Genesis of Dolomite in Middle Permian Maokou Formation in Eastern Sichuan: Constraints from In Situ Geochemistry, Sr-Mg Isotopes, and Fluid Inclusions
The dolostone reservoir of the Middle Permian Maokou Formation in Eastern Sichuan has good prospects for oil and gas exploration. Study of dolomitizing genesis of the Maokou Formation is essential for predicting the distribution of the dolostone reservoir. Petrography, in situ geochemistry, Sr-Mg is...
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| Format: | Article |
| Language: | English |
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Wiley
2021-01-01
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| Series: | Geofluids |
| Online Access: | http://dx.doi.org/10.1155/2021/6611140 |
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| author | Yanxia Jiang Xianfeng Tan Chengjiang Zhang Wei Jiang Jia Wang Long Luo Dongping Tan Wei Wang Zhifu Xiong |
| author_facet | Yanxia Jiang Xianfeng Tan Chengjiang Zhang Wei Jiang Jia Wang Long Luo Dongping Tan Wei Wang Zhifu Xiong |
| author_sort | Yanxia Jiang |
| collection | DOAJ |
| description | The dolostone reservoir of the Middle Permian Maokou Formation in Eastern Sichuan has good prospects for oil and gas exploration. Study of dolomitizing genesis of the Maokou Formation is essential for predicting the distribution of the dolostone reservoir. Petrography, in situ geochemistry, Sr-Mg isotopes, and fluid inclusions were carried out on samples from the Maokou Formation in Eastern Sichuan in order to discuss the dolomitizing process. Based on mineral and textural characteristics, dolomites were divided into four components: partially clouded dolomite (PCD), mosaic-like dolomite (MLD), cloudy-centered and clear-rimmed dolomite (CACD), and saddle dolomite (SDD). Results indicate that the Maokou Formation in Eastern Sichuan mainly experienced two stages of dolomitization. PCD, MLD, and cloudy-centered dolomite (CCD) were formed during the early dolomitization. They all show turbid crystal planes and bright orange-red CL and have similar trace element contents, 87Sr/86Sr ratios, and rare-earth patterns, indicating that they might be formed in the same fluid. This is a period when dolomitizing fluids mainly migrated along pores or microcracks and replaced protogenetic calcites, which occurred in the shallow burial stage of the Maokou Formation before the Late Permian. Clear-rimmed dolomite (CRD) and SDD were formed in the late stage of dolomitization. They all have clean crystal planes and darkly red CL. CRD of the ERY profile has trace element contents, 87Sr/86Sr ratios, and rare-earth patterns similar to SDD of the HLCH profile and Well TL6, inferring that both may be formed in the same fluid. Combined with high SrO contents and homogenous temperatures of fluid inclusions of CRD and SDD and Mg-isotopic compositions, they were generated by hydrothermal dolomitization. The hydrothermal fluid stage is related to the movement of the Emeishan Large Igneous Province, which was made up of basaltic magmatic fluids mixing with the surface water. The hydrothermal fluid mainly migrated upwards along structural fractures or faults and filled in structural fractures, occurring in the Late Permian to Middle-Late Triassic. |
| format | Article |
| id | doaj-art-84d32a26f5964076b5df7db34c6df9e9 |
| institution | Kabale University |
| issn | 1468-8115 1468-8123 |
| language | English |
| publishDate | 2021-01-01 |
| publisher | Wiley |
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| series | Geofluids |
| spelling | doaj-art-84d32a26f5964076b5df7db34c6df9e92025-02-03T01:04:36ZengWileyGeofluids1468-81151468-81232021-01-01202110.1155/2021/66111406611140Genesis of Dolomite in Middle Permian Maokou Formation in Eastern Sichuan: Constraints from In Situ Geochemistry, Sr-Mg Isotopes, and Fluid InclusionsYanxia Jiang0Xianfeng Tan1Chengjiang Zhang2Wei Jiang3Jia Wang4Long Luo5Dongping Tan6Wei Wang7Zhifu Xiong8College of Earth Science, Chengdu University of Technology, Chengdu 610059, ChinaChongqing Key Laboratory of Complex Oil and Gas Exploration and Development, Chongqing 401331, ChinaCollege of Earth Science, Chengdu University of Technology, Chengdu 610059, ChinaSchool of Earth Science and Engineering, Nanjing University, Nanjing 210046, ChinaChongqing Key Laboratory of Complex Oil and Gas Exploration and Development, Chongqing 401331, ChinaChongqing Key Laboratory of Complex Oil and Gas Exploration and Development, Chongqing 401331, ChinaChongqing Key Laboratory of Complex Oil and Gas Exploration and Development, Chongqing 401331, ChinaSinopec Exploration Company, Chengdu 610041, ChinaSinopec Exploration Company, Chengdu 610041, ChinaThe dolostone reservoir of the Middle Permian Maokou Formation in Eastern Sichuan has good prospects for oil and gas exploration. Study of dolomitizing genesis of the Maokou Formation is essential for predicting the distribution of the dolostone reservoir. Petrography, in situ geochemistry, Sr-Mg isotopes, and fluid inclusions were carried out on samples from the Maokou Formation in Eastern Sichuan in order to discuss the dolomitizing process. Based on mineral and textural characteristics, dolomites were divided into four components: partially clouded dolomite (PCD), mosaic-like dolomite (MLD), cloudy-centered and clear-rimmed dolomite (CACD), and saddle dolomite (SDD). Results indicate that the Maokou Formation in Eastern Sichuan mainly experienced two stages of dolomitization. PCD, MLD, and cloudy-centered dolomite (CCD) were formed during the early dolomitization. They all show turbid crystal planes and bright orange-red CL and have similar trace element contents, 87Sr/86Sr ratios, and rare-earth patterns, indicating that they might be formed in the same fluid. This is a period when dolomitizing fluids mainly migrated along pores or microcracks and replaced protogenetic calcites, which occurred in the shallow burial stage of the Maokou Formation before the Late Permian. Clear-rimmed dolomite (CRD) and SDD were formed in the late stage of dolomitization. They all have clean crystal planes and darkly red CL. CRD of the ERY profile has trace element contents, 87Sr/86Sr ratios, and rare-earth patterns similar to SDD of the HLCH profile and Well TL6, inferring that both may be formed in the same fluid. Combined with high SrO contents and homogenous temperatures of fluid inclusions of CRD and SDD and Mg-isotopic compositions, they were generated by hydrothermal dolomitization. The hydrothermal fluid stage is related to the movement of the Emeishan Large Igneous Province, which was made up of basaltic magmatic fluids mixing with the surface water. The hydrothermal fluid mainly migrated upwards along structural fractures or faults and filled in structural fractures, occurring in the Late Permian to Middle-Late Triassic.http://dx.doi.org/10.1155/2021/6611140 |
| spellingShingle | Yanxia Jiang Xianfeng Tan Chengjiang Zhang Wei Jiang Jia Wang Long Luo Dongping Tan Wei Wang Zhifu Xiong Genesis of Dolomite in Middle Permian Maokou Formation in Eastern Sichuan: Constraints from In Situ Geochemistry, Sr-Mg Isotopes, and Fluid Inclusions Geofluids |
| title | Genesis of Dolomite in Middle Permian Maokou Formation in Eastern Sichuan: Constraints from In Situ Geochemistry, Sr-Mg Isotopes, and Fluid Inclusions |
| title_full | Genesis of Dolomite in Middle Permian Maokou Formation in Eastern Sichuan: Constraints from In Situ Geochemistry, Sr-Mg Isotopes, and Fluid Inclusions |
| title_fullStr | Genesis of Dolomite in Middle Permian Maokou Formation in Eastern Sichuan: Constraints from In Situ Geochemistry, Sr-Mg Isotopes, and Fluid Inclusions |
| title_full_unstemmed | Genesis of Dolomite in Middle Permian Maokou Formation in Eastern Sichuan: Constraints from In Situ Geochemistry, Sr-Mg Isotopes, and Fluid Inclusions |
| title_short | Genesis of Dolomite in Middle Permian Maokou Formation in Eastern Sichuan: Constraints from In Situ Geochemistry, Sr-Mg Isotopes, and Fluid Inclusions |
| title_sort | genesis of dolomite in middle permian maokou formation in eastern sichuan constraints from in situ geochemistry sr mg isotopes and fluid inclusions |
| url | http://dx.doi.org/10.1155/2021/6611140 |
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