,Geochemistry and Sr‐Nd‐Pb‐Hf Isotopes of No. I Complex from the Shitoukengde Ni–Cu Sulfide Deposit in the Eastern Kunlun Orogen,Western China: Implications for the Magmatic Source,Geodynamic Setting and Genesis |
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Authors: | LI Liang SUN Fengyue LI Bile LI Shijin CHEN Guangjun WANG Wei YAN Jiaming ZHAO Tuofei DONG Jun and ZHANG Dexin |
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Institution: | 1 College of Earth Sciences, Jilin University, Changchun 130061, China,1 College of Earth Sciences, Jilin University, Changchun 130061, China,1 College of Earth Sciences, Jilin University, Changchun 130061, China,2 Qinghai Bureau of Geological Survey, Xining 810001, China,1 College of Earth Sciences, Jilin University, Changchun 130061, China,2 Qinghai Bureau of Geological Survey, Xining 810001, China,1 College of Earth Sciences, Jilin University, Changchun 130061, China,1 College of Earth Sciences, Jilin University, Changchun 130061, China,3 No. 108 Geological Party, Sichuan Bureau of Geology and Mineral Exploration, Chengdu 611230, China and 2 Qinghai Bureau of Geological Survey, Xining 810001, China |
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Abstract: | The Shitoukengde Ni‐Cu deposit, located in the Eastern Kunlun Orogen, comprises three mafic–ultramafic complexes, with the No. I complex hosting six Ni‐Cu orebodies found recently. The deposit is hosted in the small ultramafic bodies intruding Proterozoic metamorphic rocks. Complexes at Shitoukengde contain all kinds of mafic‐ultramafic rocks, and olivine websterite and pyroxene peridotite are the most important Ni‐Cu‐hosted rocks. Zircon U‐Pb dating suggests that the Shitoukengde Ni‐Cu deposit formed in late Silurian (426–422 Ma), and their zircons have εHf(t) values of ?9.4 to 5.9 with the older TDM1 ages (0.80–1.42 Ga). Mafic‐ultramafic rocks from the No. I complex show the similar rare earth and trace element patterns, which are enriched in light rare earth elements and large ion lithophile elements (e.g., K, Rb, Th) and depleted in heavy rare earth elements and high field strength elements (e.g., Ta, Nb, Zr, Ti). Sulfides from the deposit have the slightly higher δ34S values of 1.9–4.3± than the mantle (0 ± 2±). The major and trace element characteristics, and Sr‐Nd‐Pb and Hf, S isotopes indicate that their parental magmas originated from a metasomatised, asthenospheric mantle source which had previously been modified by subduction‐related fluids, and experienced significant crustal contamination both in the magma chamber and during ascent triggering S oversaturation by addition of S and Si, that resulted in the deposition and enrichment of sulfides. Combined with the tectonic evolution, we suggest that the Shitoukengde Ni‐Cu deposit formed in the post‐collisional, extensional regime related to the subducted oceanic slab break‐off after the Wanbaogou oceanic basalt plateau collaged northward to the Qaidam Block in late Silurian. |
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Keywords: | Sr-Nd-Pb-Hf isotopes crustal contamination oceanic slab break-off post-collisional extension Shitoukengde Ni-Cu deposit Eastern Kunlun Orogen |
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