康古尔韧性剪切带变形特征及控矿作用

康古尔韧性剪切带具明显的遥感影像特征和区域重、磁异常变化特征。韧性剪切引起的变质作用表现为强应力下的岩石变质、变形，变质相序从绿片岩相到角闪岩相，变质岩石类型为千枚岩、片岩、变粒岩、糜棱岩及糜校岩化的岩石。韧性剪切变形和塑性流动形成的面理、线理、招皱、韧性断裂等构造形迹十分明显，构成一条东百长1000多千米，南北宽20～30km的狭长线形构造带（强应变带）；它经历了多期次、多种构造作用交替叠加的变化过程，按性质分类属大型平移断裂系统。康古尔韧性剪切带控制着重要的金矿、铜镍矿床及稀有金属等矿产，是新疆东部有重要找矿意义的成矿带。     

K_o固结粘土各向异性不排水剪强度研究

在三维各向异性弹塑性本构关系基础上，求解不排水条件和破坏条件，导出各种不同试验条件下K0团结粘土的各向异性不排水剪强度表达式。对常规超固结比定义下的不排水剪强度进行研究，将理论计算结果与试验结果进行比较，验证所提理论的合理性。     

Global shear stress pattern in main seismic active belts

ＧｌｏｂａｌｓｈｅａｒｓｔｒｅｓｐａｔｅｒｎｉｎｍａｉｎｓｅｉｓｍｉｃａｃｔｉｖｅｂｅｌｔｓＬＥＩＸＩＡＯ（肖磊）ＰＥＩ－ＳＨＡＮＣＨＥＮ（陈培善）ＩｎｓｔｉｔｕｔｅｏｆＧｅｏｐｈｙｓｉｃｓ，ＳｔａｔｅＳｅｉｓｍｏｌｏｇｉｃａｌＢｕｒｅａｕ，Ｂｅｉ...     

商丹三角地区花岗伟晶岩型铀矿成矿环境研究及远景评价

花岗伟晶岩型铀矿是目前发现的一种新类型铀矿。这种矿床的晶质铀矿是从花岗岩浆分异出来的富铀岩浆中结晶而成的。下元古界秦岭群是成矿有利环境,韧性剪切带是控岩控矿的主要构造。这种类型铀矿在商丹三角地区的远景是可观的。     

Microstructural analysis of the classical spiral garnet porphyroblasts of south-east Vermont: evidence for non-rotation

New data strongly suggest that the classical spiral garnet porphyroblasts of south-east Vermont, USA, generally did not rotate, relative to geographical coordinates, throughout several stages of non-coaxial ductile deformation. The continuity of inclusion trails (S_i) in these porphyroblasts is commonly disrupted by planar to weakly arcuate discontinuities, consisting of truncations and differentiation zones where quartz–graphite S_i bend sharply into more graphitic S_i. Discontinuous, tight microfold hinges with relatively straight axial planes are also present. These microstructures form part of a complete morphological gradation between near-orthogonally arranged, discontinuous inclusion segments and smoothly curving, continuous S_i spirals. Some 2700 pitch measurements of well-developed inclusion discontinuities and discontinuous microfold axial planes were taken from several hundred vertically orientated thin sections of various strike, from specimens collected at 28 different locations around the Chester and Athens domes. The results indicate that the discontinuities have predominantly subvertical and subhorizontal orientations, irrespective of variations in the external foliation attitude, macrostructural geometry and apparent porphyroblast-matrix rotation angles. Combined with evidence for textural zoning, this supports the recent hypothesis that porphyroblasts grow incrementally during successive cycles of subvertical and subhorizontal crenulation cleavage development. Less common inclined discontinuities are interpreted as resulting from deflection of anastomosing matrix foliations around obliquely orientated crystal faces prior to inclusion. Most of the idioblastic garnet porphyroblasts have a preferred crystallographic orientation. Dimensionally elongate idioblasts also have a preferred shape orientation, with long axes orientated normal to the mica folia, within which epitaxial nucleation occurred. Truncations and differentiation zones result from the formation of differentiated crenulation cleavage seams against porphyroblast margins, in association with progressive and selective strain-induced dissolution of matrix minerals and locally also the porphyroblast margin. Non-rotation of porphyroblasts, relative to geographical coordinates, suggests that deformation at the microscale is heterogeneous and discontinuous in the presence of undeformed, relatively large and rigid heterogeneities, which cause the progressive shearing (rotational) component of deformation to partition around them. The spiral garnet porphyroblasts therefore preserve the most complete record of the complex, polyphase tectonic and metamorphic history experienced in this area, most of which was destroyed in the matrix by progressive foliation rotation and reactivation, together with recrystallization.     

单轴向拉伸实验晶粒组构的变化

采用实验室制备的具有随机取向的细晶粒多晶冰 ,在温度为 - 3 .0± 0 .0 5℃、初始八面体剪应力为 0 .2 MPa和 0 .3 MPa下 ,对六个样品进行了单轴向拉伸实验。对应于八面体剪应力为0 .2 MPa的一次实验 ,最小应变率为 2 .6× 1 0 - 8s- 1;对应于八面体剪应力为 0 .3 MPa的其余五次实验 ,最小应变率平均值为 8.6× 1 0 - 8s- 1。六次实验最小应变率均出现在总八面体剪应变为1 .1～ 1 .6 %之间。晶粒 c轴组构随总应变增大向大环型发展 ,最终形成以组构平均半角趋于稳定在 6 5度左右的大环型组构 ,但在总八面体剪应变达 2 0 %之前 ,可能受组构图本身几何性质影响 ,组构平均半角随应变增加反而减小。对比压缩实验结果 ,拉伸实验最小应变率值与同等条件下压缩实验得到的最小应变率值一致 ,但最小应变率出现时对应的总应变稍大 ,c轴组构转变所需的总应变则更大。     

滇西高黎贡断裂带糜棱岩的显微变形特征及其构造意义

采用扫描电镜(SEM)、超高压透射电镜(HTEM)及电子探针等手段研究了主高黎贡断裂带糜棱岩的显微构造特征,提出长石经历了碎粒流动和部分固态塑性流变过程;而石英晶粒经历了动态重结晶和静态回复阶段。认为高黎贡剪切带是在相当于高绿片岩相—低角闪岩相的变质条件下形成的,是晚第三纪右旋走滑活动的产物。     

郯庐剪切带的性质和意义

沿郯庐断裂带从大别山东麓经山东中部至辽北吉南的新宾—桦甸地区,暴露的早前寒武纪结晶岩石中存在着一系列北北东走向的大型韧性剪切带,其最大宽度达20km,走向断续延伸近2000km,它们分别在大别、鲁西和新宾地区形成了巨大的弧形牵引构造。剪切带中不同尺度组构要素的几何学,指示其中曾经发生了一致的大幅度左行位移;变形岩石的显微构造和矿物组合特征,说明这一韧性剪切带早期形成于低角闪岩相条件下,并且在抬升和冷却过程中经历了绿片岩相条件下的递进变形。山东中部晚元古代以后的沉积不整合于韧性剪切带及其变形岩石之上,中生代未期脆性的郯庐断裂系统追踪并改造了基底岩石中的韧性剪切带。     

韧性剪切带形成的岩石流变学特征

 本文应用流变学有限元法,建立了韧性剪切带内的温度、应力、应变和位移之间的关系。并对加速蠕变和应变软化两种情况,给出了不同时刻韧性剪切带内的温度、应力、应变、应变率、位移和粘滞系数的分布特征,描述了岩石递进变形的规律。     

Development of composite planar fabric in mylonites along the Median Tectonic Line, southwest Japan

Abstract Mylonites along the Median Tectonic Line, southwest Japan commonly contain shear bands comprising S(-C)-Ss fabrics. This paper stresses the lithologic control on the orientation, dimension and development of shear bands by comparing the microstructure of the shear bands in different rock types (P mylonites, F mylonites, micaceous phyllonite and quartzose phyllonite). There is no significant change of the α angles (average 21–24°) between Ss and S toward the centre of the shear zone (viz. increasing the intensity of mylonitization) and it is different from the S-C relationship in a narrow sense.
The generation of the composite planar fabric can be classified into four different strain partitioning models: S only type without any slip surface (model A); S-C type (model B); S-Ss type with Ss-slip precedence (model C), and S-Ss type with S-slip precedence (model D). Model C is proposed in this paper and is similar to the model for the generation of Riedel shears in brittle shear zones. An unstable slip between porphyroclasts and the matrix during ductile flow can easily initiate shear bands. Formation of a composite planar fabric is initiated according to model A, followed by model C in conditions of increasing strain, and then model D when the angle between S and the shear zone boundary becomes small enough (α/2 = 10°) to produce S-slip. Thus the generation of the shear bands probably begins in the early stages of shear deformation and continues until the latest stages.