Combined with sedimentary observation and mineralogical research on a type of drusy celestite of early diagenesis in origin, this geochemical study on the Qixia Formation at the Shuibuya Section, Badong County, Hubei ...Combined with sedimentary observation and mineralogical research on a type of drusy celestite of early diagenesis in origin, this geochemical study on the Qixia Formation at the Shuibuya Section, Badong County, Hubei Province of south China evaluates the contribution of sedimentation and diagenesis to the mass fractions of CaO, Al 2O 3, MgO, SiO 2, Fe 2O 3, Na 2O, K 2O, Mn, Sr, P and Ba in the carbonates. The Sr, initially released from the stabilization of carbonate calcium mineral, precipitated with sulfate ion as celestite in early diagenetic environment, where sulfate reduction was the minimum. Then it redistributed in burial diagenetic environment, where celestite was replaced by calcite. The fractions of the MgO and SiO 2 in the carbonates were mainly modified by the early dolomitization and silicification respectively. That of the Na 2O was overprinted by the burial diagenesis. Multivariate statistical analysis on data of sixty bulk rocks indicates that the mass fractions of the Al 2O 3, K 2O, Fe 2O 3, Mn, CaO, P and Ba were affiliated with the sedimentary factor despite the obvious decrease of CaO during early dolomitization and silicification. Among them, the Al 2O 3 and K 2O mainly represent the detrital components. In addition, a dysaerobic sedimentary background was confirmed by trace element measurement and information derived from the formation of the celestite. This genetic discrimination facilitates the interpretation of the transgressive regressive (T R) cycle and specialities featured this unusual carbonate unit.展开更多
End-Permian Gondwana siliciclastics (50 - 70 m) of the Um Irna F exposed along the NE Dead Sea, exhibit carbonate-free fining upward cycles (FUC) deposited during acid flash flood events under tropical climate. Severa...End-Permian Gondwana siliciclastics (50 - 70 m) of the Um Irna F exposed along the NE Dead Sea, exhibit carbonate-free fining upward cycles (FUC) deposited during acid flash flood events under tropical climate. Several ferruginous paleosol intercalations cover periods of drying upward formation (DUP) under semiarid/arid climates. Thin grey pelite beds interbedded between paleosol and overlying FUC, are interpreted as tephra deposits sourced in Siberian LIP- and Neo-Tethys (NT)-Degassing. The Wadi Bassat en Nimra-section exhibits the P-T transitional zone where flash flood deposits meet supra-/intertidal sediments of the southward-directed transgressive NT. Decreasing flash-flooding continued through the Lower Scythian (Ma’in F.) during transgression, reworking, and resedimentation. Two euryhaline foraminifera-bearing limestone beds are discussed as indicators for the end of mass extinction (recovery phase: ca. 250.8 - 250.4 Ma) possibly correlating with the Maximum Flooding Surface MFS Tr 10 (ca. 250.5 Ma) on the Arabian Shelf (Khuff cycles B;A). Comparable data from the Germanic Basin as FUC/DUP-cycles, tephrasuspicious “Grey Beds” with high concentrations of As, Co, Pb, Zn, and Cu as well as the U-Pb Age data of the Siberian LIP meet the PTB-Zone between the MFSs Intervals P 40 (ca. 254 Ma)/Tr 10 (ca 250.5 Ma) on the Arabian Shelf. MFS (Tr 10, 20, 30) and SBs resp. on the Arabian Plate, as well as Scythian Substage boundaries correlate with ∂<sup>13</sup> C-excursions recorded at Musandam, UAE. Thereby, the ratio of greenhouse gases (+climate forcing)/aerosols und tephra (-climate forcing) takes a significant influence on the ∂<sup>13</sup>C-Variation.展开更多
文摘Combined with sedimentary observation and mineralogical research on a type of drusy celestite of early diagenesis in origin, this geochemical study on the Qixia Formation at the Shuibuya Section, Badong County, Hubei Province of south China evaluates the contribution of sedimentation and diagenesis to the mass fractions of CaO, Al 2O 3, MgO, SiO 2, Fe 2O 3, Na 2O, K 2O, Mn, Sr, P and Ba in the carbonates. The Sr, initially released from the stabilization of carbonate calcium mineral, precipitated with sulfate ion as celestite in early diagenetic environment, where sulfate reduction was the minimum. Then it redistributed in burial diagenetic environment, where celestite was replaced by calcite. The fractions of the MgO and SiO 2 in the carbonates were mainly modified by the early dolomitization and silicification respectively. That of the Na 2O was overprinted by the burial diagenesis. Multivariate statistical analysis on data of sixty bulk rocks indicates that the mass fractions of the Al 2O 3, K 2O, Fe 2O 3, Mn, CaO, P and Ba were affiliated with the sedimentary factor despite the obvious decrease of CaO during early dolomitization and silicification. Among them, the Al 2O 3 and K 2O mainly represent the detrital components. In addition, a dysaerobic sedimentary background was confirmed by trace element measurement and information derived from the formation of the celestite. This genetic discrimination facilitates the interpretation of the transgressive regressive (T R) cycle and specialities featured this unusual carbonate unit.
文摘End-Permian Gondwana siliciclastics (50 - 70 m) of the Um Irna F exposed along the NE Dead Sea, exhibit carbonate-free fining upward cycles (FUC) deposited during acid flash flood events under tropical climate. Several ferruginous paleosol intercalations cover periods of drying upward formation (DUP) under semiarid/arid climates. Thin grey pelite beds interbedded between paleosol and overlying FUC, are interpreted as tephra deposits sourced in Siberian LIP- and Neo-Tethys (NT)-Degassing. The Wadi Bassat en Nimra-section exhibits the P-T transitional zone where flash flood deposits meet supra-/intertidal sediments of the southward-directed transgressive NT. Decreasing flash-flooding continued through the Lower Scythian (Ma’in F.) during transgression, reworking, and resedimentation. Two euryhaline foraminifera-bearing limestone beds are discussed as indicators for the end of mass extinction (recovery phase: ca. 250.8 - 250.4 Ma) possibly correlating with the Maximum Flooding Surface MFS Tr 10 (ca. 250.5 Ma) on the Arabian Shelf (Khuff cycles B;A). Comparable data from the Germanic Basin as FUC/DUP-cycles, tephrasuspicious “Grey Beds” with high concentrations of As, Co, Pb, Zn, and Cu as well as the U-Pb Age data of the Siberian LIP meet the PTB-Zone between the MFSs Intervals P 40 (ca. 254 Ma)/Tr 10 (ca 250.5 Ma) on the Arabian Shelf. MFS (Tr 10, 20, 30) and SBs resp. on the Arabian Plate, as well as Scythian Substage boundaries correlate with ∂<sup>13</sup> C-excursions recorded at Musandam, UAE. Thereby, the ratio of greenhouse gases (+climate forcing)/aerosols und tephra (-climate forcing) takes a significant influence on the ∂<sup>13</sup>C-Variation.
