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投稿时间：2022-09-03 修订日期：2023-06-08 网络发布日期：2023-09-06
中文摘要:文章对比分析了米仓山南缘旺苍-南江石墨矿带东、西2段主要石墨矿床地质及地球化学特征。矿带东段石墨矿体形态以不规则囊状为主,矿石类型以角砾状石墨大理岩型为主,矿体原岩为含有机质碳酸盐岩;矿石的V/Cr、V/(V+Ni)、U/Th平均值分别为0.75、0.42、0.94,稀土元素总量(∑REE)平均84.4 μg/g,δEu平均0.65,矿体原岩沉积于贫氧环境。西段石墨矿体以似层状为主,层控特征明显,矿石类型为石墨片岩型,具钒矿化,原岩以含碳质黏土质、泥砂质碎屑岩为主;矿石的V/Cr、V/(V+Ni)、U/Th平均值分别为3.90、0.79、1.93,稀土元素总量(REE)平均124 μg/g,δEu平均0.59,矿体原岩沉积于贫氧-缺氧环境。石墨矿δ13C值为-16.0‰~-23.0‰,平均-19.1‰,与有机质相近,显著低于大理岩围岩,表明石墨矿碳质来源以有机碳为主。米仓山南缘石墨矿床成因为沉积-变质型,石墨含矿层位经历了晋宁期-澄江期区域变质及热接触变质等多期变质成矿作用,最终形成晶质石墨矿床,其成矿与罗迪尼亚超大陆汇聚-裂解引发的区域变质-岩浆活动有关。
Abstract:In this paper, the geological and geochemical characteristics of the graphite deposits in the eastern and western sections of the Wangcang-Nanjiang graphite ore belt in the southern margin of the Micang Mountains were compared and analyzed. In the eastern section of the ore belt, most graphite ore bodies occur in irregular sack-like, the ores are dominated by brecciated graphite marble, and the primary rocks are carbonate rocks containing organic matter. The ores have an average V/Cr value of 0.75, V/(V+Ni) value of 0.42, U/Th value of 0.94, REE value of 84.4 μg/g, and δEu value of 0.65. The primary rocks of the ore bodies are deposited in an oxygen-poor environment. In the western section of the ore belt, most graphite ore bodies are stratified, with obvious stratabound characteristics. The ores are dominated by graphite schist, with vanadium mineralization. The primary rocks are dominated by carbonaceous clay and mud-sandy clastic rocks. The ores have an average V/Cr value of 3.90, V/(V+Ni) value of 0.79, U/Th value of 1.93, REE value of 124 μg/g, and δEu value of 0.59. The primary rocks of the ore bodies are deposited in an oxygen-deficient to oxygen-poor environment. The graphite ores have an δ13C value ranging from -16.0‰ to -23.0‰, with an average of -19.1‰, which is similar to that of organic matter and significantly lower than that of marble host rocks, indicating the carbonaceous matters in graphite ores are mainly sourced from organic carbon. The graphite deposits in the southern margin of the Micang Mountains are of sedimentary-metamorphic type. The graphite ore-bearing horizons had undergone multi-staged metamorphic mineralization in the Jinning-Chengjiang period, such as regional metamorphism and thermal contact metamorphism, and finally crystalline graphite deposits formed. The mineralization is related to the regional metamorphic-magmatic activities triggered by the convergence and breakup of the Rodinia supercontinent.
DUAN Wei,TANG WenChun,LIU ZhiCheng,XIONG Guan,HUANG Jian,LIU XiaoHua,CHEN Xiang,HUANG JianGuo.2023.Geochemical characteristics and genesis of typical graphite deposits in southern margin of Micang Mountains in northern Sichuan Province[J].Mineral Deposits42(4):741~758