Magnetic fabrics of Paleozoic rocks across the Lachlan Transverse Zone from eastern New South Wales ∗     

C. Vérard  R. A. Glen 《Australian Journal of Earth Sciences》2013,60(8):1037-1048

The anisotropy of magnetic susceptibility (AMS) was systematically measured for samples collected across the Lachlan Transverse Zone in the Eastern Subprovince of the Lachlan Orogen, New South Wales. Although the degree of anisotropy is usually moderate to low, it can be shown that the origin of the magnetic fabric is generally composite. Many localities are witness to a tectonic influence in addition to a magnetic foliation preserved from the time of rock formation (compaction). Furthermore, some localities indicate the presence of superimposed magnetic fabrics, potentially associated with a Silurian east–west direction of shortening, and a younger north–south (?) direction of shortening. Finally, the progressive southwards change in orientation of the magnetic lineation in the Molong area from north–south to east–west and then back to north–south again south of the Lyndhurst–Neville Fault suggests that the Lachlan Transverse Zone coincides with, and reflects, a major cross-structure in the Eastern Subprovince. AMS is thus a powerful tool to help map the fabric of Paleozoic rocks in the Tasmanides. Additional data will be required to help obtain a comprehensive picture of the tectonic history of the region.  相似文献   

东喜马拉雅构造结墨脱剪切带特征及其区域构造意义   总被引：3，自引：1，他引：2  

董汉文  许志琴  李源  刘钊 《岩石学报》2014,30(8):2229-2240

东喜马拉雅构造结东、西两侧分别为墨脱剪切带和东久-米林剪切带,本文以墨脱剪切带为研究对象,从构造变形几何学和组构运动学方面进行详细研究。结果表明:①剪切带不同部位的变形性质具有逐渐演化的特征,基于产状、变形性质及变质程度等的变化将其从南到北分为三部分:NE走向具右行兼上盘下滑性质的阿尼桥-希让段、近N-S向具右行走滑性质的旁辛-达木段及N(N)W向具右行兼逆冲性质的甘登-加拉萨段;②在墨脱剪切带内识别出两类剪切变形:高温剪切变形和低温剪切变形。除了构造变形及岩相学证据外,石英EBSD组构数据显示区内高温剪切变形以{10■-0}a滑移系为主,对应的温度为550~650℃,达到高温角闪岩相,局部(北端和中段)还出现了{10■-0}c滑移系,温度更高,大于650℃,相当于下地壳的深度;低温剪切变形以{10■-1}a和{0001}a滑移系为主,对应的温度小于550℃,即剪切变形发生在绿片岩相或绿片岩相以下的构造环境。结合西界东久-米林剪切带的构造特征,推测在印度板块和欧亚板块碰撞之后,南迦巴瓦变质体受制于这两条剪切带而相对拉萨地体向北推移,并楔入拉萨地体之下。  相似文献   

新疆克拉玛依北西西向岩墙群侵位的磁组构证据     

李乐  侯贵廷  杨彦平  肖芳锋  王延欣 《地质学报》2013,87(6):814-822

准噶尔盆地西北缘克拉玛依地区广泛发育二叠纪中基性岩墙群,该区岩墙被认为是碰撞后伸展的典型产物.本文根据岩墙宏观野外特征和镜下显微构造分析(岩墙分支、捕虏体、矿物线理和定向斑晶)得出研究区北西西-南东东向岩墙侵位方向由北西西向南东东侵位.通过对该区岩墙边界采样后进行磁化率各向异性测量得到磁组构的最大磁化率长轴优势方位分布图和磁组构各向异性特征分析,进一步指示其岩浆以一定仰角由北西西向南东东侵位.结合克拉玛依地区岩墙群与达拉布特深大断裂的时空分布特征推测该区北西西向岩墙岩浆来源于北西侧的达拉布特断裂,岩浆沿着达拉布特深大断裂上侵到先存裂隙而形成岩墙.  相似文献   

长江三峡工程库首区仙女山断裂构造变形分析     

谭成轩 《大地测量与地球动力学》1992,(2)

本文运用磁组构及显微构造方法对仙女山断裂构造变形进行分析,进而为仙女山断裂的延仲发展问题提供了理论参考依据。  相似文献   

An important role for 21st century Amateur Earth Scientists     

John F. Potter 《Proceedings of the Geologists' Association. Geologists' Association》2010,121(3):252-255

  相似文献   

Density-dependent hydromechanical behaviour of a compacted expansive soil     

Hossein Nowamooz  Farimah Masrouri 《Engineering Geology》2009,106(3-4):105-115

To further our knowledge of the coupling between the hydraulic and mechanical behaviours of the swelling soils, this paper presents an experimental study on a bentonite/silt mixture using an osmotic odometer. A loading/unloading cycle was applied to samples with different initial dry densities (1.27, 1.48, and 1.55 Mg m^− 3) at different constant suctions (0, 2, and 8 MPa). We noted that the initial state of the soils after compaction significantly influenced the values of the apparent preconsolidation stress p₀(s), the virgin compression index λ(s), and the elastic compression index κ.These experimental results provided a sufficient database to interpret the mechanical behaviour of the swelling soil and define three yielding surfaces:

– the suction limit between micro- and macrostructure (s_m/M) and the suction limit between nano- and microstructure (s_n/m), which depend completely on the soil fabrics and the diameter separating the nano-, micro-, and macrostructure,

– the Loading Collapse (LC) curve, representing the preconsolidation stress variation as a function of suction,

– the Saturation Curve (SC), representing the variation of the saturation stress (P_sat) as a function of suction.

In general, we can state that the increase of compaction pressure unified the LC and SC surfaces and decreased the (s_m/M) value without modifying the (s_n/m) value.  相似文献   

大别造山带现今构造格局的形成——来自石英C轴组构的证据   总被引：3，自引：0，他引：3  

王勇生  江来利  朱光  宋传中 《岩石学报》2009,25(1):219-231

石英C轴组构常常记录递进变形过程中晚期增量变形的构造特征,因而可以通过对大别造山带内岩石中石英C轴组构的分析来确定造山带构造变形历史中的晚期变形事件的运动学特征。本次工作在大别造山带各单元中采集了一系列样品,对其进行石英C轴组构分析。石英C轴组构结果表明,北淮阳带就位于同造山折返第一阶段,其运动型式为上盘向NW的剪切变形;南大别高压—超高压榴辉岩带与宿松杂岩带就位于同造山折返第二阶段,运动型式表现为上盘向SE的剪切变形;北大别带就位于早白垩世穹状隆升过程中。北大别带在穹状隆升过程中表现为上盘向NW的运动型式,在深部可能存在向NW方向的下地壳物质的塑性流动。  相似文献   

High Temperature Strain Structures and Quartz C-Axis Fabrics from Mylonitic Rocks in the Ailaoshan-Red River Shear Zone, Yunnan, and Their Tectonic Implication   总被引：3，自引：0，他引：3  

LIU Junlai  TANG Yuan  XIA Haoran  GUO Qiang  TRAN My Dung  CAO Shuyun  WU Hujun  WU Wenbin  ZHANG Zhaochong  ZHAO Zhidan 《《地质学报》英文版》2010,84(6):1377-1390

<正>The Ailaoshan-Red River(ASRR) shear zone is one of the major Southeast Asian tectonic discontinuities that have figured the present tectonic framework of the eastern Tibet.Several metamorphic massifs are distributed linearly along the shear zone,e.g.Xuelongshan,Diancangshan, Ailaoshan and Day Nui Con Voi from north to south.They bear a lot of lines of evidence for the tectonic evolution of the eastern Tibetan at different crustal levels in different tectonic stages.Controversy still exists on the deformation structures,microstructures and their relationship with metamorphisms along the ASRR.In this paper detailed microstructural and EBSD(Electron Backscattered Diffraction) fabric analysis of some highly sheared granitic rocks from different massifs along the ASRR are conducted.High temperature structures and microstructures are preserved in unsheared gneisses,in weakly sheared xenoliths or in some parts of the highly sheared rocks(mylonites).Several types of high temperature quartz c-axis fabrics show symmetrical patterns or transitions from symmetrical to asymmetrical patterns.The former are attributed to coaxial deformation during regional shortening in an early stage of the Indian-Eurasian tectonic interaction and the latter are related to the transitions from coaxial compression to noncoaxial shearing during the post-collisional ASRR left lateral shearing.  相似文献   

Polymineralic orientation analysis of magmatic rocks using Electron Back-Scatter Diffraction: Implications for igneous fabric origin and evolution     

I. Romeo  R. Capote  R. Lunar  N. Cayzer   《Tectonophysics》2007,444(1-4):45-62

Electron Back-Scatter Diffraction (EBSD), which provides an easy way of acquiring large numbers of individual crystallographic orientation data from different phases, has been applied to the study of magmatic fabrics. Using this technique, the crystallographic preferred orientation (CPO) of plagioclase, biotite, orthopyroxene, hornblende and quartz in natural tonalites and quartzdiorites (from the Santa Olalla Igneous Complex, SW Iberia) deformed during the magmatic stage have been determined. Plagioclase is the coarser phase defining the main fabric in each sample, whereas biotite can display either the same fabric as plagioclase or a completely different one. The differences between these two phases occur because: (1) smaller phases interact with the larger ones to produce more random orientations, (2) under simple shear, finer phases can completely rotate giving a girdle included in the XZ plane, (3) finer phases can more easily preserve relict fabrics, while the coarser phases are completely reoriented by the last stress tensor. The last phases to crystallize show weak to completely random CPOs (hornblende) or completely random distributions (quartz). The study was completed with a shape preferred orientation analysis using the Intercept Method in order to detect weak magmatic lineations, and numerical modelling simulations of theoretically equivalent simple shear situations for each sample.  相似文献   

大别山北麓侏罗系一个典型的古冲积扇--凤凰台组   总被引：4，自引：0，他引：4  

金福全  王道轩  李双应  刘因 《安徽地质》2001,11(1):1-8

安徽境内大别山北麓，发育着一套晚侏罗世厚度近2000m的巨厚砾岩层——凤凰台组。这是一个具有特征结构构造的典型的冲积扇相沉积。沿山麓呈多个扇体相互叠王状分布。对其砾石成分研究。为大别山抬升时代，提供重要地质证据。  相似文献