粤北新洲推覆构造同推覆期岩石体积变化的估算及其地质意义     

彭少梅 《地球科学与环境学报》1994,(1)

非平面应变状态下岩石体积变化的估算，一直是世界上悬而未决的问题。本文初步完善了实用于非平面应变状态下岩石体积变化的计算公式，并用这些公式计算了粤北新洲推覆体同推覆期的岩石体积变化。结果表明，在逆冲推覆时期，整个外来系统普遍发生了强烈的压溶－迁出作用．由此造成的岩石体积损耗平均达２２．８８％。同推覆期外来系统的巨大体耗，与同推覆期含金动力分异热液的形成和演化以及该区石英脉型金矿床成矿物质来源之间有着密切的内在联系．  相似文献   

晋陕豫交界区地震应变能的演变与地震趋势     

赵刚  卫金泉 《山西地震》1996,(1):31-34

本文采取动静结合、时空并举的方法，从地震应变能释放的时空分布入手，对晋陕豫交界区分时段进行了空间扫描计算，研究分析了１９７０年以来，该区的应变能释放的时空动态演变过程及其与地震的关系。指出该区地震活动存在着长趋势增强的背景。  相似文献   

Very high strains recorded in mylonites along the Alpine Fault, New Zealand: implications for the deep structure of plate boundary faults   总被引：1，自引：0，他引：1  

Richard J. Norris  Alan F. Cooper 《Journal of Structural Geology》2003,25(12):2141

Oblique displacement on the Alpine Fault, which forms the principal structure along the Australian–Pacific plate boundary in South Island, New Zealand, has resulted in exhumation of a kilometre-wide mylonite zone in the hanging wall adjacent to the current brittle fault trace. The mylonites formed under amphibolite facies conditions at depths of ca. 25 km and have been uplifted during the past 5 Ma. A suite of 65–70 Ma pegmatite veins in the hanging wall Alpine schists has been progressively deformed within the mylonite zone and sheared out over a strike length of ca. 100 km. Measurements of the thickness distribution of the pegmatite veins within the non-mylonitised schists and at three localities within the progressively strained mylonites have been used to estimate strain values within the mylonites. The thicknesses approximate a log-normal distribution, with a mean value that is progressively reduced through the protomylonites, mylonites and ultramylonites. By assuming that the thickness distribution currently observed in the schists was the same for the pegmatites within the mylonites before strain, a model of deformation incorporating simple shear and simultaneous pure shear is used to strain the undeformed veins until a fit is obtained with the strained distributions. Shear strains calculated range from 12 to 22 for the protomylonites, 120 to 200 for the mylonites and 180 to 300 for the ultramylonites, corresponding to pure shear values of 1–3 in each case. These values are compatible with the strains predicted if most of the surface displacement on the fault over the past 5 Ma were accommodated within a 1–2-km-wide mylonite zone through the middle and lower crusts. The results suggest that processes such as erosional focussing of deformation and thermal weakening may cause intense strain localisation within the lower crust, with plate boundary deformation restricted to narrow zones rather than becoming increasingly distributed over a widening shear zone with depth.  相似文献   

地表潮汐平面应变状态与地震关系的研究     

乔子云 《山西地震》2001,(1):30-33

以河北怀来台三方向伸缩仪为例，根据应变观测平面应变状态的基本理论和计算方法，通过计算得到了应变观测点的最大主应变、最小主应变、主应变方向和剪切应变的变化曲线，结合1989年10月18日山西大同－阳高6．1级地震和1998年1月10日河北张北6．2级地震，对地表平面应变状态与地震的关系进行了深入研究。得出如下结论：地表潮汐平面应变状态与地震存在一定的关系，而且在中强地震前地表潮汐平面应变状态表现出不同的变化特征。  相似文献   

黄石台ORBES-81型伸缩仪观测结果的调和分析及海潮改正   总被引：1，自引：1，他引：1  

周坤根  B. Ducarme  胡延昌 《地球物理学报》1991,(4)

本文对黄石台ORBES-81型石英伸缩仪的应变固体潮观测资料作了分析计算,其调和分析结果为:对O_1波,振幅因子0.4219,相位滞后6°36＇;对M_2波,振幅因子0.4256,相位滞后-4°42＇.同时,讨论了海潮引起的负荷潮汐应变的改正问题.模拟计算发现负荷潮汐应变与体潮应变大致为同一量级,文中列出了海潮改正后的结果,并作了讨论.最后,对黄石台伸缩仪的架设方位作了评价.  相似文献   

几个力学概念在构造地质学中的应用     

武红岭  王薇 《大地构造与成矿学》2003,27(2):109-114

本文对构造地质学中常用的几个力学概念在使用中出现的误解和问题进行了讨论,阐述了笔者的看法和建议,以期重新引起地学工作者应用力学的原理和方法解决地质构造问题的兴趣和热情,并期待更多的地质学家能正确地运用力学的相关知识探讨和解决地球动力学领域中的诸多疑难问题。  相似文献   

Changes in strain trajectories in three different types of plate tectonic boundary deduced from earthquake focal mechanisms     

J. L. Giner-Robles  J. M. Gonzlez-Casado  P. Gumiel  C. García-Cuevas 《Tectonophysics》2003,372(3-4):179-191

Principal strain orientations (minimum horizontal compression—ex and maximum horizontal compression—ey) were established at three different types of plate tectonic boundary: two transform faults, an oceanic ridge located on the Southeast Indian Ridge and a trench located close to the South Sandwich Archipelago. To establish the strain patterns in each zone, 104 earthquake focal mechanisms (centroid-moment tensor solutions for earthquakes with mb≥4; Harvard seismology data, CMT) were examined by fault population analysis. Despite the existence of only one tectonic process that controlled deformation in these zones (divergence, convergence or passive displacement), and only one main strain tensor, several coeval strain ellipsoids were found. These differed from the main strain tensor in the location of the principal strains. In general, permutations were observed between the principal strains, i.e., interchanges between the location of the principal strain axes maintaining the strain ellipsoids in the same 3D orientation. Only in some cases were changes in the ellipsoid orientation associated with major structures.  相似文献   

昆仑山口西8.1级地震与甘川应变变化的关系   总被引：2，自引：0，他引：2       下载免费PDF全文

高原  蒲小武  陈彦平  李凌飞  韩英  王金燕 《地震工程学报》2003,25(1):70-73

利用甘肃与四川4个钻孔应变台的资料进行受力分析后发现：中国西部存在着统一的应力场，2001年11月14日昆仑山口西8．1级地震破裂带的力学特征与这个统一应力场相一致．这些台的应变资料在震前都普遍存在明显的短临异常。  相似文献   

Mechanical stratigraphy as a factor controlling the development of a sandbox transfer zone: a three-dimensional analysis   总被引：3，自引：0，他引：3  

Antonio Ravaglia  Claudio Turrini  Silvio Seno 《Journal of Structural Geology》2004,26(12):2269-2283

In thrust belts, fold–fault terminations are common features of the structural architecture and can pose complicated problems to unravel, in particular when two or more terminations are in close proximity. Such terminations usually reflect pre-existing attributes. Amongst the many factors, lateral variations in the mechanical stratigraphy can control along-strike geometry and kinematics of fault-related folds.A displacement transfer zone was produced in a compressional sandbox model by means of two adjacent, mechanically different stratigraphic domains. The experiment allowed two discrete chains to develop in the different domains, so that a complex structural setting occurred in the connecting area. Periclinal folds, oblique thrust fronts and oblique ramps developed in the resulting transfer zone. The interaction between periclines in the transfer zone produced lateral culminations in the folded structures. The analysis of displacement across the structural domains revealed that a significant loss of slip along the faults occurred in the relay zone. In this area, imbricate faulting was partially replaced by layer-parallel shortening. A linear relationship appears to exist between the bed length of the thrust sheet and the related fault slip.  相似文献   

Reaction-induced weakening of plagioclase–olivine composites   总被引：1，自引：0，他引：1  

A.A. de Ronde  H. Stünitz  J. Tullis  R. Heilbronner 《Tectonophysics》2005,409(1-4):85-106

The localisation of strain into natural ductile shear zones is often associated with the occurrence of metamorphic reactions. In order to study the effects of solid–solid mineral reactions on plastic deformation of rocks, we have investigated the shear deformation of plagioclase–olivine composites during the reaction plagioclase + olivine → orthopyroxene + clinopyroxene + spinel (± garnet). Microstructures of plagioclase–olivine composites were studied after shear deformation experiments in a Griggs apparatus. Experiments were performed on anorthite–forsterite (An–Fo) and labradorite–forsterite (Lab–Fo) composites at 900 °C, confining pressures between 1000–1600 MPa and with constant shear strain rates of 5 × 10⁻⁵ s⁻¹.In absence of reaction, Lab–Fo composites are stronger than pure olivine and labradorite end-members that deform with a high temperature plasticity mechanism. Lab–Fo composites strain–harden due to the inhibition of extensive recrystallisation by interphase boundaries.In An–Fo composites, the reaction induces strain weakening by a switch from dislocation creep to grain size sensitive deformation mechanisms through the development of fine-grained (size < 0.5 μm) polyphase reaction products. Interconnecting layers of reaction products accommodate most of the applied strain by grain size sensitive creep. Recovery processes are pronounced during syndeformational reaction: original anorthite and olivine dynamically recrystallise by subgrain rotation and bulging recrystallisation. Presumably, the dynamic recrystallisation is caused by reduced stress conditions and partitioning of strain and strain rates between the new reaction products and the relict An–Fo grains. The results of our experiments are in good agreement with natural observations of shear localisation in the lower crust and upper mantle, and imply that anhydrous mineral reactions can be important causes for localisation of deformation.  相似文献