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

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.

Cite this article

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

References

[1] Bauerman H.Report on the Geology of the Country Near the  Forth-ninth Parallel of North Latitude West of the Rocky Mountains[R].Canada  Geol. Survey Rept. Prog, 1882-1884,1885b.1-42.
 [2]  James N P,Narbonne G M, Sherman A G. Molar tooth carbona tes:Shallow subtidal facies of the Mid to Late Proterozoic[J].Journal of Sed imentary Research,1998,68(5):716-722.
 [3]  Shields G A.Working towards a new stratigraphic cabibration Scheme for the Neoproterozoic-Cambrian[J].Eclogae Geologicae,Helvetiae,1999,92:221-233.
 [4]  Smith A G.The origin and deformation of some“Molar-toot h”structu re in the Precambrian Belt-Purcell supergroup[J].Journal of Geology,1968, 76:426-433.
 [5]  刘岫峰.沉积岩实验室研究方法 [M ].北京:石油工业出版社,1989.
 [6]  赵振华.微量元素地球化学原理 [M ].北京:科学出版社,1997143-159 .
 [7] 孟祥化,葛铭,Tucker M E.长山期最大海泛事件及洲际模式研究[J]. 19 95,40(9): 818-821.
 [8] 郑文武,杨杰东,洪天求,等. 辽南与苏皖北部上前寒武系Sr、C同位素对比 [J].地层学杂志,2002,26(4):376-382.
 [9] 杨杰东,张俊明,陶仙聪,等.末元古代-寒武系底Sr、C同位素对比[J] .高校地质学报,2000,6(4):532-545. [10] 杨杰东,郑文武,王宗哲,等.Sr、C同位素对苏皖北部上前寒武系时代的界定[ J].地层学杂志,2001,25(1):44-47.
[11] Kaufman A J, Knoll A H. Neoproterozoic variations in the C-isotopic com posion of seawater: Stratigraphic and biogeochemical implications[J].Precambr ian Research, 1995,73:27-49.
[12]  周传明,贵州瓮安地区上震旦统碳同位素特征[J].地层学杂志,1997,21(2):  124-129.
[13] Keith M H, Weber J N. Isotopic composition and environment cla ssification of selected limestone and fossils[J]. Geoch-        imica Cosmoc himica Acta, 1964,28:1787-1816.
[14] 郑文武.论淮南群形成时期的古海水温度及其演化规律[J].合肥工业大学学报 ,1994,17(1):152-159.
[15] 朱士兴,邢裕盛,张鹏远,等. 华北地台中、上元古界生物地层序列 [M ].北京: 地质出版社,1994.
[16] 毕守业,王德荣,贾大成,等.吉林省地体构造的基本特征[J].吉林地质,1995 ,14(1):1-14.
[17] 孟祥化,葛铭.新元古代旋回层序地层:海平面变化、古地理及微亮晶碳酸盐事件  [A ].孟祥化,葛铭.中朝板块层序、事件及演化 [C ].北京:科学出版社,2003待出版 .
 [18 ] 库兹涅佐夫 В Г.地史上碳酸盐聚集演化的若干特点——白云岩形成演化和碳酸 盐聚集与全球地质环境的关系 [J ].惠大华译,史斗校.天然气地球科学,2002,13(1):18 -28.

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