Molar-tooth structure (MTS) is an unusual carbonate fabric that is composed of variously shaped cracks and voids filled with calcite microspar. Despite a century of study, MTS remains enigmatic because it juxtaposes void formation within a cohesive yet unlithified substrate with the penecontemporaneous precipitation and lithification of void-filling carbonate microspar. MTS is broadly restricted to shallow marine carbonate strata of the Mesoproterozoic and Neoproterozoic, suggesting a fundamental link between the formation of MTS and the biogeochemical evolution of marine environments. Despite uncertainties in the origin of MTS, molar-tooth (MT) microspar remains a popular target for geochemical analysis and the reconstruction of Precambrian marine chemistry. Here we review models for the formation of MTS and show how detailed petrographic analysis of MT microspar permits identification of a complex process of precipitation and diagenesis that must be considered when the microspar phase is used as a geochemical proxy. ▪ Molar-tooth fabric is an enigmatic structure in Precambrian sedimentary rocks that is composed of variously shaped cracks and voids filled with carbonate microspar. ▪ Time restriction of this fabric suggests a link between this unusual structure and the biogeochemical evolution of marine environments. ▪ Petrographic analysis of molar-tooth fabric provides insight into fundamental processes of crystallization.

中文翻译：

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臼齿结构是了解前寒武纪碳酸盐沉积和成岩作用的窗口


臼齿结构（MTS）是一种不寻常的碳酸盐织物，由各种形状的裂缝和填充有方解石微晶石的空隙组成。尽管经过一个世纪的研究，MTS 仍然是个谜，因为它将粘性但未岩化的基质内的空隙形成与填充空隙的碳酸盐微晶石的准同期沉淀和岩化并置。 MTS 广泛局限于中元古代和新元古代的浅海碳酸盐岩地层，这表明 MTS 的形成与海洋环境的生物地球化学演化之间存在根本联系。尽管 MTS 的起源存在不确定性，但臼齿（MT）微石仍然是地球化学分析和重建前寒武纪海洋化学的热门目标。在这里，我们回顾了 MTS 形成的模型，并展示了 MT 微晶石的详细岩相分析如何能够识别复杂的沉淀和成岩作用过程，当微晶石相用作地球化学代理时必须考虑这一过程。 ▪ 臼齿结构是前寒武纪沉积岩中的一种神秘结构，由充满碳酸盐微晶石的各种形状的裂缝和空隙组成。 ▪ 这种结构的时间限制表明这种不寻常的结构与海洋环境的生物地球化学演化之间存在联系。 ▪ 臼齿结构的岩相分析可以深入了解结晶的基本过程。