Geochemical characteristics and sedimentary environment of the Middle Devonian organic-rich shales in the Northwest of Guizhong Depression, Southwest China
ABSTRACT: In order to figure out the redox conditions and paleo-sedimentary environment of the Middle Devonian shales in the northwest of Guizhong Depression, the trace element analysis was conducted on the Middle Devonian cores (320.35–938.50 m) of the typical shale gas investigation well (GY-1) at...
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| Format: | Article |
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KeAi Communications Co., Ltd.
2020-12-01
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| Series: | China Geology |
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| Online Access: | http://www.sciencedirect.com/science/article/pii/S2096519220302019 |
| _version_ | 1811170507804901376 |
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| author | Kun Yuan Wen-hui Huang Xin-xin Fang Shi-zhen Li Ting Wang Tuo Lin Guo-heng Liu |
| author_facet | Kun Yuan Wen-hui Huang Xin-xin Fang Shi-zhen Li Ting Wang Tuo Lin Guo-heng Liu |
| author_sort | Kun Yuan |
| collection | DOAJ |
| description | ABSTRACT: In order to figure out the redox conditions and paleo-sedimentary environment of the Middle Devonian shales in the northwest of Guizhong Depression, the trace element analysis was conducted on the Middle Devonian cores (320.35–938.50 m) of the typical shale gas investigation well (GY-1) at a 1.50 m sampling interval through X-ray fluorescence spectroscopy (XRF) and inductively coupled plasma mass spectrometry (ICP-MS). According to the test result, the average values of V/(V+Ni), V/Cr and Ni/Co in Nabiao formation (Fm.) are larger than 0.67, 4.65 and 7.71 respectively, and Nabiao Fm. is rich in biological assemblages such as tabasheer, ammonite, etc. These evidences indicate the rising sea level rose relatively in the sedimentation period of Nabiao Fm. and a deepwater shelf environment, which was favorable for the preservation of organic matters. The V/(V+Ni), V/Cr and Ni/Co in Luofu Fm. and Tangting Fm. are 0.38–0.65, 0.73–4.10 and 3.70–6.72 respectively, indicating that the sea level dropped relatively in their sedimentation period, during which the water bodies became shallow, and the sedimentary environment was a weak oxidizing shallow water shelf environment. In addition, the variation of TOC has a high correlation with the enrichment degree of Ba element, indicating the favorable conditions for the enrichment and preservation of organic matters under an oxygen-deficient environment. Moreover, according to the identification of trace element indexes, the northwest of Guizhong Depression experienced the sedimentary cycle of relative rise to relative fall of sea level from bottom to top in the Middle Devonian sedimentation period. The relative sea level rose to the highest in the sedimentation period of Nabiao Fm., in which the organic-rich shales with stable thickness and high organic content were deposited. Hence, the Nabiao Fm. could be regarded as the favorable exploration target interval in this area. |
| first_indexed | 2024-04-10T16:57:43Z |
| format | Article |
| id | doaj.art-b278cc4390cd4cd38bc2c6de57761262 |
| institution | Directory Open Access Journal |
| issn | 2096-5192 |
| language | English |
| last_indexed | 2024-04-10T16:57:43Z |
| publishDate | 2020-12-01 |
| publisher | KeAi Communications Co., Ltd. |
| record_format | Article |
| series | China Geology |
| spelling | doaj.art-b278cc4390cd4cd38bc2c6de577612622023-02-07T04:22:23ZengKeAi Communications Co., Ltd.China Geology2096-51922020-12-0134567574Geochemical characteristics and sedimentary environment of the Middle Devonian organic-rich shales in the Northwest of Guizhong Depression, Southwest ChinaKun Yuan0Wen-hui Huang1Xin-xin Fang2Shi-zhen Li3Ting Wang4Tuo Lin5Guo-heng Liu6China University of Geosciences (Beijing), Beijing 100083, China; Oil and Gas Resources Survey, China Geological Survey, Ministry of Natural Resources Beijing 100083, ChinaChina University of Geosciences (Beijing), Beijing 100083, ChinaInstitute of Geomechanics, Chinese Academy of Geological Sciences, Beijing 100081, China; First author: E-mail address: 271855193@qq.com (Kun Yuan). Corresponding author: E-mail address: freestarxin@163.com (Xin-xin Fang).Oil and Gas Resources Survey, China Geological Survey, Ministry of Natural Resources Beijing 100083, ChinaChina University of Geosciences (Beijing), Beijing 100083, China; Oil and Gas Resources Survey, China Geological Survey, Ministry of Natural Resources Beijing 100083, ChinaOil and Gas Resources Survey, China Geological Survey, Ministry of Natural Resources Beijing 100083, ChinaOil and Gas Resources Survey, China Geological Survey, Ministry of Natural Resources Beijing 100083, ChinaABSTRACT: In order to figure out the redox conditions and paleo-sedimentary environment of the Middle Devonian shales in the northwest of Guizhong Depression, the trace element analysis was conducted on the Middle Devonian cores (320.35–938.50 m) of the typical shale gas investigation well (GY-1) at a 1.50 m sampling interval through X-ray fluorescence spectroscopy (XRF) and inductively coupled plasma mass spectrometry (ICP-MS). According to the test result, the average values of V/(V+Ni), V/Cr and Ni/Co in Nabiao formation (Fm.) are larger than 0.67, 4.65 and 7.71 respectively, and Nabiao Fm. is rich in biological assemblages such as tabasheer, ammonite, etc. These evidences indicate the rising sea level rose relatively in the sedimentation period of Nabiao Fm. and a deepwater shelf environment, which was favorable for the preservation of organic matters. The V/(V+Ni), V/Cr and Ni/Co in Luofu Fm. and Tangting Fm. are 0.38–0.65, 0.73–4.10 and 3.70–6.72 respectively, indicating that the sea level dropped relatively in their sedimentation period, during which the water bodies became shallow, and the sedimentary environment was a weak oxidizing shallow water shelf environment. In addition, the variation of TOC has a high correlation with the enrichment degree of Ba element, indicating the favorable conditions for the enrichment and preservation of organic matters under an oxygen-deficient environment. Moreover, according to the identification of trace element indexes, the northwest of Guizhong Depression experienced the sedimentary cycle of relative rise to relative fall of sea level from bottom to top in the Middle Devonian sedimentation period. The relative sea level rose to the highest in the sedimentation period of Nabiao Fm., in which the organic-rich shales with stable thickness and high organic content were deposited. Hence, the Nabiao Fm. could be regarded as the favorable exploration target interval in this area.http://www.sciencedirect.com/science/article/pii/S2096519220302019Organic-rich shaleDevonianGeochemistrySedimentary environmentGuizhong DepressionGeological survey engineering |
| spellingShingle | Kun Yuan Wen-hui Huang Xin-xin Fang Shi-zhen Li Ting Wang Tuo Lin Guo-heng Liu Geochemical characteristics and sedimentary environment of the Middle Devonian organic-rich shales in the Northwest of Guizhong Depression, Southwest China China Geology Organic-rich shale Devonian Geochemistry Sedimentary environment Guizhong Depression Geological survey engineering |
| title | Geochemical characteristics and sedimentary environment of the Middle Devonian organic-rich shales in the Northwest of Guizhong Depression, Southwest China |
| title_full | Geochemical characteristics and sedimentary environment of the Middle Devonian organic-rich shales in the Northwest of Guizhong Depression, Southwest China |
| title_fullStr | Geochemical characteristics and sedimentary environment of the Middle Devonian organic-rich shales in the Northwest of Guizhong Depression, Southwest China |
| title_full_unstemmed | Geochemical characteristics and sedimentary environment of the Middle Devonian organic-rich shales in the Northwest of Guizhong Depression, Southwest China |
| title_short | Geochemical characteristics and sedimentary environment of the Middle Devonian organic-rich shales in the Northwest of Guizhong Depression, Southwest China |
| title_sort | geochemical characteristics and sedimentary environment of the middle devonian organic rich shales in the northwest of guizhong depression southwest china |
| topic | Organic-rich shale Devonian Geochemistry Sedimentary environment Guizhong Depression Geological survey engineering |
| url | http://www.sciencedirect.com/science/article/pii/S2096519220302019 |
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