川西南雷波小沟早寒武世磷矿床磷酸盐富集沉降机制探讨  

Discussion on the enrichment and sedimentation mechanisms of phosphates in the Early Cambrian Xiaogou phosphate deposit in Leibo,southwestern Sichuan

作　　者：王畅 程文斌[1] 张玙[3] 杨豫川 金灿海[3] 董树义[1] 张君 赵伟 李承泽 WANG Chang;CHENG Wenbin;ZHANG Yu;YANG Yuchuan;JIN Canhai;DONG Shuyi;ZHANG Jun;ZHAO Wei;LI Chengze(College of Earth Science,Chengdu University of Technology,Chengdu610059;Geology Institute of China Chemical Geology and Mine Bureau,Beijing100101;Chengdu Center of China Geological Survey,Chengdu610081;207 Geological Team of Sichuan Provincial Bureau of Geology and Mineral Exploration and Development,Leshan,Sichuan614000;Sichuan Geological Engineering Investigation Institute Group Co.LTD,Chengdu610072)

机构地区：[1]成都理工大学地球科学学院,成都610059 [2]中化地质矿山总局地质研究院,北京100101 [3]中国地质调查局成都地质调查中心,成都610081 [4]四川省地质矿产勘查开发局二零七地质队,四川乐山614000 [5]四川省地质工程勘察院集团有限公司,成都610072

出　　处：《地质论评》2024年第2期563-576,共14页Geological Review

基　　金：中国地质调查局地质调查项目(编号:121201010000150002-11、DD20160019-06);乌蒙山区地质矿产综合调查项目子课题(编号:DD20160019-16);鄂西聚磷区荆襄磷矿田勘查开发现状与远景评价矿产地质研究项目(编号:DYKJ202201)的成果。

摘　　要：为了解我国扬子地区早寒武世磷块岩矿床磷酸盐的富集沉降机制,本文以川西南雷波县小沟大型磷矿床为解剖对象,采用共焦激光拉曼和激光剥蚀等离子体质谱分析(LA-ICP-MS)技术,从岩相学和地球化学的角度对其进行了初步探讨。结果显示:小沟矿床磷块岩主要由胶磷矿、碳酸盐矿物、有机质、硅质及少量黄铁矿组成;矿石中微生物发育,鉴定其可能为Eoentophysalis和Obruchevella;胶磷矿LA-ICP-MS原位REE分析表明,所有点位均具明显的负Ce异常,指示沉积成矿过程中氧化—次氧化的底层水与孔隙水条件。综合上述研究认为,成矿与有机质沉降及胞外聚合物(EPS)关系密切:①氧化—次氧化底层水条件下,生物有机质沉降,并在埋藏过程中迅速分解导致孔隙水中溶解磷酸盐达到过饱和是磷富集沉淀的主因。②胞外聚合物(EPS)粘附细胞和有机碎屑,加速了生物有机质的聚集沉降,埋藏过程中,胞外聚合物为磷质聚集提供大量成核位点,促进了胶磷矿的快速析出与沉淀。Objectives and Methods:In order to understand the mechanism of phosphate enrichment and deposition in the Early Cambrian phosphorite deposits in the Yangtze region of China,the large phosphate deposit in Xiaogou,Leibo County,southwestern Sichuan Province,was systematically studied by confocal laser Raman and LA-ICP-MS.Results:The results show that the phosphorous block rocks in Xiaogou deposit are mainly composed of collophanite,carbonate minerals,organic matter,siliceous and a small amount of pyrite.The development of microorganisms in ore was identified as Eoentophysalis and Obruchevella.In situ REE analysis of LA-ICP-MS shows that all the sites have obvious negative Ce anomalies,indicating the bottom water and pore water conditions of Oxid—Suboxic during the sedimentary mineralization process.Conclusions:It is concluded that the mineralization is closely related to the organic matter sedimentation and extracellular polymeric substances(EPS):①Under the conditions of Oxid—Suboxic bottom water,the sedimentation of biological organic matter and its rapid decomposition during burial lead to the supratsaturation of dissolved phosphate in pore water,which is the main cause of phosphorus enrichment and precipitation;②Extracellular polymeric substances(EPS)adhere to cells and organic debris,accelerating the aggregation and settlement of biological organic matter.In the burial process,EPS provides a large number of nucleation sites for phosphorus aggregation,and promotes the rapid precipitation of collophanite.

关 键 词：川西南 雷波县小沟磷矿 富集沉降 激光拉曼分析 

分 类 号：P619.2[天文地球—矿床学]