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991.
992.
新安县孙坑铝土矿主要赋存于中石炭统本溪组中,矿石类型主要是一水硬铝石型铝土矿.笔者通过在该区进行地质工作,对该地区铝土矿的基本地质特征进行了阐述.对采取的铝土矿样品进行稀土元素测试分析,认为本区铝土矿的矿源物质主要来源于底板灰岩的风化碎屑.结合底板灰岩物质来源,表明铝土矿中的稀土元素具有一定的继承性. 相似文献
993.
994.
长江口涨潮与落潮流速和悬沙输运不对称性研究 总被引:1,自引:0,他引:1
为了量化比较海表层环境及温跃层环境对南太平洋长鳍金枪鱼渔场分布的影响程度;本研究采用2010-2012年南太平洋长鳍金枪鱼延绳钓渔船实际生产统计数据;结合卫星遥感所获取的海表面温度(sea surface temperature;SST)和海表面高度(sea surface height;SSH)数据以及Argo浮标所获取的温跃层上、下界水温和深度数据;运用外包络法分别构建了基于海表层环境变量、温跃层上界环境变量以及温跃层下界环境变量的3种栖息地适应性指数(habitat suitability index;HSI)模型。模型验证结果显示;基于海表层环境变量的HSI模型;HSI>0.6时所占产量比重为70.04%;投钩数量比重为70.86%;HSI>0.8时所占产量比重为24.92%;投钩数量比重为25.79%;基于温跃层上界环境变量的HSI模型;HSI>0.6时所占产量比重为82.17%;投钩数量比重为80.95%;HSI>0.8时所占产量比重为33.24%;投钩数量比重为32.69%;基于温跃层下界环境变量的HSI模型;HSI>0.6时所占产量比重为81.01%;投钩数量比重为81.54%;HSI>0.8时所占产量比重为43.51%;投钩数量比重为43.73%。研究发现;基于温跃层上界和下界环境变量的两个HSI模型预报精度明显高于基于表层环境变量的HSI模型;且基于温跃层下界环境变量的HSI模型预报精度高于基于温跃层上界环境变量的HSI模型。研究结果表明;相较于海表层环境;温跃层环境;尤其是温跃层下界环境特征对南太平洋长鳍金枪鱼资源分布的影响更为显著。 相似文献
995.
The assessment of deformation types within the slope of a carbonate platform can be complicated by the possible interaction of rooted (tectonically-induced) and superficial (gravity-driven) structures. An ideal case study to document and distinguish tectonically- and gravity-driven structures is provided by the Cretaceous slope-to-basin carbonates exposed in the Gargano Promontory, southern Italy. These carbonates formed adjacent to the Apulian platform margin, which was oriented approximately NE–SW to NW–SE along the southern and northern edges of the promontory, respectively. Slump-related folds are characterised by axial planes typically oriented either sub-parallel or at small angles to the strike of the inferred paleoslope. In fact, the strike of folds is roughly NE–SW in the southern portion of the study area, whereas it is NW–SE in the northern part. Correspondingly, gravity-driven normal and reverse faults strike sub-parallel and at acute angles to the adjacent Apulian paleoslope. Cretaceous tectonic faults in the slope-to-basin carbonates form two principal sets striking NW–SE and WNW-ESE. The former set is made up of normal faults and the latter one includes mainly oblique-slip normal faults. Neither normal nor oblique-slip normal faults show any relationship with the geometry of the paleoslope. The results obtained from this study may help the interpretation of subsurface data in those geological contexts in which the interplay of gravitational and tectonic processes is responsible for deformation. 相似文献
996.
997.
黔西北地区铅锌矿床流体包裹体与硫同位素地球化学研究 总被引:4,自引:2,他引:2
黔西北铅锌成矿区位于扬子地块西南缘,矿床产于不同时代的碳酸盐岩建造中,其矿物组合和热液蚀变特征类似于MVT型铅锌矿床。本文通过对该区部分铅锌矿床的矿石显微岩相学结构、矿物学与地球化学、脉石矿物和闪锌矿中流体包裹体岩相学与显微测温学以及硫同位素地球化学等研究,确定了该类型矿床成矿流体的性质及其成矿过程。结果表明,黔西北地区不同赋矿层位铅锌矿床具有相似的成矿流体特征,为中低温(160~260℃)、较高盐度(10%~22%NaCleqv)、含有低密度的CO_2、CH_4和N_2的卤水,不同于MVT型铅锌矿床成矿流体特征;硫同位素地球化学研究揭示,这些铅锌矿床硫化物的δ~(34)S范围均落在对应赋矿地层时代蒸发岩中的硫酸盐和生物成因硫化物的δ~(34)S演化曲线上或其附近,表明这些铅锌矿床硫化物中的S可能主要来源于对应地层本身。结合地球化学热力学分析,认为Pb、Zn等成矿元素的Cl络合物是成矿元素的主要搬运形式,富含Pb、Zn的成矿流体与赋矿地层中富含H_2S还原性流体的混合是铅锌富集成矿的重要机制之一。 相似文献
998.
右江盆地酸性脉岩继承锆石成因及地质意义 总被引:1,自引:1,他引:0
卡林型金矿与岩浆作用的关系一直以来是矿床学家关注的热点。右江盆地发育众多卡林型金矿床,但由于区内岩浆岩出露十分有限,岩浆活动对金成矿有无贡献目前还无定论。火成岩中的继承锆石常常可以用来指示早期的、隐伏的岩浆活动。桂西北地区晚白垩世巴马、料屯和下巴哈石英斑岩脉中含有大量的继承锆石。其中,料屯和下巴哈两处脉岩分别与料屯和明山金矿在空间上紧密相关。脉岩中锆石的LA-ICP-MS和SIMS原位U-Pb定年表明,其主要集中于130~140Ma、242Ma左右、400~450Ma、700~1000Ma和1700~1800Ma等五个年龄段。关于较年轻的两个时间段,来自料屯和下巴哈石英斑岩脉的继承锆石分别获得两组谐和年龄,即136.3±3.9Ma(2σ)和242.3±1.7Ma(2σ)、128.2±2.3Ma(2σ)和243.1±3.6Ma(2σ)。这些脉岩侵入的最年轻地层为中三叠统百逢组,因而前三叠纪继承锆石可能捕获自地层,而晚于三叠纪的130~140Ma锆石则应来自于深部隐伏岩体。关于242Ma左右锆石,尽管其与围岩地层百逢组1~2段近于同期,但其晶形较差且多呈不规则碎片状,暗示其更可能源自百逢组中的沉积碎屑锆石。结合区域地质背景,认为该期锆石所代表的岩浆事件可能与古特提斯洋闭合有关。以上130~140Ma和约242Ma左右的两组年龄,与初步确定的右江盆地卡林型金矿的两次成矿的时代基本一致,据此推断金矿化与岩浆作用可能有一定成因联系。 相似文献
999.
Effects of Material Composition and Water Content on the Mechanical Properties of Landslide Deposits Triggered by the Wenchuan Earthquake 总被引:3,自引:0,他引:3
Abundant landslide deposits were triggered by the Wenchuan earthquake, providing a rich source of material for subsequent debris flows or slope failures under rainfall conditions. A good understanding of the physical and mechanical properties of the landslide deposits is very important to the research on slope failure mechanisms and the initiation of debris flow. Laboratory biaxial compression tests are used to study the material compositions and water content impacts on the mechanical properties of landslide deposits, and a discrete element method (a bond-contact model) is used to study the particle stiffness, bond force, friction coefficient and confining stress impact on the mechanical behaviors and the relationships between the numerical and experimental parameters. The experimental results show that the failure stress of landslide deposits is decreased with increasing content of fine particles and also with increased water content, especially at the initial increasing stage. Cohesion of the saturated landslide deposits is increased, but the friction angle is decreased with the increase in the fine particle content. Shear strength parameters (the cohesion and friction angle) are decreased with the increasing water content at the initial increasing stage, and then, they slowly decrease. There is a critical value of the water content at 5%–7% (in weight) for the failure stress and shear strength parameters of the landslide deposits. Quadratic equations are presented to describe the relation between the bond force and cohesion, and the numerical friction coefficient and the experimental friction angle. 相似文献
1000.
Projected Shifts in Kppen Climate Zones over China and Their Temporal Evolution in CMIP5 Multi-Model Simulations 总被引:2,自引:0,他引:2
Previous studies have examined the projected climate types in China by 2100. This study identified the emergence time of climate shifts at a 1?scale over China from 1990 to 2100 and investigated the temporal evolution of K o¨ppen–Geiger climate classifications computed from CMIP5 multi-model outputs. Climate shifts were detected in transition regions(7%–8% of China's land area) by 2010, including rapid replacement of mixed forest(Dwb) by deciduous forest(Dwa) over Northeast China, strong shrinkage of alpine climate type(ET) on the Tibetan Plateau, weak northward expansion of subtropical winterdry climate(Cwa) over Southeast China, and contraction of oceanic climate(Cwb) in Southwest China. Under all future RCP(Representative Concentration Pathway) scenarios, the reduction of Dwb in Northeast China and ET on the Tibetan Plateau was projected to accelerate substantially during 2010–30, and half of the total area occupied by ET in 1990 was projected to be redistributed by 2040. Under the most severe scenario(RCP8.5), sub-polar continental winter dry climate over Northeast China would disappear by 2040–50, ET on the Tibetan Plateau would disappear by 2070, and the climate types in 35.9%and 50.8% of China's land area would change by 2050 and 2100, respectively. The results presented in this paper indicate imperative impacts of anthropogenic climate change on China's ecoregions in future decades. 相似文献