【作者】 关会梅；

【导师】 刘俊来；

【作者基本信息】 吉林大学 ， 构造地质学， 2004， 硕士

【摘要】 中下地壳组成、结构与演化研究一直是地球科学研究中为人们关注的重要课题。作为中下地壳的重要组成，角闪石质岩石的流变性与力学表现直接制约着中下地壳的的属性与状态，影响着大陆岩石圈板块的表现。深入开展角闪石和角闪质岩石变形特点与变形机制的研究工作，将促进加深对于中下地壳岩石的蠕变规律与流变性的了解，进而建立完整和全面的地壳岩石圈力学和流变学结构模型。本文在野外地质调查与区域地质背景分析的基础上，重点应用光学显微分析、透射电镜分析、电子探针分析和变形形态组构计算机分析，以辽东古元古宙褶皱带高级变质角闪质岩石-斜长角闪岩中三种具有不同构造特点（片麻状、条带状和糜棱状）构造岩的显微构造分析为主，深入讨论了不同类型构造岩的岩石流动机制与变化规律，并结合前人开展的力学实验研究工作对于岩石圈力学与流变学结构进行了讨论。显微构造分析结果显示，具有不同构造特点的斜长角闪岩在很多方面有显著的差异。片麻状斜长角闪岩中角闪石的粒度粗大，呈短柱状，角闪石的轴比（短轴比长轴）在0.2～0.4之间，以0.3～0.4占优势；长石的延长性较低,但角闪石却具有明显的定向性，这说明岩石可能经历了一次不是很强的构造变形作用的改造。根据条带状斜长角闪岩中角闪石和斜长石的分异及定向性可以识别出主要由角闪石组成的劈理域和主要由长石组成的微劈石域组构。角闪石存在波状消光现象、晶体挠曲现象和长条形亚颗粒，亚颗粒的长轴平行于叶理方向。角闪石定向性比片麻状斜长角闪岩中角闪石定向性更为强烈，角闪石长轴在0～20°范围内密集分布；轴比集中在0.1～0.4之间。长石—角闪石边界为舌状且凸向角闪石,说明长石—角闪石边界的颗粒边界重结晶的边界移动方向为从长石向角闪石方向移动。长石具有弱的定向性，与叶理方向呈小角度相交，轴比在0.4～0.7之间。 糜棱状斜长角闪岩剪切变形强烈，变形特征明显,构成劈理域的角闪石定向性很强，组成糜棱叶理的主要矿物是斜长石和角闪石。角闪石的粒度在0.3～0.6 mm之间，轴比主要在0.1～0.2之间的高度集中，反映出角闪石单向延伸强烈。斜长石以个体形式存在，具有明显的定向性、大量的波状消光和亚颗粒，颗粒边界不规则，存在边缘细粒化，粒度集中在0.1～0.4 mm之间，轴比集中在0.2～0.5之间。长石具有强烈的定向性,斜长石的长轴集中于10°～35°之间，表明长石对叶理的形成起到了积极的促进作用。超微构造分析揭示出了角闪石矿物晶体内的位错结构及其组合形式。片麻状斜<WP=68>长角闪岩的晶格缺陷并不明显，仅局部可见少量的自由位错、环型位错、位错列、位错链和位错缠结。条带状斜长角闪岩的位错构造并不发育，只可见少数的位错构造，如环型位错和位错列；角闪石的毛发状超微构造比较普遍。和上述两种斜长角闪岩中的角闪石相比，糜棱状斜长角闪岩中的角闪石的超微构造现象比较丰富，出现的位错以自由位错和位错列为主。由电子探针对于角闪石和斜长石进行的成分分析及应用角闪石-斜长石地质温度计和角闪石地质压力计计算出三种不同构造类型的斜长角闪岩及其原岩的形成与变形温度-压力有着规律性的变化。原岩斜长角闪岩：P=2.94kbar；T=649.91℃；片麻状斜长角闪岩大约为P=5.34kbar；T=620.38℃；条带状斜长角闪岩大约为P=4.62kbar；T=644.95℃；糜棱状斜长角闪岩大约为P=5.12kbar；T=585.99℃。从温度和压力变化的趋势和规律，结合对原岩及三种构造岩显微构造特征分析认为，三种岩石类型是同一期变形不同阶段的产物。原岩斜长角闪岩形成于相对较低的压力和较高的温度环境中（早期伸展作用？）。在后期的变形和变质演化的递进过程中，相继出现了等温升压与其后的等压降温过程。这种过程最合理的解释，说明变形和变质作用发生于区域性收缩过程中。在递进变形作用过程中，塑性变形是斜长角闪岩流动和蠕变的主要形式，其中角闪石沿其平行于c轴各个方向的滑移作用普遍存在，尤其是条带状斜长角闪岩中的角闪石的变形机制出现了位错滑移的所有类型（平移滑移、双晶滑移和扭折）；片麻状斜长角闪岩中的角闪石主要是晶体在定向重结晶作用下形成的；糜棱状斜长角闪岩中的角闪石是在动态重结晶和双晶滑移作用共同作用的结果。斜长石的变形机制以晶质塑性变形和超塑性流动两种机制为主。片麻状斜长角闪岩中的斜长石是动态重结晶作用和其后的恢复作用的结果；条带状斜长角闪岩中的斜长石是通过亚颗粒旋转动态重结晶形成的；糜棱状斜长角闪岩中的斜长石的变形机制是晶质塑性变形和超塑性流动作用。结合前人对于斜长角闪岩的实验变形研究结果，修正的大陆岩石圈结构模型中岩石圈强度从地壳的表层开始，随着深度的加大，具有多峰表现，而在地壳不同层次上，不同强度带之间并非简单的突变，更多情况下属于由岩石成分渐变导致的强度的递进变化。另一方面，从完全脆性的上部地壳向完全塑性的下部地壳之间的转变也并不是一个简单的过程，随着温度的升高、岩石中制约性矿物成分（石英、长石、角闪石、辉石）流变性的改变以及由此而致岩石流变学状态发生显著的转变，岩石的变形机制也在逐渐变化。更多还原

【Abstract】 The composition, structure and evolution of the middle-lower crust has been an subject of extensive study in Earth sciences. Since amphibolites rocks constitute the major parts of the middle-lower crust, their rheological and mechanical behavior constrains the nature and state of latter, and therefore influences the evolution of continental plate. Detailed study on the deformation characteristics and deformation mechanisms of hornblende and hornblende rocks would promote understanding the creep laws and rheology of middle-lower continental crustal rocks, and establishing a comprehensive mechanical and rheological model of crustal lithosphere.This paper discusses about, from microstructural studies of three types of tectonites with different deformation characteristics (gneissic, banded and mylonitic structures) from high grade metamorphic amphibolites from the Paleoproterozoic Fold Belt in Liaodong Peninsula, the flow mechanisms of hornblende tectonites, on the basis of field geological investigation and analysis of geological settings, and by means of optical microstructural analysis, transmission electron microscope (TEM) analysis, electron microprobe analysis and digital shape fabric analysis. In combination with experiments preformed by Hacker, this thesis discusses the dynamic and rheological structure of the lithosphere.It is shown from microstructural analysis that amphibolites with different structural characteristics differ from each other distinctly in many aspects. Hornblende grains in gneissic amphibolites have a large grain size, short prism shape and their aspect ratios (short axis to long axis) between 0.2~0.4, with a maximum at about 0.3-0.4. Plagioclase grains are not strongly elongated, but hornblende grains have obvious crystallographic preferred orientation. It may suggest that the rocks have been transformed rather weakly during structural deformation.Cleavage domains mainly of hornblende grains and microlithons of plagioclase grains constitute the banded amphibolites. They result in differentiation and orientation of the hornblende and plagioclase grains in the amphibolites. Hornblende grains show undulose extinction, crenulation and strip subgrains with their long axes paralleling to foliation. The orientation of hornblende grains in banded amphibolites is much stronger than that in gneissic amphibolites. The orientations of long axes of the hornblende grains are centered between 0 and 20°. The grains have aspect ratios between 0.1 and 0.4. The hornblende-plagioclase contacts are amoeboid shaped, bulging into hornblende grains that indicate that direction of grain boundary migration toward hornblende grains during <WP=71>recrystallization. Plagioclase grains have weak orientation that intersect with foliation in rocks in a small angle. Their aspect ratios vary between 0.4~0.7. The mylonitic amphibolites experienced intensive shearing deformation and show obvious deformation characteristics. Hornblendes grains that make up the cleavage domains are strongly oriented. Both hornblende and plagioclase grains constitute mylonitic foliation. Hornblende grains have sizes varying from 0.3mm to 0.6mm and have aspect ratios highly concentrated between 0.1 and 0.2, indicating a strong unaxial extension. Plagioclase grains occur as single grains and are obviously oriented. There are lots evidences of deformation, as is undulose extinction, irregular grain boundaries, subgrains and boundary granulation. The grain sizes the plagioclase grains vary between 0.1mm and 0.4mm and have aspect ratios from 0.2 to 0.5. They are strongly oriented at 10°～35°in reference to the orientation of the direction of the thin sections, which imply that they may have contributed to the development of foliation in the rocks.Submicrostructural analysis revealed the dislocation substructures and dislocation associations. Minor amount of free dislocations, dislocation loops, dislocation arrays, dislocation chains and tangled dislocations are observed in hornblende grains from gneissic amphibolites. Dislocations are rare更多还原