| Petrography and geochemistry of Paleocene–Eocene limestones in the Ching-dar syncline, eastern Iran |
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| 摘 要： | The Ching-dar syncline is located to the west of the city of Birjand, in the east of han. The ca. 500 m thick studied section at the eastern flank of the syncline contains a sequence of almost continuous shallow- marine limestones that exhibit no major sedimentary breaks or evidence for volcanic activity. Skeletal grains consist of large benthic foraminifera and green algae whereas non-skeletal grains are mostly peloids and intraclasts. They were deposited on a shallow-marine carbonate ramp. The limestones have undergone extensive diagenetic processes with varying intensities, the most important of which are micritization, cementation, compaction （chemical and mechanical）, internal filling and stylolitization. Chemical analysis of the limestone samples revealed high calcium and low magnesium content. Major and minor element values were used to determine the original carbonate mineralogy of these lime- stones. Petrographic evidence and elemental values indicate that calcite was the original carbonate mineral in the limestones of the Ching-dar syncline. The elemental composition of the Ching-dar car- bonates also demonstrates that they have stabilized in a meteoric phreatic environment. Variation of Sr/ Ca vs. Mn values suggests that diagenetic alteration occurred in an open geochemical system.
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| 关 键 词： | 地球化学 石灰岩 岩相学 向斜 古新世 始新世 碳酸盐矿物 元素组成 |
| 收稿时间： | 29 December 2012 |
http://www.sciencedirect.com/science/article/pii/S1674987113001102 |
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| Authors: | SHalimehHashemiAzizi GholamrezaMirabShabestari AhmadrezaKhazaei |
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| Institution: | [1]DepartmentofGeology,FacultyofSciences,HormozganUniversityofBandarAbbas,BandarAbbas.Hormozgan,Iran [2]DepartmentofGeology,UniversityofBirjand,lran |
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| Abstract: | The Ching-dar syncline is located to the west of the city of Birjand,in the east of Iran.The ca.500 m thick studied section at the eastern flank of the syncline contains a sequence of almost continuous shallowmarine limestones that exhibit no major sedimentary breaks or evidence for volcanic activity.Skeletal grains consist of large benthic foraminifera and green algae whereas non-skeletal grains are mostly peloids and intraclasts.They were deposited on a shallow-marine carbonate ramp.The limestones have undergone extensive diagenetic processes with varying intensities,the most important of which are micritization,cementation,compaction(chemical and mechanical),internal filling and stylolitization.Chemical analysis of the limestone samples revealed high calcium and low magnesium content.Major and minor element values were used to determine the original carbonate mineralogy of these limestones.Petrographic evidence and elemental values indicate that calcite was the original carbonate mineral in the limestones of the Ching-dar syncline.The elemental composition of the Ching-dar carbonates also demonstrates that they have stabilized in a meteoric phreatic environment.Variation of Sr/Ca vs.Mn values suggests that diagenetic alteration occurred in an open geochemical system. |
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| Keywords: | Ching-dar syncline Geochemistry Diagenetic sequence Limestone Paleocene Eocene |
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