【作者】 王根厚；

【导师】 宋鸿林；

【作者基本信息】 中国地质大学（北京） ， 构造地质学， 2006， 博士

【摘要】 藏东他念他翁山链变质杂岩系自北而南可以划分为吉塘变质杂岩带和嘉玉桥变质杂岩带。以构造解析为指导,以岩石流变学理论为基础,采用显微构造与宏观构造、构造变形与变质作用及同位素年代学相结合的思路,对吉塘变质杂岩带和嘉玉桥变质杂岩带构造变形、表露机制进行研究。嘉玉桥变质杂岩系包括卡贡褶叠层岩组、嘉玉桥片岩组(透入性韧性流变层)、同卡片麻岩组,各岩组之间通过韧性剪切带依次叠置。拉伸线理具SE140°—NW320°优选方位。综合宏观和微观运动学标志分析,运动学特点为上层系相对下层系自南东(140°)向北西(320°)剪切运动。对多硅白云母石英构造片岩中的石英颗粒进行应变测量,求出费林参数k=∞,表明应变椭球体为伸长的雪茄状,构造变形机制为单向伸展。由石英位错密度估算其差应力值为149.5 MPa。利用兰伯特(1959)法求出主期变形多硅白云母的形成温度为383.27℃,结合矿物组合及矿物变形为分析,主期变形具中-高绿片岩相的变质背景。根据笔者(1993)对杂岩系不同地段主期变形矿物的40Ar/39Ar法年龄测值,其角闪石坪年龄为(164.7±1.33)Ma;多硅白云母坪年龄为(166.27±0.99)Ma。两组数值相当吻合,并与杂岩系的沉积盖层时代(J1-2)及班公湖—怒江缝合带伸展扩张时代(J2)大体相当。对不同变形世代多硅白云母测温表明,主期变形之前的白云母形成温度高于主期白云母形成温度,分析认为主期之前变形变质环境局部可达角闪岩相,主期变质环境为中-高绿片岩相。吉塘变质杂岩系包括酉西片岩组、恩达片麻岩组。酉西岩组主要由钠长石白云母石英构造片岩组成,构造片理为近水平韧性剪切作用产物。构造片理上广布一期透入性拉伸线理,透入性片理上的线理具明显优选方位,方向为280°～100°。根据微观构造分析,韧性剪切指向为自西向东运动。对多硅白云母石英构造片岩中的石英颗粒进行应变测量,求出费林参数K=∞,表明应变椭球体为伸长的雪茄状,构造变形机制为单向伸展。由石英位错密度估算其差应力值为108.8 MPa、140.00 MPa。多硅白云母电子探针分析结果认为其形成环境为低温高压蓝片岩相,变质温度确定为320～500℃、压力0.6～1.1 GPa。多硅白云母40Ar/39Ar r测年结果为(230±1)Ma,为中三叠世末期。更多还原

【Abstract】 Tanitawen Mt. Range Metamorphic Complex (TMC) is located in the central partof the orogenic belt between Nujiang and Shuanghu-Chawula-Jitang sutures. The TMCis composed of Jitang metamorphic complex belt in the north and Jiayujqiaometamorphic complex in the south. This thesis analyses the deformation and exposedmechanism of both belts on the basis of analysis of rock rheology, including micro-and macro-deformation, metamorphism and geochronological constraints.The exposed tectono-column of Jiayuqiao metamorphic complex is composed ofKagong rock formation (folding layer), Jiayuqiao schistose formation and Tongka rockformation (gneiss). They flank on each other but separated by ductile shear zone.Penetrative mineral lineation on schistosity has preferred stretch orientation ofSE140-NW320, and micro-and macro-kinematic sense indicates NW-ward (320)shearing. Strain measurement and plots in the Flinn diagram for the quartz grain in thePhengites-bearing quartz schist give k=∞, indicating the Cigar-type strain ellipsoidand monaxial extension, embodying the NW-ward linear flow was formed by straightshearing strain in deep layer. The differential stress is estimated to be 149.5 MPa fromthe dislocation density of quartz from the metamorphic complex, and the phengitesformation temperature is 383.27℃ by using Ranbort method (1959), thus themetamorphic grade of the complex is inferred to be mid-to igh-greenschist during themajor deformation. The author (1993) got the Ar-Ar amphibole plateau age of164.7±1.33 Ma, and the Ar-Ar muscovite plateau age of 166.27±0.99 Ma for thecomplex. Both ages are approximately similar to the cover deposit, or the extendingtime (J2) of the Bangong-Nujiang suture zone, and thus reveal a synchronizationprocess during the major deformation and exposing for Jiayuqiao metamorphiccomplex. It is interpreted that this process formed in a extension mode withdetachment in the shallow, while ductile shear deformation in the deeper.The exposed tectono-stratigraphic column of Jitang metamorphic complex iscomposed of Youxi rock formation (schist) and Endayan rock formation (gneiss).Youxi schistose formation outcrops are distributed in the north of Baqen country, Tibet,and are composed of quartz schist, albite-quartz schist, muscovite-quartz schist withlevel penetrative schistosity and mineral lineation. The schistosity of the rockformation manifests the open antiform and synform, and the mineral lineation haspreferred orientation at 100～280° when unfold the antiform. Micro-fabric analysis ofthe ductile shear deformation indicates eastward kinematics. Strain measurement andplots in the Flinn diagram of the quartz grains in the Phengites-bearing quartz schistgives k=∞, indicating the Cigar-type strain ellipsoid and monaxial extension. ElectronMicroprobe analysis for the metamorphic mineral identified a composition ofphengites, which was further determined to be formed at a temperature of 320~500℃and a high-pressure of 0.6-1.1 GPa. The temperature-pressure condition represents agrade of blueschist metamorphism. The Ar-Ar method for the Phengite yields an age of230±1Ma, corresponding to the end of middle Triassic.更多还原