ISSN 1009-6248CN 61-1149/P 双月刊

主管单位:中国地质调查局

主办单位:中国地质调查局西安地质调查中心
中国地质学会

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    新疆西天山艾德铜矿床成因:年代学、岩石地球化学和S-Pb-Hf同位素证据

    Genesis of the Aide Copper Deposit in Western Tianshan, Xinjiang: Evidence from Geochronology, Whole-Rock Geochemistry, and S–Pb Isotopes

    • 摘要: 新疆西天山北缘的别珍套-博罗科努地区大量出露的中酸性侵入体与一系列斑岩-矽卡岩型铜多金属矿床密切相关。近年来,赛里木微地块中部新发现的艾德铜矿床产于花岗闪长岩与灰岩的接触带中。本文对艾德铜矿床中与成矿相关的花岗闪长岩开展了锆石U-Pb定年、全岩地球化学和锆石Hf同位素分析,并对矿石中硫化物开展原位S-Pb同位素测试。花岗闪长岩侵位时代为早石炭世(357.9±4.6 Ma),为过铝质高钾钙碱性系列,富集大离子亲石元素Rb、Th、U、K和Pb,亏损Ba和高场强元素Nb、P和Ti。花岗闪长岩锆石εHf(t)值为−1.6~+2.6(平均−0.2),表明岩浆源自中元古代地壳物质的部分熔融,伴有地幔岩浆加入,岩石形成于晚古生代北天山洋南向俯冲至伊犁地块之下的大陆弧环境。矿石中硫化物总δ34S值组成为7.28 ‰~8.92 ‰,206Pb/204Pb=18.320~18.400,207Pb/204Pb=15.612~15.625和208Pb/204Pb=38.518~38.571,指示成矿物质具壳幔混合来源特征,并伴有地层物质的加入。艾德铜矿床与西天山伊犁地块北缘其他的斑岩-矽卡岩型铜矿床具有一致的成岩成矿时代和同源的成矿物质来源,在时空-成因上密切相关,属于晚泥盆世-早石炭世大陆弧环境中的与中酸性侵入岩有关的斑岩-矽卡岩Cu成矿系统。

       

      Abstract: The widespread intermediate-felsic intrusions in the Biezhentao-Boluokenu area along the northern margin of the Western Tianshan, Xinjiang, are genetically associated with a series of porphyry–skarn Cu-polymetallic deposits. The Aide copper deposit, recently discovered in the central Sailimu Micro-Block, is hosted in the contact zone between limestones and granodiorite intrusions. This study reports zircon U–Pb dating, whole-rock geochemical and zircon Hf isotopic analyses of the ore-related granodiorite, together with in situ S–Pb isotopic analyses of sulfides from the ores. The granodiorite was emplaced during the Early Carboniferous (357.9 ± 4.6 Ma) and belongs to the peraluminous high-K calc-alkaline series. It is enriched in large-ion lithophile elements (Rb, Th, U, K, Pb) and depleted in Ba and high-field-strength elements (Nb, P, Ti). Zircon εHf(t) values range from −1.6 to +2.6 (average −0.2), suggesting that the magma was derived from partial melting of Mesoproterozoic crustal materials with the involvement of mantle-derived magmas. The granodiorite were formed in a continental arc setting related to the southward subduction of the North Tianshan Ocean beneath the Yili Block during the Late Paleozoic. The sulfides in the ores yield total δ34S values of 7.28 ‰–8.92 ‰, with 206Pb/204Pb=18.320–18.400, 207Pb/204Pb=15.612–15.625, and 208Pb/204Pb=38.518–38.571, indicating that the ore-forming materials have a mixed crust-mantle source with the addition of strata-derived components. The Aide copper deposit shares a consistent timing of magmatism and mineralization and similar ore-material sources with other porphyry–skarn copper deposits along the northern margin of the Yili Block, Western Tianshan, showing a close spatiotemporal and genetic coupling. It is interpreted as part of a Late Devonian–Early Carboniferous porphyry–skarn Cu metallogenic system associated with intermediate-felsic intrusions in a continental arc setting.

       

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