岩石矿物学杂志2012，Vol.31Issue(1)：50-60,11.
贵州紫云上石炭统叶状藻礁灰岩胶结物特征
Cement characteristics of the Upper Carboniferous phylloid algal reef limestone in Ziyun County, Guizhou Province
摘要
Abstract
Diagenesis and its corresponding cements are extensively developed in the upper Carboniferous phylloid algal reef and circumjacent limestone of Bianping Village, Houchang Town, Ziyun County. These cements are prominent and representative in Houchang Town. A study of crystal shape, fabric and cathodoluminescence images of cements as well as the contacts between cements can help determine paragenetic sequences, recognize dia-genetic environments, and understand the porosity evolution in the phylloid algal reef limestones. During the syndiagenetic stage, wackestone and packstone sediments generally had low porosity and permeability, pores were filled with sea-floor micrite cement, biological encrustation and sea-floor cementation sediments rich in the fragments of phylloid algal thalli had high porosity and big pores, and marine botryoidal cement and isopachous acicular cement grew in the pores. During the early diagenetic stage, cementation supplied a great amount of cements, constructed rock framework, and consequently decided the features of the limestone rock. Blocky calcite spar and calcite microspar were formed in small pores, and radiating cement fans grew in big pores. During the epidiagenetic stage, extensive dissolution and cementation occurred. Vuggy or channel porosity was created by dissolution in the recharge area, and calcite precipitation was greatly increased in downflow areas. Meteoric phreaticcements include isopachous columnar calcite and blocky or equant calcite cement. Isopachous columnar cement is volumetrically more abundant. The porosity of the reef limestone was reduced dramatically through the early-stage cementation, so the reef limestone could prevent mechanical compaction. During the middle and late diage-netic stage, nearly all porosity was occluded by cements with low rates of fluid influx and efflux, and the remaining pores were filled with isopachous bladed cement and drusy or blocky calcite spar. Some preexisting cements were altered during the middle or late diagenetic stage, the color of isopachous bladed to columnar calcite cement changed from gray to white, and the color of botryoidal cement became more blackish due to hydrocarbon infiltration. Some isopachous bladed to columnar calcite cement could be dissolved, leaving mouldic pores filled subsequently and radiating cement fans formed simultaneously. Construction fracturing is one of the main types of diagenesis during the catagenesis stage. Rusty microcrystalline layers containing Fe2C>3 line the wall of some fractures, and vadose pisoids and ferrugineous crystal silt containing Fe2O3 are deposited at the bottom of the cavities formed in the tectonic fractures, which indicates that they were formed in oxidizing vadose environments. Late-stage fractures are filled with coarse-grained white or green bladed and drusy or blocky calcite spar. The middle part of some of these fractures is filled with bitumen block. A reason for the phylloid algal reef limestone not becoming oil and gas reservoirs might be that the pores of the phylloid algal reef limestone were filled with cements before or during the late diagenetic stage, and no large interconnected secondary pores were created afterwards. Only limestone that has a great deal of secondary porosity generated during the catagenesis stage could become oil and gas reservoirs in the Nanpanjiang Basin.关键词
扁平村/上石炭统/叶状藻礁灰岩/胶结物/阴极发光Key words
Bianping Village/ Upper Carboniferous/ phylloid algal reef limestone/ cement/ cathodoluminescence image分类
天文与地球科学引用本文复制引用
孙宝亮,巩恩普,李金梅,关长庆,张永利..贵州紫云上石炭统叶状藻礁灰岩胶结物特征[J].岩石矿物学杂志,2012,31(1):50-60,11.基金项目
国家自然科学基金资助项目(40972004) （40972004）
中央高校基本科研业务费专项资金资助项目(090401011) （090401011）
