S and Sr Isotope Compositions and Trace Element Compositions of the Middle Jurassic Evaporites in Eastern Tibet: Provenance and Palaeogeographic Implications
The origin of Middle Jurassic evaporites in the Qamdo Basin is still controversial because palaeontological studies have reported that they have both marine and continental characteristics. The <sup>87</sup>Sr/<sup>86</sup>Sr ratios of the gypsum in the Middle Jurassic Dongda...
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MDPI AG
2022-08-01
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| author | Jinna Fei Lijian Shen Xin Guan Zhicheng Sun |
| author_facet | Jinna Fei Lijian Shen Xin Guan Zhicheng Sun |
| author_sort | Jinna Fei |
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| description | The origin of Middle Jurassic evaporites in the Qamdo Basin is still controversial because palaeontological studies have reported that they have both marine and continental characteristics. The <sup>87</sup>Sr/<sup>86</sup>Sr ratios of the gypsum in the Middle Jurassic Dongdaqiao Formation in the Qamdo Basin range from 0.707602 to 0.708163, which are higher than that of contemporaneous seawater. Model calculations suggest that continental water prevailed over seawater during the precipitation of these evaporites. However, the majority of the gypsum samples have δ<sup>34</sup>S values of 15.3‰ to 16.3‰, which are consistent with that of contemporaneous seawater. This range of values (15.3‰ vs. 16.3‰) was likely caused by S isotope fractionation during evaporation because the δ<sup>34</sup>S values and Sr contents are negatively correlated. The δ<sup>34</sup>S values of the other three gypsum samples are 20.0‰, 20.5‰, and 20.8‰, which are significantly higher than that of Middle Jurassic seawater. The trace element compositions and scanning electron microscopy (SEM) observations indicate that these elevated δ<sup>34</sup>S values were caused by bacterial sulphate reduction (BSR). The Sr and S isotope systematics of the gypsums from the Dongdaqiao Formation demonstrate that the parent brines from which the evaporites precipitated were marine based with a large quantity of continental input. A comparison of the lithologies and Sr isotope compositions of the Middle Jurassic sequences in the Qamdo and Qiangtang Basins revealed that the Qiangtang Basin was mainly recharged by Jurassic seawater, while the Qamdo Basin was primarily recharged by continental water with some seawater-derived overflow from the Qiangtang Basin. |
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| spelling | doaj.art-2e9c7c12a21b414785fe6657cd61aa1c2023-12-02T00:03:34ZengMDPI AGMinerals2075-163X2022-08-01128103910.3390/min12081039S and Sr Isotope Compositions and Trace Element Compositions of the Middle Jurassic Evaporites in Eastern Tibet: Provenance and Palaeogeographic ImplicationsJinna Fei0Lijian Shen1Xin Guan2Zhicheng Sun3School of Earth Sciences and Resources, The China University of Geosciences, Beijing 100083, ChinaMNR Key Laboratory of Metallogeny and Mineral Assessment, Institute of Mineral Resources, Chinese Academy of Geological Sciences, Beijing 100037, ChinaChina Energy Investment Corporation, Beijing 100011, ChinaSchool of Water Resources and Environment, The China University of Geosciences, Beijing 100083, ChinaThe origin of Middle Jurassic evaporites in the Qamdo Basin is still controversial because palaeontological studies have reported that they have both marine and continental characteristics. The <sup>87</sup>Sr/<sup>86</sup>Sr ratios of the gypsum in the Middle Jurassic Dongdaqiao Formation in the Qamdo Basin range from 0.707602 to 0.708163, which are higher than that of contemporaneous seawater. Model calculations suggest that continental water prevailed over seawater during the precipitation of these evaporites. However, the majority of the gypsum samples have δ<sup>34</sup>S values of 15.3‰ to 16.3‰, which are consistent with that of contemporaneous seawater. This range of values (15.3‰ vs. 16.3‰) was likely caused by S isotope fractionation during evaporation because the δ<sup>34</sup>S values and Sr contents are negatively correlated. The δ<sup>34</sup>S values of the other three gypsum samples are 20.0‰, 20.5‰, and 20.8‰, which are significantly higher than that of Middle Jurassic seawater. The trace element compositions and scanning electron microscopy (SEM) observations indicate that these elevated δ<sup>34</sup>S values were caused by bacterial sulphate reduction (BSR). The Sr and S isotope systematics of the gypsums from the Dongdaqiao Formation demonstrate that the parent brines from which the evaporites precipitated were marine based with a large quantity of continental input. A comparison of the lithologies and Sr isotope compositions of the Middle Jurassic sequences in the Qamdo and Qiangtang Basins revealed that the Qiangtang Basin was mainly recharged by Jurassic seawater, while the Qamdo Basin was primarily recharged by continental water with some seawater-derived overflow from the Qiangtang Basin.https://www.mdpi.com/2075-163X/12/8/1039the Qamdo BasingypsumsS and Sr isotopestrace elementsprovenance and palaeogeography |
| spellingShingle | Jinna Fei Lijian Shen Xin Guan Zhicheng Sun S and Sr Isotope Compositions and Trace Element Compositions of the Middle Jurassic Evaporites in Eastern Tibet: Provenance and Palaeogeographic Implications Minerals the Qamdo Basin gypsums S and Sr isotopes trace elements provenance and palaeogeography |
| title | S and Sr Isotope Compositions and Trace Element Compositions of the Middle Jurassic Evaporites in Eastern Tibet: Provenance and Palaeogeographic Implications |
| title_full | S and Sr Isotope Compositions and Trace Element Compositions of the Middle Jurassic Evaporites in Eastern Tibet: Provenance and Palaeogeographic Implications |
| title_fullStr | S and Sr Isotope Compositions and Trace Element Compositions of the Middle Jurassic Evaporites in Eastern Tibet: Provenance and Palaeogeographic Implications |
| title_full_unstemmed | S and Sr Isotope Compositions and Trace Element Compositions of the Middle Jurassic Evaporites in Eastern Tibet: Provenance and Palaeogeographic Implications |
| title_short | S and Sr Isotope Compositions and Trace Element Compositions of the Middle Jurassic Evaporites in Eastern Tibet: Provenance and Palaeogeographic Implications |
| title_sort | s and sr isotope compositions and trace element compositions of the middle jurassic evaporites in eastern tibet provenance and palaeogeographic implications |
| topic | the Qamdo Basin gypsums S and Sr isotopes trace elements provenance and palaeogeography |
| url | https://www.mdpi.com/2075-163X/12/8/1039 |
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