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本文通过对大青山山前活动断裂带上的变形产物进行定向采集、原态固结并进行系统微观观测，结合宏观和实验岩石学资料分析，归纳出能反映该断裂运动特性的微观粘滑与蠕滑标志，并对有关问题进行了讨论。 相似文献
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Shaocheng Ji Kazuko Saruwatari David Mainprice Richard Wirth Zhiqin Xu Bin Xia 《Tectonophysics》2003,370(1-4):49-76
Ultra high-pressure (UHP) eclogites from Sulu region (China) represent mafic components of the continental crust, which were first subducted to mantle depths greater than 100 km and then exhumed to the earth's surface. Detailed investigation of microstructures, chemical compositions, petrofabrics and seismic properties of the UHP eclogites can provide important information on the operating deformation mechanisms and rheology of subducted continental crust and on the origin of seismic reflections within the upper mantle. We present here results from field, optical and TEM observations, electron back-scattered diffraction (EBSD) measurements and numerical computations of the seismic properties of UHP eclogites collected from fresh surface outcrops at the drill site (Maobei, Donghai County, Jiangsu Province) of the Chinese Continental Scientific Drilling Program (CCSD). Two types of eclogites have been distinguished: Type-1 (coarse-grained) eclogites deformed by recovery-accommodated dislocation creep at the peak metamorphic conditions, and Type-2 (fine-grained) eclogites which are composed of reworked Type-1 materials during recrystallization-accommodated dislocation creep in shear zones which were active during the exhumation of the UHP metamorphic rocks. Both garnet and omphacite in these eclogites deformed plastically and the flow strength contrast between these two constituent minerals is apparently much less than an order of magnitude under the UHP metamorphic conditions. Plasticity of eclogites under UHP conditions can effectively facilitate channeled flow along the interplate shear zone. The preservation of the relict crustal materials within the continental lithosphere may produce regionally extensive, strong, seismic reflections in the upper mantle. This may explain the origin of mantle reflections observed in many areas of the world. 相似文献
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Recent interpretations of upper continental mantle seismic anisotropy observations have often relied on fabric measurements and calculated anisotropies of upper mantle xenoliths. Seismic ray paths of P and S waves, which provide information on azimuthal compressional wave anisotropy and shear wave splitting, are tens to hundreds of kilometers, whereas, xenoliths are usually only a few centimeters in diameter. To place better constraints on field-based anisotropy observations and to evaluate anisotropy information provided by xenoliths, it is important to examine anisotropy in large ultramafic massifs which have originated in the upper mantle. One such massif is the Twin Sisters Range located in the western portion of the North Cascades of Washington State, USA. The Twin Sisters massif, a slab of unaltered dunite, is 16 km in length, 6 km in width and 3 km thick. Exposed along its south and west sides are mafic granulite facies rocks, which likely represent lower continental crustal fragments. The ultramafic rocks are porphyroclastic in texture, consisting of strained, flattened porphyroclasts of olivine and enstatite and strain-free olivine mosaics. Olivine fabrics are typical of those formed at high temperatures and low strain rates. Petrofabrics and calculated anisotropies of individual samples vary throughout the massif, however, overall anisotropy of the body is significant, with maximum P and S waves anisotropies of 5.4% and 3.9%, respectively. The maximum delay time for split shear waves traveling through a 100-km-thick slab is 0.8 s and two directions of shear wave singularity are observed. The directions of maximum shear wave splitting and shear wave singularities do not coincide with the directions of maximum and minimum compressional wave velocity. In general, individual hand samples show significantly higher anisotropy than the overall anisotropy of the massif. It is concluded that simple averages of xenolith anisotropies are unreliable for use in the interpretation of field anisotropy observations. 相似文献
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We thank Karato for his interest in our recent paper in Tectonophysics [Xu, Z.Q., Wang, Q., Ji, S.C.. Chen, J., Zeng, L.S., Yang, J.S., Chen, F.Y., Liang, F.H., Wenk, H.R., 2006. Petrofabrics and seismic properties of garnet peridotite from the UHP Sulu terrane (China): Implications for olivine deformation mechanism in a cold and dry subducting continental slab. Tectonophysics 421, 111–127]. However, Karato is incorrect to take water or water-related species (herein referred to generically as ‘water’) as an almost unique cause for any olivine fabric transition in nature no matter what geological conditions are. In this Reply, we will first give a succinct introduction to the context of the ongoing debate, and then provide some additional arguments in favour of our conclusion that “the olivine C-type fabric of the Zhimafang garnet-bearing peridotites was formed under the conditions of high pressure, low temperature and low water content during the subduction of cold and dry supracrustal rocks of the Yangtze plate”. The map of olivine slip systems as a function of differential stress and water content, drawn by Karato and coworkers, cannot be reliably extrapolated to Earth’s interior until relevant scaling laws have been established. The role of high water content on the fabric transitions is more likely to modify recrystallization kinetics than to switch the dominant slip systems. 相似文献
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利用20% 浓度的氢氟酸（HF）对橄榄石晶体不同方向之切面进行了腐蚀实验,以期建立三维立体构型。在晶体上选
取垂直任一结晶轴的单形,如（100）,（010）,（001）等平行双面,（110）,（011）,（101）等菱方柱和（111）菱方双锥进
行了腐蚀实验,由原子力显微镜记录各个切面腐蚀像。结果显示,相同切面上的腐蚀像具有固定的几何形状及角度,且在
晶面上的结晶学方向固定。各腐蚀像形状具有共性,即长轴为[010] 方向,短轴为[100] 方向。由不同切面腐蚀像的变化规律,
建立了橄榄石腐蚀像三维立体模型。相同腐蚀剂对不同晶面腐蚀的容易程度差异巨大,以蚀坑在DIC200× 下能清晰观察到
腐蚀像形态为标准,橄榄石各切面的腐蚀速率为v（010）>v（110）>v（100）>v（111）>v（101）>v（001）>v（011）。由橄榄石晶体腐蚀像的唯一
性及其结晶学定向,在橄榄岩切片中将橄榄石颗粒切面指数化,并获得其结晶学定向及结晶优选方向。由此,在大别山碧
溪岭石榴子石二辉橄榄岩中推断橄榄石[100] 主极密垂直面理面,[010] 主极密平行于线理面。腐蚀像所确定的晶体结晶优选
性为当地构造动力提供了一定有价值资料,开拓了腐蚀像的地质应用意义。 相似文献
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The Peloritani Mountain Belt (north-eastern Sicily) represents the connection between the Southern Appenninic Range and the Appenninic Maghrebid Chain. The lithotypes outcropping in a 36 km long and approximately 8 km wide area in the eastern part of the Peloritani Mountains are considered to represent most properly the composition of the lower crust. We selected 7 representative samples of silicate rocks (amphibolite, paragneisses, augen gneiss, phyllitic quartzite, pegmatitic rock) and 3 samples of calcite rocks (calc-schist, marbles) for the petrophysical measurements. Measurements were done on sample cubes of dry rocks in a multi-anvil apparatus. Raising of pressure gives rise to velocity increase, but the rate is different in the silicate and calcite rocks and closely related to progressive closure of microcracks. Linear behaviour is approached above about 200 MPa. Increasing temperature at 600 MPa decreases velocities in most silicate and in the calcite rocks with almost linear slopes. Substantial anisotropy of P- and S-wave velocities and shear wave splitting is found in both rock types. The residual anisotropy observed above about 200 MPa is attributed to lattice preferred orientations (LPO) of major minerals. 3D velocity calculations for an amphibolite, a paragneiss and a marble sample based on the LPO of hornblende, biotite and calcite, respectively, confirm the experimental findings of a close relationship between velocity anisotropy, shear wave splitting, shear wave polarization, lattice preferred orientation and the structural frame of the rocks (foliation, lineation). In the silicate rocks, the intrinsic (600 MPa) average P-wave velocities and Poisson's (Vp / Vs) ratios exhibit a tendency for a linear increase with densities, whereas the three calcite rocks cluster at markedly higher P-wave velocities and Poisson's (Vp / Vs) ratios, compared to their densities. In the silicate rocks, there is also a linear trend for an inverse relationship between the SiO2 content, density and the Poisson's (Vp / Vs) ratio, respectively. 相似文献
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