共查询到20条相似文献，搜索用时 281 毫秒
1.
岩石圈的流变学分析和岩石构造、显微构造证据揭示出大陆岩石圈具有显著的横向和纵向上的异向性,并具有明显的非板块表现.全面开展不同温度和压力条件下变形岩石的构造与显微构造分析,正确认识岩石圈不同层次上岩石的流变学规律、流动机理及其制约因素等,将成为后板块构造研究与新的岩石圈演化理论建立的基础和主要动力.岩石流动的宏观-微观尺度问题(岩石圈结构与流变性、边界弱化效应和岩石流变学与显微构造响应等)、岩石流动的时间问题(不同时间尺度岩石的流动性、实验室模拟与天然岩石流动的协调性、浅层岩石流动变形的有效定年等)、岩石流动的制约因素(内在的成分与结构、外在的物理与化学环境)将成为岩石圈流动与岩石变形显微构造研究的重要方面.现代化实验室建设和最新实验技术、手段的利用将成为解决上述科学问题的必要条件. 相似文献
2.
侏罗纪地壳转动与中国东部岩石圈转型 总被引：8，自引：0，他引：8
对中国东部侏罗纪时期地壳增厚和岩石圈显著变薄的现象,提出一个新的形成机制假说.基于古地磁和地质学的证据认为,鄂霍次克板块朝西和伊佐奈岐板块朝西北方向运移、俯冲和碰撞,造成西伯利亚东部边缘的强烈构造变形,使东亚大陆地壳产生20°～30°的逆时针转动,形成东亚大陆北部地壳朝西运移,而东亚大陆南部(中国东部)地壳相对向东运移.这种滑移作用使中国东部发生强烈的构造-岩浆活动、地壳增厚,同时也使中国大陆东部的上地壳从大陆型岩石圈地幔滑移到大洋型岩石圈地幔之上,出现岩石圈类型的转变和厚度显著变薄的现象.看来,中国东部岩石圈变薄并不是深部地幔羽或大陆伸展作用的结果. 相似文献
3.
从地壳上地幔构造看大陆碰撞带岩石圈的克拉通化 总被引：1，自引：0，他引：1
本篇讨论超级大陆汇聚后逐渐变为克拉通或扩大克拉通的作用过程,即指经及大陆碰撞地体汇聚后新形成的大陆块逐渐转变为刚性克拉通的作用过程。增生大陆岩石圈的克拉通化的作用后果,包括大陆地壳密度的增加,岩石圈地幔的增厚和大地热流值的下降,使大陆岩石圈逐渐刚性强化。大陆碰撞后形成的大陆块必须经过克拉通化的过程,才能逐渐成为刚性克拉通。作用过程主要包括:①上地壳沉积碎屑岩石结晶岩化和中地壳岩石角闪岩化;②下地壳岩石基性化;③大陆碰撞带下凹莫霍面的磨平;④岩石圈地幔底侵加厚形成陆根。从大陆碰撞带转变为克拉通的过程也是岩石圈地幔不断增厚而地壳缓慢变硬变冷的过程。这个过程包含以下作用:区域变质作用,交代作用和岩石圈幔源岩浆的底侵。这个过程时间尺度比碰撞造山作用大一个级次。长期的底侵作用使地壳岩石密度和强度不断加大,改变岩层的矿物成分和局部结构。当大陆岩石圈克拉通化到一定程度之后,由于下方软流圈的热能供应逐渐减缓,使岩石圈地温梯度缓慢下降,最终结果会形成大陆根。由于显生宙大陆碰撞带岩石圈强度弱,大陆碰撞时更容易造成岩石圈变形,因此大陆碰撞的板内效应主要发生在大陆内的显生宙碰撞带。显生宙大陆碰撞带如果再次受到大陆碰撞板内效应的作用,其克拉通化的过程必然会推迟。 相似文献
4.
现今塔里木克拉通岩石圈厚度分析及机制探讨 总被引：2，自引：0，他引：2
塔里木盆地是青藏高原周边稳定的克拉通陆块，在印度板块与欧亚板块碰撞过程中一直保持稳定，盆地内部没有发生强烈的变形，其地壳热状态也同样保持稳定，地温梯度没有明显的变化，以热力学为基础的岩石圈热学厚度约为250km左右，该厚度是热稳态岩石圈的厚度。而最新的地震热学方法的研究成果表明塔里木盆地的岩石圈厚度仅为150km左右，这表明塔里木盆地岩石圈的热结构可能并不是处于稳态状态，其底部正在或已经发生了减薄。本文利用构造热演化方法对塔里木岩石圈减薄的热演化过程进行了定量分析，探讨了塔里木盆地岩石圈减薄可能的三种机制：印度板块与欧亚板块碰撞后青藏高原岩石圈底部的软流圈较塔里木盆地岩石圈底部的软流圈的温度要高，青藏高原的软流圈地幔向塔里木盆地岩石圈底部侵入形成的热扰动使得塔里木盆地岩石圈底部的温度升高；塔里木岩石圈与其下流动的软流圈的摩擦剪切生热导致其岩石圈地幔底部温度升高，使得岩石圈底部发生热侵蚀，从而使得与软流圈接触的岩石圈地幔不断地加入到软流圈地幔；在塔里木盆地岩石圈的下部，青藏高原的岩石圈在该处发生了拆沉，从而诱发的软流圈地幔对流，上升的软流圈地幔流使得岩石圈地幔的温度升高而熔融，成为软流圈地幔。 相似文献
5.
岩石圈下层塑性流动与板缘驱动力远程传递 总被引：1，自引：0，他引：1
王绳祖 《吉林大学学报(地球科学版)》1999,(1)
大陆岩石圈和软流圈多层简化模型的分析表明：（１）喜马拉雅碰撞边界的驱动力,主要借助高原重力势的作用,通过岩石圈下层（含下地壳和岩石圈地幔）的塑性流动及其对脆性上层（上部地壳）的曳引,实现其向中东亚大陆的远程传递,控制板内构造变形;（２）上部地壳单独传力时,因底面受下层阻碍,所能达到的最大作用距离仅约２００ｋｍ;（３）上、下层之间非连续分布的壳内软弱层（低速、高导层）和岩石圈之下的软流圈对上述流动传力有着明显的影响;（４）与岩石圈地幔高粘度导致高应力极限的传统观点不同,该层因粘度较高,应变率显著降低,从而并不形成应力峰值。 相似文献
6.
胶辽半岛金伯利岩中地幔捕虏体岩石学特征：古生代岩石圈地幔及其不均一性 总被引：29，自引：5，他引：24
华北东部古生代岩石圈地幔经历过复杂的多旋回多阶段熔融岩浆、重结晶、变质和剪切变形历史,因而岩石组成、结构复杂.地幔橄榄岩的主元素、地幔矿物特别是金刚石中的包裹体的Mg#值及Cr#值等显示古生代岩石圈地幔高度难熔亏损玄武质的成分特征,而地幔橄榄岩的不相容元素、同位素显示高度富集的特点.这种高难熔和强富集两重性是克拉通岩石圈地幔的特征.Pb同位素反映华北东部古生代岩石圈地幔具冈瓦纳大陆地幔的特点.复县和蒙阴古生代岩石圈地幔尽管都表现为太古代克拉通地幔的特征,但存在着不均一性,前者受克拉通化后的深部作用影响强于后者.与新生代地幔Sr、Nd同位素对比表明富集的古生代岩石圈地幔向亏损新生代的地幔转变和减薄伴有新生地幔物质对古老岩石圈的置换和混合作用. 相似文献
7.
8.
华南中生代构造由早期的挤压转为晚期的拉张,确定这种构造转折时期对认识华南大地构造演化具有重要意义。花岗岩的多期次侵入往往是不同构造环境的产物,不同构造环境花岗岩表现出岩石地球化学组成上的差别。本文对湘东北望湘花岗岩体不同期次岩石地球化学研究后,认为257～165 Ma,151～144 Ma,135～128 Ma 3个侵入期的花岗质岩石分别在TiO_2,K/Rb,Rb/Sr,∑REE,δEu及微量元素组成上存在较大的差异,反映为不同的产出构造环境,分别代表印支期的挤压构造环境、燕山早期的剪切—走滑环境和燕山晚期的伸展—滑脱环境。J_3—K_1(140 Ma±)是挤压—剪切与伸展—拉张构造环境的转折期,前者表现为岩石圈增厚,后者表现为岩石圈减薄,湘东南大规模金属及铀矿的形成多与岩石圈减薄期花岗质小岩体有成因联系。 相似文献
9.
变形岩石的显微构造与岩石圈流变学 总被引：3，自引：0，他引：3
岩石圈的流变学分析和岩石构造、显微构造证据揭示出大陆岩石圈具有显著的横向和纵向上的异向性，并具有明显的非板块表现。全面开展不同温度和压力条件下变形岩石的构造与显微构造分析，正确认识岩石圈不同层次上岩石的流变学规律、流动机理及其制约因素等，将成为后板块构造研究与新的岩石圈演化理论建立的基础和主要动力。岩石流动的宏观-微观尺度问题(岩石圈结构与流变性、边界弱化效应和岩石流变学与显微构造响应等)、岩石流动的时间问题(不同时间尺度岩石的流动性、实验室模拟与天然岩石流动的协调性、浅层岩石流动变形的有效定年等)、岩石流动的制约因素(内在的成分与结构、外在的物理与化学环境)将成为岩石圈流动与岩石变形显微构造研究的重要方面。现代化实验室建设和最新实验技术、手段的利用将成为解决上述科学问题的必要条件。 相似文献
10.
钦杭带侏罗纪与铜和锡矿有关的两类花岗岩对比及动力学背景探讨 总被引：4，自引：0，他引：4
钦杭成矿带是扬子地块与华夏地块自新元古代以来的碰撞拼接带,后来在不同的地质历史时期形成了不同类型的矿床和相关的岩石.在侏罗纪形成两套成岩成矿系列,一套为中侏罗世(180～ 170 Ma)与斑岩-矽卡岩-热液脉状铜金多金属矿床及其有关的钙碱性花岗闪长岩类;另一套为晚侏罗世(160～150 Ma)与云英岩-石英脉-矽卡岩钨锡多金属矿床及其有关的钙碱性-碱性花岗岩类.本文对比了上述两个系列成矿花岗质母岩的空间分布、年代、岩石地球化学和Sr-Nd同位素特征,并探讨了二者形成的构造动力学背景差异:前者可能是由于古太平洋俯冲板片沿钦杭断裂带发生局部重熔形成的,后者形成于华南岩石圈大规模伸展减薄的环境下,两者的形成过程均有地幔物质参与,但是晚侏罗世与钨锡有关的花岗岩地幔贡献可能少一些. 相似文献
11.
研究表明,不同类型岩石的形成导致不同类型元素的富集成矿,而后者与元素的自身结构密切相关:具惰性气体型离子结构的元素亲沉积岩,具过渡型或铜型离子结构的元素亲岩浆岩.进一步研究发现,陆壳大规模熔融-固结,亦即花岗岩的形成过程,不但导致不同类型元素在上陆壳及其上层圈重新分配:亲氧(造岩)元素占据壳内熔融(岩浆)层的位置,亲硫... 相似文献
12.
俯冲带部分熔融 总被引：3，自引：3，他引：0
俯冲带是地幔对流环的下沉翼，是地球内部的重要物理与化学系统。俯冲带具有比周围地幔更低的温度，因此，一般认为俯冲板片并不会发生部分熔融，而是脱水导致上覆地幔楔发生部分熔融。但是，也有研究认为，在水化的洋壳俯冲过程中可以发生部分熔融。特别是在下列情况下，俯冲洋壳的部分熔融是俯冲带岩浆作用的重要方式。年轻的大洋岩石圈发生低角度缓慢俯冲时，洋壳物质可以发生饱和水或脱水熔融，基性岩部分熔融形成埃达克岩。太古代的俯冲带很可能具有与年轻大洋岩石圈俯冲带类似的热结构，俯冲的洋壳板片部分熔融可以形成英云闪长岩-奥长花岗岩-花岗闪长岩。平俯冲大洋高原中的基性岩可以发生部分熔融产生埃达克岩。扩张洋中脊俯冲可以导致板片窗边缘的洋壳部分熔融形成埃达克岩。与俯冲洋壳相比，俯冲的大陆地壳具有很低的水含量，较难发生部分熔融，但在超高压变质陆壳岩石的折返过程中可以经历广泛的脱水熔融。超高压变质岩在地幔深部熔融形成的熔体与地幔相互作用是碰撞造山带富钾岩浆岩的可能成因机制。碰撞造山带的加厚下地壳可经历长期的高温与高压变质和脱水熔融，形成S型花岗岩和埃达克质岩石。 相似文献
13.
Based on two-dimensional gravity modeling, the density section of the lithosphere beneath Taiwan and the surrounding areas is constructed. According to the density parameters, the lithosphere of this region comprises both the continental and oceanic types. The continental lithosphere is lighter than the oceanic one and demonstrates insignificant density differentiation through the entire section. The oceanic lithosphere is more contrasting with respect of both the crust and mantle density. The complicated Taiwan density structure corresponding to Taiwan Island is defined to be superimposed on the transition zone between the continental and oceanic lithospheric blocks. This structure with contrasting density boundaries is characterized by the elevated and high density values of its constituting heterogeneities. The formation of the Taiwan density structure is related to geodynamic processes in the Taiwan area marking the collision zone between the Eurasian and Philippine Sea plates. 相似文献
14.
Insights from trace element geochemistry as to the roles of subduction zone geometry and subduction input on the chemistry of arc magmas 总被引：2，自引：0，他引：2
Heidi Wehrmann Kaj Hoernle Dieter Garbe-Schönberg Guillaume Jacques Julia Mahlke Kai Schumann 《International Journal of Earth Sciences》2014,103(7):1929-1944
Subduction zones of continental, transitional, and oceanic settings, relative to the nature of the overriding plate, are compared in terms of trace element compositions of mafic to intermediate arc rocks, in order to evaluate the relationship between subduction parameters and the presence of subduction fluids. The continental Chilean Southern Volcanic Zone (SVZ) and the transitional to oceanic Central American Volcanic Arc (CAVA) show increasing degrees of melting with increasing involvement of slab fluids, as is typical for hydrous flux melting beneath arc volcanoes. At the SVZ, the central segment with the thinnest continental crust/lithosphere erupted the highest-degree melts from the most depleted sources, similar to the oceanic-like Nicaraguan segment of the CAVA. The northern part of the SVZ, located on the thickest continental crust/lithosphere, exhibits features more similar to Costa Rica situated on the Caribbean Large Igneous Province, with lower degrees of melting from more enriched source materials. The composition of the slab fluids is characteristic for each arc system, with a particularly pronounced enrichment in Pb at the SVZ and in Ba at the CAVA. A direct compositional relationship between the arc rocks and the corresponding marine sediments that are subducted at the trenches clearly shows that the compositional signature of the lavas erupted in the different arcs carries an inherited signal from the subducted sediments. 相似文献
15.
Oceanic arcs are commonly cited as primary building blocks of continents, yet modern oceanic arcs are mostly subducted. Also, lithosphere buoyancy considerations show that oceanic arcs (even those with a felsic component) should readily subduct. With the exception of the Arabian–Nubian orogen, terranes in post-Archean accretionary orogens comprise < 10% of accreted oceanic arcs, whereas continental arcs compose 40–80% of these orogens. Nd and Hf isotopic data suggest that accretionary orogens include 40–65% juvenile crustal components, with most of these (> 50%) produced in continental arcs.Felsic igneous rocks in oceanic arcs are depleted in incompatible elements compared to average continental crust and to felsic igneous rocks from continental arcs. They have lower Th/Yb, Nb/Yb, Sr/Y and La/Yb ratios, reflecting shallow mantle sources in which garnet did not exist in the restite during melting. The bottom line of these geochemical differences is that post-Archean continental crust does not begin life in oceanic arcs. On the other hand, the remarkable similarity of incompatible element distributions in granitoids and felsic volcanics from continental arcs is consistent with continental crust being produced in continental arcs.During the Archean, however, oceanic arcs may have been thicker due to higher degrees of melting in the mantle, and oceanic lithosphere would be more buoyant. These arcs may have accreted to each other and to oceanic plateaus, a process that eventually led to the production of Archean continental crust. After the Archean, oceanic crust was thinner due to cooling of the mantle and less melt production at ocean ridges, hence, oceanic lithosphere is more subductable. Widespread propagation of plate tectonics in the late Archean may have led not only to rapid production of continental crust, but to a change in the primary site of production of continental crust, from accreted oceanic arcs and oceanic plateaus in the Archean to primarily continental arcs thereafter. 相似文献
16.
The occurrence of great earthquakes in the northwestern circum-Pacific belt is explained systematically in terms of the interaction between the oceanic and continental lithospheres. The great earthquakes in the Alaska-Aleutian region are considered to be a result of a rebound of the continental lithosphere which is dragged by the underthrusting oceanic lithosphere. The largest earthquakes in the Japan region are about one order of magnitude smaller than those in the Alaska-Aleutian region. This is interpreted as due to the weakening of the continental lithosphere caused by a frictional heating at the interface between the oceanic and the continental lithospheres. When the friction becomes very small because of the subsequent heating, a tensile force begins to prevail in the oceanic lithosphere. This tensile force is caused by a gravitational pull exerted by the sinking lithosphere. When this tensile stress surpasses the strength of the lithosphere, a large-scale normal fault occurs which extends through the entire thickness of the lithosphere. The intermittent slippages of the lithosphere on this fault plane are observed as great normal-fault earthquakes. The Sanriku earthquake of 1933 represents one of these earthquakes. The normal faulting accounts for the sharp bend of the lithosphere at the trench and the rapid increase of the dip angle of the deep seismic zone in going from northern Japan to the Izu-Bonin region. After repeated slippages, the sinking lithosphere becomes detached from the oceanic lithosphere and no further lithospheric interaction can take place. This picture is consistent with the complete lack of great shallow earthquakes in the Izu-Bonin region. 相似文献
17.
Five domains (microplates) have been recognized by seismic anisotropy in the mantle lithosphere of the Bohemian Massif. The mantle domains correspond to major crustal units and each of the domains bears a consistent fossil olivine fabric formed before their Variscan assembly. The present-day mantle fabric indicates that this process consisted of at least three oceanic subductions, each followed by an underthrusting of the continental lithosphere. The seismic anisotropy does not detect remnants of the oceanic subductions, but it can trace boundaries of the preserved continental domains subsequently underthrust along the paths of previous oceanic subductions. The most robust continent–continent collision was followed by westward underthrusting of the Brunovistulian mantle lithosphere, still detectable by seismic anisotropy more than 100 km beneath the Moldanubian mantle lithosphere. Major occurrences of the high-pressure/ultra high-pressure (HP–UHP) rocks follow the ENE and NNE oriented sutures and boundaries of the mantle–lithosphere domains mapped from three-dimensional modeling of body-wave anisotropy. The HP–UHP rocks are products of oceanic subductions and the following underthrusting of the continental crust and mantle lithosphere exhumed along the mantle boundaries. The close relation of the mantle sutures and occurrences of the HP–UHP rocks near the paleosubductions testifies for models interpreting the granulite–garnet peridotite association by oceanic/continental subduction/underthrusting followed by the exhumation of deep-seated rocks. Our findings support the bivergent subduction model of tectonic development of the central part of the Bohemian Massif. The inferences from seismic anisotropy image the Bohemian Massif as a mosaic of microplates with a rigid mantle lithosphere preserving a fossil olivine fabric. The collisional mantle boundaries, blurred by tectonometamorphic processes in easily deformed overlying crust, served as major exhumation channels of the HP–UHP rocks. 相似文献
18.
Shun-ichiro Karato 《中国地质大学学报(英文版)》2011,(2)
The strength of the oceanic and continental lithosphere has important controls on some of the major geological processes on earth including the operation of plate tectonics and the long-term stability of the continental roots.However,explaining these major geological features from the experimental and theoretical studies on the strength of rocks is challenging and some of the existing models for the strength of the lithosphere do not explain these main geological observations.A brief review is provided to s... 相似文献
19.
The rocks of Macquarie Island are part of the mid-Tertiary oceanic lithosphere from a major ocean basin. They were probably created at the Indian—Australian—Pacific spreading ridge.The basalts and dolerites are usually porphyritic, carry plagioclase (An87-80) as a dominant phenocryst phase with less abundant olivine (Fo89-85), chrome spinel and rare clinopyroxene (Ca45Mg50Fe5|Ca38Mg50Fe12) phenocrysts. Normatively the rocks range from ne- to Q-bearing, with most falling near the critical plane of normative silica undersaturation. Dykes tend to be more Fe-rich than lavas, and to include the more di-poor rocks. The rocks also range compositionally from typical ocean floor basalts through to varieties relatively enriched in some incompatible trace elements, particularly Nb (20–60 ppm), that otherwise retain ocean-floor basalt phenocryst assemblages, major-element compositions and Ti, Ni, Cr and Zr contents. This enrichment, also characteristic of ocean-floor basalts from the “abnormal” ridge segments near 45° N and 36° N (FAMOUS area) on the Mid-Atlantic Ridge, causes the rocks to plot away from the ocean-floor basalt fields on popular trace-element diagrams intended to identify tectonic affinities of basalts.The upper parts of the Macquarie Island oceanic lithosphere section can be thought of as a vertical slice through a magma column, differentiating at shallow levels. The layered and massive gabbros that underlie the basalts and dolerites are composed essentially of olivine, plagioclase and clinopyroxene. Olivine and plagioclase are cumulate phases in the layered rocks, clinopyroxene is postcumulus. Mineral compositions of the gabbros, particularly those of the layered rocks, are closely resembled by phenocryst compositions in the basalts and dolerites. Plagiogranites and trondheimites are unknown from the island, and norites very rare. Thus, Macquarie Island basalts, dolerites and gabbros form a distinctive igneous association that ought to make Macquarie Island-type ophiolite complexes from major ocean basins an easily recognized ophiolite type in continental orogenic terranes, even when dismembered. 相似文献
20.
Fluids, tectonics and crustal deformation 总被引：1，自引：0，他引：1
W.S. Fyfe 《Tectonophysics》1985,119(1-4)
In the plate tectonic process, lithosphere creation at ocean ridges and its cooling leads to volatile fixation in the oceanic crust. The outer 10 km or so of all crust contains abundant water in pores and fractures and variable amounts of volatiles in minerals. When surface rocks are buried by tectonic processes, fluids must be released and modify the mechanical properties. In the subduction process hydrated oceanic crust may be decoupled from the remaining oceanic lithosphere. At depth rising aqueous fluids or melts lead to a complex series of mass-energy transfer processes which may decouple continental crust near the Moho. Continental crust if subducted, may also be decoupled from its lithosphere by degassing. Fluid release processes which create gas-solid mixtures beneath impermeable cover create low-strength systems subject to facile deformation, hydraulic fracture processes and diapiric phenomena. 相似文献