投稿时间：2025-05-08
修订日期：2025-09-07
网络发布日期：2025-10-31
中文摘要:新元古代“大塘坡式”锰矿是华南扬子板块重要的矿床类型，但对同期异相含锰建造的成因联系与控矿规律仍缺乏清晰认识。为此，本文以位于扬子陆块与江南造山带结合部位（鄂西海槽地块边缘）的渝东南秀山小茶园与笔架山典型区域的含锰建造为研究对象，通过岩石薄片观察、扫描电镜、能谱分析及碳同位素测试等手段，开展了系统的沉积学与地球化学对比研究。结果表明：秀山地区在大塘坡早期因古地貌差异，分别沉积了小茶园深水缺氧潮下洼地相黑色页岩夹菱锰矿（Mn≈20%，δ13C平均-8.86‰）与笔架山浅水氧化还原波动的潮坪-浅滩相灰绿色粉砂岩夹含锰灰岩（Mn<2%，δ13C平均-5.64‰）两类建造。研究进一步明确，地球化学特征指示成矿物质主要来源于热液，通过“溶解Mn2+氧化-再还原-碳酸盐化”的沉积成岩机制富集成矿；早成岩阶段有机质与锰氧化物的相互作用是导致碳酸锰沉淀及δ13C明显负偏的主控因素。结论认为，秀山地区锰矿受还原性潮下洼地沉积相带的控制，低能缺氧环境最有利于锰质的聚集与保存。
Abstract:The Neoproterozoic "Datangpo-type" manganese deposits represent a significant deposit type in the South China Block. However, the genetic links and ore-controlling factors governing coeval but facies-variable manganese-bearing formations remain poorly understood. This study ivestigates the manganese-bearing formations in the Xiaochayuan and Bijiashan areas of the Xiushan region, southeastern Chongqing, located at the junction of the southeastern margin of the Yangtze Block and the Jiangnan Orogen（on the margin of the Western Hubei Sea Trough）. By employing integrated methods including rock thin-section observation, scanning electron microscopy observation, energy-dispersive spectroscopy analysis, and carbon isotope analysis, a systematic sedimentological and geochemical comparison was conducted. The results reveal that the paleotopographic differences in the Xiushan area during the early Datangpo period led to the deposition of two distinct types of manganese-bearing formations: ① the Xiaochayuan deep-water anoxic subtidal depression facies, characterized by black shale intercalated with rhodochrosite (Mn≈20%, average δ13C=-8.86‰), and ② the Bijiashan shallow-water facies with fluctuating redox conditions (intertidal-supratidal flat and high-energy shoal), characterized by gray-green siltstone intercalated with manganese-bearing limestone (Mn<2%, average δ13C=-5.64‰). Moreover, geochemical features further indicate a predominant hydrothermal origin for the ore-forming materials. Mineralization occurred through a sedimentary-diagenetic mechanism of "dissolved Mn2+oxidation-re-reduction-carbonation". The interaction between organic matter and manganese oxides during early diagenesis is identified as the primary cause for manganese carbonate precipitation and the significant negative δ13C excursion. In conclusion, manganese mineralization in the Xiushan area is fundamentally controlled by the reductive subtidal depression sedimentary facies belt, with low-energy, anoxic environments being most conducive to manganese enrichment and preservation.
文章编号：
中图分类号：
文献标志码：
基金项目:本文得到国家自然科学基金（编号：U23B20154、41672108、41302091）、中国石油西南石油大学创新联合体项目（编号：2020CX010102）和四川省科技厅重点研发项目（编号：2022YFS0466）联合资助
引用文本：
杨嘉宝,杜秋定,杜春阳,和源,马志鑫,陈浩,樊秋爽.2025.重庆秀山地区大塘坡式锰矿床沉积环境及成因[J].矿床地质,44(5):1077~1094YANG JiaBao,DU QiuDing,DU ChunYang,HE Yuan,MA ZhiXin,CHEN Hao,FAN QiuShuang.2025.Sedimentary environment and genesis of Datangpo-type manganese deposit in Xiushan area, Chongqing[J].Mineral Deposits44(5):1077~1094
图/表
