Tectonics of the western margin of the Shan plateau (central Myanmar): implication for the India–Indochina oblique convergence since the Oligocene     

Guillaume Bertrand  Claude Rangin 《Journal of Asian Earth Sciences》2003,21(10):1139-1157

We present new data and interpretations on the Neogene tectonics of the Shan scarp area (central Myanmar) and its relationship with the India–Indochina oblique convergence. We describe ductile and brittle fabrics associated with the major features in this area, the Mogok Metamorphic Belt (MMB), the Shan scarp and the Sagaing fault. From these data we identify a succession of two tectonic regimes. First, a dominant NNW–SSE-trending extension, marked by ductile stretching that characterizes the MMB, and associated N70E brittle normal faults. Later, from Middle or Upper Miocene to the Present, these structures were cross-cut by brittle right-lateral faults, among which the most important are the N20W transpressive Shan scarp fault zone and the N–S Sagaing fault. To explain this transition from a dominant transtensive to a transpressive stress regime, that occurred during Miocene, we place our data within a larger geodynamic context. We suggest that, like the intraplate deformation in the Indian Ocean, the end of spreading in the South China sea, the opening of the Andaman basin or the end of subduction within the Indo-Burma range, the change in the tectonic regime in central Myanmar could be in response to a major Miocene regional plate kinematic reorganization.  相似文献   

鄂西崆岭杂岩的组成,时代及地质演化   总被引：33，自引：1，他引：33  

马大铨  李志昌  肖志发 《地球学报》1997,18(3):233-241

崆岭杂岩包括下部基底片麻岩和上部表壳岩两部分。作者采自下部的１３个斜长角闪岩样品获得ＳｍＮｄ等时线年龄３２９０±１７０Ｍａ（２σ），加入４个伴生灰色片麻岩样品后等时线年龄变为３１５０±７９Ｍａ（２σ）。采自上部的变粒岩和斜长角闪岩分别获得锆石Ｕ＿Ｐｂ一致曲线年龄为２４２７±４２Ｍａ（２σ）和２０３１±４Ｍａ（２σ）。基于这些新的数据和前人的工作成果，探讨了崆岭杂岩的形成和地质演化。  相似文献   

中子活化分析在铼—锇法年龄测定中的应用     

屈文俊  杜安道 《岩矿测试》1997,16(4):289-292

同位素稀释中子活化分析铼与感耦等离子体质谱法测定锇相结合，应用于辉钼矿及铜＿镍硫化物矿物的铼＿锇年龄测定，取得了满意的结果，扩大了铼＿锇测年法的应用范围。  相似文献   

四川盆地西部富钾卤水水文地球化学特征及其成因意义探讨   总被引：6，自引：0，他引：6  

林耀庭  颜仰基 《盐湖研究》1996,4(1):1-12

四川盆地西部宫钾卤水以深层卤水形式赋存于地下４０００余ｍ的中三叠统雷口坡组四段（Ｔ２ｌ４）盐系的碳酸盐岩储层中。富钾卤水与海水不同浓缩阶段相比，其中含Ｋ＋含量异常高，构成液态钾矿资源；Ｂｒ－、Ｉ－、Ｂ（３＋）、Ｌｉ＋等稀有组分也远超过综合利用工业品位，为优质化工原料水。富钾卤水为沉积变质和钾盐溶滤的复合成因，具有固夜态找钾的指示意义。本文为四川盆地固液态找钾提供了有价值的线索。  相似文献   

甘肃走廊南山朱龙关群的时代及其火山岩的岩石化学特征   总被引：9，自引：0，他引：9  

徐晓春  岳书仓  刘因  周涛发 《安徽地质》1996,(4)

甘肃走廊南山朱龙关群是一套以发育大量基性火山岩为特征的浅变质火山沉积岩系，分布于托来山北坡刘口峡山至热水大坂一带以及朱龙关河北侧小柳沟和古浪峡等地。本文在前人工作的基础上，对区内地层的分布提出了新的见解，认为沙龙地区和北过龙至金龙河地区出露的一套浅变质火山－沉积岩石应划归来龙关群，并运用同位素年代学方法测定了该地层中火山岩的成岩时代，首次较确切地给出了这套浅变质岩系的时代归属，从而进一步确定了朱龙关群的时空分布。同时根据火山岩岩石化学特征研究，认为朱龙关群火山岩的成岩大地构造背景为陆内裂谷。  相似文献   

辽北－吉南地区太古宙花岗岩－绿岩带地质地球化学   总被引：9，自引：0，他引：9  

李俊建  沈保丰  李双保  毛德宝  骆辉  金文山 《地球化学》1996,(5)

辽北－吉南地区是我国典型太古宙花岗岩－绿岩带出露区之一。根据其地质地球化学特征，本区绿岩带可划分为清原型和夹皮沟型，其形成的古构造环境分别为与现代岛弧的大陆边缘活动带和弧后盆地或大陆边缘裂谷相类似的裂谷型构造环境。与绿岩带有关的花岗质岩石可划分为三类：即片麻状花岗质杂岩体、花岗闪长岩和英云闪长岩底辟岩基以及钾质花岗岩。花岗岩－绿岩带的形成时代为２．５－２．９Ｇａ。  相似文献   

华南（东）变质基底特征、古构造型式及铀、金矿化远景     

余达淦  管太阳  黄国夫 《铀矿地质》1996,(6)

华南（东）变质基底由杨子及华夏两块不同特征的地质体组成，中元古代之后，该地区分别经过了碰撞对接、拉开、再拼贴的演化过程。碰撞对接带和在古裂谷系基础上成型的陆内推覆及平移、剪切型拼贴带构成了本区基底构造主要型式。铀及金矿远景与基底特征关系密切，铀矿主要产于基底裂隆带部位，金则主要产于裂凹（裂陷）带部位。古基底构造交叉部位是中新生代构造活动活跃部位，受其控制的早期横向火山裂谷盆地，在晚期拉张条件下形成的岩浆杂岩带是铀、金、多金属成矿最佳远景区。  相似文献   

Tectonometamorphic evolution of the Himalayan metamorphic core between the Annapurna and Dhaulagiri, central Nepal   总被引：12，自引：0，他引：12  

J.-C. VANNAY  & K. V. HODGES 《Journal of Metamorphic Geology》1996,14(5):635-656

The metamorphic core of the Himalaya in the Kali Gandaki valley of central Nepal corresponds to a 5-km-thick sequence of upper amphibolite facies metasedimentary rocks. This Greater Himalayan Sequence (GHS) thrusts over the greenschist to lower amphibolite facies Lesser Himalayan Sequence (LHS) along the Lower Miocene Main Central Thrust (MCT), and it is separated from the overlying low-grade Tethyan Zone (TZ) by the Annapurna Detachment. Structural, petrographic, geothermobarometric and thermochronological data demonstrate that two major tectonometamorphic events characterize the evolution of the GHS. The first (Eohimalayan) episode included prograde, kyanite-grade metamorphism, during which the GHS was buried at depths greater than c. 35 km. A nappe structure in the lowermost TZ suggests that the Eohimalayan phase was associated with underthrusting of the GHS below the TZ. A c. 37 Ma ⁴⁰Ar/³⁹Ar hornblende date indicates a Late Eocene age for this phase. The second (Neohimalayan) event corresponded to a retrograde phase of kyanite-grade recrystallization, related to thrust emplacement of the GHS on the LHS. Prograde mineral assemblages in the MCT zone equilibrated at average T =880 K (610 °C) and P =940 MPa (=35 km), probably close to peak of metamorphic conditions. Slightly higher in the GHS, final equilibration of retrograde assemblages occurred at average T =810 K (540 °C) and P=650 MPa (=24 km), indicating re-equilibration during exhumation controlled by thrusting along the MCT and extension along the Annapurna Detachment. These results suggest an earlier equilibration in the MCT zone compared with higher levels, as a consequence of a higher cooling rate in the basal part of the GHS during its thrusting on the colder LHS. The Annapurna Detachment is considered to be a Neohimalayan, synmetamorphic structure, representing extensional reactivation of the Eohimalayan thrust along which the GHS initially underthrust the TZ. Within the upper GHS, a metamorphic discontinuity across a mylonitic shear zone testifies to significant, late- to post-metamorphic, out-of-sequence thrusting. The entire GHS cooled homogeneously below 600–700 K (330–430 °C) between 15 and 13 Ma (Middle Miocene), suggesting a rapid tectonic exhumation by movement on late extensional structures at higher structural levels.  相似文献   

冀西北两类石榴基性麻粒岩的变质演化及Gibbs方法分析   总被引：19，自引：9，他引：19  

刘树文  沈其韩 《岩石学报》1996,12(2):261-275

  相似文献   

安徽省大别山南部宿松杂岩变质作用研究   总被引：7，自引：13，他引：7  

魏春景  单振刚 《岩石学报》1997,13(3):356-368

宿松杂岩的变质作用可分为３个阶段：早期、主期和晚期阶段。主期阶段的矿物组合在云母片岩中为石榴石＋多硅白云母＋石英＋磁铁矿±钠云母±绿帘石／黝帘石；在白云母钠长（二长）片岩和片麻岩中为石榴石＋多硅白云母＋钠长石＋石英＋绿帘石／黝帘石±冻蓝闪石；在石榴石钠长角闪岩中为石榴石＋冻蓝闪石＋钠长石＋黝帘石＋石英±钠云母±金红石／磁铁矿。根据多种地质温压计和变质反应可以推测主期变质条件为：Ｔ＝５２０℃～５８０℃，Ｐ＝１．２～１．４ＧＰａ，地热梯度为１２℃／ｋｍ，相当于高压过渡型。晚期阶段变质条件为：Ｔ＝４６０℃～４８０℃，Ｐ＝０．６～０．７ＧＰａ，为中压绿帘角闪岩相。宿松杂岩的变质条件介于其南部的蓝闪绿片岩相和北部的榴辉岩相之间，三者是扬子板块向华北板块之下俯冲到不同深度的产物。  相似文献