摘要
铝土矿的形成受到气候条件的严格限制。通过对黔北务川—正安—道真地区下二叠统铝土矿层钻孔岩心样品主量元素和黏土矿物的综合研究,探讨了铝土矿层形成时期黔北地区的古气候环境以及淋滤作用对矿层的改造。从下至上,铝土矿层化学蚀变指数(CIA)由80左右上升至大于90,成分分异指数(ICV)由0.8下降至0.1。X射线衍射分析发现,研究区铝土矿层中的黏土矿物组分为高岭石、伊利石与绿泥石,其中高岭石在各个钻孔中广泛存在且在大部分层位中含量较高,平均含量为34.2%,并呈机械碎屑或基质形态产出且有进一步风化成为铝矿物的现象;伊利石主要以机械碎屑形式产出,平均含量为21.5%,赋存于矿层的黏土质部分,结晶度变化范围为0.22°～0.71°;绿泥石多为基质,部分层位中含量极高且伴随ICV值上升,平均含量为44.3%,为后期成岩过程中由高岭石转化而成。矿层内极高的CIA值与广泛存在的高岭石证明,铝土矿形成时为炎热潮湿的古气候。而矿层内部ICV值的波动可能与淋滤作用所引起的矿层内元素迁移活动有关。
Bauxite, as a kind of climatically sensitive deposit, mainly formed during the pedogene- sis under the tropical or subtropical climatic condition. The integrated information of major elements and clay minerals from drilling core samples of bauxite beds in Wuchuan-Zheng＇an-Daozhen area, northern Guizhou Province, was measured to investigate the palaeoclimate environment during the formation process of bauxite. Chemical index of alteration （CIA） and index of compositional variability （ICV） of samples from bottom to top of the drilling core revealed that CIA increased from 80 to 〉90, while ICV decreased from 0. 8 to O. 1. Both of them indicated the strong chemical weathering which changed composition of bauxite beds greatly. The clay mineral compositions of bauxite beds were dominated by kaolinite, illite and chlorite. Kaolinites, which appeard in debris or matrix, widely distributed in every drilling core and had a high content in most layers; illites mainly appeard in debris, occurring in clay layers of the deposit, with illite crystalline index varying in wide range; while chlorite matrix derived from kaolinite during later diagenesis. High CIA value and clay mineral composition in bauxite beds indicated moist and warm palaeo- climate environment in northern Guizhou Province during the Early Permian which related to palaeogeogra- phy position of this area. Change of ICV value in the bauxite beds was related to element migration during leaching process.
出处
《古地理学报》
CAS
CSCD
北大核心
2014年第1期30-40,共11页
Journal of Palaeogeography：Chinese Edition
基金
贵州省地勘基金"贵州务正道地区铝土矿基础地质与成矿背景"项目资助
关键词
铝土矿
地球化学
黏土矿物
古气候
早二叠世
黔北
bauxite, geochemistry, clay mineral, palaeoclimate, Early Permian, northern GuizhouProvince
