Rapid vertical motions and formation of volcanic arc gaps: Plateau collision recorded in the forearc geological evolution (Costa Rica margin)     

《Basin Research》2018,30(5):863-894

The collision of bathymetric features with modern convergent margins has been investigated with the full range of tools used in geosciences. Hence, a comprehensive picture exists of the characteristic effects of collision events on the evolution of convergent margins. In contrast, much less studies documented past collisions of bathymetric features with convergent margins, as colliding features were generally lost to subduction. The arc‐trench system of southern Central America provides modern and past textbook examples of active margin interaction with incoming bathymetric reliefs. Here, we propose a synthesis which combines basin and terrane analysis of the forearc of northern Costa Rica and takes up the challenge of documenting past episodes of plateau accretion to the active margin. As illustrated in modern examples, our study shows that kilometric uplift of the overriding plate and termination of the volcanic arc activity are the most profound effects of colliding/accreting oceanic plateaus. Kilometric uplift of the forearc is documented by short‐lived (ca. 3 m.y.) occurrences of shallow‐water deposits in an overall deep‐water forearc record. These shallow deposits contain material reworked from underlying sedimentary and basement lithologies. The development of spatial gaps in arc volcanism is deduced from the transition from arc‐derived turbidites to pelagic sediments. Eventually, end of the collision event is evidenced by the subsidence of the whole forearc to deep‐water environments. Basin subsidence is accompanied or followed by renewed volcanic arc activity and coeval arc‐derived sedimentation, which may occur 1–7 m.y. after plateau collision. These past episodes of plateau accretion are archetypal for the following reasons: (a) they may be studied in outcrop, whereas most of the modern collisions of plateaus largely occur underwater; (b) no tectonic or metamorphic imprint has significantly complicated the forearc geological record; (c) the colliding feature and the sedimentary response to its collision are both preserved in the forearc geology; (d) they may be used as analogues for any setting where a bathymetric feature is suspected to have caused rapid forearc uplift and cessation of the volcanic arc activity.  相似文献   

阿尔金喀腊大湾地区中酸性火山岩SHRIMP年龄及其构造环境   总被引：3，自引：0，他引：3  

陈柏林  李松彬  蒋荣宝  陈正乐  韩凤彬  崔玲玲  李丽  赵树铭  祁万修  杨屹  王世新  王永  周永贵  郝瑞祥 《地质学报》2016,90(4):708-727

阿尔金山喀腊大湾地区位于北东向阿尔金走滑断裂北侧与东西向阿尔金北缘断裂所夹持的区域,是区域上红柳沟-拉配泉构造带的中段。该区广泛发育火山-沉积岩系,前人将其确定为中元古代。本文运用锆石SHRIMP U-Pb方法对区内火山-沉积岩系中的中酸性火山岩进行测年,获得477~485Ma的年龄,确认喀腊大湾地区早古生代中酸性岩浆喷发活动的存在。同时根据岩石地球化学研究,显示这套火山岩具有活动大陆边缘(岛弧)构造环境,其岩浆源具有I型及I与S过渡类型特点。结合前人对红柳沟-拉配泉一带的蛇绿混杂岩、高压变质泥岩、榴辉岩、中酸性侵入岩等相关年代资料及构造环境示踪,作者认为喀腊大湾地区中酸性火山岩形成于活动大陆边缘(岛弧)大地构造环境,其时限与蛇绿混杂岩的末期非常接近,代表了洋壳俯冲碰撞过程中形成的同碰撞中酸性火山岩。据此可以将区域上红柳沟-拉配泉一带的构造演化划分为洋壳扩张期(晚元古代末-寒武纪,蛇绿混杂岩年龄510~580Ma,但扩张起始会早一些)、洋壳板块俯冲碰撞期(早奥陶世-中奥陶世早期,中酸性岩浆岩(包括侵入岩和火山岩)年龄为477~488 Ma(部分花岗岩年龄延迟到467Ma左右),以及高压变质岩的退变质年龄479~491Ma),碰撞后伸展期(晚奥陶世—志留纪,蛇绿混杂岩变质基质岩系的变质年龄450~455Ma,代表蛇绿混杂岩最后就位,碰撞—碰撞后S型碱性花岗岩年龄417~431Ma,代表碰撞后伸展构造环境)三个演化阶段。  相似文献   

控制点布设对无人机影像空三精度的影响   总被引：1，自引：0，他引：1  

朱进  丁亚洲  陈攀杰  王新安  郭丙轩  肖雄武  牛科科 《测绘科学》2016,41(5):116-120

针对无人机航测按照传统的摄影测量布点方式,不仅需要较多的控制点,而且实施起来不太便利的缺点,提出了一种适合无人机航测的最优布点方案。通过对6种无人机控制点布设方案(传统的摄影测量布点方案和5种适合无人机航测的布点方案)进行空三精度对比实验,试验表明,该布点方案精度最高,与传统的摄影测量布点方式相比,其不仅实施方便,而且需要的控制点数量要少,大大减少了内、外业工作量。该方法的意义在于较好地解决了无人机航测因像幅小、重叠度不规则而导致的外业和内业工作量大的难题。  相似文献   

江西南部震旦—寒武纪寻乌岩组变沉积岩地球化学特征及构造意义          下载免费PDF全文

杨世文  楼法生  杨坤光  张芳荣  凌国卿  曹员兵 《中国地质》2016,(1):349-364

寻乌岩组变沉积岩发育在江西南部新元古代—早古生代南城—寻乌盆地内,时代为震旦—寒武纪。寻乌岩组的Si O2含量变化较大,除1个含量较低的样品外,平均为63.01%,具有相对较高的K2O、Al2O3及(TFe O+Mg O)值,较低的Na2O、Ca O。相容元素含量与后太古代澳大利亚页岩(PAAS)十分接近,高于中国东部上地壳,与其较高的(TFe O+Mg O)特征相吻合,说明源区具有一定数量的中基性组分。稀土元素总量高于上地壳及PAAS,但其球粒陨石标准化配分模式与典型的上地壳及PAAS相似,表现为明显向右倾斜,轻稀土富集,重稀土平坦,铕负异常显著,铈负异常不明显。岩石地球化学特征显示其原岩属于一种中等成熟度的陆源碎屑岩,物源主要为被改造的上地壳长英质和花岗质物源区,少部分物源为中基性火山岩。高场强元素及稀土元素等不活动元素地球化学特征表明其沉积环境为浅海—半深海,其构造环境属于发育有裂谷系的被动大陆边缘,该认识从沉积岩地球化学方面为华南早古生代构造属性提供了新资料。  相似文献   

新疆阿舍勒铜锌矿区潜玄武安山岩的岩石地球化学特征及其地质意义   总被引：1，自引：0，他引：1  

吴玉峰  杨富全  刘锋 《岩石矿物学杂志》2016,35(1):65-80

对新疆阿舍勒铜锌矿区潜玄武安山岩进行了岩石学、岩石地球化学和同位素地球化学研究,结果表明:岩石具有中等的SiO_2(51.90%~52.85%)、MgO(4.44%~5.08%)、Al_2O_3(14.94%~16.11%)、TiO_2(0.99%~1.03%)含量,较低的K_2O(0.01%~0.27%)含量,属于低钾拉斑玄武岩系列;岩石具有较低的稀土元素总量,ΣREE=38.07×10~(-6)~41.70×10~(-6),亏损轻稀土元素,LREE/HREE=0.57~0.61,(La/Yb)N=0.84~0.91,具有明显Eu正异常(δEu=1.13~1.23);富集Sr、Ba、Th等大离子亲石元素,亏损Nb、Ta、Zr、Hf等高场强元素,具有洋中脊玄武岩(MORB)和岛弧拉斑玄武岩(IAB)的特征,形成于岛弧(或弧前)环境;具有相对高的εNd(t)值(+6.9~+7.6),表明其原始岩浆来源于俯冲流体交代地幔楔的部分熔融,没有明显深海沉积物加入。结合阿尔泰造山带南缘的区域地质资料及潜玄武安山岩的地球化学特征,认为阿尔泰南缘在晚古生代处于活动大陆边缘,阿舍勒盆地处于岛弧(或弧前)背景。  相似文献   

Geochemistry and palaeotectonic setting of amphibolites from the Western Tatra Mountains,southern Poland     

A. Gaw&#x;da  J. A. Winchester  K. Koz&#x;owski  W. Nar&#x;bski  J. G. Holland 《Geological Journal》2000,35(2):69-85

Amphibolites from the crystalline basement of the Western Tatra Mountains, which are found as small lenses within migmatitic gneisses and mica schists, were formed during pre‐ or early Variscan amphibolite‐facies metamorphic events, and subsequently intruded by the post‐metamorphic Variscan Tatra Granite. The amphibolites occur in both the upper and lower metamorphic complexes, which are separated by a major subhorizontal shear zone in the Western Tatra Mountains. The amphibolites can be divided into three types: massive, striped and garnetiferous. The striped and massive amphibolites, concordant with a dominant S₁ foliation, and the garnet amphibolites, which cross‐cut the S₁ banding in the gneisses, were all originally intrusive dolerites. The striped amphibolites (consisting primarily of hornblende, andesine and quartz), and later, cross‐cutting garnet‐hornblende‐andesine‐quartz‐bearing amphibolites, predominate in the lower part of the dominantly migmatitic upper complex, and are exposed mainly on the ridges. The massive amphibolites, which contain a similar mineral assemblage, mainly occur in the usual unmigmatized lower structural unit. Chemical studies indicate that three amphibolite suites are present, which probably originated as a series of enriched tholeiites, similar to more recent plume‐influenced magmas, which were derived by partial melting of a spinel lherzolite with primitive mantle composition and compositionally slightly modified by crustal contamination. The amphibolites were intruded as dolerites into clastic sediments which had accumulated in an extensional basin floored by attenuated continental crust, a situation similar to that of amphibolites found in metamorphic complexes within the Variscan belt, e.g. in the Orlica–Snieznik area of the Sudetes, where amphibolites chemically similar to those in the Western Tatra also occur. Copyright © 2000 John Wiley & Sons, Ltd.  相似文献   

鲁南山区基岩蓄水构造类型及找水定井方法     

贾德旺 《江苏地质》2020,44(3):318-325

以鲁南地区地下水为研究对象,通过分析其赋存特征及影响因素,总结地下水蓄水构造类型及特征,提出找水定井示范方法,评价及开发利用地下水资源。研究显示,受地质构造、地层岩性、地形地貌、裂隙岩溶发育程度及裂隙充填情况等影响,不同地区地下水赋存特征也不相同,鲁南地区蓄水构造主要包括岩溶蓄水构造和裂隙蓄水构造两大类,针对不同地层岩性找水定井方法也不相同。建议相关部门采取措施改变鲁南山区的缺水现状。  相似文献   

大兴安岭中部柴河地区晚侏罗世花岗质岩石成因及构造意义     

施璐  唐振  郑常青  秦涛  张立东  汪岩  钱程  杨帆 《吉林大学学报(地球科学版)》2020,50(1):112-128

本文对大兴安岭中部柴河地区晚侏罗世花岗质岩石进行了岩石学、同位素年代学、地球化学等研究,探讨了其岩石成因及形成的构造背景。岩石学研究表明,大兴安岭中部柴河地区晚侏罗世花岗质岩石主要岩石组合为花岗闪长岩、二长花岗岩和碱长花岗岩。LA-ICP-MS锆石U-Pb测年结果获得2个二长花岗岩年龄分别为（152±1）Ma和（150±1）Ma。岩石主量元素具有富钾钠、富铝的特点,属铁质碱-钙性岩石。稀土元素相对富集轻稀土元素、亏损重稀土元素,具有弱到中等的Eu负异常,微量元素主要富集大离子亲石元素（Rb、Th、U、K、LREE）和Zr、Hf元素,亏损高场强元素（Nb、Ta、P、Ti）和Ba、Sr元素。地球化学特征指示这些晚侏罗世花岗质岩石来源于新元古代和早古生代期间从亏损地幔新增生的地壳物质部分熔融,形成于蒙古-鄂霍茨克洋闭合陆壳加厚之后挤压到伸展的转换环境。  相似文献   

汪清大梨树沟-红太平-新华村地区找矿前景探讨     

钟卫士  刘浩  松权衡  牛继辉  于政涛 《吉林地质》2004,23(4):49-55,96

本文主要从地层、构造、岩浆岩等区域成矿地质背景因素加以总结;对区域的重力场、磁场的特征及遥感特征进行分析、解译;对区域的地球化学场、1／20万化探异常进行深入研究;对区域矿产加以概述;在此基础之上对大梨树沟、红太平、新华村3个区域的成矿地质背景、重磁场特征及1／5万化探异常特征进行深入研究,最后总结了区域上的找矿前景。  相似文献   

大兴安岭哈达陶勒盖组火山岩年龄、地球化学特征及其陆缘弧构造背景          下载免费PDF全文

申亮  赵胜金  于海洋  柳志辉  周颖帅  张猛  朴丽丽 《中国地质》2020,47(4):1041-1055

根据野外调查,将大兴安岭北段新巴尔虎右旗地区的一套火山岩归属为哈达陶勒盖组。通过SHRIMP锆石U-Pb测年,获得哈达陶勒盖组绿帘石化安山岩的年龄加权平均值为(254.3±7.9)Ma(MSWD=4.7),结合区域地层对比,将该组的形成时代置于早三叠世。根据元素地球化学分析,可将哈达陶勒盖组火山岩划分为中基性和酸性火山岩两类。其中,中基性火山岩岩浆可能来源于受俯冲作用影响的岩石圈地幔,并遭受到地壳物质的混染;而酸性火山岩岩浆则形成于地壳。结合区域地质特征,通过构造环境判别,该组火山岩的形成可能与蒙古—鄂霍茨克板块向南俯冲引起的陆缘弧背景密切相关。哈达陶勒盖组的厘定丰富了大兴安岭北段地层层序,也为大兴安岭地区区域构造演化和岩浆活动提供了证据。  相似文献