Types and origin of Cambrian-Ordovician dolomites in Tarim basin

	Types and origin of Cambrian-Ordovician dolomites in Tarim basin
	Wu ShiQiang 1,2; Zhu JingQuan 1; Wang GuoXue 1,2; Hu WenXuan 3; Zhang JunTao 3; Wang XiaoLin 3
刊名	ACTA PETROLOGICA SINICA
	2008-06-01
卷号	24 期号:6 页码:1390-1400
关键词	dolomite dolomitization orgin dolomite petrography Tarim basin Cambrian to Ordovician
ISSN号	1000-0569
文献子类	Article
英文摘要	Cambrian-Ordovician dolomites in Tarim basin, which are characterized by thickly and extensively distributed horizon, are very important hydrocarbon reservoirs. Detailed petrographic investigations have documented 4 dolomite types and their origins are figured out based on petrographic, chemical, isotopic studies, X-ray diffraction and cathodoluminescence analysis. (1) Mud-silt-sized dolomite consists of anhedral and less ordered micritic crystals and exhibits bright-pink luminescent. It yields the highest Na, K, Sr contents, high delta(13)C, Z values (with the average values of -0.94 parts per thousand and 122.3, respectively) and low Fe, Mn contents. It always presents as laminas together with evaporated signatures. These characteristics reveal that this kind of dolomite was formed in hypersaline and oxidizing environment and involved fast dolomitization process. It was dolomitized by evaporated seawater in sabkha environment. (2) Algal laminated dolomite (ALD) is Composed Of euhedral and finely crystallines (<0.05mm) and its main primary fabric of algal lamination can still be identified. Its delta(13)C (-0.50 parts per thousand) and Z (123.2) values are the highest, however, Na, K, Sr contents are the lowest. The appearance of sedimentary pyrite Suggests that sulfate reduction was active in these sediments shortly after deposition. These characteristics indicate that ALD was dolomitized during early diagenesis and algae possibly played an important role. The ALD was likely formed under mediation of organic matter and Mg(2+) were supplied by magnesium concentrated algal laminites and sea water. The highest delta(13)C and Z values don't represent the hypersaline condition but possibly suggest the mediation by organic matter. (3) The dolomite which consists of crystals with cloudy centers and clear rims (CCCR) presents mainly as patchy occurrence, and most of its crystals are euhedral and microsucrosic. Patchy are represented by the distribution of CCCR crystals in the vicinity of or within stylolites. The cores of the dolomites are always rich in inclusions and contain some limestone remnants, but the rims are relatively inclusion-free. The cores exhibit bright-pink luminescent, however, the rims are dull or nonluminescent. The dolomite yields the lowest delta(13)C, Z values and the highest Mn content, and its K, Na, Sr, Fe contents are low, and moreover, it is relatively highly ordered. These characteristics reveal that this kind of dolomite was formed under reducing conditions and involved less hypersaline fluids. It can be inferred that the pore fluids which were rich in Mg(2+) were responsible for the formation of cloudy cores in shallow early diagenetic environments. Whereas the clear rims were likely formed in subsequent burial into deeper subsurface environments, and the Mg(2+) needed for further dolomitization possibly was supplied by the transformations of clay minerals. (4) Neomorphic dolomite consists of coarse, turbid Crystals and exhibits sucrosic and mosaic textures. Saddle dolostones are present sometimes indicating it involved a deep burial diagenesis. Zonation and grain-ghost were observed occasionally suggesting strong recrystallization. Dull luminescent together with the highest Fe and high Mn contents, low Na, K, Sr contents point to a reducing and less hypersaline environment. Low delta(13)C, the lowest Z value and the highest order degree (average in 0.95) possibly resulted from the recrystallization.
WOS关键词	HOLOCENE DOLOMITIZATION ; BURIAL DOLOMITIZATION ; RECRYSTALLIZATION ; PRECIPITATION ; RESERVOIRS ; CALIFORNIA ; EVOLUTION ; SEDIMENTS ; ISOTOPE ; FLORIDA
WOS研究方向	Geology
语种	英语
出版者	SCIENCE PRESS
WOS记录号	WOS:000259628800022
内容类型	期刊论文
源URL	[http://ir.iggcas.ac.cn/handle/132A11/70006]
专题	中国科学院地质与地球物理研究所
通讯作者	Wu ShiQiang
作者单位	1.Chinese Acad Sci, Inst Geol & Geophys, Beijing 100029, Peoples R China 2.Chinese Acad Sci, Grad Sch, Beijing 100029, Peoples R China 3.Nanjing Univ, Dept Earth Sci, Nanjing 210093, Peoples R China
推荐引用方式 GB/T 7714	Wu ShiQiang,Zhu JingQuan,Wang GuoXue,et al. Types and origin of Cambrian-Ordovician dolomites in Tarim basin[J]. ACTA PETROLOGICA SINICA,2008,24(6):1390-1400.
APA	Wu ShiQiang,Zhu JingQuan,Wang GuoXue,Hu WenXuan,Zhang JunTao,&Wang XiaoLin.(2008).Types and origin of Cambrian-Ordovician dolomites in Tarim basin.ACTA PETROLOGICA SINICA,24(6),1390-1400.
MLA	Wu ShiQiang,et al."Types and origin of Cambrian-Ordovician dolomites in Tarim basin".ACTA PETROLOGICA SINICA 24.6(2008):1390-1400.