微生物诱导白云石沉淀研究进展及面临的挑战

白云岩成因机理一直是地质学家们关注的焦点，微生物诱导沉淀白云石模式是对“白云岩问题”的重要补充。一方面，微生物作用能显著改善邻近水体化学条件，形成利于白云石沉淀的微环境；另一方面，微生物及代谢产物为白云石沉淀提供成核位点。两者共同克服低温白云石沉淀的动力学障碍。但对于古老地层而言，判识白云石是否为微生物成因具有难度，目前依然缺乏强有力的手段予以约束。基于特殊微观形貌的判识方法，要谨慎使用，需综合评判。大量的证据表明，水化学条件和水文学条件是影响白云石沉淀的关键。虽然，现今白云石的分布环境不能与地质历史时期相对比，前寒武时期微生物白云石发育的环境可能比现今广泛的多，其微生物诱导白云石的规模也可能相当巨大。但截至目前，微生物作用对于古老白云岩的贡献还难以得到有效评估，故其对于解释地质历史时期规模性白云岩的形成还存在不少挑战。即便如此，毫无疑问的是，微生物活动能广泛促进超高镁方解石和原白云石等潜在中间产物的生成，因此其必然有利于白云石的形成。

A Review of Microbial Dolomite:Advances and challenges

The formation mechanism of dolomite has always been the focus of geologists. The microbial dolomite model is an important supplement to the "dolomite problem". Microbial processes can not only provide nucleation sites， but also significantly improve the chemical conditions of adjacent water columns， thus forming a microenvironment that favours dolomite precipitation. However， for ancient strata， due to the lack of convincing evidence， it is difficult to determine whether dolomite is of microbial origin. In particular， the special microscopic morphologies of minerals should be carefully used to evaluate the origin of dolomite. A great deal of evidence indicates that hydrochemical and hydrologic conditions are the key factors for dolomite precipitation. Although the distribution and forming environment of modern dolomite cannot be compared with the geologic historical period， the scale and optimal environment for microbial dolomite may be much more extensive in the Precambrian period. However， to date， the contribution of microbial processes to ancient dolomites is still difficult to effectively evaluate， so there are still many challenges in explaining the formation of large-scale dolomites in geological history with this model. It is worth noting that microbial activity is still beneficial to the formation of dolomite to some extent since the potential intermediates， such as very high magnesium， calcite， and proto-dolomite， can be widely promoted.