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排序方式: 共有326条查询结果,搜索用时 218 毫秒
71.
文章以青藏高原东缘龙门山活动构造的地貌标志为切入点,在汶川-茂汶断裂、北川断裂、彭灌断裂和大邑断裂等主干活动断裂的关键部位,对断错山脊、洪积扇、河流阶地、边坡脊、断层陡坎、河道错断、冲沟侧缘壁位错、拉分盆地、断层偏转、砾石定向带、坡中槽、弃沟和断塞塘等活动构造地貌和断裂带开展了详细的野外地质填图和地貌测量,利用精确的地貌测量数据和测年数据,定量计算了龙门山主干断裂的逆冲速率和走滑速率,结果表明在晚新生代时期龙门山构造带仅具有微弱的构造缩短作用,其中逆冲速率的速度值小于1.1mm/a,走滑速率的速度值小于1.46mm/a,表明走滑分量与逆冲分量的比率介于6 ∶ 1~1.3 ∶ 1之间,以右行走滑作用为主。在此基础上,对各主干活动断裂的逆冲速率和走滑速率进行了定量的对比研究,结果表明自北西向南东4条主干断裂的最大逆冲分量滑动速率具有变小的趋势,而走滑分量的滑动速率则具有逐渐变大的趋势,显示了从龙门山的后山带至前山带主干断裂的走滑作用越来越强。由此推测现今的龙门山及其前缘盆地不完全是由于构造缩短作用形成的,而主要是走滑作用和剥蚀卸载作用的产物。另外,根据沉积、构造、盆地充填体的几何形态、地貌、古地磁等标定和对比了龙门山在中生代和新生代的走滑方向,表明龙门山构造带在中生代与新生代之交走滑方向发生了反转,即由中生代时期的左行变为新生代时期的右行。 相似文献
72.
Elisabeth Kastellet Atle Nesje & Einar Solheim Pedersen 《Geografiska Annaler: Series A, Physical Geography》1998,80(1):51-65
Documentary data provide long time series and sometimes high-resolution, detailed data from historical times to the present and can give valuable information about palaeoclimate, and for the prediction of future climates. In this paper, documentary data containing qualitative information on climate, in the form of a diary written by the farmer I.G. Grude, and two newspapers, were used for the reconstruction of the palaeoclimate at Jæren, in the county of Rogaland, in southwestern Norway, during the period 1821–50. An index method to quantify the qualitative climate data was developed and used for a low-resolution reconstruction of winter, summer and annual temperatures. A high-resolution climate reconstruction of temperature and precipitation for the winter of 1837/38 is also presented, making use of a method that keeps the climate data in a qualitative form. The climate reconstructions are compared to an instrumental temperature series from Bergen, for the same period. The two data sets are in good agreement except for summer temperature (annual temperature: r = 0.75, winter temperature: r = 0.77, summer temperature: r = 0.44). Compared to average temperatures during 1961–90, the instrumental data from Bergen during the 1821–50 period show slightly different temperatures: annual average was 0.3°C lower, winter 0.4°C lower, and summer 0.1°C lower than at present, implying conditions consistent with the "Little Ice Age" climate. 相似文献
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74.
在分析了武义地区构造、岩性、地球化学和现有萤石矿床蚀变类型和编制出1:50000遥感解译地质图基础之上,提出本区的萤石控矿因素及遥感找矿标志,建立遥感找矿模型。用主成分分析方法提取与萤石矿化密切相关的硅化、高岭土化蚀变信息,用“证据权重模型”法进行区域找矿预测;找到了断裂硅化蚀变带。 相似文献
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76.
Expertsystemforearthquakeprediction(ESEP)(2)-KnowledgerepresentationandevidencecombinationHong-ShunFAN(范洪顺)andBi-QuanWANG(王碧泉... 相似文献
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78.
BassamFAIBassam 《中国地质大学学报(英文版)》2003,14(3):283-292
Gengma region, Sanjiang district is known to have some large-scale gold deposits. GIS predictive model for hydroghermal gold potential was carried out in this region using weights of evidence modeling technique. Datasets used include large-scale hydroghermal gold deposit records, geological, geophysical and remote sensing imagery. Based on the geological and mineral characteristics of areas with known gold occurrences in Sanjiang, several geological features were thought to be indicative of areas with potential for the occurrence of hydroghtermal gold deposits. Indicative features were extracted from geoexploration datasets for use as input in the predictive model. The features include host rock lithology, geologic structures, wallrock alteration and associated (volcanic-plutonic) igneous rocks. To determine which of the indicative geological features are important spatial predictors of area with potential for gold deposits, spatial analysis was done through the modeling method. The input maps were buffered and the optimum distance of spatial association for each geological feature was determined by calculating the contrast and studentized contrast. Five feature maps were converted to binary predictor patterns and used as evidential layers for predictive modeling. The binary patterns were integrated in two combinations, each of which consists of four patterns in order to avoid over prediction due to the effect of duplicate features in the two structural evidences. The two produced potential maps define almost similar favorable zones. Areas of intersections between these zones in the two potential maps placed the highest predictive favorable zones in the region. 相似文献
79.
Qualitative and quantitative knowledge about the spatial association between mineral occurrences and geological features are important in mineral potential mapping. Two existing methods for quantifying spatial association between mineral occurrences and curvilinear geological features are applied to the Baguio district of the Philippines. An experimental method is described and applied to the study area as well. The results of the three methods are highly similar, which demonstrates the effectiveness of the experimental method presented here for quantifying spatial association between mineral occurrences and curvilinear geological features. It is shown that gold occurrence in the Baguio district are strongly spatially associated with northeasterly trending faults/fractures rather than with northwesterly trending faults/fractures. It is also shown that the spatial association between the gold occurrence and older batholithic intrusives is stronger than the spatial association between gold occurrence and younger porphyry intrusives. These spatial geoinformation characteristics can be used as evidential data layers in GIS-based mineral potential mapping. 相似文献
80.
胶东金矿形成期间地幔流体参与成矿过程的碳氧氢同位素证据 总被引:57,自引:21,他引:57
胶东地区发育有两种类型的金矿床,以玲珑,焦家,三山岛,乳山为代表的石英脉型-破碎蚀变岩型和以大庄子,蓬家夼为代表的胶莱盆地北缘滑脱破碎带内的角砾岩型金矿,本文选择了两种类型中的玲珑,三山岛和大庄子金矿床进行碳氧氢同位素测定。初步认为两类金矿属于同一成矿系统,它们形成于120Ma左右的华北克拉通岩石圈减薄和软流圈上涌期间,岩浆流体和地幔脱气与胶东世界级金矿的形成密切相关,在石英脉型-破碎蚀变岩型矿石中可见深刻的地幔流体和岩浆流体的“烙印”。形成于滑脱破碎带中的角砾岩金矿流体与中生代大气降水和海相碳酸盐岩发生了强烈的交换作用。 相似文献