The Study of Microfacies Characteristics and Diagenesis of Late Carboniferous Phylloid Algal Reef in the Ziyun County, Guizhou
|Course||Mineral prospecting and exploration|
|Keywords||Guizhou Ziyun Late Carboniferous Phylloid Algal Reef Microfacies Characteristics Diagenesis|
Phylloid algal is the importance reef-builder of Carboniferous and developed well in late Carboniferous stratum of Ziyun. Gong Enpu etc. systematically studied on the growth characteristics and reef building of late Carboniferous Phylloid Algal Reef in Gui Zhou Ziyun, excepted diagenesis of reef rocks, receving comprehensive cognition and fruits. In this Paper based on lithology and diagenesis theory, we mainly studied microfacies characteristics and diagenesis of reef rocks in large phylloid algal reef section by microfacies analysis and cathodoluminescence.According to sedimentary grain types, the textures and the structures,6 main types of corbonate microfacies are distinguished in the deposits.They are bioclastic packstone, bioclastic wackstone, pellet bioclastic packstone, phylloid algal wackstone and packstone, brachiopod packstone, bioclastic sparite grainstone. Six sedimentary cycles are recognized alternated appearing in the formation,which formed a partical facies model sequence in the belt from open carbonate platform to platform margin. They are the depth open carbonate platform facies, phylloid algal reef facies, inner carbonate platform slope facies, inner carbonate platform shallow slope facies, shallow open carbonate platform facies, intraplatform shoal facies. We analyze that the sedimentary environment of phylloid aglal reef is lee slope of open carbonate platform. Based on the distribution of microfacies in the section, we can speculate it’s the open carbonate platform environment in subtidal zone.Seven types of diagenesis are discovered in the reef rocks. They are bio-binding and baffling actions, micritization, cementation, compaction-pressure solution, breakage, recrystallization and dissolution. Bio-binding and baffling actions, cementation and compaction-pressure solution are more common than the others. Basing on thin section analysis and cathodoluminescence we plot out four diagenesis stages:quasi-contemporaneous phase, early diagenesis, burial diagenesis and catagenesis. Diagenesis characteristics indicate that the diagenesis of reef had gone through marine diagenetic environment, meteoric diagenetic environment, buried diagenetic environment. The phylloid algal reef in Ziyun has high organic matter content, this research on diagenesis of reef offers data for exploring on the reservoir characteristics of reef oil and gas. In this paper we first study the microfacies characteristics and diagenesis of phylloid alga reef rocks, making up the researching blank. The research on late Carboniferous phylloid algal reefs of Ziyun makes the research on Carboniferous reefs much systematism and offers an important example for the studying of the diagenesis and diagenesis environment of the whole Carboniferous reefs, China.