西南印度洋龙旂矿化区烟囱体形成过程重构：来自微区元素和同位素的信息

There are some unique imprint within the hydrothermal sulfide along the ultraslow-spreading Southwest Indian Ridge due to extremely low magma supply and complex structural activities. Researches in recent year have bone some work about the sources and process of ore-forming, and genesis of the ore deposits in the Longqi hydrothermal area. However, they have all been based on the study of sporadic massive sulfide samples. For the different types of chimneys, research of the formation process, elemental migration and precipitation process, and their control factors in the Longqi area are not systematic enough. In this study, sulfide chimneys collected by the Chinese submersible “Jiaolong” from the Longqi area will be mainly concerned. In-situ analysis will be used to extract the records from the growth zoning of chimneys, such as the structural, topographical and compositional characteristics and isotopic information. The issues of physiochemical conditions during the formation of the chimney, and the main controlling factors for the migration and precipitation of the elements will be focused in order to reveal the detailed formation process of the chimneys in the Longqi area. The research will reveal the micro-environmental characteristics of mineralization in Longqi area, enrich the knowledge of sulfide mineralization along ultraslow-spreading ridge, and provide reference for the resource exploration and evaluation of China's sulfide contract area.

超慢速扩张西南印度洋脊以岩浆供给贫瘠、构造活动复杂等特征而在形成的热液硫化物内留下了独特的烙印。近年来，一些研究对龙旂矿化区的成矿物质来源、成矿过程和矿床成因等方面进行了初步探讨，但都是基于零星块状硫化物样品的研究，对不同类型烟囱体形成过程中元素的迁移沉淀过程及其控制因素的研究还不够系统，对龙旂区种类丰富的烟囱体的形成原因缺乏深入认识。本研究以蛟龙号载人深潜器在西南印度洋超慢速扩张脊龙旂矿化区采集的硫化物烟囱体为对象，采用微区原位分析为主的手段，提取烟囱体环带中记录的结构、形貌和成分特征及原位同位素信息，重点剖析烟囱体形成过程中的物理化学条件变化，探讨元素迁移沉淀的主要控制因素，揭示龙旂烟囱体的精细形成过程。研究成果将揭示龙旂矿化区成矿的微环境特征，丰富超慢速扩张脊硫化物成矿作用信息，并对我国海底硫化物合同区的资源勘查和评价提供一定的参考和借鉴。

超慢速扩张西南印度洋脊以岩浆供给贫瘠、构造活动复杂等特征而在形成的热液硫化物内留下了独特的烙印。近年来，一些研究对龙旂矿化区的成矿物质来源、成矿过程和矿床成因等方面进行了初步探讨，但都是基于零星块状硫化物样品的研究。本研究以蛟龙号载人深潜器在西南印度洋超慢速扩张脊龙旂矿化区采集的硫化物烟囱体为对象，开展了以微区原位分析为主的手段，提取了烟囱体环带中记录的结构、形貌和成分特征及原位同位素信息，对不同类型烟囱体形成过程中元素的迁移沉淀过程及其控制因素。该区烟囱体矿物组合由内向外大致为磁黄铁矿+闪锌矿+黄铜矿→黄铜矿+方黄铜矿+少量黄铁矿→黄铜矿+闪锌矿→硬石膏+黄铁矿+白铁矿+闪锌矿+黄铜矿，与典型烟囱体生长模式相似。原位微量元素及S同位素研究显示，热液-海水混合过程中的冷凝，是龙旂热液区绝大部分微量元素沉淀的主控因素；在烟囱体生长过程中，整体呈酸性还原环境且变化并不明显；超基性岩在成矿元素的贡献主要体现在Co含量较高，但该区硫化物中Ni含量并未显著高于其他玄武岩基底的热液区。研究成果进一步丰富了超慢速扩张洋中脊硫化物成矿作用的信息，也为我国海底硫化物合同区的资源勘查和评价提供了一定的参考和借鉴。