The Experts below are selected from a list of 30 Experts worldwide ranked by ideXlab platform
Lixin Chen - One of the best experts on this subject based on the ideXlab platform.
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distinguishing cambrian from upper ordovician source rocks evidence from sulfur isotopes and biomarkers in the tarim basin
Organic Geochemistry, 2009Co-Authors: Chunfang Cai, Ma Anlai, Chunming Zhang, Richard H Worden, Baoshou Zhang, Lixin ChenAbstract:Abstract The reported source rocks for the abundant petroleum in the Tarim Basin, China range from Cambrian to Lower Ordovician and/or Upper Ordovician in age. However, the difference between the two groups of source rocks is not well characterized. In this study, pyrite was removed from eleven mature to over mature kerogen samples from source rocks using the method of CrCl 2 reduction and grinding. The kerogen and coexisting pyrite samples were then analyzed for δ 34 S values. Results show that the kerogen samples from the Cambrian have δ 34 S values between +10.4‰ and +19.4‰. The values are significantly higher than those from the Lower Ordovician kerogen ( δ 34 S of between +6.7‰ and +8.7‰), which in turn are generally higher than from the Upper Ordovician kerogen samples ( δ 34 S of between −15.3 and +6.8‰). The associated pyrite shows a similar trend but with much lower δ 34 S values. This stratigraphically controlled sulfur isotope variation parallels the evolving contemporary marine sulfate and dated oil δ 34 S values from other basins, suggesting that seawater sulfate and source rock age have an important influence on kerogen and pyrite δ 34 S values. The relatively high δ 34 S values in the Cambrian to Lower Ordovician source rocks are associated with abundant aryl isoprenoids, gammacerane and C 35 homohopanes in the extractable organic matter, indicating that these source rocks were deposited in a bottom water Euxinic Environment with water stratification. Compared with the Upper Ordovician, the Cambrian to Lower Ordovician source rocks show abundance in C 28 20R sterane, C 23 tricyclic terpanes, 4,23,24-trimethyl triaromatic dinosteroids and depletion in C 24 tetracyclic terpane, C 29 hopane. Thus, δ 34 S values and biomarkers of source rock organic matter can be used for distinguishing the Cambrian and Upper Ordovician source rocks in the Tarim Basin.
Chunfang Cai - One of the best experts on this subject based on the ideXlab platform.
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distinguishing cambrian from upper ordovician source rocks evidence from sulfur isotopes and biomarkers in the tarim basin
Organic Geochemistry, 2009Co-Authors: Chunfang Cai, Ma Anlai, Chunming Zhang, Richard H Worden, Baoshou Zhang, Lixin ChenAbstract:Abstract The reported source rocks for the abundant petroleum in the Tarim Basin, China range from Cambrian to Lower Ordovician and/or Upper Ordovician in age. However, the difference between the two groups of source rocks is not well characterized. In this study, pyrite was removed from eleven mature to over mature kerogen samples from source rocks using the method of CrCl 2 reduction and grinding. The kerogen and coexisting pyrite samples were then analyzed for δ 34 S values. Results show that the kerogen samples from the Cambrian have δ 34 S values between +10.4‰ and +19.4‰. The values are significantly higher than those from the Lower Ordovician kerogen ( δ 34 S of between +6.7‰ and +8.7‰), which in turn are generally higher than from the Upper Ordovician kerogen samples ( δ 34 S of between −15.3 and +6.8‰). The associated pyrite shows a similar trend but with much lower δ 34 S values. This stratigraphically controlled sulfur isotope variation parallels the evolving contemporary marine sulfate and dated oil δ 34 S values from other basins, suggesting that seawater sulfate and source rock age have an important influence on kerogen and pyrite δ 34 S values. The relatively high δ 34 S values in the Cambrian to Lower Ordovician source rocks are associated with abundant aryl isoprenoids, gammacerane and C 35 homohopanes in the extractable organic matter, indicating that these source rocks were deposited in a bottom water Euxinic Environment with water stratification. Compared with the Upper Ordovician, the Cambrian to Lower Ordovician source rocks show abundance in C 28 20R sterane, C 23 tricyclic terpanes, 4,23,24-trimethyl triaromatic dinosteroids and depletion in C 24 tetracyclic terpane, C 29 hopane. Thus, δ 34 S values and biomarkers of source rock organic matter can be used for distinguishing the Cambrian and Upper Ordovician source rocks in the Tarim Basin.
Shaoyong Jiang - One of the best experts on this subject based on the ideXlab platform.
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depositional Environments for stratiform witherite deposits in the lower cambrian black shale sequence of the yangtze platform southern qinling region sw china evidence from redox sensitive trace element geochemistry
Palaeogeography Palaeoclimatology Palaeoecology, 2014Co-Authors: Shaoyong Jiang, Li Luo, Jinghong Yang, Hongfei LingAbstract:Abstract A very large stratiform witherite mineralization occurs in Lower Cambrian black shales and siliceous rocks in the southern Qinling region of SW China. Two types of witherite ores are divided according to their colors, i.e., the white ores and the dark-gray ores. We analyzed a number of redox-sensitive trace elements in both the white and dark-gray ores from various witherite deposits. The redox-sensitive metal concentrations and the distribution of the two types of ores provide good evidence for their depositional redox conditions in the Early Cambrian ocean in the southern Qinling region. Our geochemical data suggest that both the dark-gray and white witherite ores may have been deposited in reducing Environments, with the dark-gray ores deposited in an anoxic–Euxinic Environment, whereas the white ores deposited under a suboxic–anoxic condition.
Hongfei Ling - One of the best experts on this subject based on the ideXlab platform.
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depositional Environments for stratiform witherite deposits in the lower cambrian black shale sequence of the yangtze platform southern qinling region sw china evidence from redox sensitive trace element geochemistry
Palaeogeography Palaeoclimatology Palaeoecology, 2014Co-Authors: Shaoyong Jiang, Li Luo, Jinghong Yang, Hongfei LingAbstract:Abstract A very large stratiform witherite mineralization occurs in Lower Cambrian black shales and siliceous rocks in the southern Qinling region of SW China. Two types of witherite ores are divided according to their colors, i.e., the white ores and the dark-gray ores. We analyzed a number of redox-sensitive trace elements in both the white and dark-gray ores from various witherite deposits. The redox-sensitive metal concentrations and the distribution of the two types of ores provide good evidence for their depositional redox conditions in the Early Cambrian ocean in the southern Qinling region. Our geochemical data suggest that both the dark-gray and white witherite ores may have been deposited in reducing Environments, with the dark-gray ores deposited in an anoxic–Euxinic Environment, whereas the white ores deposited under a suboxic–anoxic condition.
Baoshou Zhang - One of the best experts on this subject based on the ideXlab platform.
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distinguishing cambrian from upper ordovician source rocks evidence from sulfur isotopes and biomarkers in the tarim basin
Organic Geochemistry, 2009Co-Authors: Chunfang Cai, Ma Anlai, Chunming Zhang, Richard H Worden, Baoshou Zhang, Lixin ChenAbstract:Abstract The reported source rocks for the abundant petroleum in the Tarim Basin, China range from Cambrian to Lower Ordovician and/or Upper Ordovician in age. However, the difference between the two groups of source rocks is not well characterized. In this study, pyrite was removed from eleven mature to over mature kerogen samples from source rocks using the method of CrCl 2 reduction and grinding. The kerogen and coexisting pyrite samples were then analyzed for δ 34 S values. Results show that the kerogen samples from the Cambrian have δ 34 S values between +10.4‰ and +19.4‰. The values are significantly higher than those from the Lower Ordovician kerogen ( δ 34 S of between +6.7‰ and +8.7‰), which in turn are generally higher than from the Upper Ordovician kerogen samples ( δ 34 S of between −15.3 and +6.8‰). The associated pyrite shows a similar trend but with much lower δ 34 S values. This stratigraphically controlled sulfur isotope variation parallels the evolving contemporary marine sulfate and dated oil δ 34 S values from other basins, suggesting that seawater sulfate and source rock age have an important influence on kerogen and pyrite δ 34 S values. The relatively high δ 34 S values in the Cambrian to Lower Ordovician source rocks are associated with abundant aryl isoprenoids, gammacerane and C 35 homohopanes in the extractable organic matter, indicating that these source rocks were deposited in a bottom water Euxinic Environment with water stratification. Compared with the Upper Ordovician, the Cambrian to Lower Ordovician source rocks show abundance in C 28 20R sterane, C 23 tricyclic terpanes, 4,23,24-trimethyl triaromatic dinosteroids and depletion in C 24 tetracyclic terpane, C 29 hopane. Thus, δ 34 S values and biomarkers of source rock organic matter can be used for distinguishing the Cambrian and Upper Ordovician source rocks in the Tarim Basin.
