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31.
The diagenetic transformation of biogenic silica from opal-A to opal-CT was recognised on seismic reflection data over an area of 78 × 103 km2 on the mid-Norwegian margin. The opal-A/CT diagenetic boundary appears as a positive, high amplitude reflection that generally cross-cuts the hosting stratigraphy. We demonstrate that it is not a sea bottom simulating reflection (BSR) and also that is not in thermal equilibrium with the present day isotherms. We present arguments that three styles of deformation associated with the opal-A/CT reflection – polygonal faulting, regional anticlines and synclines and differential compaction folding – indicate that the silica diagenesis reaction front is fossilised at a regional scale. Isochore maps demonstrate the degree of conformity between the opal-A/CT reflection and three seismic horizons of Late Miocene to Early Pliocene age that potentially represent the paleo-seabed when ‘fossilisation’ of the reaction front took place. The seismic interpretational criteria for recognition of a fossilised diagenetic front are evaluated and the results of our study are integrated with previous studies from other basins of the NE Atlantic in order to determine if the arrest of silica diagenesis was diachronous along this continental margin. 相似文献
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A constitutive model for mechanical and chemo‐mechanical compaction in sedimentary basins and finite element analysis
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Compaction and associated fluid flow are fundamental processes in sedimentary basin deformation. Purely mechanical compaction originates mainly from pore fluid expulsion and rearrangement of solid particles during burial, while chemo‐mechanical compaction results from Intergranular Pressure‐Solution (IPS) and represents a major mechanism of deformation in sedimentary basins during diagenesis. The aim of the present contribution is to provide a comprehensive 3D framework for constitutive and numerical modeling of purely mechanical and chemo‐mechanical compaction in sedimentary basins. Extending the concepts that have been previously proposed for the modeling of purely mechanical compaction in finite poroplasticity, deformation by IPS is addressed herein by means of additional viscoplastic terms in the state equations of the porous material. The finite element model integrates the poroplastic and poroviscoplastic components of deformation at large strains. The corresponding implementation allows for numerical simulation of sediments accretion/erosion periods by progressive activation/deactivation of the gravity forces within a fictitious closed material system. Validation of the numerical approach is assessed by means of comparison with closed‐form solutions derived in the context of a simplified compaction model. The last part of the paper presents the results of numerical basin simulation performed in one dimensional setting, demonstrating the ability of the modeling to capture the main features in elastoplastic and viscoplastic compaction. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
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三山岛金矿控矿断层F1的力学性质及补强措施 总被引:1,自引:0,他引:1
作者以正在开采中的三山岛金矿采场为研究对象,分析矿区开采过程中的岩体结构特征及重力方向矿柱、护顶矿柱与控矿断层F1断层泥及其上覆岩体之间的关系和力学机制。通过试验研究了断层泥的物质成分和力学性质,总结了力学特性与断层泥厚度及含水量之间的关系。在此基础上提出锚固大于中倾角的结构面,提高结构面的抗滑阻力;增加含有高、陡倾角结构面矿柱的刚度等对矿柱的补强措施。对护顶矿柱提出预先锚固;分阶段开采的补强方法。在裂隙密集带设置排水设施,改善断层泥的赋存条件,提高它的力学性能。 相似文献
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Summary In many parts of the world, particularly in humid tropical regions, residual soils are abundant. In this paper the suitability of a residual lateritic soil as a construction material is investigated, with respect to its strength and compaction characteristics. In comparison with other typical construction fills available in Southeast Asia, compacted lateritic soils produce excellent shear strengths and CBR values. However, the brittleness and tensile cracking of this compacted material become enhanced on the dry side of the optimum moisture content, or if excessive compaction is imparted. Nevertheless, at a moisture content of 2% wetter than the optimum, the tensile mode of failure is suppressed and the lateritic fills become ideally suited for the construction of high embankments and impervious dam cores. 相似文献
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介绍滇中红层形成的地质历史背景,红层分布范围,主要地层岩性及区内地质构造。重点讨论滇中红层特别是红层软岩的岩体原生结构,及后期受构造改造的岩体结构特性,岩体风化特性,岩体水理作用特性,岩体物理力学性质等四方面的工程地质特性。 相似文献
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Andrew G. Tomkins 《Mineralium Deposita》2007,42(6):627-637
The relative importance of mechanical re-mobilisation, hydrothermal dissolution and re-precipitation, and sulphide melting
in controlling redistribution of metals during concurrent metamorphism and deformation is evaluated at the middle amphibolite
facies Montauban deposit in Canada. As at many other deposits, ductile deformation was important in driving mechanical re-mobilisation
of massive sulphides from limb regions into hinge regions of large-scale folds and is thus the most important for controlling
the economics of Pb and Zn distribution. Two possible stages of hydrothermally driven re-mobilisation are discussed, each
of which produces characteristically different alteration assemblages. Prograde hydrothermal re-mobilisation is driven by
pyrite de-sulphidation and concurrent chlorite dehydration and is thus an internally driven process. At Montauban, the H2S-rich fluid generated through this process allowed re-mobilisation of gold into the wall rock, where it was deposited in
response to sulphidation of Fe Mg silicates. Retrograde hydrothermal re-mobilisation is an externally driven process, whereby
large volumes of fluids from outside the deposit may dissolve and re-precipitate metals, and cause hydration of silicate minerals.
This second hydrothermally driven process is not recognised at Montauban. Sulphide melting occurred as temperatures neared
the peak metamorphic conditions. Melting initiated in the massive sulphides through arsenopyrite breakdown, and a small volume
of melt was subsequently re-mobilised into the wall rock. Trace element partitioning and fractional crystallisation of this
melt generated a precious metal-rich fractionate, which remained mobile until well after peak metamorphism. Thus, prograde
hydrothermal re-mobilisation and sulphide melting were the most important mechanisms for controlling the distribution of Au
and Ag. 相似文献
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