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241.
台湾增生楔的构造单元划分及其变形特征 总被引:6,自引:0,他引:6
台湾增生楔位于欧亚板块、菲律宾海微板块和南海的结合部位,是现代弧陆碰撞研究的理想场所。通过对南海973航次在该区域的多道地震剖面的解释,对该增生楔进行了构造单元的划分,并分析了变形特征。认为台湾增生楔是由3个部分,即弧陆碰撞产生的增生部分、洋内俯冲产生的增生部分和增生楔后端在恒春海脊和北吕宋海槽之间的构造楔组成,研究区的高屏斜坡、恒春海脊和北吕宋海槽西端变形带分别是3个部分的反映。自中中新世以来,南海洋壳开始沿着马尼拉海沟向菲律宾海微板块俯冲,形成增生楔中洋内俯冲增生部分;与此同时菲律宾海微板块开始向NW方向移动,前缘的吕宋岛弧自6.5Ma B.P以来与亚洲陆缘斜向碰撞,形成增生楔中弧陆碰撞增生部分。碰撞首先发生在台湾岛的北部,由于弧陆强烈的挤压作用,增生楔后端部分向北吕宋海槽倒冲楔人,使得上部的北吕宋海槽的沉积发生隆升变形。滨海的各个地貌单元可以和台湾陆上的地貌单元相联系,它们具有相似的地质特征,但是由于陆上部分增生历史久,不仅抬升为陆,而且地层的年代也更老。 相似文献
242.
长春-延吉缝合带:性质与意义 总被引:1,自引:1,他引:0
长春-延吉缝合带(或长春-延吉增生杂岩带),是由佳木斯-兴凯地块与华北板块之间俯冲拼贴形成的增生杂岩带。该缝合带自西向东分为三个部分,具体包括西段吉林-红旗岭、中段桦甸-两江和东段华集岭-开山屯组成。长春-延吉增生杂岩带以延边地区发育的开山屯混杂岩为代表,自西向东包括石头口门-烟囱山高压红帘石片岩,以及原定为"呼兰群"、"色洛河群"、"青龙村群"等一系列沿着缝合带分布的构造杂岩等,它们均发育"基质包裹外来岩块(block-in-matrix)"的混杂岩结构,并在吉林东部石头口门、烟囱山和延边开山屯等地区发现高压矿物组合,因此,这些杂岩应代表了佳木斯-兴凯地块向华北板块俯冲-拼贴过程中形成的增生杂岩。长春-延吉增生杂岩原岩年龄大致为晚古生代-早中生代(最小峰期240~250Ma),并被时代为~220Ma的晚三叠世大酱缸组磨拉石层序不整合覆盖,这一直接证据与近期发表的年代学证据一致,共同证明了长春-延吉缝合带的就位时代为中三叠世(220~240Ma),而不是前人认为的晚古生代或更早。区域构造分析显示,长春-延吉增生杂岩带不是天山-北山-西拉木伦河-长春断裂带的东延部分,而是佳木斯-兴凯地块西南缘分布的吉林-黑龙江高压变质带的南部组成部分,形成于三叠纪-早侏罗世太平洋板块西向俯冲过程中,佳木斯-兴凯地块自东向西的"剪刀式"闭合过程。因此,长春-延吉增生杂岩带记录了古亚洲构造域的结束和太平洋俯冲开始的关键时期,为两大构造域叠加与转换的关键性地质证据。 相似文献
243.
龙陵-瑞丽早白垩世流纹岩带断续延伸约100km,其形成的构造背景是揭示怒江洋演化及腾冲与保山地块关系的重要证据。笔者在野外调研的基础上,对本区流纹岩开展了岩石学、地球化学、锆石U-Pb定年和Hf同位素等方面的研究。结果表明流纹岩具有高硅贫钠、高钾钙碱性和高分异特征;锆石LA-ICP-MS U-Pb年龄分布在129~123Ma区间,代表流纹岩的喷发时代。流纹岩锆石εHf(t)值分布于-12.3~-6.3之间,对应的地壳模式年龄为1591~1826Ma;其微量元素蛛网图、稀土元素配分模式图和Nb/Ta比值、Th/U比值等与大陆中上地壳相似;岩石中无斜长石斑晶、Sr含量极低以及在Al2O3/(MgO+FeOT)]-[CaO/(MgO+FeOT)]和Rb/Ba-Rb/Sr图解上,样品都分布在变泥质岩部分熔融区;表明流纹岩岩浆来源于古老地壳物质部分熔融的产物,其低钠是源区中斜长石含量低或斜长石未参与部分熔融造成的。流纹岩轻稀土元素和大离子亲石元素(Th、U和K)富集,Nb、Ta、Ti、P和Sr强烈负异常;在构造环境判别图解上样品全部落在活动大陆边缘区;在空间上,这些流纹岩呈带状分布,构成俯冲增生杂岩带的一部分,并与同时代侵入岩紧密相邻,成因上类似于区域内同期S型花岗岩。这些特征表明研究区内流纹岩与高黎贡构造带内同时代花岗岩类相似,形成于俯冲的大陆边缘弧环境,即幔源岩浆底侵至下地壳,这一过程提供了足够的热源使壳源物质(可能为富云母、贫斜长石的变沉积岩类)发生部分熔融生成酸性岩浆,它们在经历了高度的结晶分异后喷出地表形成低钠流纹岩,并在弧前或弧间盆地内被浅海相碎屑沉积物覆盖。 相似文献
244.
Feixiong Liao 《International journal of geographical information science》2019,33(5):900-921
Space–time prism (STP), which envelops the spatial and temporal opportunities for travel and activity participation within a time frame, is a fundamental concept in time geography. Despite many variants, STPs have been mostly modeled for one flexible activity between two anchor points. This study proposes a systemic approach to construct the STP bounds of activity programs that usually include various possible realizations of activity chains. To that effect, multi-state supernetworks are applied to represent the relevant path sets of multi-activity travel patterns. A goal-directed search method in multi-state supernetworks is developed to delineate the potential space–time path areas satisfying the space–time constraints. Particularly, the approximate lower and upper STP bounds are obtained by manipulating the goal-directed search procedure utilizing landmark-based triangular inequalities and spatial characteristics. The suggested approach can in an efficient fashion find the activity state dependent bounds of STP and potential path area. The formalism of goal-directed search through multi-state supernetworks addresses the fundamental shift from constructing STPs for single flexible activities to activity programs of flexible activity chains. 相似文献
245.
聚焦新疆区内集中出露的61处蛇绿岩,据其物质组成、构造属性、形成时代、空间分布等特征,将其划分为14条蛇绿混杂岩带,其中多处发育洋岛海山、洋内弧等大洋岩石圈岩石组合,并以塔里木-敦煌地块为界,提出以北属古亚洲洋构造域、以南属特提斯洋构造域.结合俯冲增生造山过程中不同阶段的岩石学记录,确认古亚洲洋形成于新元古代末期至晚石... 相似文献
246.
247.
Abstract The Cansiwang Melange underlies the Southeast Bohol Ophiolite Complex (SEBOC) and is composed mainly of sheared ophiolite-derived blocks such as harzburgites, microgabbros, basalts and cherts in a pervasive serpentinite matrix. Available field, as well as geophysical evidence show that this melange unit is not diapiric, nor does it have a sedimentary origin considering that it lacks slump and flow structures. A tectonic origin for the Cansiwang Melange is favored in view of the numerous thrust faults, which cut across the exposures, as well as the tectonic contacts that the melange has with the overlying and underlying formations. The presence of the Cansiwang Melange in between the SEBOC and the Alicia Schist provides evidence that the amphibolite of the Alicia Schist do not correspond to the metamorphic sole of SEBOC. Similar to what is recognized in the Josephine Ophiolite, this suggests a 'cold' emplacement of the ophiolite over the Alicia Schist. The Cansiwang Melange represents an accretionary prism product which marks the location of an ancient subduction zone in what is now Central Philippines. 相似文献
248.
249.
王翔 《地球科学与环境学报》1994,(3)
坦比地区的构造格架以华力西期冲断构造为特征.本文通过大量的野外观察与室内分析,对该区冲断构造的样式、平衡剖面及构造缩短量进行了研究,并应用“增生楔”模式对冲断构造成因进行了探讨。 相似文献
250.
This paper presents the results of numerical modelling to investigate the regional occurrence of prehnite‐bearing metamorphic rocks at shallow levels in subduction zones. The modelling assumes a simple geometrical configuration in which the thermal structure in a prism is controlled by boundary conditions at the top and base of the prism. It is expected that the predominant metamorphic facies in a prism will change with decreasing age of the descending slab. The results of thermal modelling show that the facies boundary between pumpellyite–actinolite and prehnite–actinolite facies (including prehnite–pumpellyite facies) overlaps with an array of P–T conditions in the prism when the age of a descending slab is younger than 10 Myr. This implies that the change of the predominant metamorphic facies from pumpellyite–actinolite to prehnite–actinolite facies will switch drastically. The critical age of the switch depends on subduction parameters. In particular, the critical age of the descending slab is <5 Myr in the case of no shear heating, with a subduction rate of v=75–200 mm y?1 and subduction angle of θ=5–15°. For shear heating (constant shear stress=30 MPa) with a subduction rate of v=75 mm y?1 and subduction angle of θ=10° the critical age is 7 Myr. To test this switching behaviour in the development of prehnite–actinolite facies in the prism, petrologic data from the Cretaceous Shimanto Accretionary Complex (CSAC) in Kyushu, Japan were compiled. The regional occurrence and mineral assemblages of prehnite‐bearing metamorphic rocks suggest that the most of CSAC was metamorphosed under prehnite–actinolite facies. This conclusion is consistent with subduction of a young, hot slab, as has been proposed based on other geological observations. This suggests that the regional extent of the prehnite–actinolite facies metamorphic rocks may be a unique evidence for the subduction of a young, hot slab. 相似文献