中文摘要：

新疆三塘湖盆地中二叠统芦草沟组发育湖泊背景下的白云岩、灰岩、黑色泥岩、页岩及碎屑岩的互层沉积。白云岩主要有两类：一类为粉—泥晶白云岩,主要由含量约70%的泥晶白云石和含量约30%的粉晶白云石构成,白云石有序度为0.48,扫描电镜下主要有菱形、他形、球状和管状4种微形态,自形程度较好的菱形晶体多为含铁白云石;另一类为方沸钾长白云岩,主要由晶粒为0.08-0.35mm的细粒方沸石、泥晶钾长石（透长石）、泥晶白云石和铁白云石构成,个别为粗晶白云石,白云石有序度0.58。与粉—泥晶白云岩中的白云石相比,方沸钾长白云岩中的白云石以高的铁、锰含量为特征,扫描电镜下多为半自形的菱形晶体。两类白云岩中白云石的有序度均较低,且均为富Sr白云石,内部均缺乏次生交代证据。通过对两类白云岩成分、微量元素及稳定同位素的差异性分析,认为尽管两类白云岩都形成于浅—半深湖相强还原沉积环境,但是它们的形成机制有所不同,粉—泥晶白云岩具有原生沉淀白云石的特征,其中球状及管状的白云石可能与微生物吸附作用有关,而他形及菱形的白云石为直接沉淀的原生白云石;另一类方沸钾长白云岩中的白云石及铁白云石可能与湖底热泉的喷流沉积作用有关。

英文摘要：

The Santanghu Basin is a small intermountain basin located in northeastern Xinjiang,NW China.The Middle Permian comprises the Wulapo,Jingjingzigou,Lucaogou and Hongyanchi Formations from bottom to top.The Lucaogou Formation was formed of interbeded sedimentary rocks such as dolostone,limestone,black mudstone,shale and detrital rock in lacustrine environment.Two kinds of dolostones were found in this basin.One was named silt-micrite dolostone which contains 70 percent of clay-sized dolomite,30 percent of silt-sized dolomite.The dolomite exhibit weak ordering with degree of 0.48.Morphologically,the dolomite was divided into micro-rhombohedra,xenomorphic crystal,microsphere,and microtubule types under the SEM.Part of the micro-rhombohedra dolomite was ferric dolomite.The other kind of dolostone was named analcime-sanidine dolostone which was composed of fine grained analcime with the granularity of 0.08～0.35mm,micrite potash feldspar（almost sanidine）,micrite dolomite,ankerite,and few coarse crystalline dolomite.This kind of dolomite also showed weak ordering with degree of 0.58.Compared with the dolomites in silt-micrite dolostone,the dolomites in analcime-sanidine dolostone which were almost subhedral rhombohedras under the SEM were characterized as high iron and manganese.The similarities between these two dolostones were that they were poor ordering dolomites,abundant in strontium,and lacking of the evidence in replacement during the buried period.Although these two dolostones were deposited in the similar shallow and semi-deep lake anoxic reduction environment,their differences in composition,trace elements and stable isotopes indicated that they had great diversity in their genesis.The silt-micrite dolostone revealed the features of primary precipitation.The microbe was likely to play a formative role in the precipitation of the microspheroidal and microtubular dolomites.Moreover,the micro-rhombohedrala and xenomorphic dolomites were directly precipitated from lake water.Contrastly,the dolomites in ana