Archaean Kuru-Vaara eclogites in the northern Belomorian Province,Fennoscandian Shield: crustal architecture,timing, and tectonic implications     

Victor Balagansky  Andrey Shchipansky  Alexander I. Slabunov  Il’ya Gorbunov  Sergey Mudruk  Mikhail Sidorov 《International Geology Review》2015,57(11-12):1543-1565

This paper addresses the relationships between relic amphibole-eclogite facies (AE) eclogites and their host units, Archaean amphibolites, enveloped by Archaean tonalite–trondhjemite–granodiorite (TTG) gneisses, in the Kuru-Vaara study area in the northern Belomorian Province. According to observational constraints, the crystallization of the relic peak omphacite + Mg-garnet ± kyanite assemblage and the subsequent replacement of omphacite by clinopyroxene–plagioclase symplectite occurred before the earliest deformational, metamorphic, and migmatization events that are recorded in the amphibolites. The amphibolites and their TTG hosts have a shared deformational and metamorphic history that is composed of the Archaean and Palaeoproterozoic periods. This history favours the conclusion that the AE metamorphism recorded in the relic eclogites within the amphibolites occurred during the Mesoarchaean to Neoarchaean periods. The deformation and metamorphism of the amphibolite facies of the second period resulted from the Lapland–Kola collisional orogeny at 1.91–1.93 Ga, which led to eclogite–high-pressure granulite (E–HPG) facies conditions in the lowermost portions of the over-thickened crust in Belomorian Province (the southwestern foreland of the Lapland–Kola collisional orogen). The Palaeoproterozoic E–HPG overprint was reported from the Palaeoproterozoic Gridino mafic dikes. Although the ages of the oldest low Th/U zircons are close to the time of the Lapland–Kola collision, the low Th/U 1.9–1.8 Ga zircons reflect a zircon response to regional fluid infiltration in the eclogites during slow exhumation following the Lapland–Kola orogeny and do not record any metamorphic event. Contrary to the Palaeoproterozoic E–HPG overprint, the areal occurrence of the 2.7–2.8 Ga AE eclogites with mid-ocean ridge basalt-like chemistry and their paragenetic link with the TTG gneisses suggest a tectonic regime that involves subduction. This research favours concepts suggesting that the modern-style plate tectonics has operated in some places, at least since the late Mesoarchaean.  相似文献   

合肥市绿地国际花都高层建筑物的沉降观测     

孙晓雯 《安徽地质》2011,21(4):312-314

通过实例研讨了高层建筑物的沉降观测。对水准点、沉降观测点的布设及沉降观测的资料整理进行了论述,谈了一些变形测量的体会。  相似文献   

震动变形构造所表征的震积岩:以河北宣化中元古界高于庄组第三段为例   总被引：1，自引：0，他引：1       下载免费PDF全文

梅冥相 《地学前缘》2012,19(2):239-247

地震变形构造主要包括小级别的张性或压性断层、不协调的软沉积物变形褶皱等,这些变形构造以震动变形作用为特点从而成为识别和定义地震岩的主要标志。在河北宣化一带的高于庄组第三段下部的白云质灰岩或灰质白云岩层之中,发育了极为典型的地震变形构造,包括层内断层、层内褶皱以及极为典型的碎裂角砾岩等。高于庄组第三段地震变形构造的发现,为探索和研究地震作用对沉积岩层的破坏和改造而区分于其他的事件沉积如海啸沉积和风暴沉积提供了极为重要的实例,也为更加深入理解高于庄组第三段非叠层石碳酸盐岩沉积序列的产出背景提供了重要资料。  相似文献   

Influence of bedding orientation on the anisotropy of hydraulic conductivity in a well-sorted fluvial sediment   总被引：2，自引：0，他引：2  

Dong-hui CHENG  Xun-hong CHEN  Ai-di HUO  Min GAO  Wen-ke WANG 《国际泥沙研究》2013,28(1):118-125

The paper describes a permeameter test method for determination of the hydraulic conductivity(AT) along multi-directions in fluvial sediments with cross beddings.Unlike existing in-situ permeameter methods that determine hydraulic conductivity for submerged streambeds,our method was intended to measure hydraulic conductivity of exposed streambeds or fluvial sediments.The method was applied to the Wei River,Shaanxi Province,Central China for characterization of the anisotropy of K in a well-sorted fluvial sediment.The results illustrated that even in well-sorted sediments,cross-bedding and sediment fabrication(or texture) can lead to varied K values along different measurement directions.The K value was the largest along the dip direction(or the major direction) that is parallel to the orientation of cross bedding and the smallest in the direction perpendicular to the bedding(or the minor direction). The K value in a given direction between the major and minor direction often fell in the range bounded by the K values in the major and minor directions.The anisotropy ratio of K(the ratio of K value between the major and minor directions) in two trenches for this well-sorted fluvial sediment was up to 1.14 to 1.23,respectively.Our results also demonstrated that even for well-sorted sediments,the K values between two sampling points only about 10 cm apart can differ.It is clear that the K distribution strongly correlates to the bedding orientation.  相似文献   

川西顺层斜坡破坏模式及层间弱面连通率对斜坡稳定性的影响     

周洪福  冉涛  陈波  高澍  吴文贤 《现代地质》2021,35(1):137-144

顺层岩质斜坡是沉积岩地区常见的一种斜坡类型,也是各种工程建设重点关注的一类斜坡。以川西雅安地区典型的顺层岩质斜坡为例,采用现场调查、无人机测绘、钻探、物探和稳定性计算等技术方法,归纳总结目前斜坡存在的变形破坏模式。分析计算斜坡在不同工况条件下,层间破碎带连通率与斜坡稳定性之间的关系。研究结果表明:层间破碎带对斜坡稳定性具有重要的影响或控制作用,当斜坡浅表部强风化岩体内层间破碎带连通率小于86%时,斜坡稳定性与现状调查结果吻合。研究结果对川西地区基础设施规划建设和防灾减灾具有重要的工程意义。  相似文献   

Simulating the role of tides and sediment characteristics on tidal flat sorting and bedding dynamics     

Zeng Zhou  Qian Liu  Daidu Fan  Giovanni Coco  Zheng Gong  Iris Möller  Fan Xu  Ian Townend  Changkuan Zhang 《地球表面变化过程与地形》2021,46(11):2163-2176

Understanding sediment sorting and bedding dynamics has high value to unravelling the mechanisms underlying geomorphological, geological, ecological and environmental imprints of tidal wetlands and hence to predicting their future changes. Using the Nanhui tidal flat on the Changjiang (Yangtze) Delta, China, as a reference site, this study establishes a schematized morphodynamic model coupling flow, sediment dynamics and bed level change to explore the processes that govern sediment sorting and bedding phenomena. Model results indicate an overall agreement with field data in terms of tidal current velocities, suspended sediment concentrations (SSCs), deposition thicknesses and sedimentary structures. Depending on the variation of tidal current strength, sand-dominated layers (SDLs) and mud-dominated layers (MDLs) tend to form during spring and neap tides, respectively. Thinner tidal couplets are developed during daily scale flood–ebb variations. A larger tidal level variation during a spring–neap tidal cycle, associated with a stronger tidal current variation, favours the formation of SDLs and tidal couplets. A larger boundary sediment supply generally promotes the formation of tidal bedding, though the bedding detail is partially dependent on the SSC composition of different sediment types. Sediment properties, including for example grain size and settling velocity, are also found to influence sediment sorting and bedding characteristics. In particular, finer and coarser sediment respond differently to spring and neap tides. During neap tides, relatively small flow velocities favour the deposition of finer sediment, with limited coarser sediment being transported to the upper tidal flat because of the larger settling velocity. During spring tides, larger flow velocities transport more coarser sediment to the upper tidal flat, accounting for distinct lamination formation. Model results are qualitatively consistent with field observations, but the role of waves, biological processes and alongshore currents needs to be included in further studies to establish a more complete understanding.  相似文献   

基床的水下爆夯试验研究     

吴绵拔  高建光 《岩土力学》1996,17(4):8-14

分析了水下爆炸夯实基床的基本原理及作用机理，并应用于海南和帮码头基床的爆夯，取得预期的效果，表明基床的水下爆夯法有效，可行，具有广阔的应用前景。  相似文献   

胶辽吉地区古元古代早期花岗岩的侵位模式及其与隆滑构造的关系   总被引：8，自引：10，他引：8  

李三忠  杨振升 《岩石学报》1997,13(2):189-202

通过对胶辽吉地区古元古代裂谷带的深入研究，提出了伸展构造环境下中深部地壳花岗质岩浆侵位的一种模式，即花岗质岩浆沿基底与盖层之间的拆离滑脱带多次贯入，形成岩席，之后随着地壳拉伸（或伸展）作用，这些岩席逐渐远离侵位中心，发生侧向迁移。这种大陆壳内中深部花岗质岩浆的侵位和地壳的侧向伸展的模式，与有些学者提出的大洋中脊玄武质岩浆的侵位和洋壳扩张的模式是基本相似的。这一模式也是大陆地壳快速生长加厚的一种有效机制。由于花岗质岩浆的上涌引起上覆盖层因重力失稳形成一系列顺层滑脱构造组合。它们与花岗岩和基底共同构成中深构造层次岩浆隆起－顺层分层滑脱构造系  相似文献   

大榭岛西北海域海底断陷构造     

宋连清 《海洋学研究》1996,14(2):10-18

本文依据大榭岛西北海域的测深、浅地层剖面和底质土工试验资料，详细分析了该海域海底地形形态、微地貌状况、浅部地层结构及底质工程性质，发现该海域海底地层断陷构造明显，并圈定了地层断陷的范围，探讨了其形成的原因和发生的时间。  相似文献   

新疆额尔齐斯河源花岗岩景观与成因浅析     

郭建强  吴昊  罗中云  卢志明 《四川地质学报》2007,27(1):47-52

笔者在开展新疆富蕴可可托海国家地质公园地质遗迹景观调查评价、规划时,发观沿额尔齐斯河源分布的花岗岩地貌,较黄山、华山、泰山等地的花岗岩地貌奇特,可谓独树一帜。通过调查,弄清其形态是受变质花岗岩内部平行山坡面的层节理制约。花岗岩主要沿平行坡面的层节理,不断地拆离崩解垮塌,并使山体山峰的表面形态既圆润平滑,又十分陡峭,从而造就了千姿百态的额河源花岗岩景观,为此,命名为“阿尔泰地貌”。  相似文献