Calcimicrobialites across the Permian-Triassic boundary in Huayingshan （华蓥山） region were investigated using the fluorescence microscopic measurements to understand the occurrence of organic matter. The microbiali...Calcimicrobialites across the Permian-Triassic boundary in Huayingshan （华蓥山） region were investigated using the fluorescence microscopic measurements to understand the occurrence of organic matter. The microbialites are composed of micrite matrix and coarse spar cement. Abundant rhombic or magnetic needle-like carbonate minerals were observed adrift within the cement. The fluorescence microscopic measurement indicates the micrite matrix in microbialites shows the most abundant organic matter, with the rhombic or magnetic needle-like carbonate minerals and coarse spar cement coming to the 2nd and the 3rd, respectively. Organic matter is mainly preserved in the space between the grains of the micrite minerals but almost evenly distributed in the rhombic or magnetic needle-like carbonate minerals. As one of the common diagenesis types, dolomitization is observed to occur in the microbialites in Huayingshan. However, the carbonate cement in microbialites still has high content of element Sr as shown by the microprobe analysis, reflecting that the dolomitization might have happened in a restricted environment. Observation under the fluorescence microscope shows that dolomitization just led to the redistribution of organic matter in the grain space of dolomite minerals, inferring that the diagenesis has a slight effect on the preservation, and thus on the content of organic matter in the microbialites.展开更多
The Early Permian bauxite in the Sichuan Basin is an important part of karst-type bauxite deposits in South China Block and its provenance is poorly understood.Here we present results of mineralogy,wholerock geochemis...The Early Permian bauxite in the Sichuan Basin is an important part of karst-type bauxite deposits in South China Block and its provenance is poorly understood.Here we present results of mineralogy,wholerock geochemistry,detrital zircon U-Pb ages and trace element compositions of the bauxitic claystone from the Lower Permian Dazhuyuan Formation and those of the siltstone from the underlying Lower Silurian Hanjiadian Formation in Huayingshan region,Sichuan Basin,South China Block to constrain the provenance of the bauxitic claystone.Detrital zircons from bauxitic claystone and siltstone have similar age spectra,and the ages of bauxitic claystone are classified into five groups of 2600-2200 Ma,1800-1600 Ma,1200-900 Ma,900-650 Ma,and 650-400 Ma respectively.Those of the siltstone are classified into four groups of 2600-2200 Ma,1200-900 Ma,900-650 Ma,and 650-400 Ma respectively.We propose that the bauxitic claystone in the study region has mixed sources:the siltstone of the Lower Silurian Hanjiadian Formation probably constitutes the dominant source,and the Late Paleoproterozoic magmatic rocks along the western margin of the Yangtze Block are probably the secondary source.Moreover,the source materials of the Hanjiadian Formation siltstone are mainly sourced from Grenville-aged magmatic rocks in the Cathaysia Block and Neoproterozoic magmatic rocks in the Jiangnan orogen,with minor contributions from the underlying clastic sediments in the Cathaysia Block and Pan-African magmatic rocks in the orogen in eastern Gondwana.展开更多
基于Bayes反演理论(Tarantola,1987,2005),在接收函数非线性复谱比反演方法基础上(刘启元等,1996),本文讨论了接收函数与地震环境噪声Rayleigh波相速度频散的联合反演.本文采用修正后的快速广义反射/透射系数方法(Pei et al.,2008,2009...基于Bayes反演理论(Tarantola,1987,2005),在接收函数非线性复谱比反演方法基础上(刘启元等,1996),本文讨论了接收函数与地震环境噪声Rayleigh波相速度频散的联合反演.本文采用修正后的快速广义反射/透射系数方法(Pei et al.,2008,2009)计算Rayleigh波相速度频散,并引入地壳泊松比的全局性搜索.数值检验表明:(1)接收函数与环境噪声的联合反演能够有效地解决反演结果对初始模型依赖的问题,即使对地壳速度结构仅有非常粗略的初始估计(例如,垂向均匀模型),本文方法仍能给出模型参数的可靠估计;(2)由于环境噪声与接收函数在频带上的适配性明显优于地震面波,接收函数与环境噪声的非线性联合反演能更好地约束台站下方近地表的速度结构;对于周期范围为2～40s的环境噪声相速度频散,利用本文方法能够可靠推测台站下方0～80km深度范围的S波速度结构,其浅表速度结构的分辨率可达到1km(3)本文方法能够可靠地估计地壳泊松比,泊松比的全局性搜索有助于合理解释接收函数和环境噪声的面波频散数据.利用本文方法对川西台阵KWC05台站观测的接收函数与环境噪声的联合反演表明,该台站下方地壳厚度为44km,上地壳具有明显的高速结构,24～42km范围的中下地壳具有低速结构.该台站下方地壳的平均泊松比为0.262,壳内低速带的泊松比为0.27.展开更多
基金supported by the National Natural Science Foundation of China (Nos. 40730209, 40572002)the 111 Project (B08030)the SINOPEC project (G0800-06-ZS-319)
文摘Calcimicrobialites across the Permian-Triassic boundary in Huayingshan （华蓥山） region were investigated using the fluorescence microscopic measurements to understand the occurrence of organic matter. The microbialites are composed of micrite matrix and coarse spar cement. Abundant rhombic or magnetic needle-like carbonate minerals were observed adrift within the cement. The fluorescence microscopic measurement indicates the micrite matrix in microbialites shows the most abundant organic matter, with the rhombic or magnetic needle-like carbonate minerals and coarse spar cement coming to the 2nd and the 3rd, respectively. Organic matter is mainly preserved in the space between the grains of the micrite minerals but almost evenly distributed in the rhombic or magnetic needle-like carbonate minerals. As one of the common diagenesis types, dolomitization is observed to occur in the microbialites in Huayingshan. However, the carbonate cement in microbialites still has high content of element Sr as shown by the microprobe analysis, reflecting that the dolomitization might have happened in a restricted environment. Observation under the fluorescence microscope shows that dolomitization just led to the redistribution of organic matter in the grain space of dolomite minerals, inferring that the diagenesis has a slight effect on the preservation, and thus on the content of organic matter in the microbialites.
基金supported financially by the National Key Research and Development Program of China(Project 2017YFC0602704)the Research Project of Xi'an Geological Survey Center of China Geological Survey(Project DD20189612)。
文摘The Early Permian bauxite in the Sichuan Basin is an important part of karst-type bauxite deposits in South China Block and its provenance is poorly understood.Here we present results of mineralogy,wholerock geochemistry,detrital zircon U-Pb ages and trace element compositions of the bauxitic claystone from the Lower Permian Dazhuyuan Formation and those of the siltstone from the underlying Lower Silurian Hanjiadian Formation in Huayingshan region,Sichuan Basin,South China Block to constrain the provenance of the bauxitic claystone.Detrital zircons from bauxitic claystone and siltstone have similar age spectra,and the ages of bauxitic claystone are classified into five groups of 2600-2200 Ma,1800-1600 Ma,1200-900 Ma,900-650 Ma,and 650-400 Ma respectively.Those of the siltstone are classified into four groups of 2600-2200 Ma,1200-900 Ma,900-650 Ma,and 650-400 Ma respectively.We propose that the bauxitic claystone in the study region has mixed sources:the siltstone of the Lower Silurian Hanjiadian Formation probably constitutes the dominant source,and the Late Paleoproterozoic magmatic rocks along the western margin of the Yangtze Block are probably the secondary source.Moreover,the source materials of the Hanjiadian Formation siltstone are mainly sourced from Grenville-aged magmatic rocks in the Cathaysia Block and Neoproterozoic magmatic rocks in the Jiangnan orogen,with minor contributions from the underlying clastic sediments in the Cathaysia Block and Pan-African magmatic rocks in the orogen in eastern Gondwana.
文摘基于Bayes反演理论(Tarantola,1987,2005),在接收函数非线性复谱比反演方法基础上(刘启元等,1996),本文讨论了接收函数与地震环境噪声Rayleigh波相速度频散的联合反演.本文采用修正后的快速广义反射/透射系数方法(Pei et al.,2008,2009)计算Rayleigh波相速度频散,并引入地壳泊松比的全局性搜索.数值检验表明:(1)接收函数与环境噪声的联合反演能够有效地解决反演结果对初始模型依赖的问题,即使对地壳速度结构仅有非常粗略的初始估计(例如,垂向均匀模型),本文方法仍能给出模型参数的可靠估计;(2)由于环境噪声与接收函数在频带上的适配性明显优于地震面波,接收函数与环境噪声的非线性联合反演能更好地约束台站下方近地表的速度结构;对于周期范围为2～40s的环境噪声相速度频散,利用本文方法能够可靠推测台站下方0～80km深度范围的S波速度结构,其浅表速度结构的分辨率可达到1km(3)本文方法能够可靠地估计地壳泊松比,泊松比的全局性搜索有助于合理解释接收函数和环境噪声的面波频散数据.利用本文方法对川西台阵KWC05台站观测的接收函数与环境噪声的联合反演表明,该台站下方地壳厚度为44km,上地壳具有明显的高速结构,24～42km范围的中下地壳具有低速结构.该台站下方地壳的平均泊松比为0.262,壳内低速带的泊松比为0.27.
