Isotopic characteristics of carbon and oxygen within ordovician carbonate paleokarst in the tazhong region and their paleoenvironmental significance
The Tazhong region is a key area for oil and gas exploration and development within the Tarim basin. In this region, development of Ordovician carbonate paleokarsts has been found to be extremely heterogeneous. To investigate the developmental stages of these Ordovician carbonate karsts and their co...
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Frontiers Media S.A.
2023-01-01
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| Series: | Frontiers in Earth Science |
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| Online Access: | https://www.frontiersin.org/articles/10.3389/feart.2022.1047535/full |
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| author | Qingyu Zhang Qingyu Zhang Bin Liang Bin Liang Shaocong Ji Shaocong Ji Jingrui Li Jingrui Li |
| author_facet | Qingyu Zhang Qingyu Zhang Bin Liang Bin Liang Shaocong Ji Shaocong Ji Jingrui Li Jingrui Li |
| author_sort | Qingyu Zhang |
| collection | DOAJ |
| description | The Tazhong region is a key area for oil and gas exploration and development within the Tarim basin. In this region, development of Ordovician carbonate paleokarsts has been found to be extremely heterogeneous. To investigate the developmental stages of these Ordovician carbonate karsts and their corresponding paleoenvironmental conditions, oxygen and carbon isotopic characteristics of calcite paleokarst fissure fillings were examined in conjunction with rock-structure analyses. Results show that δ18O (PDB) values tend towards negative values in general, ranging from −3.97% to −12.7% (average value −7.64%), which is indicative of the presence of paleokarstification via dissolution by atmospheric freshwater. Values of δ13C (PDB) span a relatively large range, from 2.48% to −2.13% (average value of 0.23%). This shows that the paleokarst in this area has gone through two stages of supergene and burial diagenesis, and the process of paleokarst is complex. The paleotemperature at which the karst fissure-filling deposits were formed ranged from 6.5 to 47.1°C (average value of 21.8°C), and the salinity of the medium has Z values from 117.48 to 130.24 (average value of 123.94). Four different paleokarsification settings were thus revealed: a marine depositional environment, an atmospheric freshwater karst-filling environment, a shallow-burial paleokarsification environment and a deep-burial high-temperature environment. It has thus been shown that the karst pores, fissures and caves formed by paleokarstification over multiple stages are the main reservoir spaces in this region. This study will serves as a basis for karst reservoir predictions, and exploration and development in this region. |
| first_indexed | 2024-04-11T00:35:25Z |
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| language | English |
| last_indexed | 2024-04-11T00:35:25Z |
| publishDate | 2023-01-01 |
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| series | Frontiers in Earth Science |
| spelling | doaj.art-f24535d6b54441adba8ba905ce6d6d142023-01-06T20:37:09ZengFrontiers Media S.A.Frontiers in Earth Science2296-64632023-01-011010.3389/feart.2022.10475351047535Isotopic characteristics of carbon and oxygen within ordovician carbonate paleokarst in the tazhong region and their paleoenvironmental significanceQingyu Zhang0Qingyu Zhang1Bin Liang2Bin Liang3Shaocong Ji4Shaocong Ji5Jingrui Li6Jingrui Li7Institute of Karst Geology, Chinese Academy of Geological Sciences Karst Dynamics Laboratory, Ministry of Natural Resources, Guilin, ChinaInternational Research Center on Karst Under the Auspices of UNESCO, National Center for International Research on Karst Dynamic System and Global Change, Guilin, ChinaInstitute of Karst Geology, Chinese Academy of Geological Sciences Karst Dynamics Laboratory, Ministry of Natural Resources, Guilin, ChinaInternational Research Center on Karst Under the Auspices of UNESCO, National Center for International Research on Karst Dynamic System and Global Change, Guilin, ChinaInstitute of Karst Geology, Chinese Academy of Geological Sciences Karst Dynamics Laboratory, Ministry of Natural Resources, Guilin, ChinaInternational Research Center on Karst Under the Auspices of UNESCO, National Center for International Research on Karst Dynamic System and Global Change, Guilin, ChinaInstitute of Karst Geology, Chinese Academy of Geological Sciences Karst Dynamics Laboratory, Ministry of Natural Resources, Guilin, ChinaInternational Research Center on Karst Under the Auspices of UNESCO, National Center for International Research on Karst Dynamic System and Global Change, Guilin, ChinaThe Tazhong region is a key area for oil and gas exploration and development within the Tarim basin. In this region, development of Ordovician carbonate paleokarsts has been found to be extremely heterogeneous. To investigate the developmental stages of these Ordovician carbonate karsts and their corresponding paleoenvironmental conditions, oxygen and carbon isotopic characteristics of calcite paleokarst fissure fillings were examined in conjunction with rock-structure analyses. Results show that δ18O (PDB) values tend towards negative values in general, ranging from −3.97% to −12.7% (average value −7.64%), which is indicative of the presence of paleokarstification via dissolution by atmospheric freshwater. Values of δ13C (PDB) span a relatively large range, from 2.48% to −2.13% (average value of 0.23%). This shows that the paleokarst in this area has gone through two stages of supergene and burial diagenesis, and the process of paleokarst is complex. The paleotemperature at which the karst fissure-filling deposits were formed ranged from 6.5 to 47.1°C (average value of 21.8°C), and the salinity of the medium has Z values from 117.48 to 130.24 (average value of 123.94). Four different paleokarsification settings were thus revealed: a marine depositional environment, an atmospheric freshwater karst-filling environment, a shallow-burial paleokarsification environment and a deep-burial high-temperature environment. It has thus been shown that the karst pores, fissures and caves formed by paleokarstification over multiple stages are the main reservoir spaces in this region. This study will serves as a basis for karst reservoir predictions, and exploration and development in this region.https://www.frontiersin.org/articles/10.3389/feart.2022.1047535/fullcarbon-oxygen isotopespaleokarstspaleoenvironmentscarbonatesordoviciantarim basin |
| spellingShingle | Qingyu Zhang Qingyu Zhang Bin Liang Bin Liang Shaocong Ji Shaocong Ji Jingrui Li Jingrui Li Isotopic characteristics of carbon and oxygen within ordovician carbonate paleokarst in the tazhong region and their paleoenvironmental significance Frontiers in Earth Science carbon-oxygen isotopes paleokarsts paleoenvironments carbonates ordovician tarim basin |
| title | Isotopic characteristics of carbon and oxygen within ordovician carbonate paleokarst in the tazhong region and their paleoenvironmental significance |
| title_full | Isotopic characteristics of carbon and oxygen within ordovician carbonate paleokarst in the tazhong region and their paleoenvironmental significance |
| title_fullStr | Isotopic characteristics of carbon and oxygen within ordovician carbonate paleokarst in the tazhong region and their paleoenvironmental significance |
| title_full_unstemmed | Isotopic characteristics of carbon and oxygen within ordovician carbonate paleokarst in the tazhong region and their paleoenvironmental significance |
| title_short | Isotopic characteristics of carbon and oxygen within ordovician carbonate paleokarst in the tazhong region and their paleoenvironmental significance |
| title_sort | isotopic characteristics of carbon and oxygen within ordovician carbonate paleokarst in the tazhong region and their paleoenvironmental significance |
| topic | carbon-oxygen isotopes paleokarsts paleoenvironments carbonates ordovician tarim basin |
| url | https://www.frontiersin.org/articles/10.3389/feart.2022.1047535/full |
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