豫西巩义地区上石炭统本溪组泥岩地球化学和富锂特征及其控制因素

泥岩的沉积序列和地球化学特征包含大量地质信息,广泛应用于沉积学及其物源分析等。豫西巩义地区上石炭统本溪组富集锂资源,但对于锂资源的来源、沉积条件等控制因素及赋存的矿物等不明确。基于野外露头等资料,综合分析豫西巩义地区上石炭统本溪组主量、微量和稀土元素特征,阐明本溪组锂富集特征,探讨本溪组的源岩、岩石风化程度、沉积物分选状况和古环境特征,进而分析本溪组锂富集的成因。结果表明:本溪组锂资源丰富,主要富集在泥岩中(Li平均质量分数为1 487×10^-6),而铝土矿Li含量较低; 沉积序列表明,本溪组主要以细粒沉积物为主,形成于潟湖环境; B/Ga、Sr/Cu值等参数表明沉积时期海水为微咸水,气候条件为温湿—干热气候,处于还原环境; 微量和稀土元素等综合图解分析表明,物源区母岩以长英质岩浆岩为主,灰岩和泥岩等是次要物源,化学蚀变指数、风化指数参数及图解表明源岩遭受强烈的风化作用,经历沉积再旋回作用。本溪组富锂泥岩的物源、沉积特征等综合分析表明,锂资源的富集与泥岩中高岭石、绿泥石等黏土矿物关系密切,本溪组源岩为锂富集提供物质基础,沉积物的再旋回过程、沉积环境等沉积特征影响锂资源的富集。

Geochemistry and Li-rich Characteristics of Mudstones from Upper Carboniferous Benxi Formation in Gongyi Area,the Western Henan,China and Their Controlling Factors

The sedimentary sequences and geochemistry characteristics of mudstone contain much geological information and are widely used in sedimentology and provenance analysis. The Upper Carboniferous Benxi Formation in Gongyi area, the western Henan is rich in lithium resources. However, the source rocks, deposition conditions, and other controlling factors of lithium resouces and the occurrence minerals are not clear. Based on the field outcrop and the characteristics of major, trace and rare earth elements, the comprehensive analysis of Upper Carboniferous Benxi Formation in the western Henan were carried out. The lithium enrichment characteristics of Benxi Formation was illustrated, the source rocks, weathering degree, sediment sorting and recycling, paleoenvironment of Benxi Formation were discussed, and then the controlling factors of lithium enrichment were analyzed. The results show that lithium is mainly concentrated in mudstone with the average content of 1 487×10^-6, and the content of lithium in bauxite is low; Benxi Formation is mainly composed of fine-grained sediments, and the sedimentary sequences indicate that the sediments are deposited in lagoon; B/Ga ratio indicates that the sea water is brackish during the sedimentation; Sr/Cu ratio and other parameters show that the sediments are deposited in a warm humid-dry hot climate under anoxic conditions; the different diagrams of trace and rare earth elements in Benxi Formation indicate that the source rocks are mainly felsic igneous rock, and secondary limestones and mudstones; the chemical index of alteration and weathering index of parker parameters and related diagrams show that the source rocks have undergone strong weathering and sedimentary recycling. Lithium enrichment in Benxi Formation is closely related to the content of clay minerals(such as kaolinite and chlorite). Source rocks provide materials for lithium enrichment, and sedimentary characteristics such as sedimentary recycling processes and sedimentary environment, affect the enrichment of lithium resources.