微亮晶(臼齿)碳酸盐岩:21世纪全球地学研究的新热点

国际地质对比计划委员会批准启动了 IGCP44 7-元古代臼齿碳酸盐岩和地球演化项目 ( 2 0 0 1～ 2 0 0 5 )〔1〕。本文简要地回顾了臼齿碳酸盐岩的研究历史和最新进展。臼齿碳酸盐岩是一种具有类似大象臼齿的肠状褶皱构造的岩石 ,具有特殊的时限范围 (中 -新元古代 )。试图解释其成因和可能用于古大陆地层对比是本项目研究的重要课题 ,其重要意义还在于它们是解决前寒武纪生物学和地球化学事件的关键。臼齿碳酸盐岩的发育和衰退关系到地球生命起源和海洋碳酸盐岩沉积地球化学的突变。 87Sr/86 Sr年龄同位素测定证明 ,微亮晶 (臼齿 )碳酸盐消失的时限很可能为75 0 Ma。另外 ,中 -新元古代碳酸盐岩地层具有重要的生烃潜力。

Molar-tooth Carboantes: Carbon ate Research Highlight of the World in the 21st Century

The IGCP 447 (Proterozoic Molar tooth Carbonates and the Evolution of the Earth) was approved in February, 2001 by the International Geological Correlation Program Scientific Board and marked the new progress of this field. The IGCP project 447 a successor of IGCP 319, aims to investigate the origin and structures of Middle to Late Precambrian microsparites and to assess their global correlation by stressing depositional, palaeoenvironmental, biogeochemical, geotectonical and stratigraphical significance (Episodes, New IGCP Projects was accepted and started in 2001). Molar-tooth carbonates are specialized and peculiarly named early diagenetic sedimentary features. The name of ‘Molar-tooth’ carbonates originated from their tapered, ptygmatically folded texture comparable to an elephant's tooth. Molar-tooth structures (MTS) have a specified time range of 1900 to 550 Ma - (mainly developed in Mesoproterozoic to Neoproterozoic era), To try our best to interpret the origin of these enigmatic structures and their possible use in correlation is a significant object of this research. This project will undertake a thorough survey of the Proterozoic carbonates in China, Arctic Europe (Spitsbergen), Russia (South Siberia), North America (Mackenzie Mountains/Victoria Island.), West Africa and so on. MTS are significant for serving as the key Precambrian biological and geochemical events. They might be a link in the revolutionary changes of the biosphere, which heralded the appearance of the complex multi-cellular animals of the late Precambrian. There are more and more evidences which suggest that MTS probably originated from organic substance. Like a bridge, MTS connected the inorganic world with the organic one and is closely related to the evolution of the paleoseas, the atmosphere and the biosphere. Their development and/or recession are related to the origin of life and the abruption of sedimentary geochemistry of marine carbonates. It was proved by the isotopic age of 87Sr/ 86Sr that the disappearance of the MT carbonate might be possibly occurred in 750 Ma. Based on the research of home and abroad, the Meso-neoproterozoic strata might be of important potential of hydrocarbon generation, and of a better reservoir as well.