中新元古代沉积纪录--臼齿碳酸盐岩对比研究与形成机制

The Molar tooth carbonate (briefly called MTC), as the responsive deposit and record for the Precambrian global change, has scientific significance and application value in the aspect of Precambrian ocean, stratigraphy and the depositional palaeogeography. Until now, the research is far from complete although some achievements has made, such as, the consent of the origin still hasn't reached, the micro-fabric isn't entirely clear-cut and the correlation and application haven't been carried out. Based on the research results around world, focusing on the microfabric and the formation process for different types of MTC by the international cooperation, applying C, O, Sr, S isotopic test analysis, combining with the feature of sedimentology and geochemistry, this application will carry out the regional correlation of the MTC to reveal the origin of MTC. Combining with the existing geological data, the feature library of MTC from Jiao-Liao-Xu-Huai(Shandong, Liaoning, Jiangsu and Anhui Provinces) in North China, Henan Province, the Yimen County of Yunnan Province, the western Liaoning and Jixian of Tianjing, etc. will be built, and furthermore, a correlation will be made with the MTC of South Africa, North America, Australia and so on. From the sedimentology, morphology, crystal mineralogy and geochemistry，this research will perfect the original model of MTC, discuss on the controlled factors of MTC formation and their relationship amongst the controlled factors and the Meso-Neoproterozoic palaeoocean，as well as the paleaoenvironment, explore the nature of palaeoocean during the period of the Meso-Neoproterozoic, and finally, provide initial data and geological evidences for the research of Meso-Neoproterozoic stratigraphy, sedimentology and paleogeographic reconstruction.

臼齿碳酸盐岩（MTC）是前寒武纪全球变化的沉积记录，它在前寒武纪古海洋、沉积学、地层学研究方面具有重要科学意义和应用价值。前期的研究虽取得了一定成果，但相关研究还远未完成，如，其成因还未完全达成共识，微观组构还不完全明确，不同地点、时代及形态的MTC的系统对比研究还未开展。本申请立足于国内外现有研究成果，以国际合作为锚点，侧重不同类型的MTC微观组构及形成过程研究，应用C、O、Sr、S同位素测试分析为手段，结合沉积学和地球化学特征，开展MTC对比研究；建立华北胶辽徐淮、河南、云南、辽西、天津等中、新元古界MTC特征库，进而对比研究北美、澳大利亚等地MTC的异同；从沉积学、形态学、晶体矿物学、地球化学等角度完善MTC成因模型，探讨MTC形成受控因素与中、新元古代古海洋、古环境的关系，探索中、新元古代时期的古海洋性质，为中、新元古代地层学、沉积学、古地理恢复提供基础资料和地质学证据。

“臼齿碳酸盐岩(Molar-Tooth carbonate,简称MTC)”是一种由微亮晶方解石晶体形成的具有特殊形态和结构构造的仅出现在前寒武纪的碳酸盐岩类及沉积构造(MTS)｡围绕研究目标,以MTC微观组构､岩石矿物地球化学测试分析为突破点,揭示区域或洲际MTC发育特征和规律(岩石学､地球化学､微观组构､受控因素),完善MTC成因模型,探索前寒武纪古海洋性质｡通过四年的研究,以下几方面取得了较好的进展:1)新发现辽宁本溪新元古代康家组和山东栖霞蓬莱群香夼组发育大量MT构造,其特征可对比胶辽徐淮地区新元古代发育的MT构造；2)踏勘了苏､鲁､豫､皖及云南昆阳群的MTC发育的地层剖面,采集大量样品,同时与田纳西大家Linda Kah教授开展合作交流,对北美Belt超群中元古代MT开展对比研究；3)研究结果表明,MTC的形成于早成岩期,其产生､发育和消失取决于元古代时期的古海洋化学性质､温度､氧化还原条件以及微生物参与下异化铁还原作用(microbial dissimilatory iron reduction)；4)叠层石作为地球上最古老的与生物有关的生物-沉积构造,其繁盛与衰落均具有幕式沉积特点,这与MTS在地球上的发育与分布具有相似性；5)以MTC为对比标志,开展中新元古代地层对比与古大陆恢复研究,具有较好的应用效果。