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971.
972.
Strain softening and microstructural evolution of anorthite aggregates and quartz-anorthite layered composites deformed in torsion 总被引:1,自引:0,他引:1
Shaocheng Ji Zhenting Jiang Richard Wirth Bin Xia 《Earth and Planetary Science Letters》2004,222(2):377-390
Torsion experiments of anorthite (An) aggregates and layered composites with equal volume fractions of quartz (Qtz) and An were performed in a gas-medium apparatus at a confining pressure of 400 MPa, temperatures from 1373 to 1473 K, and twist rates from 1.0×10−4 to 3.0×10−4 rad/s. Dense specimens were fabricated from An glass and Qtz crystalline powder using hot isostatic pressing (HIP) techniques. Both An aggregates and Qtz-An layered composites show a continuous strain weakening from a peak stress at γ=0.2-0.3 to γ=3.2, and steady-state flow has not reached under the experimental conditions. The weakening is even more pronounced in the layered composites than the monolithic aggregates, suggesting channeling or localization of flow into the weak material between strong layers. The sheared An specimens developed pervasively C-S-C′ structures which are similar to those observed in natural ductile shear zones. TEM and electron backscattering diffraction (EBSD) fabric analyses suggest that grain boundary migration recrystallization-accommodated dislocation creep with (010)[100] as the dominant slip system was operating in the An. The strain softening may be due to the development of crystallographic preferred orientation (CPO), the operation of dynamic recrystallization and the formation of extremely fine-grained recrystallized material in the narrow C′ shear bands. 相似文献
973.
扬子板块北缘碧口群火山岩的地球化学特征及其构造环境 总被引:26,自引:1,他引:26
碧口群火山岩系中部的基性熔岩以拉斑系列为主 ,基性火山岩的Sr同位素初始比值和Nd同位素初始比值较低 ,分别为 0 .70 12 4 8~ 0 .70 4 4 13和 0 .5 110 80~ 0 .5 12 341,大部分样品的εNd(t) >0 ,表明母岩浆主要来自地幔源区。岩石显示明显的富2 0 7Pb及2 0 8Pb特征。在以部分熔融作用为主的演化过程中岩浆发生了一定程度的分异 ,LREE、大离子亲石元素等表现了从亏损到富集的变化特点。基性熔岩的稀土与微量元素表现出与俯冲碰撞型的弧区玄武岩相同的特点。分析表明 :碧口群火山岩系形成于岛弧环境 ,它与横丹群浊积岩系在扬子板块西北缘构筑了一个弧盆系统 ,其时代为新元古代。 相似文献
974.
975.
X形和三角形钢板阻尼器的阻尼力模型(Ⅰ)--基于双线性本构关系 总被引:3,自引:1,他引:3
利用软钢的双线性本构关系,依据经典力学原理推导建立了X形和三角形钢板阻尼器的阻尼力滞回模型。首先,导出了单调加载下钢板阻尼器的力与位移关系及其渐近曲线;其次,对于软钢材料本构关系分别考虑在理想弹塑性和双线性强化模型基础上,推导建立了钢板阻尼器的阻尼力模型;最后,将钢板阻尼器的阻尼力模型及其参数与试验结果进行了比较,验证了理论模型的有效性,并分析了误差存在的原因。 相似文献
976.
Asbjrn Johan Breivik Rolf Mjelde Paul Grogan Hideki Shimamura Yoshio Murai Yuichi Nishimura 《Tectonophysics》2005,401(1-2):79-117
The western Barents Sea and the Svalbard archipelago share a common history of Caledonian basement formation and subsequent sedimentary deposition. Rock formations from the period are accessible to field study on Svalbard, but studies of the near offshore areas rely on seismic data and shallowdrilling. Offshore mapping is reliable down to the Permian sequence, but multichannel reflection seismic data do not give a coherent picture of older stratigraphy. A survey of 10 Ocean Bottom Seismometer profiles was collected around Svalbard in 1998. Results show a highly variable thickness of pre-Permian sedimentary strata, and a heterogeneous crystalline crust tied to candidates for continental sutures or major thrust zones. The data shown in this paper establish that the observed gravity in some parts of the platform can be directly related to velocity variations in the crystalline crust, but not necessarily to basement or Moho depth. The results from three new models are incorporated with a previously published profile, to produce depth-to-basement and -Moho maps south of Svalbard. There is a 14 km deep basement located approximately below the gently structured Upper Paleozoic Sørkapp Basin, bordered by a 7 km deep basement high to the west, and 7–9 km depths to the north. Continental Moho-depth range from 28 to 35 km, the thickest crust is found near the island of Hopen, and in a NNW trending narrow crustal root located between 19°E and 20°E, the latter is interpreted as a relic of westward dipping Caledonian continental collision or major thrusting. There is also a basement high on this trend. Across this zone, there is an eastward increase in the VP, VP/VS ratio, and density, indicating a change towards a more mafic average crustal composition. The northward basement/Moho trend projects onto the Billefjorden Fault Zone (BFZ) on Spitsbergen. The eastern side of the BFZ correlates closely with coincident linear positive gravity and magnetic anomalies on western Ny Friesland, apparently originating from an antiform with high-grade metamorphic Caledonian terrane. A double linear magnetic anomaly appears on the BFZ trend south of Spitsbergen, sub-parallel to and located 10–50 km west of the crustal root. Based on this correlation, it is proposed that the suture or major thrust zone seen south of Svalbard correlates to the BFZ. The preservation of the relationship between the crustal suture, the crustal root, and upper mantle reflectivity, challenges the large-offset, post-collision sinistral transcurrent movement on the BFZ and other trends proposed in the literature. In particular, neither the wide-angle seismic data, nor conventional deep seismic reflection data south of Svalbard show clear signs of major lateral offsets, as seen in similar data around the British Isles. 相似文献
977.
MING Caibing 《中国地球化学学报》2005,24(4):370-376
Zeolite/TiO2 composite photocatalysts were prepared by adding a certain amount of mordenite in TiO2, and degradation experiments on toluene through photocatalytic reactions were implemented. In this paper, these photocatalysts were characterized by using SEM, IR, RAMAN, XRD and UV-Vis to shed light on the microstructure and photocatalytic performance of the composite photocatalysts. The results indicated that the structural hydroxy of zeolite can participate in bonding reaction with TiO2, the addition of zeolite can greatly reduce the diameter of nanometer TiO2 particles in the composite photocatalysts, and enhance the ultraviolet light absorptance of the composite photocatalysts. When the percentage content of zeolite reached 20%, the photocatalytic performance of this catalyst would be highest, with the toluene conversion rate up to 94.58%. 相似文献
978.
通过对“CM桩复合地基”(以下简称CM地基 )承载力试验结果的分析 ,获得了一些有益的结论 ,对其在徐州地区的推广和应用提供参考。 相似文献
979.
文章介绍了地幔柱理论研究的一系列进展,诸如地幔柱特征、动力学模式及其地质意义。在重力分异过程中,随着地球质量不断向地心集中,地球自转动能也不断向地核集中,从而产生圈层分化和差异旋转。地核相对地壳、地幔高速旋转,具有巨大动能,旋转阻力不断将其转化为热能,在核幔边界聚积起来,为液核对流和热幔柱提供足够的能量。核幔边界是产生热幔柱的位置。阐明了地幔柱构造与板块构造的关系。地幔柱理论涉及地幔深部物质垂直运动的机制,对了解地球深部动力学机制有重大意义。 相似文献
980.