王琼;李溪遥;赵德怀;华北;吴承泉;张正伟;徐进鸿;靳子茹;

• 1:贵州省有色金属和核工业地质勘查局
• 2:中国科学院地球化学研究所矿床地球化学国家重点实验室
• 3:中国科学院大学
• 4:中国冶金总局新疆地质勘查院

摘要(Abstract)：

晚古生代，康西瓦洋壳指向西昆仑地块俯冲，在恰尔隆盆地内沉积了下石炭统—上二叠统的一套以海进-海退为特征的旋回序列。新发现的主乌鲁克碳酸锰矿床位于恰尔隆盆地北部，含锰层位为下石炭统他龙群中段细碎屑岩夹碳酸盐岩，锰矿层为黑色泥质碳质页岩夹铁锰质微晶灰岩，显示明显韵律。锰矿石的Mn品位为8.00%～16.59%,Mn/Fe比值为0.36～1.46，铁锰分异不明显。矿石矿物主要为锰碳酸盐矿物，具有典型生物结构。碳酸锰矿石的正Eu异常（δEu=3.46±2.00）显示成矿物质主要为海底热水来源。碳酸锰矿石以及围岩的⁽⁸⁷⁾Sr/(87)Sr/⁽⁸⁶⁾Sr偏向于大陆地壳组成（0.711925±0.000601），表明成矿物质主要来自西昆仑古老陆壳基底。锰矿石中不明显的Ce异常（δCe=0.96±0.14）和低的(Mo/U)_(auth)（自生矿物的Mo/U摩尔浓度比值，5.36±4.41）显示其主要沉积于局部快速氧化环境；而明显的Mo富集（平均Mo_(auth)=99.14±97.04）和纹层状自形黄铁矿表明围岩主要形成于还原环境。碳酸锰矿石的有机碳同位素组成（δ(86)Sr偏向于大陆地壳组成（0.711925±0.000601），表明成矿物质主要来自西昆仑古老陆壳基底。锰矿石中不明显的Ce异常（δCe=0.96±0.14）和低的(Mo/U)_(auth)（自生矿物的Mo/U摩尔浓度比值，5.36±4.41）显示其主要沉积于局部快速氧化环境；而明显的Mo富集（平均Mo_(auth)=99.14±97.04）和纹层状自形黄铁矿表明围岩主要形成于还原环境。碳酸锰矿石的有机碳同位素组成（δ⁽¹³⁾C_(org-PDB)=-24.65‰±2.12‰）、无机碳同位素的组成和变化趋势（δ(13)C_(org-PDB)=-24.65‰±2.12‰）、无机碳同位素的组成和变化趋势（δ⁽¹³⁾C_(carb-PDB)=-12.67‰±3.86‰）以及总有机碳含量（TOC）与锰品位成负相关，表明锰可能最初以（氢）氧化物形式沉淀，而后在成岩埋藏过程中被有机质还原。总之，在早石炭世的恰尔隆盆地内，海侵过程带来丰富的自由氧和有机质，沉积了一套黑色泥质碳质页岩夹铁锰质微晶灰岩。同生断层活动带来富Mn(13)C_(carb-PDB)=-12.67‰±3.86‰）以及总有机碳含量（TOC）与锰品位成负相关，表明锰可能最初以（氢）氧化物形式沉淀，而后在成岩埋藏过程中被有机质还原。总之，在早石炭世的恰尔隆盆地内，海侵过程带来丰富的自由氧和有机质，沉积了一套黑色泥质碳质页岩夹铁锰质微晶灰岩。同生断层活动带来富Mn⁽²⁺⁾热水；Mn(2+)热水；Mn⁽²⁺⁾在短暂的氧化条件下被氧化为Mn(2+)在短暂的氧化条件下被氧化为Mn⁽³⁺⁾/Mn(3+)/Mn⁽⁴⁺⁾的（氢）氧化物。由于含氧量不足，铁和锰未完全分离。随着沉积作用进行，这些（氢）氧化物被表层沉积物覆盖而埋藏。随后在缺氧孔隙水中，Mn(4+)的（氢）氧化物。由于含氧量不足，铁和锰未完全分离。随着沉积作用进行，这些（氢）氧化物被表层沉积物覆盖而埋藏。随后在缺氧孔隙水中，Mn⁽³⁺⁾/Mn(3+)/Mn⁽⁴⁺⁾的（氢）氧化物被有机质还原为Mn(4+)的（氢）氧化物被有机质还原为Mn⁽²⁺⁾碳酸盐矿物。晚石炭世，海平面上升，Mn(2+)碳酸盐矿物。晚石炭世，海平面上升，Mn⁽²⁺⁾的氧化作用逐渐减弱，使得上覆地层缺乏含锰层位。

关键词(KeyWords)： 晚古生代;西昆仑山;弧后盆地;恰尔隆盆地;锰碳酸盐矿床

Abstract:

Keywords:

基金项目(Foundation): 国家自然科学基金项目（编号：U1603245; 41503051; U181240004）;; 中国科学院西部之光项目;; 贵州省科学技术基金（编号：[2018]1171）;; 中国冶金地质总局山东局青年科技基金项目（编号：SDYJ-QNKY202005）;; 贵州省地质勘查基金项目（编号：MCHC-ZG20212206-2）

作者(Authors): 王琼;李溪遥;赵德怀;华北;吴承泉;张正伟;徐进鸿;靳子茹;

DOI: 10.16461/j.cnki.1000-4734.2022.42.088

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