THE ENVIRONMENTAL CONDITIONS OF THE MICROSPARITE (MOLAR TOOTH)&nbsp; C ARBONATES OPENED OUT BY GEOCHEMISTRY：AN EXAMPLE FROM THE&nbsp; MICROSPARITE CARB ONATES OF NEOPROTEROZOIC IN&nbsp; JI-LIAO REGION, CHINA

KUANG Hong-wei, JIN Guang-chun,LIU Yan-xue, MENG Xiang-hua, GE Ming

doi:10.11764/j.issn.1672-1926.2004.02.150

2004 , Vol. 15 >Issue 2: 150 - 155

DOI: https://doi.org/10.11764/j.issn.1672-1926.2004.02.150

THE ENVIRONMENTAL CONDITIONS OF THE MICROSPARITE (MOLAR TOOTH) C ARBONATES OPENED OUT BY GEOCHEMISTRY：AN EXAMPLE FROM THE MICROSPARITE CARB ONATES OF NEOPROTEROZOIC IN JI-LIAO REGION, CHINA

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(1.Department of Geophysics, Yangtze University, Jingzhou 434023, Ch ina;
2. Department of Geochemistry, Yangtze University, Jingzhou 434023, China;
3. Chinese Academy of Geological Sciences, Beijing 100037, China;
4.Institute of Sedimentary Basin of China University of Geosciences, Beijing 100083, China)

Received date: 2004-02-02

Revised date: 2004-03-02

Online published: 2004-04-20

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Abstract

Along with the research progress on Precambrian, the Molar tooth carbonates (briefly called MT, or called microsparite carbonates or MT st ructure) being formed in mid-late Proterozoic become a target of crossing firer ecently. The Proterozoic Molar-tooth (MT) carbonate rocks refer to those Meso- to Neoproterozoic (1 700～650 Ma) carbonates with MT structure, being a series o f pecular, ptygmatically folded and spar-filled cracks in fine-grained carbona tes of Precambrian age, located in the environment of mid-to inner ramp and sha llow platform. Like a bridge, MTS connected the inorganic world with the organic one and is closely related to the evolution of the paleo-oceans, the atmospher e and the biosphere. Their development and/or recession are related to the origi n of life and the abruption of sedimentary geochemistry of marine carbonates. By using of morden instruments and testing methods adequately in this paper, cont ents of sandstone oxides and the model curve of REE distribution were measured; the ⁸⁷Sr/⁸⁶Sr isotopic ratio obtained an accurate value, tha t is, the age of MT formation is about 750～900 Ma; C and O isotopes of some fre sh micrite limestone samples were analyzed; the energy spectrum analysis found t hat MT consists of microspar calcite mainly, while chemical composition of the m atrix is abundantly of peaks Ca, M, Al, Si, K.The geochemical indicators proved that the MT carbonates of Neoproterozoic in the Ji-Liao region developed in the margin of the stable continent, formed in the torrid zone and the paleo-temper atures were about 50℃, the sea water was normal salinity when MT formed during the wanlong period in the southern Jilin, the Yingchengzi period and the Xingmin cun period in the eastern Liaoning. the sedimentary environment located in the i nner ramp. In summary, it is of important significance for the origin of the MT, also for the paleo-climate, the paleo-environment, ascertaining the age and t he stratigraphy division and correlation of the Proterozoic to study the geochem ical features of the MT carbonates and its formation environment.

Key words： Molar tooth; Microsparite carbonate; Geochemistry; Ji-liao region; Neoproterozoic

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KUANG Hong-wei, JIN Guang-chun,LIU Yan-xue, MENG Xiang-hua, GE Ming . THE ENVIRONMENTAL CONDITIONS OF THE MICROSPARITE (MOLAR TOOTH) C ARBONATES OPENED OUT BY GEOCHEMISTRY：AN EXAMPLE FROM THE MICROSPARITE CARB ONATES OF NEOPROTEROZOIC IN JI-LIAO REGION, CHINA[J]. Natural Gas Geoscience, 2004 , 15(2) : 150 -155 . DOI: 10.11764/j.issn.1672-1926.2004.02.150

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