Abstract:

The Molartooth carbonate (briefly, MT) is one type of carbonates which is developed widely with special origin implication. Until now, MT structures have been found in over 50 stratigraphic sections of Mesoand Neoproterozoic in more than twenty regions in the world. Since more than one hundred years, the research of MT has achieved significant progress, but it is still a question for geologists. Studying from the relationship between MT and host rocks, especially the relationship between MT and geochemical characteristic of host rocks and its geological implication, and using testing methods such as thin section, electron probe, backscattering spectrometry, cathodoluminescence (CL), and the systematic testing of C, O, Sr isotopes, the paper focuses on the composition, structure, microscopic structure of MT and its host rocks from Neoproterozoic Nanguanling, Yingchengzi and Xingmincun formations in Dalian, eastern Liaoning Province. It is proved that MT is the production of original or early diagenesis, which was crystallized or diagenesised from the original sea water directly. MT and its host rocks have similar geochemistry with syngenetic or Penecontemporaneous characteristics, and formed in warm normal oceanic environment and disappeared before glaciagenic Sturtian Period. The analogy of the Sr and C isotopes of MT to the global theory curves of Mesoand Neoproterozoic Sr and C isotopes shows that the geological age of the Neoproterozoic Nanguanling and Yingchengzi Formations in Dalian is 760950 Ma, and the Xingmincun Formation is 720800 Ma. The Neoproterozoic strata in JiaoLiaoXuHuai subprovince are well correlated.

Key words:  Molartooth Carbonates, Geochemistry, implication, Neoproterozoic, Dalian