国外深地震反射研究之现状     

吴其斌 《地质科技情报》1993,12(1):85-91

本文概括地总结和回顾了深地震反射研究成果,并针对存在的一系列问题进行了讨论。许多国家利用深地震反射法来研究大陆地壳和上地幔的内部结构。研究成果表明,大陆地壳和上地幔的反射特征具有显著的差异,这些差异反映了不同的构造单元和状态。  相似文献   

桂东超单元花岗岩各单元特征及其归属探讨     

吴俊华  彭志新 《湖南地质》1993,12(4):226-230

通过对桂东超单元各单元特征的对比,我们认为桂东超单元包括了两类不同地质、岩石、矿物学及地球化学特征的花岗岩,进而探讨了这两类花岗岩的成因及其形成构造环境,得出牛塘、三洞两单元为1型花岗岩,形成于板块碰撞的环境,大塘、寨前、子公坑、五峰仙单元为S型花岗岩,形成于陆一陆同碰环境。建议将牛塘、三洞两单元建立桂东序列,其余四单元归属江西汤湖超单元。  相似文献   

伊宁地块构造单元划分——来自火山岩浆作用的证据     

李永军  佟丽莉  王祚鹏  李卫东  郭文杰  李甘雨  杨高学 《岩石学报》2020,36(7):1986-2000

伊宁地块不是一个之前一贯认为的"均匀地块"或"均一地块",而是以乌孙山-塔勒得近东西向区域性大断裂为界的南、北两大次级构造带("弧-盆"体系)叠加拼贴增生而成,火山岩浆作用为这一新的构造单元划分与建立提供了佐证。南构造带由喀拉峻岛弧带和其北的阿腾套弧后盆地构成,主要发育于晚泥盆世-早石炭世早期,火山岩同位素年龄峰值为355～350Ma,17个年龄平均值为351Ma;北构造带由北而南可再细分出清水河-苏布台弧后盆地→阿吾拉勒叠加岛弧带→特克斯-新源弧前盆地,主要发育于早石炭世中-晚期,同位素年龄峰值集中于345～329Ma,18个火山岩年龄平均值为340Ma。这两个"弧-盆"体系以大哈拉军山组钙碱性火山岩为主体,共生早石炭世海相阿克沙克组弧前及弧后沉积岩组合。大哈拉军山组火山岩主体以岛弧火山岩为主,见有富Nb玄武岩、高镁安山岩等,共生埃达克岩和高分异I型花岗岩等小岩体;在弧后还见有碱性火山岩、碱性球泡流纹岩,共生双峰式火山岩。不仅大哈拉军山组火山岩在各构造相中显著有别,而且共生的阿克沙克组在各构造相中差异极为显著。两大次级构造带具有独立的基底建造史,差异显著的盆地沉积史,独特的火山岩浆史和构造演化史。早晚石炭世之间的鄯善运动使南、北两个次级构造带叠加拼贴,构成统一的伊宁地块,晚石炭世进入统一的陆内构造发展演化阶段,发育以伊什基里克组碱性双峰式火山岩为代表的裂谷火山岩浆建造。  相似文献   

Mesozoic evolution of the Tisza Mega-unit     

János?HaasEmail author  Csaba?Péró 《International Journal of Earth Sciences》2004,93(2):297-313

The south-eastern part of the basement of the Pannonian Basin is made up of Variscan crystalline complexes and early Mesozoic formations showing striking affinity with the corresponding formations in the southern margin of the European Plate. This large composite structural unit, which is actually an exotic terrane of European Plate origin, has been named the Tisza Mega-unit. Based upon relevant data of the pre-Tertiary basement of southern Hungary the reconstruction of the position of the Tisza Terrane in the early Alpine evolutionary stages, the process of its separation and break-off from the European Plate, and results of its Eo-Alpine deformations are summarised in the present paper. In the Variscan and early Alpine evolutionary stages the area of the later Tisza Mega-unit was located at the margin of the European Plate. During Variscan orogeny terrane accretion led to intensive deformation and metamorphism in this belt. This was followed by transpressional tectonics and the development of molasse basins in the late and post-Variscan stages, and passive margin evolution after the Neotethys opening in the Middle Triassic. The separation of the Tisza Mega-unit began with incipient continental rifting along the axis of the later Ligurian–Penninic–Vahic oceanic branch in the Late Triassic. The end of terrigenous material deposition in the most external zones, and a coeval change in fossil assemblage, point to the separation of the Tisza Block from the European Plate in the Early Bathonian. Significant rotation of the Tisza Mega-unit and coeval paroxysm of alkaline rift-type basalt volcanism took place in the Early Cretaceous. In the mid-Cretaceous, due to the northward motion of the Adria Block and the related closure of the westernmost Neotethys basin, the extensional regime changed to a compressional one, leading to onset of the nappe stacking and low-grade regional metamorphism within the Tisza microplate. In the foreland of the nappe systems flexural basins came into existence that are characterised by flysch-type sedimentation. In the Early Tertiary the north-eastward motion of the Alcapa and Tisza + Dacia Blocks led to the formation of the present-day heterogeneous basement of the Pannonian Basin.  相似文献   

Hydrogeological investigation of mud-mound springs developed over a weathered basalt aquifer on the Liverpool Plains,New South Wales,Australia   总被引：1，自引：0，他引：1  

R.?Ian?AcworthEmail author  Wendy?A.?Timms 《Hydrogeology Journal》2003,11(6):659-672

The growth and collapse of mud mounds at a site on the Liverpool Plains in northern New South Wales, Australia has been observed over a 12-year period. The mud mounds appeared in a flat field for the first time in living memory in 1989, but their prior existence in the early Holocene is indicated by archaeological data. The piezometric head in bores drilled through a 7-m bed of clayey silt and screened in weathered basalt at a depth of 8 m was more than 2 m above ground level. Clay has been carried in suspension by water seeping to the ground surface where it has accumulated and formed a mound. Approximately eight years after their initial appearance, the growth of the mounds stopped and within a further three years they had almost completely disappeared.Mechanisms for the growth and decay of the mounds are reviewed. The chemistry of the shallow bore water and the water seeping from the surface of the mounds was dominated by sodium bicarbonate with a 4 mEq/l increase between the weathered basalt and the surface of the mound. Inverse modelling (PHREEQC) is used to determine possible chemical reactions that can account for this increase.

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Electronic Supplementary Material Supplementary material is available in the online version of this article at http://dx.doi.org/10.1007/s10040-003-0278-0.

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Resumen Se ha observado durante 12 años el crecimiento y el colapso de montículos de lodo en un emplazamiento ubicado en las Llanuras de Liverpool, en el estado australiano de Nueva Gales del Sur. Según la memoria existente, los montículos de lodo aparecieron en un campo llano por vez primera en 1989, pero, por datos arqueológicos, se conoce de su existencia a comienzos del Holoceno. Los niveles piezométricos en sondeos perforados a través de 7 m de limos arcillosos y ranurados en el basalto meteorizado a 8 m son superiores en más de 2 m a la superficie del terreno. La arcilla es portada en suspensión por el agua que descarga hacia la superficie del terreno, donde se acumula y forma el montículo. Unos 8 años después de su aparición, el crecimiento de los montículos se detiene y éstos acaban prácticamente desapareciendo en otros 3 años.Se revisa los mecanismos que originan el crecimiento y desaparición de los montículos. La química de las aguas someras de los sondeos y del agua que se filtra desde la superficie de los montículos está dominada por bicarbonato sódico, con un incremento de 4 meq/L entre el basalto meteorizado y la superficie del montículo. Se utiliza la modelación inversa (PHREEQC) para determinar las reacciones químicas que pueden explicar dicho aumento.

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Résumé La croissance et l'effondrement de monticules de vase situés dans les plaines de Liverpool, dans le nord des Nouvelles Galles du Sud, ont été observés pendant 12 ans. Les monticules de vase sont apparus en terrain plat pour la première fois de mémoire d'homme en 1989; mais leur existence antérieure dès le début de l'Holocène est attesté par des données archéologiques. Le niveau piézométrique dans des forages traversant 7 m de silt argileux et recouvrant un basalte altéré à 8 m était de plus de 2 m au-dessus de la surface du sol. L'argile a été apportée en suspension par l'eau suintant à la surface du sol où elle s'est accumulée pour former un monticule. Environ 8 ans après leur première apparition, la croissance des monticules s'est arrêtée et ils ont presque complètement disparu dans les 3 ans qui ont suivi.Les mécanismes de croissance et de régression de ces monticules sont passés en revue. La chimie de l'eau des forages à proximité de la surface et de l'eau filtrant à la surface des monticules était dominée par le bicarbonate de sodium, avec une augmentation de 4 meq/l entre le basalte altéré et la surface du monticule. Une modélisation inverse (PHREEQC) a été mise en uvre pour déterminer les réactions possibles pouvant rendre compte de cet accroissement.

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大湄公河次地区构造单元划分   总被引：22，自引：2，他引：22       下载免费PDF全文

李兴振  刘朝基  丁俊 《沉积与特提斯地质》2004,24(4):13-20

大湄公河次地区在地质构造上是西南三江构造带和华南加里东褶皱带的向南或南西的延伸。在理清了各构造单元的延伸趋势及其相互关系的基础上，对该区大地构造单元作了统一划分和对比。以印缅山脉结合带、澜沧江-文冬-劳勿结合带、金沙江-哀牢山-马江结合带作为主结合带，将该区划分为印澳板块、中缅马陆块、印支陆块和华南陆块4个一级单元。然后在亲冈瓦纳的中缅马陆块和亲华南型的印支陆块内再以次级结合带分别划分出4个二级构造单元：亲冈瓦纳型的西缅微陆块、腾冲-毛淡棉微陆块，保山-掸泰微陆块、临沧-景栋微陆块，亲华南型的景洪-帕府-东马来西亚微陆块、思茅-大叻微陆块、昆嵩微陆块和长山微陆块；华南陆块以越北斋江结合带为界分为扬子和华夏两微陆块。简要论述了各构造单元的基本地质特征，提出将可可西里-澜沧江-文冬-劳勿结合带作为南部冈瓦纳大陆和北部劳亚大陆的分界，指出昆嵩微陆块和长山微陆块是华夏微陆块的南西延伸，其西部的对应体可能是昌都微陆块。  相似文献   

山东安丘地区郯庐断裂带古近纪冲积物震积岩序列   总被引：5，自引：3，他引：5       下载免费PDF全文

田洪水  张增奇 《地质科学》2006,41(2):208-216

在郯庐断裂带的安丘—夏庄箕状盆地的古近纪朱壁店组厚层冲积层中,发育许多震积岩层。它们是由地震液化、地震裂隙充填、振动塌落、地震断裂和地震沉陷作用而形成的震积岩组合。通过野外观测、室内鉴定和比较地震地质学研究,鉴别出了液化砂岩脉、液化砂岩墙、液化砂岩团块、裂隙充填砂砾岩墙、震塌岩、地震成因层内断裂及地震沉陷构造等震积岩构造。根据震积岩构造的特征和有关的研究成果,本文建立了由A、B和C3个震积岩单元组成的震积岩序列。水饱和砂受强烈振动液化作用形成A单元;随后,由砂砾层或砂层的地震裂隙充填和震动塌落而形成B单元;最后,由层内断裂作用及地面沉陷作用生成C单元;该序列的3个单元反映了厚层冲积物的地震作用全过程。  相似文献   

地勘单位如何实现“跨跃式”转制的探讨     

潘文好  龙盛海 《南方国土资源》1998,(3)

在全国企事业单位改革攻坚战中,地勘单位如何由事业体制跨越传统企业阶段,直接向现代企业转制,是关系到地勘事业生存和发展的大课题,文章根据地勘单位实际,从产权管理、所有制结构、产业结构、人事用工制度、分配制度等方面改革入手,提出地勘单位如何实现跨跃式转制的建议。  相似文献   

福建省地层多重划分,对比研究（续）   总被引：1，自引：0，他引：1  

李兼海  王国平 《福建地质》1996,15(1):20-54

福建省地层多重划分、对比研究（续）李兼海，王国平，郑铁藩，梁诗经（福建省区域地质调查队，三明，３６５００１）３晚三叠世一新第三纪印支运动后，福建地壳发生了重大变革，全境由海转变成陆地。晚三叠世一中佛罗世，除闽西南局部地区有海湾泻湖相沉积外，皆为河流一...  相似文献   

Recent environmental changes inferred from the sediments of small lakes in Yellowstone's northern range (Engstromet al., 1991)     

Wayne L. Hamilton 《Journal of Paleolimnology》1994,10(2):153-157

Sedimentation rate data of Engstromet al. (1991) were analyzed in relation to the elevation of the eight ponds studied. The ... asynchroneity of the stratigraphic changes among the lakes ... that they noted was transformed into a pattern of time-transgressive change of sedimentation rate with elevation. Sediment units representing increasing (and decreasing) sedimentation rate and accelerating (and decelerating) sediment accumulation were correlated from pond to pond, suggesting that the sediment-producing condition somehow moved upslope over time at a rate of 3.4 to >5 m yr^–1. Climatic data appear not to explain this monotonic pattern, but dendrochronological data and elk population numbers suggest that ungulate foraging patterns might. Engstromet al. (1991) concluded that ...the lake-sediment records in the northern range do not convincingly show systematic direct or indirect effects of ungulate grazing during the history of the Park. Reinterpretation of these sediment data suggests that detailed reanalysis might lead to a different conclusion.  相似文献