山东玲珑和郭家岭岩体的同位素年龄及其地质意义   总被引：18，自引：2，他引：18  

胡世玲  王松山  桑海清  裘冀  张任祜 《岩石学报》1987,3(3)

本文采用~(40)K-Ar/~(39)Ar快中子活化和K-Ar稀释法定年技术对玲珑岩体和郭家岭岩体进行了年龄测定。~(40)Ar/~(39)Ar阶段加热年龄谱表明,玲珑岩体和郭家岭岩体的坪年龄分别为164.2±0.7Ma和134.8±1.7Ma,其形成时代同属燕山期,为同一成因不同阶段的产物。同位素年龄提供的数据支持了两岩体为交代混合岩化的成因观点。~(40)Ar/~(39)At和K-Ar年龄结果还表明:角闪石和黑云母均是~(40)Ar/~(39)Ar理想定年矿物,对K-Ar法而言,角闪石最理想,黑云母次  相似文献   

天山古生代增生造山作用及其构造转换事件     

王博  宋芳  倪兴华  曹婷婷  刘珈硕  钟凌林  孙朝晨  孙雨欣  邓聚  李盈莹  朱鑫  刘洪升  何智远 《地质学报》2022,96(10):3514-3540

天山造山带自新元古代以来，经历了漫长而复杂的俯冲增生造山作用和陆内构造活化过程，属于典型的复合型造山带。基于近年研究进展，本文对伊犁、境内外中天山和南天山构造带前寒武纪基底、古生代沉积序列、多期陆缘弧岩浆岩和构造缝合带的变形变质特征、形成环境和年代学等进行了总结分析，梳理了天山古生代增生造山作用中的三次重要构造转换事件及其地质记录。① 伊犁南北两缘、中天山、南天山和塔里木北缘，均发育中奥陶世—志留纪的大陆弧岩浆作用，伊犁北缘、南天山 塔里木北部早古生代沉积环境发生显著变化，表明天山 塔里木北缘在中—晚奥陶世发生了从被动陆缘向活动陆缘的转换。② 伊犁南、北两缘和中天山的早古生代岩层在晚志留世—早泥盆世普遍发生了强烈的韧性变形和角闪岩相变质作用，其上不整合覆盖有弱变形未变质的晚泥盆世—石炭纪火山 沉积地层；该区域不整合是哈萨克斯坦微大陆拼合事件在研究区的构造响应，也标志着准噶尔洋和南天山洋的俯冲方式在泥盆纪发生了由前进式（东太平洋型）向后撤式（西太平洋型）的构造转换，导致伊犁和中天山在晚泥盆世—石炭纪经历了伸展背景下的大陆弧岩浆作用，在南天山 塔里木北缘则形成了一系列弧后有限洋盆。③ 天山各构造单元及其边界缝合带中普遍发育晚石炭世逆冲推覆构造和二叠纪走滑韧性剪切带、晚石炭世—早二叠世滑塌堆积和二叠纪后造山岩浆岩，指示晚石炭世—早二叠世发生了由汇聚造山向陆内构造的转换。这些构造转换事件是认识古亚洲洋各分支洋盆从初始俯冲、俯冲方式转换到俯冲终结过程的基础，也是探讨增生造山动力学的关键。  相似文献   

Geochronology and geochemistry of Middle Devonian mafic dykes in the East Kunlun orogenic belt,Northern Tibet Plateau: Implications for the transition from Prototethys to Paleotethys orogeny   总被引：3，自引：0，他引：3  

Fuhao Xiong  Changqian Ma  Hong’an Jiang  Bin Liu  Jian Huang 《Chemie der Erde / Geochemistry》2014

The tectonic transition from Prototethys to Paleotethys orogeny in the East Kunlun orogenic belt is not completely clear, and is a major unresolved geologic issue in Northern Tibet Plateau. Here, we present zircon geochronology, whole-rock elemental and zircon Hf isotopic geochemistry for newly discovered mafic dykes in the East Kunlun orogenic belt, to provide constraints on this issue. The studied mafic dykes are hornblende gabbros, consisting of hornblende (60–65 vol.%), plagioclase (15–25 vol.%) and augite and biotite (0–5 vol.%). LA–ICP–MS zircon U–Pb dating shows that these mafic dykes were emplaced at about 393 Ma. All the mafic dykes are characterized by high contents of CaO (8.82–11.48 wt.%), MgO (9.07–11.39 wt.%), V (275–336 ppm), Cr (370–467 ppm) and Ni (78.3–120 ppm), with high Mg# (63–67), flat CI-normalized REE distribution and depleted ?Hf(t) values (2.03–5.35), showing tholeiitic affinities and geochemical characteristics similar to those of mid-ocean ridge basalts. They were derived from low degree (about 5–15%) partial melting of a fertile spinel lherzolite source, which have been metasomatized by fluids introduced to the mantle by former subducted slab. The geologic–petrologic evidence suggests that the mafic dykes were emplaced in a shift tectonic setting related to continental rifting, which was caused by the extensional collapse related to the lithospheric thinning after the Prototethys orogeny. The delamination-induced thermal disturbance and extensional decompression triggered partial melting of the mantle and the emplacement of the mafic dykes. Combined with previous work, we propose that the Middle Devonian mafic dykes may be the early magmatic response to the transition from Prototethys to Paleotethys marking the opening of the Paleotethys in the East Kunlun orogenic belt.  相似文献   

Tectonic evolution of an active tectonostratigraphic boundary in accretionary wedge: An example from the Tulungwan-Chaochou Fault system,southern Taiwan     

《Journal of Structural Geology》2014

The Tulungwan-Chaochou Fault system in southern Taiwan represents the boundary between a slate belt of moderate metamorphic grade and a relatively unmetamorphosed fold-and-thrust belt. The offset between hanging wall and footwall of this fault ranges from 7 to 11 km and is considered one of the major tectonostratigraphic faults in Taiwan. This 75-km-long fault system is also one of the most conspicuous topographic features in Taiwan. The geometry, kinematic history and associated subsidiary structures have not been resolved. Field mapping of fabrics and brittle faults show that a 45-km-long west-northwest-vergent antiform defined by folded slaty cleavage exists in the hanging wall of the fault. This antiform has not been previously described and apparently formed in a brittle environment. The flat crest and tight forelimb of the antiform suggests a two-stage deformation model composed of a fault-bend fold followed by a trishear fold. We infer that regional scale fold is associated with a thrust that splays upward from the main detachment.  相似文献   

太行山—秦岭中、新生代板内变形及交接转换机制   总被引：1，自引：0，他引：1  

程世秀  李三忠  许立青  余珊  曹现志  王鹏程  索艳慧  刘鑫  赵淑娟  熊莉娟 《地质论评》2014,60(6):1245-1258

中—新生代,秦岭是中国大陆中轴隆升的东西向山脉,而太行山为华北地块中部隆升的南北向山脉,两者走向近垂直。为了探讨中-新生代期间同属欧亚板块内部的这两条山脉的隆升历史及其构造应力场转换过程,本文通过对其区域挤压与伸展构造的系统对比分析,结合两带中生代和新生代构造体制转换的对比,最后得出中—新生代期间这两条近垂直山脉由挤压体制转换为伸展体制的时间约为早白垩世晚期;并通过同时代应力场的转换的分析对比,揭示出其挤压变形与古老造山带形成时导致的板内岩石圈不均一性结构有关;而其伸展变形与中国东部弥散性板内裂解密切相关,因而表现出宽裂谷的特征,但其总体构造格局仍受早期基底构造格局影响。总之,板内差异构造变形受早期基底构造格局控制,同时板内不同块体多方位先存边界对板缘动力作用响应存在巨大差异;在筛除板块俯冲的远程效应外,板内自身变形机制可能与板内热—力学结构的不均匀性具有密切联系。  相似文献   

北秦岭造山带早古生代多期变质与深熔作用：锆石U-Pb年代学证据   总被引：5，自引：4，他引：1  

向华  钟增球  李晔  周汉文  祁敏  雷恒聪  林彦蒿  张泽明 《岩石学报》2014,30(8):2421-2434

北秦岭造山带中的秦岭群以多期变质作用和强烈混合岩化为特征,出露有早古生代的榴辉岩和高压麻粒岩,以及区域性分布的中低压麻粒岩-角闪岩相变质岩石和混合岩。本文对西峡双龙地区混合岩化片麻岩(中色体)、石榴子石黑云母片岩(暗色体)和淡色花岗岩脉体进行了详细的锆石U-Pb定年和微量元素研究。结果表明片麻岩的原岩年龄为941±11Ma(2σ,MSWD=0.59),石榴子石黑云母片岩的原岩年龄为756±9.9Ma(2σ,MSWD=1.07)。石榴子石黑云母片岩中的变质锆石获得了484±9.6Ma(2σ,MSWD=0.88)的年龄,与片麻岩中锆石变质增生边获得的单点年龄498±11Ma在误差范围内一致。这些变质锆石多数具有平坦的HREE分配模式,弱Eu负异常,与高压变质岩中的变质锆石特征相似。该年龄与秦岭榴辉岩和高压麻粒岩的变质年龄相一致。石榴子石黑云母片岩中锆石的最外层增生边记录了424±9.1Ma的年龄,同时淡色脉体中的锆石也给出了422±4.0Ma(2σ,MSWD=0.77)的加权平均年龄,代表了深熔脉体的结晶年龄。这些锆石均为新生锆石,阴极发光弱,具有低的Th/U比值,平坦的HREE分配模式,强烈的Eu负异常,指示部分熔融过程中存在大量石榴子石和斜长石。深熔脉体的年龄与秦岭群中的中低压高温-超高麻粒岩相变质的年龄相符。结合已有的结果,我们认为秦岭群普遍记录了500~480Ma的高压、超高压变质作用,并叠加了440~400Ma的中压-高温变质和深熔作用。秦岭群可能是Rodinia超大陆裂解过程中从华南陆块或相似构造属性陆块分离并漂移到华北克拉通南缘的微陆块。在500~480Ma时发生碰撞造山作用导致北秦岭微陆块深俯冲并发生了高压-超高压变质作用,在志留纪由于商丹洋壳北向俯冲导致秦岭微陆块发生了以中压-高温变质、深熔和同时的岩浆作用为特征的增生造山作用。  相似文献   

Surface Expressions of Rayleigh-Taylor Instability in Continental Interiors     

WANG Huilin  Claire A CURRIE  ZHAN Yan 《《地质学报》英文版》2014,88(3):1004-1016

Two-dimensional thermal-mechanical numerical models show that Rayleigh-Taylor-type （RT） gravitational removal of high-density lithosphere may produce significant surface deformation （vertical deflection 〉1000 m） in the interior of a continental plate.A reasonable range of crustal strengths and thicknesses,representing a variation from a stable continental interior to a hot orogen with a thick crust,is examined to study crustal deformation and the surface deflection in response to an RT instability.In general,three types of surface deflection are observed during the RT drip event：（1） subsidence and negative topography; （2） uplift and positive topography; （3） subsidence followed by uplift and inverted topography.One key factor that determines the surface expression is the crustal thickness.Models with a thin crust mainly show subsidence and develop a basin.In the thick crust models,surface expressions are more variable,depending on the crustal strength and depth of highdensity anomaly.With weak crust and a deep high-density anomaly,the RT drip is decoupled from the overlying crust,and the surface exhibits uplift or little deflection,as the RT drip induces contraction and thickening of the overlying crust.In contrast,with a strong crust and shallow anomaly,the surface is more strongly coupled with the drip and undergoes subsidence,followed by uplift.  相似文献   

中非造山带：喀麦隆北部地质构造与河流沉积物重矿物分析     

叶浩  Merlain Houketchang Bouyo  赵越  刘健 《地质力学学报》2014,20(2):103-113

简要叙述冈瓦纳超大陆聚合过程和中非造山带泛非期地质构造过程,剖析了西冈瓦纳喀麦隆北部和乍得西南地区岩石构造单元及其形成的构造背景并对喀麦隆北部河流冲积物进行了重矿物分析。分析结果表明重矿物可能来自近源基岩,为西喀麦隆地体(Western Cameroon Domain)内的雷博巴(Rey Bouba)绿岩带和马约科比(Mayo Kebbi)弧岩浆岩带;重矿物中的自然金可能主要来自雷博巴绿岩带。分析结果为该地区砂金矿开采提供了一定的指示。  相似文献   

Backarc mafic–ultramafic magmatism in Northeastern Vietnam and its regional tectonic significance     

《Journal of Asian Earth Sciences》2014

The geology of Northern Vietnam offers critical clues on the convergence history between the South China and Indochina blocks. We constrain the tectonic evolution of the South China and Indochina blocks using geochemical, mineral chemical and geochronological data collected from mafic–ultramafic rocks exposed in the Cao Bang area, Northeastern Vietnam. These rocks show significant enrichment in large ionic lithophile elements (LILEs) such as Cs, Rb, Ba, Th, U, and Pb and depletion in high field strength elements (HFSEs) such as Nb, Ta, Zr, and Ti showing [Nb/La]_N between 0.28–0.41, [La/Yb]_N = 3.94–10.00 and Zr/Y = 2.0–4.4. These geochemical features as well as the petrology and mineral chemistry of the Cao Bang mafic–ultramafic magmas are comparable to those of magmatic complexes formed in a back-arc environment. The basalts yield Rb–Sr whole rock ages of 263 ± 15 Ma, that are consistent with the zircon U–Pb and K–Ar ages reported in previous studies from the same area. The spatial and temporal distribution of the arc magmas within the Indochina block and along the southern margin of the South China block suggest that the Permo-Triassic mafic–ultramafic magmas formed during a tectonic event that is different from the subduction and collision event between the Indochina and South China blocks.  相似文献   

神奇美丽的横断山:地壳演化塑造的奇迹——“三江并流”世界自然遗产地形成地质背景浅析     

王义昭 《地质通报》2006,(Z1)

三江并流是反映地球演化主要阶段的杰出代表,区内保存着反映特提斯演化不同阶段和喜马拉雅期陆内造山阶段留下的丰富的地质遗迹,这些地质遗迹为解读三江并流地壳演化的历史提供了重要的依据。有关资料表明,三江并流是与青藏高原和横断山脉一起发育成长起来的,它们均经历了特提斯的演化,并且都是印度板块与欧亚板块强烈碰撞造山作用的产物。本文比较详细地介绍了横断山脉的形成演化过程及其与青藏高原形成演化之间的关系。  相似文献