Post-Collisional Transition from Subduction- to Intraplate-type Magmatism in the Westernmost Mediterranean: Evidence for Continental-Edge Delamination of Subcontinental Lithosphere   总被引：14，自引：0，他引：14  

DUGGEN  S.; HOERNLE  K.; VAN DEN BOGAARD  P.; GARBE-SCHONBERG  D. 《Journal of Petrology》2005,46(6):1155-1201

Post-collisional magmatism in the southern Iberian and northwesternAfrican continental margins contains important clues for theunderstanding of a possible causal connection between movementsin the Earth's upper mantle, the uplift of continental lithosphereand the origin of circum-Mediterranean igneous activity. Systematicgeochemical and geochronological studies (major and trace element,Sr–Nd–Pb-isotope analysis and laser ⁴⁰Ar/³⁹Ar-agedating) on igneous rocks provide constraints for understandingthe post-collisional history of the southern Iberian and northwesternAfrican continental margins. Two groups of magmatic rocks canbe distinguished: (1) an Upper Miocene to Lower Pliocene (8·2–4·8Ma), Si–K-rich group including high-K (calc-alkaline)and shoshonitic series rocks; (2) an Upper Miocene to Pleistocene(6·3–0·65 Ma), Si-poor, Na-rich group includingbasanites and alkali basalts to hawaiites and tephrites. Maficsamples from the Si–K-rich group generally show geochemicalaffinities with volcanic rocks from active subduction zones(e.g. Izu–Bonin and Aeolian island arcs), whereas maficsamples from the Si-poor, Na-rich group are geochemically similarto lavas found in intraplate volcanic settings derived fromsub-lithospheric mantle sources (e.g. Canary Islands). The transitionfrom Si-rich (subduction-related) to Si-poor (intraplate-type)magmatism between 6·3 Ma (first alkali basalt) and 4·8Ma (latest shoshonite) can be observed both on a regional scaleand in individual volcanic systems. Si–K-rich and Si-poorigneous rocks from the continental margins of southern Iberiaand northwestern Africa are, respectively, proposed to havebeen derived from metasomatized subcontinental lithosphere andsub-lithospheric mantle that was contaminated with plume material.A three-dimensional geodynamic model for the westernmost Mediterraneanis presented in which subduction of oceanic lithosphere is inferredto have caused continental-edge delamination of subcontinentallithosphere associated with upwelling of plume-contaminatedsub-lithospheric mantle and lithospheric uplift. This processmay operate worldwide in areas where subduction-related andintraplate-type magmatism are spatially and temporally associated. KEY WORDS: post-collisional magmatism; Mediterranean-style back-arc basins; subduction; delamination; uplift of marine gateways  相似文献   

Environmental changes over the past 25 000 years in the southern Middle Atlas,Morocco          下载免费PDF全文

Jalal Tabel  Carla Khater  Ali Rhoujjati  Laurent Dezileau  Ilham Bouimetarhan  Matthieu Carre  Laurence Vidal  Abdelfattah Benkaddour  Majda Nourelbait  Rachid Cheddadi 《第四纪科学杂志》2016,31(2):93-102

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Upper Cretaceous marine‐continental transition (Leonese Area,NW Spain) defined from integrated outcrop and seismic stratigraphy     

Antonio Herrero‐Hernndez  Fernando Gmez‐Fernndez  Francisco Javier Lpez‐Moro 《Geological Journal》2015,50(1):39-55

The Upper Cretaceous succession of the Leonese Area (NW Spain) comprises mixed clastic and carbonate sediments. This succession is divided into two lithostratigraphic units, the Voznuevo Member and the Boñar Formation, which represent fluvial, shoreface, intertidal, subtidal and open‐shelf sedimentary environments. Regional seismic interpretation and sequence stratigraphic analysis have allowed the study of lateral and vertical changes in the sedimentary record and the definition of third‐order levels of stratigraphic cyclicity. On the basis of these data, the succession can be divided into two second‐order depositional sequences (DS‐1 and DS‐2), incorporating three system tracts in a lowstand to transgressive to highstand system tract succession (LST–TST–HST). These sequences are composed of fluvial systems at the base with palaeocurrents that flowed westward and south‐westward. The upper part of DS‐1 (Late Albian–Middle Turonian) shows evidence of intertidal to subtidal and offshore deposits. DS‐2 (Late Turonian–Campanian) comprises intertidal to subtidal, tidal flat, shallow marine and lacustrine deposits and interbedded fluvial deposits. Two regressive–transgressive cycles occurred in the area related to eustatic controls. The evolution of the basin can be explained by base‐level changes and associated shifts in depositional trends of successive retrogradational episodes. By using isobath and isopach maps, the main palaeogeographic features of DS‐1 and DS‐2 were constrained, namely coastline positions, the existence and orientation of corridors through which fluvial networks were channelled and the location of the main depocentres of the basin. Sedimentation on the Upper Cretaceous marine platform was mainly controlled by (i) oscillations of sea level and (ii) the orientation of Mesozoic faults, which induced sedimentation along depocentres. Copyright © 2013 John Wiley & Sons, Ltd.  相似文献   

模拟水深测量实习设计与实现     

罗海滨  孙景领 《测绘与空间地理信息》2016,(2):3-5

针对海洋测绘实践教学中,水深测量实习受场地、经费和安全因素影响大,难以开展的问题,设计并实现了模拟水深测量实习。该模拟实习能较为真实地模拟了水深测量的主要步骤,易于开展和推广。  相似文献   

Progradational and backstepping shoreface deposits in the Ladinian to Early Norian Snadd Formation of the Barents Sea          下载免费PDF全文

Tore G. Klausen  Alf Ryseth  William Helland‐Hansen  Helge K. Gjelberg 《Sedimentology》2016,63(4):893-916

Shoreface sandstone deposits within the Early Carnian part of the Snadd Formation of the Norwegian Barents Sea can be traced for hundreds of kilometres in the depositional strike direction and for tens of kilometres in the depositional‐dip direction. This study uses three‐dimensional seismic attribute mapping and two‐dimensional regional seismic profiles to visualize the seismic facies of these shoreface deposits and to map their internal stratigraphic architecture at a regional scale. The shoreface deposits are generally elongate but show variable width from north‐east to south‐west, which corresponds to a sediment source in the northern part of the basin and a southward decrease in longshore sediment transport. The Snadd Formation presents an example of how large‐scale progradational shoreface deposits develop. The linear nature of its shoreface deposits contrasts with more irregular, cuspate wave‐dominated deltaic shorelines that contain river outlets, and instead implies longshore drift as the main sediment source. In map view, discrete sets of linear features bounded by truncation surfaces scale directly to beach ridge sets in modern counterparts. The shoreface deposits studied here are characteristic in terms of scale and basin‐wide continuity, and offer insight into the contrast between shallow marine deposition under stable Triassic Greenhouse and fluctuating Holocene Icehouse climates. Findings presented herein are also important for hydrocarbon exploration in the Barents Sea, because they describe a hitherto poorly understood reservoir play in the Triassic interval, wherein the most prominent reservoir plays have so far been considered to be found in channelized deposits in net‐progradational delta‐plain strata that form the topsets to shelf‐edge clinoforms. The documented presence of widespread wave‐dominated shoreface deposits also has implications for how the relative importance of different sedimentary processes is considered within the basin during this period.  相似文献   

新疆西天山松湖铁矿床火山岩年代学和岩石地球化学     

段士刚  张作衡  蒋宗胜  李凤鸣  任毅  肖燕洪  史维鑫 《矿床地质》2016,35(5):913-932

新疆西天山阿吾拉勒铁成矿带内众多铁矿床的围岩火山岩时代、岩石成因和构造背景迄今尚未得到很好地约束。文章对该铁成矿带内的松湖铁矿床围岩粗面英安岩和流纹岩进行了锆石LA_ICP_MS U_Pb测年和地球化学研究。粗面英安岩和流纹岩的锆石206Pb/238U加权平均年龄分别为(326.8±2.7)Ma和(327.3±1.7)Ma。粗面英安岩和流纹岩准铝质,均富集轻稀土元素、Rb、K、Zr、Hf,显示中等Eu负异常,亏损Ba、Sr、P、Ta、Nb和Ti。锆石饱和温度计算结果显示,粗面英安岩的母岩浆温度较高(774~812℃,平均792℃),流纹岩母岩浆的温度较低(713~790℃,平均750℃)。粗面英安岩具有非常低Sr高Yb的特征,Nb/Ta比值为10.8~11.4,具有较高的w(Th)(≥8.1×10-6)和高的Th/Ce比值(≥0.31);流纹岩具有低Sr低Yb特征,Nb/Ta比值为8.5~9.7,w(Th)(≥5.3×10-6)较高,Th/Ce比值为0.14~0.75,据此推测粗面英安岩母岩浆可能是上地壳部分熔融的产物,流纹岩母岩浆可能源于比粗面英安岩母岩浆更深的地壳的部分熔融。松湖铁矿区粗面英安岩和流纹岩具有弧火山岩的地球化学特征,结合构造环境判别图解和区域地质情况,推断其形成于大陆弧环境。  相似文献   

湖南省沉积型锰矿地质环境及成矿作用   总被引：2，自引：0，他引：2  

石少华 《地质与勘探》2016,52(2):209-219

湖南省沉积型锰成矿时代跨度大,最早由早元古代板溪群马底驿期至早二叠世孤峰期。其中,早南华纪大塘坡期、中奥陶世烟溪期及中二叠世孤峰期为三个最主要成锰集中期,并且大体呈现出朝东南方向成矿时代变新的趋势。成锰沉积盆地是锰矿床就位的重要场所,相应的岩相古地理环境为锰成矿创造了有利条件,即相对缺氧的、滞流的安静环境。这种环境在诸多古地理环境中都可以形成,导致了锰成矿岩相古地理环境的多样性,如浅海陆棚相、次深海棚缘盆地相、次深海台缘斜坡相及陆表次深海海盆相。三个主要成锰期锰成矿作用具有统一性,成矿作用与地壳拉张、海侵事件、缺氧事件等区域性重大地质事件关联密切。  相似文献   

四川盆地海相碳酸盐岩的油气成藏条件     

陈英富 《地质与勘探》2016,52(2):357-362

四川盆地位于亚洲大陆中南部,是我国最大的外流盆地。油气资源评价结果(2008)表明,四川盆地海相地层待发现资源量约为50111.84×108m~3,资源勘探潜力巨大。本文从地层的划分、层序格架及层序岩相古地理特征等方面,对四川盆地海相碳酸盐岩油气成藏条件做了进一步研究。认为研究区烃源岩包括下志留统、中二叠统、上二叠统龙潭组和上三叠统须家河组等4套岩石,及局部发育的上二叠统大隆组。储集层粉为构造成因类和沉积成因类,构造成因主要包括裂缝性储层;沉积成因类储层主要是礁滩储层、内幕白云岩储层和风化壳岩溶储层。中二叠统气藏主要为自生自储的裂缝性气藏和台内滩相气藏;茅口组顶部和雷口坡组顶部发育风化壳型气藏;吴家坪组、长兴组及飞仙关组地层含礁滩型气藏;嘉陵江组和雷口坡组地层含内幕白云岩型气藏。  相似文献   

重力场对飞行器制导的影响及海洋重力测线布设     

黄谟涛  刘敏  欧阳永忠  邓凯亮  翟国君  陆秀平  吴太旗 《测绘学报》2016,45(11):1261-1269

重点围绕远程飞行器飞行轨道控制保障需求,开展了空中扰动引力计算和地面重力异常测量精度指标及海洋重力测量测线布设方案的分析与论证。首先通过解析和简化飞行器导航误差解表达式,定量估计了地球重力场对远程飞行器飞行轨迹的影响,并以一定量值的落点偏差为限定指标,研究论证了空中扰动引力的计算精度要求。在此基础上,通过对地面重力异常截断误差及数据传播误差的估计和分析,研究确定了地面/海面网格平均重力异常的观测分辨率和计算精度指标。以此为依据,提出了相对应的海洋重力测量测线布设方案,并通过数值计算验证了所提方案的合理性和有效性。  相似文献   

论虚拟地理环境对地理知识的表达与共享     

林珲  张春晓  陈旻  郑新奇 《遥感学报》2016,20(5):1290-1298

地理知识是通过对地理科学领域独特的背景、过程和结果进行解释而得到的知识。如何有效表达和共享地理知识是地理学研究和应用中的重要问题。本文首先将地理知识划分为3个层次,事实型知识、规则及控制型知识和决策型知识,分析了不同阶段地理语言对地理知识表达与共享的支持能力。对比地图和GIS语言,发现新一代地理语言—虚拟地理环境VGEs(Virtual Geographic Environments)能够较为全面地支持3个层次的地理知识。针对VGEs,从多个角度分析了其服务于地理知识表达与共享的能力,包括虚实结合理论、地理模型库及管理系统、动态可视化表达和异地协同工作环境。结合面向珠江三角洲地区空气质量研究问题的虚拟地理环境平台,对上述各方面进行了阐述。最后从地理知识生成、管理与应用角度对未来研究提出展望。  相似文献