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31.
岩质边坡设计坡角和锚固方案的确定 总被引:3,自引:0,他引:3
本文运用赤平极射投影、块体理论和岩体力学的基本原理, 试探求一种可供边坡工程设计采用的确定人工岩质边坡最大安全设计坡角和锚固方案的简易方法。 相似文献
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电吸附找矿方法寻找隐伏金矿床的研究 总被引:7,自引:0,他引:7
电吸附找矿方法是指对采集的样品在室内特别装置中通电,并用吸附体吸附试样中电运移元素,通过这些元素所形成的异常来发现矿体的一种方法,该方法是依据野外地电提取方法的理论发展起来的,具有设备简单,成本低,工效效率高,工作条件及质量容易控制等优点。 相似文献
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大营子蚀变岩型金矿床地质特征及控矿因素的研究 总被引:3,自引:0,他引:3
大营子蚀变岩型金矿主档是冀北地区新发现的一种金矿类型。矿体赋存于太古代角闪角变质岩系,特别是变质闪长岩体周边及内侧,受NE、NNE向剪切破碎带控制,常在其傍侧断裂形成羽状矿脉。 相似文献
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现代成矿预测若干理论述评 总被引:2,自引:0,他引:2
以成矿理论为支撑的现代成矿预测理论取得了长足的进展,对现代矿产勘查与评价实践工作具有重要的指导意义;据成矿预测理论近年来的进展,结合笔者等的研究工作体会,述评地质异常、矿床的成矿系列、矿床模型和超大型矿床勘查等成矿预测理论。 相似文献
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Chemical analyses suggest that the metavolcanic rocks of the Almas Greenstone Belt (AGB), Tocantins State, Brazil have a continental affinity, possibly related to a continental rift environment. They were metamorphosed to amphibolite facies during a regional tectono-metamorphic event (Dn), retrogressed to greenschist facies assemblages and then hydrothermally altered within dextral strike–slip shear zones (Dn+1). Fracture sets related to Dn+2 intersect Sn+1.The Paiol Gold Mine is one of several mineralised zones within metabasic and meta-intermediate rocks of the AGB. It exploits shoots of sulphide–Au–quartz mineralisation that occupy dilational zones approximately perpendicular to an elongation lineation (Ln+1) within mylonitic foliation Sn+1 (Sn+1=S within the S–C fabric). The dilational zones probably formed due to dextral displacement on sinistrally en echelon C surfaces. Minor amounts of gold may have been introduced or remobilised during Dn+2.Coexisting primary and pseudosecondary fluid inclusions in mineralised quartz veins from ore shoots comprise a high-salinity three-phase type (Type II) and a lower salinity two-phase type (Type I). Homogenisation temperatures for Type II inclusions range from 200 to 410 °C and Type I from 90 to 320 °C. The inclusions and their temperature ranges are believed to reflect heat exchange and some mixing between the two fluid types under relatively constant ambient temperatures, but variable (though broadly declining) fluid temperatures. This took place late in Dn+1 in conjunction with greenschist facies retrogression and localised hydrothermally induced metasomatism. 相似文献
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本文综合运用不同时代幔源包体平衡温压对比、玄武岩地球化学性质对岩石圈厚度的反演以及不同时代岩石圈地幔地球化学性质的对比的方法,把华北地块东部岩石圈的减薄时间限定在晚中生代至新生代之间。减薄的机制可能是华北东部地区晚白垩世以来大陆岩石圈的拉张作用。由于机械性拉薄和热、机械和化学侵蚀作用,岩石圈厚度最终减薄到70km以下。但古老的岩石圈地幔并没有完全因减薄而消失,残留部分受到了来自软流圈物质的强烈改造,使其Sr、Nd同位素组成类似于软流圈,但Os同位素没有受到明显的改变。改造后的岩石圈地幔成为华北地块东部新生代岩石圈地幔的主体。在时空上,岩石圈的减薄具有不均一的性质。 相似文献
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Derek Blundell Nicholas Arndt Peter R. Cobbold Christoph Heinrich 《Ore Geology Reviews》2005,27(1-4):333
Metallogenic provinces in Europe range in age from the Archaean to the Neogene. Deposit types include porphyry copper and epithermal Cu–Au, volcanic-hosted massive sulphide (VMS), orogenic gold, Fe-oxide–Cu–Au, anorthosite Fe–Ti-oxide and sediment-hosted base-metal deposits. Most of them formed during short-lived magmatic events in a wide range of tectonic settings; many can be related to specific tectonic processes such as subduction, hinge retreat, accretion of island arcs, continental collision, lithosphere delamination or slab tear. In contrast, most sediment-hosted deposits in Europe evolved in extensional, continental settings over significant periods of time. In Europe, as elsewhere, ore formation is an integral part of the geodynamic evolution of the Earth's crust and mantle. Many tectonic settings create conditions conducive to the generation of water-rich magma, but the generation of ore deposits appears to be restricted to locations and short periods of change in temperature and stress, imposed by transitory plate motions. Crustal influence is evident in the strong structural controls on the location and morphology of many ore deposits in Europe. Crustal-scale fault–fracture systems, many involving strike-slip elements, have provided the fabric for major plumbing systems. Rapid uplift, as in metamorphic core complexes, and hydraulic fracturing can generate or focus magmatic–hydrothermal fluid flow that may be active for time spans significantly less than a million years. Once a hydrologically stable flow is established, ore formation is strongly dependent on the steep temperature and pressure gradients experienced by the fluid, particularly within the upper crust. In Europe, significant fracture porosity deep in the crystalline basement (1%) is not only important for magmatic–hydrothermal systems, but allows brines to circulate down through sedimentary basins and then episodically upward, expelled seismically to produce sediment-hosted base-metal deposits and Kupferschiefer copper deposits. Emerging research, stimulated by GEODE, can improve the predicting power of numerical simulations of ore-forming processes and help discover the presence of orebodies beneath barren overburden. 相似文献