中文摘要：

应用岩石薄片鉴定、阴极发光及电子探针技术,研究白云岩岩相特征,应用全岩及矿物微区碳、氧稳定同位素测试及X衍射分析方法,研究白云岩地球化学及成岩环境特征。研究后可知,奥陶系白云岩主要有6类：1形成于准同生白云化作用的块状泥晶云岩,以高白云石含量、泥晶结构、低有序度和较高的δ^18O,δ^13C为特征;2形成于准同生及微生物白云化作用的生屑云岩和藻云岩,以高白云石含量、生物骨架结构、低有序度、较高δ^18O和较低δ^13C为特征;3形成于准同生白云化及淡水淋滤与溶蚀作用的角砾白云岩,以含灰质及溶孔、角砾结构、低有序度、较低δ^13C为特征;4形成于卤水回流渗透白云化作用的细—粉晶白云岩,以含残余灰质、细粉晶结构、高有序度、较高δ^18O和δ^13C为特征,经淡水淋滤之后发育晶间孔,同时δ^13C明显下降;5形成于海水交代白云化作用的残余结构中—细晶白云岩,以含灰质组分及晶间孔、残余颗粒结构、高有序度、高δ^18O和δ^13C为特征;6形成于埋藏封闭环境重结晶作用的镶嵌结构中—粗晶白云岩,以高白云石含量、镶嵌结构和似斑状构造、异形白云石及高有序度、保持原岩δ^18O和δ^13C为特征。孔、缝中的热液或淡水白云石均以高有序度、极低的δ^13C为特征,淡水白云石较热液白云石,具有较高的δ^18O,Fe^2＋及较低的Mn^2＋。研究结果表明,白云岩的δ^18O,δ^13C以及白云石有序度等地球化学参数是识别白云岩岩相、成岩条件和成岩环境的重要指标。

英文摘要：

The lithofacies characteristics such as lithology,texture andstructure have been studied by the means of thin section,cathodoluminescence image analysis,electron probe and wave spectrum. Based on carbon and oxygen stable isotope testing and dolomite X diffraction analysis of whole-rock and mineral microarea,the dolomite geochemistry and diagenetic conditions and environment have been studied. The results show that,the Ordovician dolomite can be divided into the following six major types.（ 1） the blocky micrite dolomite：shaped under the penecontemporaneous dolomitization,with features of high dolomite content,vivid micritic structure,low dolomite ordered index,and higher δ^18O and δ^13C;（ 2） the biological framework dolomite：formed in penecontemporaneous and microbial dolomitization and charactered by high dolomite content,clear biological skeleton structure,low dolomite ordered index,and higher δ^18O and lower δ^13C;（3） the breccia dolomite： shaped under the penecontemporaneous dolomitizationand freshwater leaching in early diagenesis and epidiagenetic on carbonate platform,with properties of gray pseudocrystal,dissolved pore,brecciated structure,lower dolomite ordered index,and lower δ^13C;（ 4） the block powder-fine crystal dolomite： made in seepage-reflux dolomitization,particularly containing different amounts of gray component,fine powder,highordered dolomite,and higher δ^18O and δ^13C,ifleached byfreshwater in early diagenesistergranular pores appeared and δ^13Cdecreased;（ 5） residual grain structure fine-middle dolomite： built up during seawater replacing dolomitization and distinguished by containing different amounts of gray component or intergranular pores,residual particles structure,high dolomite ordered index,and high δ^18O and δ^13C;（ 6） the mosaic structure middle-coarse crystalline dolomite： generated by recrystallization in buried closed environment with peculiarities as high content of dolomite,mosaic structure,porphyritic-like structure,saddle-shaped