中文摘要：

新疆乌鲁木齐地区红雁池南剖面中二叠统芦草沟组主要发育浅湖至半深湖背景下的中、薄层深灰色白云岩、灰岩、粉砂岩与中、厚层灰黑色页岩、泥岩互层。白云岩主要由泥晶白云石、铁白云石及少量方解石、高镁方解石组成，富含有机质。白云石粒径约3～10μm，阴极发光呈现均匀昏暗的砖红色。白云石主要有微球状（直径约5～8μm）、微簇状（长度约2μm）及他形（1—10μm）等3种微形貌。微球状白云石具有显微纹层结构，似为生长纹层，放大至6万倍发现显微纹层是由无数纳米级颗粒构成。他形白云石放大至4万倍发现主要由大量直径约0．25μm的球状微粒聚集粘结而成，具有微生物矿化的特征。将研究区白云石与现代典型微生物成因白云石相比，其显微形态特征非常相似。研究区白云岩δ13CPDB为1．8‰0～13．8‰,δ18OPDB为-12．1‰～-4．1‰，偏高的δ13C可能是产甲烷菌活动引起有机质碳同位素分馏的结果。以上特征表明，芦草沟组具有特殊形貌白云石的沉淀很可能与厌氧微生物密切相关。

英文摘要：

The dark-gray, middle to thin-bedded dolostone, limestone, siltstone, and gray orblack shale and mudstone, deposited in shallow to open lake settings, are mainly developed in the Middle Permian Lucaogou Formation in southern Hongyanchi section of ürümqi in Xinjiang. Dolostone which is rich in organic matter is mainly composed of dolomite and ankerite with small amount of calcite and Mg- calcite. The dolomite ranges from 3 to 10 μm in crystal sizes and shows homogeneously dark-red lumines- cence. Micromorphologies of the dolomite vary from microspherules （5 ～ 8 μm in diameter）, clusters （about 2 μm long）, to anhedral dolomite under the SEM. Microsphernles have microlaminae structure called “growth coating”which consists of numerous nanoscale particles in the 60 000 times enlarged SEM photomicrographs. Anhedral dolomite which is mainly composed of massive particles （ about 0.25μm） in 40 000 times enlarged SEM photomicrographs shows the features of microbial mineralization. The above morphologies of dolomite are highly similar to the typical modern microbial dolomite in experiment-culture and natural environments. The δ13CPDB value of dolomite ranges from 1.8‰ to 13.8‰, and δ18OPDB value ranges from -12. 1‰to -4.1‰. The higher δ13CPDB value may be the result of isotope fraetionation led by methane-producing bacteria. The characteristics of micromorphologies and stable isotope indicate that the precipitation of the Middle Permian dolomite had close relation to activities of anaerobic organisms.