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Anjiang Shen - One of the best experts on this subject based on the ideXlab platform.
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la icp ms u pb geochronology and clumped isotope constraints on the formation and evolution of an ancient Dolomite reservoir the middle permian of northwest sichuan basin sw china
Sedimentary Geology, 2020Co-Authors: Anjiang Shen, Jianxin Zhao, Anping Hu, Feng Liang, Yuexing Feng, Xiaofang WangAbstract:Abstract Recent advances in laser-ablation inductively coupled-plasma mass spectrometry (LA-ICP-MS) in-situ U-Pb radiometric dating and clumped isotope thermometry (Δ47) of carbonate minerals provide potential for refining the fluid flow and diagenetic history of carbonate successions. In this study, the Middle Permian Dolomites proximal to the Longmenshan fold and thrust belt in northwest Sichuan Basin, southwest China, were investigated using combined U-Pb geochronology, clumped isotope thermometry, and routine isotopic (δ13C, δ18O and 87Sr/86Sr) and elemental geochemistry, in an attempt to reveal the possible relevance of carbonate diagenesis and porosity evolution to the basin-scale tectonic/fluid flow events in the framework of absolute time. Overall, formation and evolution of these Dolomites temporally correlated well with major tectonic episodes of the Longmenshan fold and thrust belt. Contrary to the previously-assumed volcanic-related model, U-Pb dating and Δ47 analyses suggest a mid- to late-Triassic replacive dolomitization event (U-Pb ages of 240 ± 12 Ma to 233.8 ± 6.4 Ma) by a hot (Δ47 temperatures 88– 104 °C) basinal brine, which was likely driven by thrust-related compression of the Longmenshan fold and thrust belt during the Triassic. Replacive dolomitization was immediately followed by cementation of euhedral Dolomites (U-Pb age of 228 ± 10 Ma) and blocky calcites (U-Pb ages of 224.8 ± 1.8 Ma to 213.4 ± 3.3 Ma) precipitated from the basinal brine in the same tectonic regime. Afterwards, there was long-term cessation of diagenesis that was coincident with, and thus may well be attributed to, tectono-thermal quiescence during most of the Mesozoic Era and Paleogene. Finally, saddle Dolomite cements yield Miocene ages (U-Pb ages of 16.40 ± 0.74 Ma to 12.3 ± 1.2 Ma) and precipitated in pre-existing vugs, representing a hydrothermal fluid flow event (Δ47 temperatures up to 170 °C) during the reactivation of thrusting. In addition, similarities in U-Pb ages and geochemical signatures between host rocks (replacive Dolomites) and the vug-lining Dolomite cements suggest that most porosity in these Dolomite reservoirs was inherited from the precursor limestones, which probably experienced meteoric leaching during late Permian uplift. This study highlights that there are geodynamic controls on fluid flow and consequent diagenetic evolution of carbonates in tectonically active sedimentary basins. It illustrates that burial alone in this setting is not a sufficient driver for diagenetic alteration and porosity reduction. The combination of U-Pb radiometric dating, clumped isotope thermometry and routine geochemical analyses is a useful approach in refining the diagenetic and porosity evolution history of ancient carbonate successions.
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la icp ms upb geochronology and clumped isotope constraints on the formation and evolution of an ancient Dolomite reservoir the middle permian of northwest sichuan basin sw china
Sedimentary Geology, 2020Co-Authors: Anjiang Shen, Jianxin Zhao, Anping Hu, Feng Liang, Yuexing Feng, Xiaofang WangAbstract:Abstract Recent advances in laser-ablation inductively coupled-plasma mass spectrometry (LA-ICP-MS) in-situ U Pb radiometric dating and clumped isotope thermometry (Δ47) of carbonate minerals provide potential for refining the fluid flow and diagenetic history of carbonate successions. In this study, the Middle Permian Dolomites proximal to the Longmenshan fold and thrust belt in northwest Sichuan Basin, southwest China, were investigated using combined U Pb geochronology, clumped isotope thermometry, and routine isotopic (δ13C, δ18O and 87Sr/86Sr) and elemental geochemistry, in an attempt to reveal the possible relevance of carbonate diagenesis and porosity evolution to the basin-scale tectonic/fluid flow events in the framework of absolute time. Overall, formation and evolution of these Dolomites temporally correlated well with major tectonic episodes of the Longmenshan fold and thrust belt. Contrary to the previously-assumed volcanic-related model, U Pb dating and Δ47 analyses suggest a mid- to late-Triassic replacive dolomitization event (U Pb ages of 240 ± 12 Ma to 233.8 ± 6.4 Ma) by a hot (Δ47 temperatures 88–104 °C) basinal brine, which was likely driven by thrust-related compression of the Longmenshan fold and thrust belt during the Triassic. Replacive dolomitization was immediately followed by cementation of euhedral Dolomites (U Pb age of 228 ± 10 Ma) and blocky calcites (U Pb ages of 224.8 ± 1.8 Ma to 213.4 ± 3.3 Ma) precipitated from the basinal brine in the same tectonic regime. Afterwards, there was long-term cessation of diagenesis that was coincident with, and thus may well be attributed to, tectono-thermal quiescence during most of the Mesozoic Era and Paleogene. Finally, saddle Dolomite cements yield Miocene ages (U Pb ages of 16.40 ± 0.74 Ma to 12.3 ± 1.2 Ma) and precipitated in pre-existing vugs, representing a hydrothermal fluid flow event (Δ47 temperatures up to 170 °C) during the reactivation of thrusting. In addition, similarities in U Pb ages and geochemical signatures between host rocks (replacive Dolomites) and the vug-lining Dolomite cements suggest that most porosity in these Dolomite reservoirs was inherited from the precursor limestones, which probably experienced meteoric leaching during late Permian uplift. This study highlights that there are geodynamic controls on fluid flow and consequent diagenetic evolution of carbonates in tectonically active sedimentary basins. It illustrates that burial alone in this setting is not a sufficient driver for diagenetic alteration and porosity reduction. The combination of U Pb radiometric dating, clumped isotope thermometry and routine geochemical analyses is a useful approach in refining the diagenetic and porosity evolution history of ancient carbonate successions.
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geochemical characteristics and origin of Dolomite a case study from the middle assemblage of ordovician majiagou formation member 5 of the west of jingbian gas field ordos basin north china
Petroleum Exploration and Development, 2014Co-Authors: H E Xunyun, Jianfeng Shou, Anjiang Shen, W U Xingning, Yongsheng Wang, H U YuanyuanAbstract:Abstract The trace elements, rare earth elements (REE), carbon and oxygen isotopic compositions and strontium isotopes were analyzed to study systematically the geochemical characteristics and origin of the middle assemblage Dolomites from the Ordovician Majiagou Formation Member 5 in the Jingxi area (the west of Jingbian Gas Field), Ordos Basin. The analytical results of samples demonstrate that the MgO and CaO contents of the middle assemblage Dolomite are negatively correlated, and the Mg/Ca values are high; the Dolomites are characterized by high Fe content, relatively high Mn content and low Sr and Na content, while part Dolomites have low Fe and Mn content but high Na content; the Dolomites have very low REE content and similar REE distribution patterns, which are generally characterized by enrichment of light REE, losses of heavy REE, obviously negative anomaly of Eu and weak negative anomaly of Ce; The δ 13 C values of Dolomites are consistent with those of the coeval seawater, while most of the δ 18 O values of Dolomites are more negative than those of the coeval seawater; most of the 87 Sr/ 86 Sr values of Dolomites are significantly higher than those of the coeval seawater while only a few are close to those of the coeval seawater. Combined with the geological setting and geochemical characteristics of the middle assemblage Dolomites, the middle assemblage Dolomites of the Majiagou Member 5 are probably the origin of seepage reflux dolomitization, and were superimposed by burial dolomitization during the burial period. The eastern part of the Jingxi area is favorable reservoir development area, the favorable area can extend eastward.
Xiaofang Wang - One of the best experts on this subject based on the ideXlab platform.
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la icp ms u pb geochronology and clumped isotope constraints on the formation and evolution of an ancient Dolomite reservoir the middle permian of northwest sichuan basin sw china
Sedimentary Geology, 2020Co-Authors: Anjiang Shen, Jianxin Zhao, Anping Hu, Feng Liang, Yuexing Feng, Xiaofang WangAbstract:Abstract Recent advances in laser-ablation inductively coupled-plasma mass spectrometry (LA-ICP-MS) in-situ U-Pb radiometric dating and clumped isotope thermometry (Δ47) of carbonate minerals provide potential for refining the fluid flow and diagenetic history of carbonate successions. In this study, the Middle Permian Dolomites proximal to the Longmenshan fold and thrust belt in northwest Sichuan Basin, southwest China, were investigated using combined U-Pb geochronology, clumped isotope thermometry, and routine isotopic (δ13C, δ18O and 87Sr/86Sr) and elemental geochemistry, in an attempt to reveal the possible relevance of carbonate diagenesis and porosity evolution to the basin-scale tectonic/fluid flow events in the framework of absolute time. Overall, formation and evolution of these Dolomites temporally correlated well with major tectonic episodes of the Longmenshan fold and thrust belt. Contrary to the previously-assumed volcanic-related model, U-Pb dating and Δ47 analyses suggest a mid- to late-Triassic replacive dolomitization event (U-Pb ages of 240 ± 12 Ma to 233.8 ± 6.4 Ma) by a hot (Δ47 temperatures 88– 104 °C) basinal brine, which was likely driven by thrust-related compression of the Longmenshan fold and thrust belt during the Triassic. Replacive dolomitization was immediately followed by cementation of euhedral Dolomites (U-Pb age of 228 ± 10 Ma) and blocky calcites (U-Pb ages of 224.8 ± 1.8 Ma to 213.4 ± 3.3 Ma) precipitated from the basinal brine in the same tectonic regime. Afterwards, there was long-term cessation of diagenesis that was coincident with, and thus may well be attributed to, tectono-thermal quiescence during most of the Mesozoic Era and Paleogene. Finally, saddle Dolomite cements yield Miocene ages (U-Pb ages of 16.40 ± 0.74 Ma to 12.3 ± 1.2 Ma) and precipitated in pre-existing vugs, representing a hydrothermal fluid flow event (Δ47 temperatures up to 170 °C) during the reactivation of thrusting. In addition, similarities in U-Pb ages and geochemical signatures between host rocks (replacive Dolomites) and the vug-lining Dolomite cements suggest that most porosity in these Dolomite reservoirs was inherited from the precursor limestones, which probably experienced meteoric leaching during late Permian uplift. This study highlights that there are geodynamic controls on fluid flow and consequent diagenetic evolution of carbonates in tectonically active sedimentary basins. It illustrates that burial alone in this setting is not a sufficient driver for diagenetic alteration and porosity reduction. The combination of U-Pb radiometric dating, clumped isotope thermometry and routine geochemical analyses is a useful approach in refining the diagenetic and porosity evolution history of ancient carbonate successions.
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la icp ms upb geochronology and clumped isotope constraints on the formation and evolution of an ancient Dolomite reservoir the middle permian of northwest sichuan basin sw china
Sedimentary Geology, 2020Co-Authors: Anjiang Shen, Jianxin Zhao, Anping Hu, Feng Liang, Yuexing Feng, Xiaofang WangAbstract:Abstract Recent advances in laser-ablation inductively coupled-plasma mass spectrometry (LA-ICP-MS) in-situ U Pb radiometric dating and clumped isotope thermometry (Δ47) of carbonate minerals provide potential for refining the fluid flow and diagenetic history of carbonate successions. In this study, the Middle Permian Dolomites proximal to the Longmenshan fold and thrust belt in northwest Sichuan Basin, southwest China, were investigated using combined U Pb geochronology, clumped isotope thermometry, and routine isotopic (δ13C, δ18O and 87Sr/86Sr) and elemental geochemistry, in an attempt to reveal the possible relevance of carbonate diagenesis and porosity evolution to the basin-scale tectonic/fluid flow events in the framework of absolute time. Overall, formation and evolution of these Dolomites temporally correlated well with major tectonic episodes of the Longmenshan fold and thrust belt. Contrary to the previously-assumed volcanic-related model, U Pb dating and Δ47 analyses suggest a mid- to late-Triassic replacive dolomitization event (U Pb ages of 240 ± 12 Ma to 233.8 ± 6.4 Ma) by a hot (Δ47 temperatures 88–104 °C) basinal brine, which was likely driven by thrust-related compression of the Longmenshan fold and thrust belt during the Triassic. Replacive dolomitization was immediately followed by cementation of euhedral Dolomites (U Pb age of 228 ± 10 Ma) and blocky calcites (U Pb ages of 224.8 ± 1.8 Ma to 213.4 ± 3.3 Ma) precipitated from the basinal brine in the same tectonic regime. Afterwards, there was long-term cessation of diagenesis that was coincident with, and thus may well be attributed to, tectono-thermal quiescence during most of the Mesozoic Era and Paleogene. Finally, saddle Dolomite cements yield Miocene ages (U Pb ages of 16.40 ± 0.74 Ma to 12.3 ± 1.2 Ma) and precipitated in pre-existing vugs, representing a hydrothermal fluid flow event (Δ47 temperatures up to 170 °C) during the reactivation of thrusting. In addition, similarities in U Pb ages and geochemical signatures between host rocks (replacive Dolomites) and the vug-lining Dolomite cements suggest that most porosity in these Dolomite reservoirs was inherited from the precursor limestones, which probably experienced meteoric leaching during late Permian uplift. This study highlights that there are geodynamic controls on fluid flow and consequent diagenetic evolution of carbonates in tectonically active sedimentary basins. It illustrates that burial alone in this setting is not a sufficient driver for diagenetic alteration and porosity reduction. The combination of U Pb radiometric dating, clumped isotope thermometry and routine geochemical analyses is a useful approach in refining the diagenetic and porosity evolution history of ancient carbonate successions.
Feng Liang - One of the best experts on this subject based on the ideXlab platform.
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la icp ms u pb geochronology and clumped isotope constraints on the formation and evolution of an ancient Dolomite reservoir the middle permian of northwest sichuan basin sw china
Sedimentary Geology, 2020Co-Authors: Anjiang Shen, Jianxin Zhao, Anping Hu, Feng Liang, Yuexing Feng, Xiaofang WangAbstract:Abstract Recent advances in laser-ablation inductively coupled-plasma mass spectrometry (LA-ICP-MS) in-situ U-Pb radiometric dating and clumped isotope thermometry (Δ47) of carbonate minerals provide potential for refining the fluid flow and diagenetic history of carbonate successions. In this study, the Middle Permian Dolomites proximal to the Longmenshan fold and thrust belt in northwest Sichuan Basin, southwest China, were investigated using combined U-Pb geochronology, clumped isotope thermometry, and routine isotopic (δ13C, δ18O and 87Sr/86Sr) and elemental geochemistry, in an attempt to reveal the possible relevance of carbonate diagenesis and porosity evolution to the basin-scale tectonic/fluid flow events in the framework of absolute time. Overall, formation and evolution of these Dolomites temporally correlated well with major tectonic episodes of the Longmenshan fold and thrust belt. Contrary to the previously-assumed volcanic-related model, U-Pb dating and Δ47 analyses suggest a mid- to late-Triassic replacive dolomitization event (U-Pb ages of 240 ± 12 Ma to 233.8 ± 6.4 Ma) by a hot (Δ47 temperatures 88– 104 °C) basinal brine, which was likely driven by thrust-related compression of the Longmenshan fold and thrust belt during the Triassic. Replacive dolomitization was immediately followed by cementation of euhedral Dolomites (U-Pb age of 228 ± 10 Ma) and blocky calcites (U-Pb ages of 224.8 ± 1.8 Ma to 213.4 ± 3.3 Ma) precipitated from the basinal brine in the same tectonic regime. Afterwards, there was long-term cessation of diagenesis that was coincident with, and thus may well be attributed to, tectono-thermal quiescence during most of the Mesozoic Era and Paleogene. Finally, saddle Dolomite cements yield Miocene ages (U-Pb ages of 16.40 ± 0.74 Ma to 12.3 ± 1.2 Ma) and precipitated in pre-existing vugs, representing a hydrothermal fluid flow event (Δ47 temperatures up to 170 °C) during the reactivation of thrusting. In addition, similarities in U-Pb ages and geochemical signatures between host rocks (replacive Dolomites) and the vug-lining Dolomite cements suggest that most porosity in these Dolomite reservoirs was inherited from the precursor limestones, which probably experienced meteoric leaching during late Permian uplift. This study highlights that there are geodynamic controls on fluid flow and consequent diagenetic evolution of carbonates in tectonically active sedimentary basins. It illustrates that burial alone in this setting is not a sufficient driver for diagenetic alteration and porosity reduction. The combination of U-Pb radiometric dating, clumped isotope thermometry and routine geochemical analyses is a useful approach in refining the diagenetic and porosity evolution history of ancient carbonate successions.
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la icp ms upb geochronology and clumped isotope constraints on the formation and evolution of an ancient Dolomite reservoir the middle permian of northwest sichuan basin sw china
Sedimentary Geology, 2020Co-Authors: Anjiang Shen, Jianxin Zhao, Anping Hu, Feng Liang, Yuexing Feng, Xiaofang WangAbstract:Abstract Recent advances in laser-ablation inductively coupled-plasma mass spectrometry (LA-ICP-MS) in-situ U Pb radiometric dating and clumped isotope thermometry (Δ47) of carbonate minerals provide potential for refining the fluid flow and diagenetic history of carbonate successions. In this study, the Middle Permian Dolomites proximal to the Longmenshan fold and thrust belt in northwest Sichuan Basin, southwest China, were investigated using combined U Pb geochronology, clumped isotope thermometry, and routine isotopic (δ13C, δ18O and 87Sr/86Sr) and elemental geochemistry, in an attempt to reveal the possible relevance of carbonate diagenesis and porosity evolution to the basin-scale tectonic/fluid flow events in the framework of absolute time. Overall, formation and evolution of these Dolomites temporally correlated well with major tectonic episodes of the Longmenshan fold and thrust belt. Contrary to the previously-assumed volcanic-related model, U Pb dating and Δ47 analyses suggest a mid- to late-Triassic replacive dolomitization event (U Pb ages of 240 ± 12 Ma to 233.8 ± 6.4 Ma) by a hot (Δ47 temperatures 88–104 °C) basinal brine, which was likely driven by thrust-related compression of the Longmenshan fold and thrust belt during the Triassic. Replacive dolomitization was immediately followed by cementation of euhedral Dolomites (U Pb age of 228 ± 10 Ma) and blocky calcites (U Pb ages of 224.8 ± 1.8 Ma to 213.4 ± 3.3 Ma) precipitated from the basinal brine in the same tectonic regime. Afterwards, there was long-term cessation of diagenesis that was coincident with, and thus may well be attributed to, tectono-thermal quiescence during most of the Mesozoic Era and Paleogene. Finally, saddle Dolomite cements yield Miocene ages (U Pb ages of 16.40 ± 0.74 Ma to 12.3 ± 1.2 Ma) and precipitated in pre-existing vugs, representing a hydrothermal fluid flow event (Δ47 temperatures up to 170 °C) during the reactivation of thrusting. In addition, similarities in U Pb ages and geochemical signatures between host rocks (replacive Dolomites) and the vug-lining Dolomite cements suggest that most porosity in these Dolomite reservoirs was inherited from the precursor limestones, which probably experienced meteoric leaching during late Permian uplift. This study highlights that there are geodynamic controls on fluid flow and consequent diagenetic evolution of carbonates in tectonically active sedimentary basins. It illustrates that burial alone in this setting is not a sufficient driver for diagenetic alteration and porosity reduction. The combination of U Pb radiometric dating, clumped isotope thermometry and routine geochemical analyses is a useful approach in refining the diagenetic and porosity evolution history of ancient carbonate successions.
Anping Hu - One of the best experts on this subject based on the ideXlab platform.
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la icp ms u pb geochronology and clumped isotope constraints on the formation and evolution of an ancient Dolomite reservoir the middle permian of northwest sichuan basin sw china
Sedimentary Geology, 2020Co-Authors: Anjiang Shen, Jianxin Zhao, Anping Hu, Feng Liang, Yuexing Feng, Xiaofang WangAbstract:Abstract Recent advances in laser-ablation inductively coupled-plasma mass spectrometry (LA-ICP-MS) in-situ U-Pb radiometric dating and clumped isotope thermometry (Δ47) of carbonate minerals provide potential for refining the fluid flow and diagenetic history of carbonate successions. In this study, the Middle Permian Dolomites proximal to the Longmenshan fold and thrust belt in northwest Sichuan Basin, southwest China, were investigated using combined U-Pb geochronology, clumped isotope thermometry, and routine isotopic (δ13C, δ18O and 87Sr/86Sr) and elemental geochemistry, in an attempt to reveal the possible relevance of carbonate diagenesis and porosity evolution to the basin-scale tectonic/fluid flow events in the framework of absolute time. Overall, formation and evolution of these Dolomites temporally correlated well with major tectonic episodes of the Longmenshan fold and thrust belt. Contrary to the previously-assumed volcanic-related model, U-Pb dating and Δ47 analyses suggest a mid- to late-Triassic replacive dolomitization event (U-Pb ages of 240 ± 12 Ma to 233.8 ± 6.4 Ma) by a hot (Δ47 temperatures 88– 104 °C) basinal brine, which was likely driven by thrust-related compression of the Longmenshan fold and thrust belt during the Triassic. Replacive dolomitization was immediately followed by cementation of euhedral Dolomites (U-Pb age of 228 ± 10 Ma) and blocky calcites (U-Pb ages of 224.8 ± 1.8 Ma to 213.4 ± 3.3 Ma) precipitated from the basinal brine in the same tectonic regime. Afterwards, there was long-term cessation of diagenesis that was coincident with, and thus may well be attributed to, tectono-thermal quiescence during most of the Mesozoic Era and Paleogene. Finally, saddle Dolomite cements yield Miocene ages (U-Pb ages of 16.40 ± 0.74 Ma to 12.3 ± 1.2 Ma) and precipitated in pre-existing vugs, representing a hydrothermal fluid flow event (Δ47 temperatures up to 170 °C) during the reactivation of thrusting. In addition, similarities in U-Pb ages and geochemical signatures between host rocks (replacive Dolomites) and the vug-lining Dolomite cements suggest that most porosity in these Dolomite reservoirs was inherited from the precursor limestones, which probably experienced meteoric leaching during late Permian uplift. This study highlights that there are geodynamic controls on fluid flow and consequent diagenetic evolution of carbonates in tectonically active sedimentary basins. It illustrates that burial alone in this setting is not a sufficient driver for diagenetic alteration and porosity reduction. The combination of U-Pb radiometric dating, clumped isotope thermometry and routine geochemical analyses is a useful approach in refining the diagenetic and porosity evolution history of ancient carbonate successions.
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la icp ms upb geochronology and clumped isotope constraints on the formation and evolution of an ancient Dolomite reservoir the middle permian of northwest sichuan basin sw china
Sedimentary Geology, 2020Co-Authors: Anjiang Shen, Jianxin Zhao, Anping Hu, Feng Liang, Yuexing Feng, Xiaofang WangAbstract:Abstract Recent advances in laser-ablation inductively coupled-plasma mass spectrometry (LA-ICP-MS) in-situ U Pb radiometric dating and clumped isotope thermometry (Δ47) of carbonate minerals provide potential for refining the fluid flow and diagenetic history of carbonate successions. In this study, the Middle Permian Dolomites proximal to the Longmenshan fold and thrust belt in northwest Sichuan Basin, southwest China, were investigated using combined U Pb geochronology, clumped isotope thermometry, and routine isotopic (δ13C, δ18O and 87Sr/86Sr) and elemental geochemistry, in an attempt to reveal the possible relevance of carbonate diagenesis and porosity evolution to the basin-scale tectonic/fluid flow events in the framework of absolute time. Overall, formation and evolution of these Dolomites temporally correlated well with major tectonic episodes of the Longmenshan fold and thrust belt. Contrary to the previously-assumed volcanic-related model, U Pb dating and Δ47 analyses suggest a mid- to late-Triassic replacive dolomitization event (U Pb ages of 240 ± 12 Ma to 233.8 ± 6.4 Ma) by a hot (Δ47 temperatures 88–104 °C) basinal brine, which was likely driven by thrust-related compression of the Longmenshan fold and thrust belt during the Triassic. Replacive dolomitization was immediately followed by cementation of euhedral Dolomites (U Pb age of 228 ± 10 Ma) and blocky calcites (U Pb ages of 224.8 ± 1.8 Ma to 213.4 ± 3.3 Ma) precipitated from the basinal brine in the same tectonic regime. Afterwards, there was long-term cessation of diagenesis that was coincident with, and thus may well be attributed to, tectono-thermal quiescence during most of the Mesozoic Era and Paleogene. Finally, saddle Dolomite cements yield Miocene ages (U Pb ages of 16.40 ± 0.74 Ma to 12.3 ± 1.2 Ma) and precipitated in pre-existing vugs, representing a hydrothermal fluid flow event (Δ47 temperatures up to 170 °C) during the reactivation of thrusting. In addition, similarities in U Pb ages and geochemical signatures between host rocks (replacive Dolomites) and the vug-lining Dolomite cements suggest that most porosity in these Dolomite reservoirs was inherited from the precursor limestones, which probably experienced meteoric leaching during late Permian uplift. This study highlights that there are geodynamic controls on fluid flow and consequent diagenetic evolution of carbonates in tectonically active sedimentary basins. It illustrates that burial alone in this setting is not a sufficient driver for diagenetic alteration and porosity reduction. The combination of U Pb radiometric dating, clumped isotope thermometry and routine geochemical analyses is a useful approach in refining the diagenetic and porosity evolution history of ancient carbonate successions.
Denis Lavoie - One of the best experts on this subject based on the ideXlab platform.
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magnesium isotope and ree compositions of lower ordovician carbonates from eastern laurentia implications for the origin of Dolomites and limestones
Chemical Geology, 2013Co-Authors: Karem Azmy, Denis Lavoie, Uwe Brand, Ihsan S Alaasm, Zhengrong Wang, S E Jackson, Isabelle GirardAbstract:Abstract Carbonates representing different depositional and diagenetic settings (near-surface to deep burial), including modern sabkha, were collected from the Lower Ordovician St. George Group in eastern Laurentia (western Newfoundland, Canada). Based on petrographic examination, three Dolomite phases were identified: D1 dolomicrite (crystals ranging from 4 to 50 μm), D2 Dolomite (50 to 150 μm) and D3 saddle Dolomite (≥ 500 μm). They occur as replacements and cements, and exhibit dull (for D1 and D3) to zoned (for D2) luminescence. The occurrence of near-micritic Dolomites (D1) suggests that dolomitization started at low temperatures under near-surface conditions during an early stage of diagenesis, whereas microthermometric studies of the D2 and D3 Dolomites confirmed their formation at higher temperatures, on average, of 112 ± 19 °C and 153 ± 30 °C, respectively, under deeper burial conditions. The D1 dolomicrite yields an average δ26Mg value of − 1.92 ± 0.30‰ (DSM3), which is slightly more negative than those of the D2 Dolomite with − 1.75 ± 0.34‰ (DSM3) and D3 saddle Dolomite with − 1.58 ± 0.31‰ (DSM3). The slightly more positive δ26Mg values of the higher-temperature Dolomites (D2 and D3) suggest insignificant kinetic fractionation and slight overprinting by 26Mg-enriched diagenetic fluids recirculating in siliciclastic and 26Mg-rich crustal rocks under closed to semi-closed diagenetic conditions. The Sr-isotope signatures support the formation of D1 dolomicrite in an early diagenetic stage and the REE compositions of the investigated Dolomites favor their formation in semi-closed to closed diagenetic systems with fluid compositions evolving by circulation through crustal rocks with progressive burial. Furthermore, the Mg isotopes suggest that the lime mudstones of the St. George Group had an algal origin, whereas the D2 Dolomite was sourced and subsequently altered mostly from the D1 dolomicrites of the succession.
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Hydrothermal dolomitization in the Lower Silurian La Vieille Formation in northern New Brunswick: Geological context and significance for hydrocarbon exploration
Bulletin of Canadian Petroleum Geology, 2006Co-Authors: Denis Lavoie, G. ChiAbstract:Hydrothermal Dolomites are potential hydrocarbon reservoirs in the Late Ordovician—Middle Devonian Gaspe Belt in eastern Canada. These Dolomites are recognized in the Lower Silurian Sayabec Formation, Upper Silurian-lowermost Devonian West Point Formation and Lower Devonian Upper Gaspe Limestones and are also recognized in the Lower Silurian La Vieille Formation in northeastern New Brunswick. Hydrothermal dolomitization is expressed in local pervasive dolomitization fronts originating from fracture feeders and by saddle Dolomite and high temperature late calcite cements filling fractures and associated dissolution voids. Field evidence such as Dolomite clasts in a post-Salinic (early Ludlovian) conglomerate indicates a dolomitization event early in the burial history. Petrographic study documents a complex history of multiple fracture generation and saddle Dolomite and/or calcite cement precipitation. Saddle Dolomite is locally brecciated and cemented by a later phase of dull luminescent, mm-sized calcite crystals (calcite 1), the latter, in some cases, also completely filling fractures. Saddle Dolomite is locally dedolomitized which is expressed as bright luminescent sub-millimetre-sized calcitic zones. Dedolomitization is associated with calcite-cemented (calcite 2), late stage fractures. δ18OVPDB values of the saddle Dolomite (-17.3 to −10‰) and calcite 1 (-13.8 to −8.8‰) cements indicate precipitation from an 18O-depleted fluid and/or at relatively high temperatures. Fluid inclusion homogenization temperatures (86 to 212°C, average of 132°C) support a high temperature origin for calcite 1 from very saline fluids (from 12 to 23 wt% NaClequiv.). Calcite 2 is characterized by similar δ18OVPDB values (-9.5 to −8.7‰) with notably different δ13CVPDB values (-4.1 to −3.1‰ and 0.9 to 3.0‰ for calcite 2 and 1, respectively). Moreover, calcite 2 is characterized by fluid inclusions with very low salinities (about 0 wt% NaClequiv.) and is interpreted as late meteoric calcite cement likely precipitated during the Late Silurian global sea level lowstand (Salinic Unconformity) or following the Middle Devonian (Acadian Orogeny) subaerial exposure of the Lower Silurian ramp. The Early Silurian tectono-magmatic setting of the Gaspe Belt basin played a significant role in the regional hydrothermal alteration of the carbonates. The occurrence of hydrothermal Dolomite suggests previously unrecognized reservoir potential of Silurian carbonates that should be considered along with the presence of good Middle and Upper Ordovician source rocks and favourable thermal maturation.
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Hydrothermal dolomitization in the Lower Ordovician Romaine Formation of the Anticosti Basin: Significance for hydrocarbon exploration
Bulletin of Canadian Petroleum Geology, 2005Co-Authors: Denis Lavoie, G. Chi, P. Brennan-alpert, André Desrochers, R. BertrandAbstract:This study deals with the diagenetic evolution of dolostones of the Romaine Formation, from cores and outcrops on Anticosti and Mingan islands, and reports evidence for hydrocarbon migration in secondary porosity generated by high temperature / hydrothermal alteration. Four types of calcite (grouped into early (C1) and late (C2) assemblages) and six types of Dolomite (grouped into 3 different (D1, D2 and D3) assemblages) are distinguished. According to fluid-inclusion and stable C-O isotope data, the early calcite group, which consists of sedimentary micrite, replacement microspar and early pore-filling calcite records near surface diagenetic environments. Early and pervasive replacement Dolomites (RD1 and RD2 in the first Dolomite (D1) assemblage) were formed during early burial, and are not related to porosity generation. Later replacement Dolomites (RD3 and RD4 in the second Dolomite (D2) assemblage) and pore-filling Dolomite cements (PD1 and PD2 in the third Dolomite (D3) assemblage) as well as minor sphalerite were formed from warm, saline fluids, which were likely hydrothermal in origin. Vuggy porosity was produced through brecciation and fracturing, and through some dissolution of the D1 Dolomite assemblage by these hydrothermal fluids. Intercrystalline porosity was also created during formation of the D2 Dolomite assemblage. The vugs were partly occluded by late-stage pore filling Dolomite and calcite cements, pyrite and barite. Bitumen droplets in vugs together with hydrocarbon inclusions recorded in C2 calcite and in contemporaneous barite indicate a hydrocarbon migration event after the porosity-generating processes. The brecciation / leaching of a precursor Dolomite host is uncommon in hydrothermal Dolomite hydrocarbon fields, but is recognized in the adjacent coeval pool in Newfoundland. This type of alteration in the Ordovician carbonates with the presence of a rich hydrocarbon source rock and favourable maturation are key elements for the on-going exploration efforts in this basin.
