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| 微亮晶（臼齿）碳酸盐成因及其在元古宙地球演化中的意义 | |
| 引用本文： | 孟祥化 葛铭 旷红伟 J K Nielsen.微亮晶（臼齿）碳酸盐成因及其在元古宙地球演化中的意义[J].岩石学报,2006,22(8):2133-2143. |
| 作者姓名： | 孟祥化 葛铭 旷红伟 J K Nielsen |
| 作者单位： | 1. 中国地质大学(北京)沉积盆地研究所,北京,100083 2. 长江大学,地球物理与石油资源学院,荆州,434033 3. 特罗姆瑟大学地质系,挪威 |
| 基金项目： | 国际地质对比计划;国家重点基础研究发展计划(973计划);国家自然科学基金;中国地质调查局区域地质调查项目 |
| 摘 要： | 本文应用多种技术方法,对微亮晶碳酸盐岩的成岩作用及其成因从宏观至微观进行了分析。根据岩石矿物学、地球化学和有机地球化学等研究证明,它是早期成岩过程中,在超高压的大气 CO_2,水平急剧下降的转折期,快速石化作用形成的具等粒结构μm级的微亮晶方解石集合体。MT 碳酸盐岩微亮晶成岩作用有两种类型:一是主要发生在海底沉积软泥中,在其底基质软泥中经差异压实作用形成褶皱肠状及复杂形的 MT 构造;二是直接在海水中或重力流搬运过程中形成的微亮晶球粒(核)。简言之,MT 碳酸盐岩石是在地球早期浅海环境下,由于微生物自养作用形成的地球化学成因产物。微亮晶碳酸盐岩是约束古大气圈和古海洋环境变化的最灵敏标志。通过详测 MT 丰度值和编制地球古大气圈 CO_2水平演化模式等,在前寒武纪发现有太古宙末期、早元古宙末期、中元古宙中期和新元古宙早-中期四个 MT 碳酸盐岩发育高峰值期,证明全球古大气圈 CO_2水平发生过四次不连续性、跳跃式下降周期,直到晚新元古宙未,全球雪球事件的发生,导致了 MT 碳酸盐岩的消失。其后,才进入显生宙的 CO_2低水平状态。MT 碳酸盐岩具有重要的油气资源远景,应予以重视。 |
| 关 键 词： | 微亮晶碳酸盐岩 成岩作用 成因机制 元古宙 地球演化 大气圈CO2 |
| 文章编号： | 1000-0569/2006/022(08)-2133-43 |
| 收稿时间： | 02 28 2005 12:00AM |
| 修稿时间： | 04 16 2006 12:00AM |
Origin of Microsparite carbonates and the significance in the evolution of the Earth in Proterozoic |
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| MENG XiangHu,GE Ming,KUA.NG HongWei,Nielsen J K.Origin of Microsparite carbonates and the significance in the evolution of the Earth in Proterozoic[J].Acta Petrologica Sinica,2006,22(8):2133-2143. | |
| Authors: | MENG XiangHu GE Ming KUANG HongWei Nielsen J K |
| Institution: | 1.Institute of Sedimentary Basin,China University of Geosciences,Beijing 100083,China;2.School of Geophysics and Oil Resources,Yangtze University ,Jingzhou 434023,China;3.Depatrment of Geology,University of Tromsoe ,Dramsveien 201,NO-9037 Tromsoe,Norway. |
| Abstract: | The diagenesis and origin of Mierosparite(MT-Molar tooth)carbonates have been analyzed based on macroscopic and microscopic characteristics obtained with a variety of techniques.The study on petrology,mineralogy,geochemistry and organic geochemistry of the MT carbonates demonstrated that the MT carbonates were composed of micrometer-scale,equigranular and hexahedron microspars,and were formed by the early and fast lithificaiton during a rapid drop of atmospheric CO_2 pressure.There were two types of diagenesis which had been involved in formation of the MT carbonates;one took place in the soft mud of the sea floor where the differential compaction formed the ptygmatic fold structures or other complex shaped structures,another was the microsparite core of globules which were directly precipitated from sea water or was carried in by the carbonate gravity.All of above confirmed that MT carbonates were formed by biogeoehemical reaction in shallow sea.The MT carbonates were the most sensitive indicator of the paleo- atmospheric and paleo-oceanic conditions.The abundance of the MT carbonates can be measured and used to model the evolution of CO_2 level in paleo-atmosphere.Four-peak development stages of the MT carbonates were found in the Precambrian,including the Late Archaean Era,last stage of the Early Proterozoic,middle period of the Mesoproterozoic and Neoproterozoic.These four stages were coincident with the four stepping-down events of the CO_2 level in paleo-atmosphere.After these four stages,the CO_2 level dropped down to a lowest level in the Phanernzoic.Moreover,the MT carbonates are of importance for oil-gas resources perspective. |
| Keywords: | Microsparite carbonates Diagenesis Origin Proterozoic Earth evolution |
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