Tectonics and earthquake mechanism of the shallow earthquake seismic belt,the Himalaya

The foci distribution of upper mantle earthquakes occurred between 1961 and 1972 in Himalayan, Tibetan and Hindukush regions, were studied and compared. The V-shaped pockets above a vertical plane have shown a relationship with the dip-slip type or normal faulting at the borders of the continental plates. The left-lateral and right-lateral displacements of Kirthar-Sulaiman shear zone and Brailly fault respectively found by the focal mechanism indicate a relative difference in motion between the Kashmir region and Nepal region and the uniform and right angle displacement of Tibetan Plateau has produced the Saradah depression. On the basis of seismic and geological evidences a simple tectonic model is proposed.     

Tectonics of the ophiolite belt from Naga Hills and Andaman Islands,India

The ophiolitic rocks of Naga Hills-Andaman belt occur as rootless slices, gently dipping over the Paleogene flyschoid sediments, the presence of blue-schists in ophiolite melange indicates an involvement of the subduction process. Subduction was initiated prior to mid-Eocene as proved by the contemporaneous lower age limit of ophiolite-derived cover sediment as against the accreted ophiolites and olistostromal trench sediment. During the late Oligocene terminal collision between the Indian and Sino-Burmese blocks, basement slivers from the Sino-Burmese block, accreted ophiolites and trench sediments from the subduction zone were thrust westward as nappe and emplaced over the down-going Indian plate. The geometry of the ophiolites and the presence of a narrow negative gravity anomaly flanking their map extent, run counter to the conventional view that the Naga-Andaman belt marks the location of the suture. The root-zone of the ophiolite nappe representing the suture is marked by a partially-exposed eastern ophiolite belt of the same age and gravity-high zone, passing through central Burma-Sumatra-Java. The ophiolites of the Andaman and Naga Hills are also conventionally linked with the subduction activity, west of Andaman islands. This activity began only in late Miocene, much later than onland emplacement of the ophiolites; it further developed west of the suture in its southern part. Post-collisional northward movement of the Indian plate subparallel to the suture, also developed leaky dextral transcurrent faults close to the suture and caused Neogene-Quatemary volcanism in central Burma and elsewhere.     

蒙古-鄂霍茨克成矿带中段金矿床地质特征及构造背景

蒙古—鄂霍茨克成矿带是重要的金、稀有元素成矿带。作者将我国境内大兴安岭北部上黑龙江盆地和额尔古纳隆起区的砂宝斯金矿、小伊诺盖沟金矿等与俄罗斯赤塔州的达拉松、克留切夫等典型矿床进行了对比研究，以探讨该成矿带内金矿床的成因和形成的构造背景。研究表明，上述矿床均受蒙古—鄂霍茨克缝合带控制，矿床形成于西伯利亚地台与蒙古—华北陆块碰撞造山环境；我国上黑龙江盆地区与俄罗斯东后贝加尔地区同属蒙古—鄂霍茨克成矿带中段，以中温热液矿床为主，矿床类型主要为造山型金矿床。     

Tectonics and plate tectonics model for the Variscan belt of Europe

A plate tectonics model is presented to explain the tectonometamorphic characteristics of the European Variscides. After the closing of two oceanic domains by two-sided subduction (500-420 Ma) and obduction (420-380 Ma), collision of the European and African continental plates occurred. We propose that the subsequent complex intracontinental deformation (380-290 Ma) is the result of a double subduction of the continental lithosphere accompanied by crust-mantle décollement. This mechanism explains the progressive crustal thickening and migration of the deformation through time from the sutures toward the external parts of the Variscan Belt. Accounting for this model and for the relationships between the European Variscides and the other Paleozoic peri-Atlantic belts (Caledonides, Appalachian, Mauritanides and Morocco), we infer the relative positions of Africa, America and Europe between the Silurian and the Permian.     

Tectonics and volcanism along the Pacific Marginal Zone of Central America

The relation of volcanism to tectonics in the Central American region has been established by a review of the literature as well as by field and photogeological work of the authors. The association of a deep trench off the Pacific coast, a parallel seismic belt, and a similarly oriented chain of volcanic vents farther inland, has been recognized by numerous earlier workers. These features form a tectonic unit, and are here termed the Pacific marginal zone.Seismic foci on the northeastern edge of the southern part of the Middle American Trench define a fault zone which dips under the continent and suggests movement of the oceanic plate underneath the Central American continent.An impressive chain of volcanic cones and associated shallow seismic foci is aligned along a prominent graben, best developed in Nicaragua where it is known as the Nicaraguan Depression. This feature probably originated in late Tertiary time. The southeastern end of the graben terminates at the northern ranges of the Talamanca Cordillera in Costa Rica. At the Gulf of Fonseca the trend of the graben changes from NW to E-W; the graben continues as the Central Depression of El Salvador at a higher elevation. Only the fault of the seaward border of the graben is defined in Guatemala, where it is represented by a NW trending volcanic chain.In Nicaragua and El Salvador the oldest cones are situated on the north-eastern boundary fault zone of the graben. These include remnants of the largest volcanic structures of the region. All the active volcanoes are on the southwestern boundary fault belt. Cross fracturing of this fault system controlled later northerly trending cone alignments, often with the youngest cones on the south end.The main graben and associated faults are considered results of tensional stresses on the crest of geanticlinal arching on the landward side of the Middle American Trench. This arching is believed to be due to regional compression originated by the movement of the oceanic plate against the mainland.In northwestern Central America the youngest stresses produced N-S normal faults that are marked by well-defined scarps. These stresses may be the result of right-lateral motion along the underthrust fault zone. The complex Comayagua graben north of the Gulf of Fonseca, the Ipala graben and associated faults in southeastern Guatemala, and the Guatemala City graben are all north-south features illustrating the extent and youth of this structural trend.The distribution of volcanic vents along the Nicaraguan Depression and the N-S trends underscores the close tectonic control of volcanism.

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Zusammenfassung Der Zusammenhang zwischen Tektonik und Vulkanismus im mittelamerikanischen Raum wird aufgezeigt aufgrund einer Literaturdurchsicht und feldgeologischer Arbeiten der Verfasser. Die Beziehungen zwischen einem Tiefseegraben vor der pazifischen Küste, einem dem Festland parallelen seismischen Gürtel und einer ebenso orientierten Vulkankette weiter im Inland sind von früheren Bearbeitern bereits erkannt worden. Diese drei Einheiten werden hier zusammengefaßt und als pazifische Randzone bezeichnet.Erdbebenherde am Nordostrand des mittelamerikanischen Tiefseegrabens weisen auf eine Störungszone hin, die unter den Kontinent einfällt. Der Bewegungssinn spricht für ein Abtauchen der ozeanischen Platte unter das mittelamerikanische Festland.Eine eindrucksvolle Vulkankette und die mit ihr verbundenen Erdbebenherde sind längs eines bedeutenden Grabens aufgereiht, der in Nicaragua am deutlichsten ausgebildet ist und dort Nicaragua-Senke genannt wird. Diese tektonische Einheit entstand wahrscheinlich im Jung-Tertiär. Der Graben beginnt im Südosten an den nördlichen Ausläufern der Talamanca-Kordillere in Costa Rica.In Nicaragua verläuft er NW. Am Golf von Fonseca schwenkt er in eine E-W-Richtung und setzt sich in El Salvador in einem höheren Niveau als Zentral-Depression fort. In Guatemala ist nur der Südrand des Grabens erkennbar. Er ist gekennzeichnet durch eine in NW-Richtung aufgereihte Vulkankette. In Nicaragua und El Salvador liegen die ältesten Vulkane auf dem nordöstlichen Grenzbruch des Grabens. Zu dieser Gruppe zählen die größten Rumpfvulkane. Die meisten Kegel und alle tätigen Vulkane liegen hingegen auf dem südwestlichen Grenzbruchstreifen. Auf Querbrüchen haben sich jüngere, nördlich ausgerichtete Kegelreihen gebildet. Die jüngsten Kegel liegen meistens am südlichen Ende der Querbrüche.Es wird angenommen, daß der Hauptgraben und seine Störungen im Scheitel einer zum mittelamerikanischen Tiefseegraben parallel verlaufenden Aufwölbung entstanden sind. Die Aufwölbung kann auf Kompression der ozeanischen Platte gegen das Festland zurückgeführt werden.Im nordwestlichen Zentralamerika bewirkten jüngere Beanspruchungen die Bildung von N-S-Brüchen, die heute morphologisch als Steilkanten hervortreten. Diese Beanspruchungen können durch rechtslaterale Bewegungen entlang der pazifischen Störungszone ausgelöst worden sein. Beispiele dieser N-S-Struktur sind: Die Comayagua-Grabenzone, nördlich des Golfs von Fonseca, der Ipala-Graben und sein Störungssystem in Südost-Guatemala und der Guatemala-Stadt-Graben. Diese N-S-Störungen kennzeichnen das Ausmaß und das geringe Alter der Grabenbildung.Die Anordnung der Vulkane entlang der Nicaragua-Senke und der N-S-Brüche stellen die engen Beziehungen zwischen Tektonik und Vulkanismus in der pazifischen Randzone Mittelamerikas heraus.

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Resumen Mediante información tomada de la literatura, trabajos de campo e interpretation fotogeológica, se establece la relación entre el volcanismo y la tectónica en la región de América Central. Se usa la denominación de zona marginal del Pacífico para identificar, como una unidad, la asociación ya reconocida por otros autores de la profunda Fosa Mesoamericana frente a la costa del Pacífico de America Central y las franjas paralelas de actividad sísmica y de cadenas volcánicas.Los focos sísmicos en el borde nororiental de la Fosa Mesoamericana definen una gran zona de afallamiento inclinada hacia el continente, cuyos movimientos indican que un bloque de la corteza oceánica se sumerge bajo la porción continental de America Central.Una imponente serie de conos volcánicos, asociada a focos sísmicos poco profundos, está situada a lo largo de un gran graben conocido como Depresión de Nicaragua, por ser en ese país donde aparece más claramente definido. Este graben, que posiblemente se originó durante el Terciario tardío, termina en su extremo suroriental contra las estribaciones de la parte norte de la Cordillera de Talamanca, en Costa Rica. En Nicaragua el graben está orientado hacia el NW hasta el Golfo de Fonseca donde toma un rumbo E-W a través de El Salvador, donde se encuentra a mayor elevación. En Guatemala se conoce únicamente una línea de fallas, la más próxima al mar, definida por una cadena de volcanes que tiene nuevamente dirección NW.En Nicaragua y El Salvador los conos volcánicos más antiguos están situados a lo largo de las fallas que limitan al graben en su lado nororiental. Allí se encuentran las ruinas de los edificos volcánicos más grandes de la región. La mayoría de los conos que incluye todos los actualmente activos, se localizan a lo largo de las fallas del borde suroccidental del graben. Fracturas transversales controlan la localization de varios grupos de conos alineados de N-S. Los volcanes más jóvenes se encuentran frecuentemente en el extremo sur.Se postula que el graben principal y otras fallas del mismo sistema han sido formados como resultado de esfuerzos de tensión, en la cresta de un geanticlinal que resultó del arqueamiento del lado terrestre de la zona marginal del Pacífico. Dicho arqueamiento se cree que resulta de la compresión regional debida al movimiento del bloque oceánico contra el continente.En la parte noroccidental de América Central los esfuerzos más recientes produjeron fallas orientadas N-S, fácilmente identificables por sus bien marcadas escarpas. Estos esfuerzos pueden haber resultado del desplazamiento dextromóvil a lo largo de las zonas de afallamiento paralelas a la Fosa Mesoamericana.El complejo graben de Comayagua, al norte del Golfo de Fonseca, y los graben de Ipala y de la Ciudad de Guatemala, orientados también de norte a sur, ilustran la extension y la joven edad de las fracturas.La distribución de los focos volcánicos a lo largo de la Depresión de Nicaragua y de las fracturas N-S muestran de manera evidente, la estrecha relación que existe entre la tectónica y la localización del volcanismo en la zona marginal del Pacifico de America Central.

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, - . - , . . , , . , , - . - Talamanca Kordillere -. - - . Fanseca . . , , . - . . . , . . - N-S , . . : Comayagua, Fanseca, Ipala - . - . , .

     

Pseudotachylite from the Main Zone of the Hidaka metamorphic belt, Hokkaido, northern Japan

Pseudotachylite veins have been found in the mylonite zone of the Hidaka metamorphic belt, Hokkaido, northern Japan. They are associated with faults with WNW-ESE to ENE-WSW or NE-SW trends which make a conjugate set, cutting foliations of the host mylonitic rocks with high obliquity. The mylonitic rocks comprise greenschist facies to prehnite-pumpellyite facies mineral assemblages. The mode of occurrence of the pseudotachylite veins indicates that they were generated on surfaces of the faults and were intruded as injection veins along microfractures in the host rocks during brittle deformation in near-surface environments. An analysis of the deformational and metamorphic history of the Hidaka Main Zone suggests that the ambient rock temperature was 200–300° C immediately before the formation of the Hidaka pseudotachylite. Three textural types of veins are distinguished: cryptocrystalline, microcrystalline and glassy. The cryptocrystalline or glassy type often occupies the marginal zones of the microcrystalline-type veins. The microcrystalline type is largely made up of quench microlites of orthopyroxene, clinopyroxene, biotite, plagioclase and opaque minerals with small amounts of amphibole microlites. The interstices of these microlites are occupied by glassy and/or cryptocrystalline materials. The presence of microlites and glasses in the pseudotachylite veins suggests that the pseudotachylites are the products of rapid cooling of silicate melts at depths of less than 5 km. The bulk chemical composition of the pseudotachylite veins is characterized by low SiO₂ and a high water content and is very close to that of the host mylonitic rocks. This indicates that the pseudotachylite was formed by virtual total melting of the host rocks with sufficient hydrous mineral phases. Local chemical variation in the glassy parts of the pseudotachylite veins may be due to either crystallization of quench microlites or the disequilibrium nature of melting of mineral fragments and incomplete mixing of the melts. Pyroxene microlites show a crystallization trend from hypersthene through pigeonite to subcalcic augite with unusually high Al contents. The presence of pigeonite and high-Al pyroxene microlites, of hornblende and biotite microlites and rare plagioclase microlites may indicate the high temperature and high water content of the melt which formed the pseudotachylite veins. The melt temperatures were estimated to be up to 1100° C using a two-pyroxene geothermometer. Using published data relating water solubilities in high-temperature andesitic magmas to pressure, a depth estimate of about 4 km is inferred for the Hidaka pseudotachylites. Evidence derived from pseudotachylites in the Hidaka metamorphic belt supports the conclusion that pseudotachylite is formed by frictional melting along fault surfaces at shallow depths from rocks containing hydrous minerals.     

Tectonics and metallogeny of the junction zone between the North Asian craton and Pacific tectonic belt

The tectonics and metallogeny of the junction zone between the North Asian craton and Pacific tectonic belt are considered. This zone is characterized by a wide variety of structures superposed on the metamorphic basement, which was formed in the course of a multistage geologic development of the craton from the Precambrian to the Cenozoic. They are related to the craton evolution and its response to the collision and subduction processes in the adjacent orogenic belt, processes in the passive and active continental margins, and plume magmatism. The geological structure of the region includes blocks of metamorphic rocks of the Aldan–Stanovoi shield, Paleoproterozoic volcanogenic troughs, Mesoproterozoic–Neoproterozoic and Early Paleozoic structures of the platform cover, Late Paleozoic volcanic and terrigenous troughs, structures of the Late Mesozoic Okhotsk–Chukotka volcanic belt of the active continental margin, and Late Cretaceous riftogenic structures formed in response to plume magmatism. In total, six metallogenic epochs are recognized in the development of ore mineralization: Archean–Early Paleoproterozoic, Late Paleoproterozoic, Mesoproterozoic, Neoproterozoic, Late Paleozoic, and Late Mesozoic. The minerageny of the junction zone between the craton and Pacific belt is highly diversified, being characterized by distinct evolution in time and space. Each development stage features its own set of mineral resources.     

滑动构造影响下煤层厚度与构造破碎带关系分析

徐庄滑动构造是河南省荥巩煤田主要构造之一,对区内二1煤层的赋存特征影响较大。经对大量计河井田勘查资料分析,发现滑动构造破碎带厚度与其下伏二1煤层厚度相关程度较高,表现为两者在中、浅部厚度变化大,并沿倾向呈薄、厚相间的条带状展布,大致在二1煤层-300m水平附近,滑动构造破碎带厚度变薄尖灭,煤层厚度亦相应变小且趋于稳定。通过对钻孔数据的回归分析,认为二1煤层厚度与其上滑动构造破碎带厚度呈正相关关系,这一结论对后期矿山开发中工作面的布置及做好安全防范措施有指导意义。     

Tectonothermal evolution of a foreland fold and thrust belt: the Cantabrian Zone (Iberian Variscan belt,NW Spain)

Analysis of the conodont colour alteration index and the Kübler index of illite allowed us the characterization of four types of very low‐ or low‐grade metamorphism in the Cantabrian Zone (CZ) and determination of their regional and temporal distribution. These types are: (1) an orogenic Variscan metamorphism present only in restricted areas of the western and north‐western parts of the CZ where epizonal conditions are reached; (2) a burial metamorphism that appears in the basal part of some nappes, where anchizonal conditions are sometimes achieved; the thermal peak preceded emplacement of the nappes; (3) a late‐Variscan metamorphism in the southern and south‐eastern parts of the CZ; a cleavage, cutting most of the Variscan folds, is associated with this metamorphism, which has been related to an extensional episode; (4) a contact metamorphism and hydrothermal activity associated with minor intrusive bodies. The extension continued after the Variscan deformation giving rise to hydrothermal activity during Permian times.     

Geotectonic subdivision and areal extent of the Sangun belt, Inner Zone of Southwest Japan

The Sangun belt has long been considered to be a major coherent glaucophanitic terrane of Permian to Triassic age, and to be paired with the low-P/T Hida belt to the north. However, recent progress in geochronology, metamorphic geology, and tectonics has revealed that the belt is in fact comprised of two geologic units of different ages and with contrasting conditions of formation. The older unit is named the Renge belt and the younger the Suo belt. The Renge belt is the oldest of the high-P/T metamorphic belts in the Japanese Islands and extends from northern Kyushu, through the San-in coastal regions, to the Hida marginal belt. It is characterized by 330–280 Ma ages and the association of glaucophane–schist to epidote–amphibolite facies schists. The Renge belt is also typically associated with meta–ophiolite sequences (470–340 Ma) including serpentinite. The Suo belt is characterized by 230–160 Ma high-P/T schists closely related to weakly metamorphosed Permian accretionary rocks of the Akiyoshi belt. Metamorphic facies series is from the prehnite–pumpellyite facies through the pumpellyite–actinolite and glaucophane–schist facies to the epidote–amphibolite facies. The belt is widespread in west Kinki to north and central Kyushu via Chugoku, but also stretches further to the southwest and is present in the Ishigaki-Iriomote Islands of the southern Ryukyu Arc. Throughout this belt, there are scattered small blocks or lenses of meta–ophiolite, whose K–Ar ages of relict hornblendes are 590 to 220 Ma. Bounded by low-angle faults and thrusts, both belts define subhorizontal nappes dipping gently north. The geotectonic framework in the Inner Zone of Southwest Japan is made up of, from north to south, the Hida-Oki, Renge, Akiyoshi, Suo, Maizuru plus ultra-Tamba, Mino-Tamba, and Ryoke belts, with a tectonically downward-younging polarity. This has resulted from stepwise accretions during Palaeozoic to Mesozoic time.     

Tectonics of Anadyr' basin (northeastern end of Asiatic fork of Circumpacific mobile belt)

A modern tectonic plan of the area (fig. 2) and redesigned geological map (fig. 3) represent, among other things, the impositions of Late Senonian-Cenozoic onto Jurassic-Lower Cretaceous structures and a radical change in the structural orientations and the geological consequences of this reversal. Re-interpretations of history of the basin, once a part of the Beringian massif, lead to a clearer understanding of the Chukotka-Alaska relations, as well as of the basin's position and function within the Pacific mobile belt.     

南海北部阳江‒一统暗沙断裂带与新近纪岩浆活动

阳江?一统暗沙断裂带是南海北部珠江口盆地极其重要的中?新生代构造带和转换带.基于钻井资料和大范围、高密度的二维、三维地震资料,本文初步揭示阳江?一统暗沙断裂带走向为NW-NWW向、宽约30 km,沿着断裂走向从陆架至洋陆边界断裂带可分为北?中?南三段,断裂在新生代选择性活化,具有多重走滑断裂叠合和基底岩浆底辟强烈等特点...     

构造枢纽带的确定、类型划分及其油气意义

中国中西部发育大量的叠合盆地,中深层纵向上形成了隆起、凹陷、正向叠加（古隆起）、负向叠加（凹陷或洼陷）、跷跷板式等叠加样式.它们对于油气的富集与保存有着不同的作用.跷跷板式叠加作用是盆地边缘最为常见的叠加样式.分析表明,在盆地垂向调整、改造过程中构造枢纽带是必然产物,是调整范围的一部分,是新的构造圈闭区范围.向盆地区也存在调整区,地层产状变缓,但方向没有改变.构造枢纽带后方,下部层位产状发生极性变化.构造枢纽带位置在地质历史是变化的.随着造山带向盆地的推进,枢纽带有不断向盆内推进的趋势,形成继承型、新生和反转型（废弃）3种类型的构造枢纽带.其中晚期继承型最有利油气的富集保存;晚期新生构造枢纽带有利油气聚集;反转型（废弃）构造枢纽带不利于油气的保存.      

缅甸Tarlay 2011年地震与古特提斯缝合带的活动构造

An earthquake of 6.8 magnitude struck the eastern Shan State in Myanmar at 20:29:30 Myanmar Standard Time (01:55:12 PM UTC) on 24 March 2011. It is one of the earthquakes in plate-interior setting. Six after-shocks occurred the same year. The nucleation point of this earthquake was defined by an epicenter at 20 km west of Tarlay (20.705°N, 99.949°E) at a depth of 10 km and its magnitude was 6.8. The earthquake damage was disastrous. The geological disasters were linearly distributed along the surface rupture zone. The earthquake produced cracks, arch bend, erupting sand, gush water, etc. in many places. As a result of this strong earthquake, 224-305 houses were seriously damaged, 74 people were killed, 124 injured. The event was named after the nearest village Tarlay and the NE-or ENE-striking Nan Ma fault was responsible for it. A detailed morphotectonic study was carried out in the area using satellite image 1:24,000 scale aerial photographs and 1:63360 scale topographic maps, to correlate the seismicity with tectonics. It is found that there are two prominent lineaments striking in NE-or ENE- and N-S or NNE- SSW direction. The present-day deformation of the Than Lwin suture zone is consistent with roughly NW-SE extension and NE-SW striking compression, but with more conjugate strike-slip faulting and only minor normal faulting.     

Tectonics of the North Qilian orogen,NW China

The Qilian Orogen at the northern margin of the Tibetan Plateau is a type suture zone that recorded a complete history from continental breakup to ocean basin evolution, and to the ultimate continental collision in the time period from the Neoproterozoic to the Paleozoic. The Qilian Ocean, often interpreted as representing the “Proto-Tethyan Ocean”, may actually be an eastern branch of the worldwide “Iapetus Ocean” between the two continents of Baltica and Laurentia, opened at ≥ 710 Ma as a consequence of breakup of supercontinent Rodinia.Initiation of the subduction in the Qilian Ocean probably occurred at ~ 520 Ma with the development of an Andean-type active continental margin represented by infant arc magmatism of ~ 517–490 Ma. In the beginning of Ordovician (~ 490 Ma), part of the active margin was split from the continental Alashan block and the Andean-type active margin had thus evolved to western Pacific-type trench–arc–back-arc system represented by the MORB-like crust (i.e., SSZ-type ophiolite belt) formed in a back-arc basin setting in the time period of ~ 490–445 Ma. During this time, the subducting oceanic lithosphere underwent LT-HP metamorphism along a cold geotherm of ~ 6–7 °C/km.The Qilian Ocean was closed at the end of the Ordovician (~ 445 Ma). Continental blocks started to collide and the northern edge of the Qilian–Qaidam block was underthrust/dragged beneath the Alashan block by the downgoing oceanic lithosphere to depths of ~ 100–200 km at about 435–420 Ma. Intensive orogenic activities occurred in the late Silurian and early Devonian in response to the exhumation of the subducted crustal materials.Briefly, the Qilian Orogen is conceptually a type example of the workings of plate tectonics from continental breakup to the development and evolution of an ocean basin, to the initiation of oceanic subduction and formation of arc and back-arc system, and to the final continental collision/subduction and exhumation.     

Tectonics and Geochronology of the Northern Margin of the Zhongba Terrane, Southern Tibet: Implications for the Closure of the Western Yarlung Zangbo Suture Zone

<正>The Zhongba terrane represents a special tectonic unit sitting between the northern and the southern ophiolitic sub-belt in the western segment of the Yarlung Zangbo Suture Zone(YZSZ),which separates the Indian and the Eurasian continental plates.Thus,the structural characteristics and evolution of this terrane should offer     

Tectonics of the Virgin Islands Basin,north eastern Caribbean

The tectonics of the Virgin Islands Basin are controlled by the plate boundary between the Puerto Rico‐Virgin Islands Microplate and the stable part of the Caribbean Plate. Several contradicting theories about the formation and development of this basin have previously been proposed. As part of the Danish Galathea 3 expedition, extensive marine geological investigations of the basin were carried out in March 2007 including sediment coring and acquisition of multi‐beam and two‐dimensional seismic data. This paper represents a summary of the key observations from the multi‐beam and the seismic data set. The interpretation of these observations leads to the proposition of a tectonic model for the Virgin Islands Basin. The model consists of N–S to NW–SE directed extension combined with E‐W trending sinistral strike‐slip and the new structural evidence from the Virgin Islands Basin is entirely consistent with the most recently published GPS data.     

大陆漂移,板块构造,地质力学

本文简要地介绍了魏格纳大陆漂移说的主要内容及其提出的依据:论述了在大陆漂移说的基础上,由于海洋地质地球物理调查发现了大洋中脊、洋底扩张,解释了大陆张裂的机制,并建立了全球板块构造理论,形成现代地学思想的革命;李四光在大陆漂移说提出的同时已在积极地探讨和论述大陆地壳水平运动问题,并结合中国大陆实际,发展了陆内碰撞变形理论,即包括全球大陆构造体系在内的地质力学理论和方法.他强调地质力学是一支脚站在地质上,另一支脚站在力学上来研究地壳运动和变形现象.后来更扩大了其在资源、环境方面的应用.文章对魏格纳大陆漂移说、全球板块构造理论及地质力学三者的关系做了深入探讨,论述了李四光地质力学理论方法的现代意义、超前意义,提出要重视和发扬李四光留给中国人民的宝贵遗产,建议深入学习李四光的著述,结合地质调查新成果去丰富它和发展它.     

内蒙古色尔腾山──大青山地区推覆构造

内蒙古包尔腾山──大青山地区推覆构造，随着1∶5万区域地质调查工作的开展，在原来发现的几个孤立的推覆构造的基础上，相继识别出一些新的推覆构造，从而使我们有可能纵观本区推覆构造的全貌。它们呈近东西向展布，主要发生在东西向侏罗纪成煤盆地的南北两侧，前中生代地层及侵入体做为外来系统逆冲推覆在中生代盆地之上，并发育大小不等的飞来峰、构造窗。它们形成于中侏罗世末和早白垩世末，是在南北向水平挤压的统一的构造应力场中发生发展的。推覆构造研究，对认识本区地质构造的演化和地壳的层圈式结构将是十分有益的，对指导找矿也有一定的意义。