Meso-Neoproterozoic dolostone is abnormally well-developed in the platform areas in China,detailly,in the Mesoproterozoic Calymmian Wumishan Formation of North China Basin,Neoproterozoic Edia-caran Qigbulak Formation of Tarim Basin,and the Neoproterozoic Ediacaran Dengying Formation of Sichuan Basin.The outcrops and drilling cores from these basins show that these dolostones are mostly thick-bedded to massive,with mud-sized to silt-sized crystalline dolostone reaching 86％-97％of the total dolostone thickness.These dolostones basically suffered no secondary metasomatism,regardless of containing microorganisms(such as algae and bacteria)or not.The analyses of sedimentary palaeogeographic features indicate that:(1)the Meso-Neoproterozoic dolostone nearly covered the entire area basins,and was widely deposited in supratidal to intertidal zones,as well as in open platform environments;(2)the dolostone was subdivided according to the crystalline size,with the distribution controlled by geomorphology,i.e.,the pure mud-sized crystalline dolostone developing in depression areas,whereas the grainy mud-sized crystalline dolostone or the mound stromatolitic mud-sized crystalline dolostone developing in uplift areas;(3)deep-water basins developed between the carbonate platforms,and the seismic profiles show that these basins were formed by syngenetic deep faults in the Meso-Neoproterozoic strata.These syngenetic faults increased Mg2+concen-tration in the seawater by injecting rich-Mg2+-bearing hydrothermal fluids into the carbonate platforms.The analyses of geochemical and paleoclimatic indexes reveal that there is no obvious difference in carbon and oxygen isotope ratios between dolostones having different textures,with the ratios similar to those of the global seawater of the Meso-Neoproterozoic,indicating that the silt-sized crystalline dolostone has the same sedimentary origin as the mud-sized crystalline dolostone,i.e.,the former is from authigenic recrystallization of the latter rather than secondary metasomatism.Therefore,whatever the crystalline sizes are,the dolo-stones are all originated from sedimentation.All the petrological,sedimentary and geochemical data suggest that the dolostones covering almost the whole Meso-Neoproterozoic typical platform areas of China are of relatively primary sedimentary origin.

利用大量的岩心实验分析资料系统地研究了柴达木盆地西部同沉积体系和不同区带之间下干柴沟组下段碎屑岩储层物性差异的主控因素,指出沉积环境、岩石学特征、砂体厚度、地层埋藏史、地温梯度背景和湖水古盐度的不同是造成储层物性差异的重要因素.柴达木盆地西部下干柴沟组下段广泛发育的三角洲平原分流河道砂、三角洲前缘水下分流河道砂和滨浅湖滩坝砂是优质储层发育的基本条件.储层砂体厚度、杂基含量和碎屑粒径是储层物性的重要控制因素,成岩作用对储层的演化和储集性能具有决定性作用,其中压实作用对储层物性影响最大,胶结作用是局部区带储层物性重要控制因素.同沉积体系三角洲平原分流河道砂的碎屑颗粒分选和杂基含量控制储层压实程度的差异,三角洲前缘水下分流河道砂和滨浅湖滩坝砂厚度控制了储层胶结强度差异;不同区带地层埋藏史和地温梯度背景造成储层的较大压实差异,湖水古盐度沿盐湖中心环带状分布造成储层在平面上的胶结强度差异.