A geochronological study of zircon U-Pb on the volcanic rocks from the stratotype section of the Qingshan Group within the Jiaozhou Basin, eastern Shandong Province, is presented. The zircons were analyzed using the m...A geochronological study of zircon U-Pb on the volcanic rocks from the stratotype section of the Qingshan Group within the Jiaozhou Basin, eastern Shandong Province, is presented. The zircons were analyzed using the method of in situ ablation of a 193 nm excimer laser system coupled with an up to date ICP-MS system. Among the three formations of the Qingshan Group, zircons recovered from the lowest part of the Houkuang Fm. were dated at 106±2 Ma (95% confidence, the same below), whereas those from the lower and upper parts of the Shiqianzhuang Fm. were given ages of 105±4 Ma and 98±1 Ma, respectively. A spatially decreasing trend for the Mesozoic magmatic timing from west to east in the province is observed through comparing the data of this study with those by previous works on the Qingshan volcanic lavas occurring at western Shandong and within the Yishu fault zone. The Qingshan volcanic rocks are constituent of the 'Shoshonite Province' in East China. Exposed at most provinces of central East China along the Tan-Lu fault and the Yangtze fault zones, these volcanic suites are characterized by shoshonite and high-K calcalkalic rocks in lithology and thought to be correlated with the partial melting of continental mantle in genesis. It is also shown that the Qingshan potassic volcanic suite from eastern Shandong basins is distinctly younger than those from other ar-eas of the shoshonite province. By contrary, ages of the Mesozoic to Cenozoic alkaline basalts, sourced by asthenospheric mantle, from both northern Huaiyan basin and northern Dabie belt along the Tan-Lu fault zone and from the Ningwu, Lishui and Luzong basins along the Yangtze fault zone are observably older than those occurring within eastern Shandong. The revealed temporal and spatial patterns in magmatism for the two types of volcanic suites make an important geochronological con-straint on the Mesozoic to Cenozoic dynamic evolution model of the subcontinental lithosphere in East China.展开更多
The study on soft-sediment deformation structures(SSDS) of Lingshan Island has been one of the hot topics of sedimentology researches in China in recent years,and SSDS developed in turbidite system in the Laiyang Grou...The study on soft-sediment deformation structures(SSDS) of Lingshan Island has been one of the hot topics of sedimentology researches in China in recent years,and SSDS developed in turbidite system in the Laiyang Group are widely known by domestic researchers.However,few studies were conducted on the SSDS in fan delta system in the Qingshan Group,Lingshan Island.This study analyzes the classification and characteristics of SSDS especially their lithofacies association and tithologic characteristics through field outcrops investigation and thin section analysis as well.A conclusion was acquired that the paleoenvironment was a fan delta system with occurrence of several volcanic eruptions,where the water became gradually shallower.The SSDS types in the Qingshan Group includes load and flame structure,ball and pillow structure,waterescape structure,hydroplastic deformation structure,plastic sandstone breccia structure,volcanic drop stone and V-shaped ground fissure mainly caused by volcanic earthquakes of three types:(1)seismic waves,(2)gravity and inertia effect of pyroclastic flows,(3)instant differential air pressure;which is different from slumping and tectonic earthquakes occurred in the Laiyang Group.In addition,with the lithofacies association analysis between pyroclastic flow and SSDS beds,a distribution model of SSDS related to volcanic earthquakes can be established:SSDS types changed gradually with their distance further away from the volcanic activity core.Brittle deformation which was common in the proximal zone disappeared gradually;liquefied and plastic SSDS continued to dominate in the medial zone;and slightly liquefied SSDS were developed in the distal zone.Meanwhile,the scale and size of SSDS is negatively correlated with the distance of SSDS depositional locations from the volcanic vent.展开更多
青山群火山岩是华北克拉通破坏期间最具代表性的地幔或地壳熔融产物,记录了华北深部地质演化的重要信息。本文对胶东青山群基性火山岩进行了40Ar/39Ar定年和岩石地球化学分析,结合前人报道的胶东青山群酸性火山岩资料,发现:(1)基性火山...青山群火山岩是华北克拉通破坏期间最具代表性的地幔或地壳熔融产物,记录了华北深部地质演化的重要信息。本文对胶东青山群基性火山岩进行了40Ar/39Ar定年和岩石地球化学分析,结合前人报道的胶东青山群酸性火山岩资料,发现:(1)基性火山岩喷发年龄为122～113Ma,早于青山群酸性火山岩(110～98Ma);(2)基性和酸性火山岩显示了不同的元素和同位素地球化学特征。岩石成因分析表明,基性火山岩为交代富集地幔部分熔融作用的产物,而酸性火山岩为古老下地壳和中生代底侵岩浆的熔融产物(Ling et al.,2009)。因此,胶东地区青山群火山岩记录了岩浆熔融源区从地幔向下地壳的转变。这与长时间尺度的岩石圈减薄过程中热能由地幔向地壳传递过程相吻合,而不同于地壳拆沉作用所预测的岩浆演化趋势。展开更多
基金the National Natural Science Foundation of China (Grant No. 40133020)Innovation Term Grant of Ministry of Education of China
文摘A geochronological study of zircon U-Pb on the volcanic rocks from the stratotype section of the Qingshan Group within the Jiaozhou Basin, eastern Shandong Province, is presented. The zircons were analyzed using the method of in situ ablation of a 193 nm excimer laser system coupled with an up to date ICP-MS system. Among the three formations of the Qingshan Group, zircons recovered from the lowest part of the Houkuang Fm. were dated at 106±2 Ma (95% confidence, the same below), whereas those from the lower and upper parts of the Shiqianzhuang Fm. were given ages of 105±4 Ma and 98±1 Ma, respectively. A spatially decreasing trend for the Mesozoic magmatic timing from west to east in the province is observed through comparing the data of this study with those by previous works on the Qingshan volcanic lavas occurring at western Shandong and within the Yishu fault zone. The Qingshan volcanic rocks are constituent of the 'Shoshonite Province' in East China. Exposed at most provinces of central East China along the Tan-Lu fault and the Yangtze fault zones, these volcanic suites are characterized by shoshonite and high-K calcalkalic rocks in lithology and thought to be correlated with the partial melting of continental mantle in genesis. It is also shown that the Qingshan potassic volcanic suite from eastern Shandong basins is distinctly younger than those from other ar-eas of the shoshonite province. By contrary, ages of the Mesozoic to Cenozoic alkaline basalts, sourced by asthenospheric mantle, from both northern Huaiyan basin and northern Dabie belt along the Tan-Lu fault zone and from the Ningwu, Lishui and Luzong basins along the Yangtze fault zone are observably older than those occurring within eastern Shandong. The revealed temporal and spatial patterns in magmatism for the two types of volcanic suites make an important geochronological con-straint on the Mesozoic to Cenozoic dynamic evolution model of the subcontinental lithosphere in East China.
文摘The study on soft-sediment deformation structures(SSDS) of Lingshan Island has been one of the hot topics of sedimentology researches in China in recent years,and SSDS developed in turbidite system in the Laiyang Group are widely known by domestic researchers.However,few studies were conducted on the SSDS in fan delta system in the Qingshan Group,Lingshan Island.This study analyzes the classification and characteristics of SSDS especially their lithofacies association and tithologic characteristics through field outcrops investigation and thin section analysis as well.A conclusion was acquired that the paleoenvironment was a fan delta system with occurrence of several volcanic eruptions,where the water became gradually shallower.The SSDS types in the Qingshan Group includes load and flame structure,ball and pillow structure,waterescape structure,hydroplastic deformation structure,plastic sandstone breccia structure,volcanic drop stone and V-shaped ground fissure mainly caused by volcanic earthquakes of three types:(1)seismic waves,(2)gravity and inertia effect of pyroclastic flows,(3)instant differential air pressure;which is different from slumping and tectonic earthquakes occurred in the Laiyang Group.In addition,with the lithofacies association analysis between pyroclastic flow and SSDS beds,a distribution model of SSDS related to volcanic earthquakes can be established:SSDS types changed gradually with their distance further away from the volcanic activity core.Brittle deformation which was common in the proximal zone disappeared gradually;liquefied and plastic SSDS continued to dominate in the medial zone;and slightly liquefied SSDS were developed in the distal zone.Meanwhile,the scale and size of SSDS is negatively correlated with the distance of SSDS depositional locations from the volcanic vent.
文摘青山群火山岩是华北克拉通破坏期间最具代表性的地幔或地壳熔融产物,记录了华北深部地质演化的重要信息。本文对胶东青山群基性火山岩进行了40Ar/39Ar定年和岩石地球化学分析,结合前人报道的胶东青山群酸性火山岩资料,发现:(1)基性火山岩喷发年龄为122～113Ma,早于青山群酸性火山岩(110～98Ma);(2)基性和酸性火山岩显示了不同的元素和同位素地球化学特征。岩石成因分析表明,基性火山岩为交代富集地幔部分熔融作用的产物,而酸性火山岩为古老下地壳和中生代底侵岩浆的熔融产物(Ling et al.,2009)。因此,胶东地区青山群火山岩记录了岩浆熔融源区从地幔向下地壳的转变。这与长时间尺度的岩石圈减薄过程中热能由地幔向地壳传递过程相吻合,而不同于地壳拆沉作用所预测的岩浆演化趋势。
