摘要:
本文在叙述玄武岩屑砂岩成岩序列的基础上,依据多种实验分析手段所获得的资料,对其成岩阶段和环境作了划分,并讨论了含Ti—Fe蒙脱石、绿泥石、菱铁矿、铁白云石、铁方解石等自生矿物的成因。它们的形成受控于下列因素的综合作用:1)砂岩的成分和结构;2)沉积层间的组合特征;3)有机质的还原作用和热成熟作用;4)粘土岩中粘土矿物的脱水和转化作用;5)温度和孔隙的水的酸、碱度;6)压实作用。
Abstract:
The Upper permian Series in Langdai district of Liuzhi County, western Gui-zhou, is composed of cyclical sequences of basaltic lithic sandstones, siltssones, mudstones and coalbeds. An examination of sedimantary features reveals that all these layers were deposited in didal-swamp and subtidal enviroments. The description of diagenetic sequence for the basaltic lithic sandstone is given in the present paper, and the genesis of the authigenic minerals, i.e., Ti-Fe montmorillonite, Chlorite, ferrodolomite and ferrocalcite, in this sort of rock are discussed in detail on the basis of the authors study mean of various laboratory procedures such as thin section petrography, scanning electron microscopic analysis, electron prooe analysis, X-ray diffraction analysis,and carbon and oxygen isotope analysis for the carbonate, etc. . It is pointed out that: 1. The diagenetic sequence of basaltic lithic sandstones is Ti-Fe montmorillonite →c→ompaction→chloritization→dissolution→silicif ication, pyritization→ ferrodolomitization→ferrocalcitization→ferritzation, hemetitization. 2. The diagenetic stage and enviroment of basaltic lithic sandstones may be divided into. 1 )Shallow burial, early diagenetic stage, acid water enviroment; 2 ) Deepburial-mesodiagentic stage, weak base acid alkalinity water enviroment; 3 ) Nearsurface, late diagenetic, meteoric freshwater enviroment. 3. Geneses of these authingenic minerals are essentially controlled by the variety of combination patterns of the following factors: 1 ) composition and textur-e of the sandstones) 2 ) characteristics of assemblages of the sedimentary layers; 3 ) the reduction level of organic matter and its thermal maturation; 4 ) trasfor-mation and dehydration of clay minerals in the mudstones; 5 ) compection and 6 ) temperature and acidity or alkalinity of pore water