磁化率各向异性（Anisotropy of Magnetic Susceptibility：AMS）能揭示沉积物中磁性矿物的定向排列,用于判定水流大小和方向变化。目前,关于沉积微相的磁化率各向异性研究仍较少。本文通过对台儿沟东剖面进行高分辨率磁化率各向异性研...磁化率各向异性（Anisotropy of Magnetic Susceptibility：AMS）能揭示沉积物中磁性矿物的定向排列,用于判定水流大小和方向变化。目前,关于沉积微相的磁化率各向异性研究仍较少。本文通过对台儿沟东剖面进行高分辨率磁化率各向异性研究,发现各沉积微相和亚相的磁化率各向异性较大差异,对于水动力较大的沉积微相,如分支河道、水下支流河道、河口砂坝等,其磁化率和磁化率各向异性度相对较大;对于水动力较小的沉积微相,如分支间湾、天然堤等,磁化率和磁化率各向异性度次之;对于滨浅湖、前三角洲泥、沼泽等静水环境,磁化率和磁化率各向异性度最小。根据各沉积微相或亚相χ与P的相关系数变化,可将河湖相地层分为两段：其中,在7.8～90m深度范围内,χ与P的相关系数为正值;在之下90～130m深度范围内,χ与P的相关系数主要为负值。与郝家台、东谷坨剖面磁化率各向异性结果相似,台儿沟东剖面各沉积微相和亚相的磁化率最大轴主要倾向NNE和NNW方向,而磁化率最小轴主要倾向SW方向,表明泥河湾盆地的物源除了可能来自盆地东部外,还可能来自盆地西南部。展开更多
Mantle xenoliths hosted in Tertiary alkali basalts in Yangyuan, Hebei Province, located to the west of the Taihangshan gravity lineament, include lherzolites, harzburgites and pyroxenite. In the plot of olivine mode v...Mantle xenoliths hosted in Tertiary alkali basalts in Yangyuan, Hebei Province, located to the west of the Taihangshan gravity lineament, include lherzolites, harzburgites and pyroxenite. In the plot of olivine mode vs Fo, most of the Yangyuan peridotites deviate from the oceanic trend, falling within the fields of Archean and Proterozoic mantles. Some LREE- enriched samples exhibit EMI-type isotopic signature with εNd ranging from –6.9 to –10.6 and 87Sr/86Sr from 0.7044 to 0.7047. By contrast, another LREE-en- riched sample has a positive εNd (+5.7) similar to that for LREE-depleted peridotites. This observation suggests that the upper mantle beneath Yangyuan underwent a multi-stage metasomatism. Given the fact that EMI-type isotopic signature is usually ob- served in the lithosphere mantle underneath ancient cratons, the isotopic composition of the Yangyuan xenoliths provides new evidence for the existence of the old lithosphere mantle beneath western North China.展开更多
文摘磁化率各向异性（Anisotropy of Magnetic Susceptibility：AMS）能揭示沉积物中磁性矿物的定向排列,用于判定水流大小和方向变化。目前,关于沉积微相的磁化率各向异性研究仍较少。本文通过对台儿沟东剖面进行高分辨率磁化率各向异性研究,发现各沉积微相和亚相的磁化率各向异性较大差异,对于水动力较大的沉积微相,如分支河道、水下支流河道、河口砂坝等,其磁化率和磁化率各向异性度相对较大;对于水动力较小的沉积微相,如分支间湾、天然堤等,磁化率和磁化率各向异性度次之;对于滨浅湖、前三角洲泥、沼泽等静水环境,磁化率和磁化率各向异性度最小。根据各沉积微相或亚相χ与P的相关系数变化,可将河湖相地层分为两段：其中,在7.8～90m深度范围内,χ与P的相关系数为正值;在之下90～130m深度范围内,χ与P的相关系数主要为负值。与郝家台、东谷坨剖面磁化率各向异性结果相似,台儿沟东剖面各沉积微相和亚相的磁化率最大轴主要倾向NNE和NNW方向,而磁化率最小轴主要倾向SW方向,表明泥河湾盆地的物源除了可能来自盆地东部外,还可能来自盆地西南部。
基金This work was supported by the Baren Project of Chinese Academy of Sciences and the National Natural Science Foundation of China （Grant No： 49925308 ＆ 40421303）.
文摘Mantle xenoliths hosted in Tertiary alkali basalts in Yangyuan, Hebei Province, located to the west of the Taihangshan gravity lineament, include lherzolites, harzburgites and pyroxenite. In the plot of olivine mode vs Fo, most of the Yangyuan peridotites deviate from the oceanic trend, falling within the fields of Archean and Proterozoic mantles. Some LREE- enriched samples exhibit EMI-type isotopic signature with εNd ranging from –6.9 to –10.6 and 87Sr/86Sr from 0.7044 to 0.7047. By contrast, another LREE-en- riched sample has a positive εNd (+5.7) similar to that for LREE-depleted peridotites. This observation suggests that the upper mantle beneath Yangyuan underwent a multi-stage metasomatism. Given the fact that EMI-type isotopic signature is usually ob- served in the lithosphere mantle underneath ancient cratons, the isotopic composition of the Yangyuan xenoliths provides new evidence for the existence of the old lithosphere mantle beneath western North China.
