一种严格受控于环境和时间的特殊碳酸盐岩——臼齿构造碳酸盐岩

臼齿构造碳酸盐岩是一种具有类似于大象臼齿特征的特殊碳酸盐岩，其微亮晶脉由纯净的、基本等粒的方解石（或白云岩）构成，而基质物质则由细粒的、富泥质的灰岩组成。通过对中朝板块东部吉辽徐淮地区前寒武纪臼齿构造碳酸盐岩研究，结合国外研究资料，臼齿构造碳酸盐岩具有特定的生存时限，目前只在前寒武纪（主要发育在中、新元古代）地层中发现。研究表明，臼齿构造碳酸盐岩发育在缓坡型台地，宿主岩性以富含泥质的粉屑灰岩、泥晶灰岩为主，位于潮汐流、风暴流影响范围内，为浅潮下和环潮坪环境，潮上带与深缓坡均不发育，具有鲜明的环境和相指示意义。由于缺乏现代相似沉积物，臼齿构造碳酸盐岩的成因还是一个谜，需要进一步研究和探索。 

MOLAR-TOOTH CARBONATE CONSTRAINED BY DEPOSITIONAL ENVIRONMENT AND GEOLOGICAL HISTORY

Microspar structures carbonate is characterized by elphent tooth-like structure consisting of fine,equant sparry calcite (or dolomite)crystals,and hosting rocks is mainly fine-grained carbonates with mud.Studies in the areas of Jilin,Liaonig,Jiangsu and Anhui,North China and new researches worldwide indicate that formation of microspar structures carbonates are constrained by geological history,and occurrences are only limited within Precambrian (Neo-MidProterozoic) strata.This study suggests that microspar structures carbonates be formed in ramp carbonate platform and hosting rocks be mainly subtidal-peritidal fine-grained muddy limestone driven by tidal and storm current. The are rarely happen within supertidal and deep-ramp,which display an important significance in environmental interpretation. Microspar structures,so far,are enigmatic of Precambrian,and generation interpretation is still to go.