中文摘要：

运用多种技术方法,如电子探针、扫描电镜、电子显微镜等,对滇中地区大龙口组中的微亮晶碳酸盐岩进行了宏观、微观、成岩作用和成因分析。研究表明,大龙口组中的微亮晶以3种形式存在于底基质中：呈散乱的微亮晶颗粒分散于底基质中,呈等粒微亮晶集合体分布于臼齿构造条带内,或呈鲕粒、内碎屑或藻团块的胶结物形式存在。臼齿构造内部的微亮晶并不是完全致密状排列的,晶间有石膏充填,电子探针分析结果表明其含有Ca、Si、Al、Ti,为晚期成岩阶段晶间水中析出的产物。藻叠层石与臼齿构造出现共生的现象表明,臼齿构造可能与藻类存在某种成因联系,微亮晶集合体作为藻屑或鲕粒的胶结物出现,显示高能动荡水体中生物化学作用和水动力化学作用的结果。文中同时解释了中间宽、两端尖细的臼齿构造的成因,分叉的次级臼齿构造是应力降低的结果,受岩石的非均质性和各向异性的影响。对臼齿构造的成因分析表明,母岩中的有机质被埋藏后经细菌分解产生生物气造成局部高压环境,当超过临界压力时岩石就破裂产生裂隙,而后裂隙中充填的溶液快速结晶成岩,使压力转移而在另一部位聚集高压,然后重复上一过程,从而使岩石中出现密集的臼齿构造,直到与围岩压力平衡为止。

英文摘要：

In this paper,the macroscopic and microscopic features,diagenesis and origin of microsparite（molar-tooth） carbonates of Dalongkou Formation have been analyzed based on various kinds of technical methods,such as EMPA,SEM and EM.The results demonstrate that microsparite calcite can exist in the substrate in three forms： it can be distributed disorderly in the micrite,or it serves as the equal-grained microsparite assemblage filling in the general molar-tooth structure belt,or it can act as the cement between the ooids,intraclast,and algae aggregate composed of microcrystal calcite.The microsparite calcite crystals in the molar tooth structure are not wholly arranged in the dense form,and there are some gypsums infilling the intercrystal pores.It can be seen from the result of EMPA that it contains Ca,Si,Al and Ti,which precipitated from the intercrystal pore at the late diagenetic stage.The algal stromatolite can exist with molar tooth structures,suggesting that the formation of molar tooth structure had some relationship with algal;the assemblage of microsparite can serve as the cement of algae aggregates and oolite,exhibiting biochemical acting and hydrodynamic sorting in high energy water,which couldn＇t be caused directly by the algae.This paper has also interpreted the reason why the molartooth structures with wide middle part and tip end point appeared.The branched secondary molar tooth structures were induced by the reduction of stress which was affected by the heterogeneity and anisotropy of the rocks.It is shown from the genetic analysis that the formation processes of molar-tooth structure were as follows： the partly high pressure environment in the rock was caused by the decomposition of organic matter in the substrate induced by the bacteria.When the pressure exceeded the breakdown pressure,the rock failed and all kinds of cracks came into being.After that,the liquid filled up the cracks and crystallized quickly,causing the transference of high pressure to other places,resulting in the continua