震旦系陡山沱组磷块岩的成岩作用和成岩环境

本文重点讨论了磷块岩的成岩作用及其与沉积环境的联系,进而提出了磷块岩成岩环境的五个序列。各成岩自然序列,具有各自独岩的成岩作用特点,代表着不同成岩作用环境。不同成岩环境又与不同的磷酸盐相和沉积环境有关,且在很大程度上依赖于原始沉积及其环境的发展和演化。 探讨磷块岩成岩作用必须考虑到成岩作用发生过程的地质历史演化和条件,必须联系其环境背景。

DIAGENESIS AND DIAGENETIC ENViRONMENTS OF PHOSPHORITE FROM DOUSHANTUO FORMATION, SINIAN SYSTEM

This paper lays emphasis on the diagenesis of the phosphorite and its connection to the sedimentary environments. Five diagenetic sequences have been recognized based on the primary character of the sediments, and then later changes, especially their diagenetic changes.Sequence 1, dewatering,ageing, pelletting-lumping and finally granulating of the original cryptocrystalline cellophane.Sequence 2, equal thickness forming of fibrous crystals of the interstitial deposit of phosphate.Sequence 3, pore filling, strato-geode and sparry mullion development the instromatolitic phosphate.Sequence 4,phosphatization and silicification of the phosphorous dolomitic and seliceous deposits.Sequence 5,phosphatization of the original phosphorous carbonate deposit.Each sequence cited above, bears with distinct diagenetic characters as well as distinct textures,structures andmineral composition representing distinct diagenetic enviroment. But it should be noted that in discussing the diagenesis of phosphorite, we have to pay attention to the original sediments and their sedimentary environments and have to consider the later history of the basin evolution.