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近十余年来,一种新的大地构造假说--岩石圈板块构造说,正在中外地学界广泛地流行着,激起了许多地质学和地球物理学工作者的强烈兴趣。一些学者运用这个假说已经解答了存在于地球科学方面长期以来所遗留下的不少难题。目前,板块构造假说正以空前旺盛的活力在向前发展并日臻完善起来。 相似文献
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中国主要镍矿类型及其与古板块构造的关系 总被引：3，自引：1，他引：3
新中国成立后,开展了大规模持续的地质找矿工作,发现了一系列镍矿床。这些矿床的探明,充分证实我国是一个镍矿资源十分丰富的国家。本文在归纳划分了镍矿类型之后,试图对在古板块构造作用下镍矿区域成矿问题作些探讨。主要依据现代海洋资料建立起来的板块构造学说,生动而又精辟地阐述了晚近地质时期某些地质构造规律和成矿作用。但是,对于古板块构造作用和受古板块制约的古成矿作用来 相似文献
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北祁连山古大洋俯冲带高压变质岩研究评述 总被引：5，自引：1，他引：4
北祁连山是中国研究古板块构造和俯冲带的经典地区,肖序常先生在此进行了开创性的研究工作。该俯冲带记录了490~440Ma的高压变质年龄,是目前世界上最老的大洋冷俯冲带之一。较系统地总结了北祁连造山带的研究历史、近年来在高压变质岩及相关岩石研究领域的最新进展,并根据详细的矿物学、岩石学、地球化学和同位素年代学资料,对本区大洋扩张、俯冲和大陆碰撞造山的构造演化过程进行了新的透视和评述。 相似文献
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<正> 1972年尹赞勋综合大量国外资料,在我国首次较系统地介绍了板块构造理论,接着李春昱、傅承义等又著文进一步介绍板块构造的基本理论,在我国广大地质工作者中引起了强烈的反响。由于当时还处在十年动乱时期,板块构造这一新兴学说得不到应有的重视,研究工作未能广泛开展,只有局部地区的探索。李春昱先生不顾古稀之年,带领西北地质研究所少数几人,首先开展了祁连山—秦岭地区的板块构造研究工作,这对我国板块构造研究起了先锋作用。 相似文献
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祁连山构成青藏高原的北东边界,是研究青藏高原的隆升与向内陆扩展的关键区域,利用新生代湖相沉积的碳氧同位素组成估算祁连山古海拔对认识青藏高原的隆升有重要意义。在中祁连陆块不同地点出露的始新统、渐新统、中新统和中晚更新统分别取样并进行碳氧同位素分析,估算相应地质时期的古年均温和古海拔高度。结果表明,祁连山地区古近纪的海拔约为2711 m,中新世早期的海拔为2848 m左右,中新世中晚期祁连山海拔达到约3586 m,中晚更新世祁连山的古海拔约为3790~3890 m。古近纪祁连山的海拔较低,但已经构成了青藏高原的东北边界;中新世中晚期祁连山强烈隆升,形成了盆-山构造地貌格局;第四纪祁连山地壳重新活跃并呈阶段性快速隆升,河流堆积和侵蚀交替进行。根据碳氧同位素估算的祁连山古海拔高度变化为认识青藏高原隆升的过程提供参考。 相似文献
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Five domains (microplates) have been recognized by seismic anisotropy in the mantle lithosphere of the Bohemian Massif. The mantle domains correspond to major crustal units and each of the domains bears a consistent fossil olivine fabric formed before their Variscan assembly. The present-day mantle fabric indicates that this process consisted of at least three oceanic subductions, each followed by an underthrusting of the continental lithosphere. The seismic anisotropy does not detect remnants of the oceanic subductions, but it can trace boundaries of the preserved continental domains subsequently underthrust along the paths of previous oceanic subductions. The most robust continent–continent collision was followed by westward underthrusting of the Brunovistulian mantle lithosphere, still detectable by seismic anisotropy more than 100 km beneath the Moldanubian mantle lithosphere. Major occurrences of the high-pressure/ultra high-pressure (HP–UHP) rocks follow the ENE and NNE oriented sutures and boundaries of the mantle–lithosphere domains mapped from three-dimensional modeling of body-wave anisotropy. The HP–UHP rocks are products of oceanic subductions and the following underthrusting of the continental crust and mantle lithosphere exhumed along the mantle boundaries. The close relation of the mantle sutures and occurrences of the HP–UHP rocks near the paleosubductions testifies for models interpreting the granulite–garnet peridotite association by oceanic/continental subduction/underthrusting followed by the exhumation of deep-seated rocks. Our findings support the bivergent subduction model of tectonic development of the central part of the Bohemian Massif. The inferences from seismic anisotropy image the Bohemian Massif as a mosaic of microplates with a rigid mantle lithosphere preserving a fossil olivine fabric. The collisional mantle boundaries, blurred by tectonometamorphic processes in easily deformed overlying crust, served as major exhumation channels of the HP–UHP rocks. 相似文献
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The evolution of oceanic crust on the Kolbeinsey Ridge, north of Iceland, is discussed on the basis of a crustal transect obtained by seismic experiment from the Kolbeinsey Ridge to the Jan Mayen Basin. The crustal model indicates a relatively uniform structure; no significant lateral velocity variations are observed, especially in the lower crust. The uniform velocity structure suggests that the postulated extinct axis does not exist over the oceanic crust formed at the Kolbeinsey Ridge, but supports a model of continuous spreading along the ridge after oceanic spreading started west of the Jan Mayen Basin. The oceanic crust formed at Kolbeinsey Ridge is 1–2.5 km thicker than normal oceanic crust due to hotter-than-normal mantle from the Iceland Mantle Plume. The observed generally uniform thickness throughout the transect might also indicate that the temperatures of the astheno-spheric mantle ascending along the Kolbeinsey Ridge have not changed significantly since the age of magnetic anomaly 6B. 相似文献
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Lateral and vertical variability in crustal velocity structure in a small area of the North Atlantic
The detailed velocity structure of a 70 by 35 km area of 6–10 Ma old crust on the flank of the mid Atlantic Ridge at 24°N was studied using 358 explosive charges and several hundred 16.4-1 airgun shots fired into an array of eight ocean bottom hydrophones. Inversion of the first arrival refracted travel times shows that the crust comprises a normal oceanic section about 5 km thick with a steep velocity gradient in the upper crust increasing from about 3.5 km/sec at the seafloor overlying a typical oceanic layer 3 and a probably anisotropic mantle. Delay time function mapping using two datasets containing arrivals from layer 3 and from the mantle show that lateral variability is generally low over most of the survey area, with a small region of high delay times in the northwest corner caused by the presence of abnormal crust probably associated with a minor fracture zone. We find that the topography of the base of layer 2 is similar to that of the top, indicating that the normal faulting which occurs along the margins of the median valley extends down at least into layer 3. Our observations from mantle arrivals are consistent with a much flatter Moho which constrains possible models of crustal formation at the spreading centre. 相似文献
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TTG岩石构造组合(或岩类)表征洋壳俯冲作用。本文提出TTG岩类的4个亚类：(1)镁安山岩系列(MA)低压型TTG亚类,形成于非常年轻和很热的洋壳俯冲,压力≤1 500~1 600 MPa,深度≤50~60 km,例如活动洋中脊俯冲的板片窗的边缘;(2)镁安山岩系列(MA)高压型TTG亚类,形成于比较年轻和较热的洋壳俯冲,压力≥1 500~1 600 MPa,深度≥50~60 km;(3)低镁(或非镁)安山岩系列(LMA)低压型TTG亚类,形成于洋内弧下地壳,压力≤1 500~1 600 MPa,深度≤50~60 km;(4)低镁(或非镁)安山岩系列(LMA)高压型TTG亚类,形成了大陆边缘弧山根带,压力≥1 500~1 600 MPa,深度≥50~60 km。对TTG岩类4个亚类的研究,并结合对无TTG形成的老的冷的俯冲带洋壳和冷的弧地壳以及幔楔有无岩浆产生等方面的研究,可以重建岩浆弧的壳幔结构和热结构,进而可为与洋俯冲有关的成矿作用提供地质背景。 相似文献
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Seiichi Miura Shuichi Kodaira Ayako Nakanishi Tetsuro Tsuru Narumi Takahashi Naoshi Hirata Yoshiyuki Kaneda 《Tectonophysics》2003,363(1-2):79-102
The Japan Trench is a plate convergent zone where the Pacific Plate is subducting below the Japanese islands. Many earthquakes occur associated with plate convergence, and the hypocenter distribution is variable along the Japan Trench. In order to investigate the detailed structure in the southern Japan Trench and to understand the variation of seismicity around the Japan Trench, a wide-angle seismic survey was conducted in the southern Japan Trench fore-arc region in 1998. Ocean bottom seismometers (15) were deployed on two seismic lines: one parallel to the trench axis and one perpendicular. Velocity structures along two seismic lines were determined by velocity modeling of travel time ray-tracing method. Results from the experiment show that the island arc Moho is 18–20 km in depth and consists of four layers: Tertiary and Cretaceous sedimentary rocks, island arc upper and lower crust. The uppermost mantle of the island arc (mantle wedge) extends to 110 km landward of the trench axis. The P-wave velocity of the mantle wedge is laterally heterogeneous: 7.4 km/s at the tip of the mantle wedge and 7.9 km/s below the coastline. An interplate layer is constrained in the subducting oceanic crust. The thickness of the interplate layer is about 1 km for a velocity of 4 km/s. Interplate layer at the plate boundary may cause weak interplate coupling and low seismicity near the trench axis. Low P-wave velocity mantle wedge is also consistent with weak interplate coupling. Thick interplate layer and heterogeneous P-wave velocity of mantle wedge may be associated with the variation of seismic activity. 相似文献
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Along the Rio Muni transform margin, the transition from continental to oceanic crust occurs across a region of approximately 75-km width. The crust in this transition region, termed proto-oceanic crust (POC), is neither purely oceanic nor continental in composition and structure. Improved seismic reflection images from the PROBE deep-imaging dataset, combined with gravity modelling, have shed new light on the structural architecture of the margin and the composition of the POC. On these newly migrated seismic reflection sections, four fracture zones associated with large steps in the Moho are identified, splitting the POC into three segments. Models in which these segments are composed of oceanic or stretched continental crust do not provide satisfactory predictions of the gravity anomaly. A model of serpentinized peridotite for two segments of POC, with the third segment composed of oceanic crust in between, does satisfy the observed gravity anomaly. Three alternative geological scenarios are proposed to explain the segmentation and composition of the POC: (a) serpentinized upper mantle becoming unroofed and emplaced at basement surface level along detachment surfaces confined to discrete segments by the fracture zones, (b) oblique-slip on transform faults that allow the circulation of water into the mantle and emplacement of serpentinized upper mantle material; or (c) intense faulting of anomalous oceanic crust as a result of magma depletion allowing hydrothermal circulation and the emplacement of serpentinized peridotites. 相似文献
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青藏高原的地幔结构:地幔羽、地幔剪切带及岩石圈俯冲板片的拆沉 总被引：22，自引：1，他引：22
通过横穿青藏高原近 80 0 0km长的 4条天然地震层析剖面 ,获得 4 0 0km深度以上的地壳和地幔速度图像及地震波各向异性 ,揭示了青藏高原 4 0 0km深度范围内的地壳和地幔结构特征。地幔速度图像显示 ,青藏高原腹地的深地幔中存在以大型低速异常体为特征的地幔羽 ,其可能通过热通道与大面积分布的可可西里新生代高钾碱性火山作用有成因联系 ;阿尔金、康西瓦、金沙江、嘉黎及雅鲁藏布江等走滑断裂可下延至 30 0～ 4 0 0km深度 ,显示了低速高热物质组成的垂向低速异常带特征及大型超岩石圈或地幔剪切带的产出 ;发现康西瓦、东昆仑—金沙江、班公湖—怒江和雅鲁藏布缝合带下部存在不连续的高速异常带 ,可以解释为青藏高原地体拼合及碰撞过程中可能保留的加里东、古特提斯和中特提斯大洋岩石圈“化石”残片 ,是“拆沉”的地球物理证据。印度大陆岩石圈的巨厚俯冲板片以 15～ 2 0°倾角向北插入唐古拉山下 30 0km深处 ,并被高热物质组成的地幔剪切带分开。结合新的横穿喜马拉雅及青藏高原的地幔层析资料 ,提出青藏高原碰撞动力学新模式 :青藏高原南部印度岩石圈板片的翻卷式陆内超深俯冲 ,北缘克拉通向南的陆内俯冲 ,腹地深部的地幔羽上涌 ,以及地幔范围内的高原“右旋隆升”及物质向东及北东方向运动及挤出。 相似文献
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蛇绿岩型金刚石和铬铁矿深部成因 总被引：5，自引：0，他引：5
地球上的原生金刚石主要有3种产出类型,分别来自大陆克拉通下的深部地幔金伯利岩型金刚石、板块边界深俯冲变质岩中超高压变质型金刚石,和陨石坑中的陨石撞击型金刚石。在全球5个造山带的10处蛇绿岩的地幔橄榄岩或铬铁矿中均发现金刚石和其他超高压矿物的基础上,我们提出地球上一种新的天然金刚石产出类型,命名为蛇绿岩型金刚石。认为蛇绿岩型金刚石普遍存在于大洋岩石圈的地幔橄榄岩中,并提出蛇绿岩型金刚石和铬铁矿的深部成因模式。认为早期俯冲的地壳物质到达地幔过渡带(410~660 km深度)后被肢解,加入到周围的强还原流体和熔体中,当熔融物质向上运移到地幔过渡带顶部,铬铁矿和周围的地幔岩石以及流体中的金刚石等深部矿物一并结晶,之后,携带金刚石的铬铁矿和地幔岩石被上涌的地幔柱带至浅部,经历了洋盆的拉张和俯冲阶段,最终在板块边缘就位。 相似文献
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Seiichi Miura Narumi Takahashi Ayako Nakanishi Tetsuro Tsuru Shuichi Kodaira Yoshiyuki Kaneda 《Tectonophysics》2005,407(3-4):165-188
The Japan Trench subduction zone, located east of NE Japan, has regional variation in seismicity. Many large earthquakes occurred in the northern part of Japan Trench, but few in the southern part. Off Miyagi region is in the middle of the Japan Trench, where the large earthquakes (M > 7) with thrust mechanisms have occurred at an interval of about 40 years in two parts: inner trench slope and near land. A seismic experiment using 36 ocean bottom seismographs (OBS) and a 12,000 cu. in. airgun array was conducted to determine a detailed, 2D velocity structure in the forearc region off Miyagi. The depth to the Moho is 21 km, at 115 km from the trench axis, and becomes progressively deeper landward. The P-wave velocity of the mantle wedge is 7.9–8.1 km/s, which is typical velocity for uppermost mantle without large serpentinization. The dip angle of oceanic crust is increased from 5–6° near the trench axis to 23° 150 km landward from the trench axis. The P-wave velocity of the oceanic uppermost mantle is as small as 7.7 km/s. This low-velocity oceanic mantle seems to be caused by not a lateral anisotropy but some subduction process. By comparison with the seismicity off Miyagi, the subduction zone can be divided into four parts: 1) Seaward of the trench axis, the seismicity is low and normal fault-type earthquakes occur associated with the destruction of oceanic lithosphere. 2) Beneath the deformed zone landward of the trench axis, the plate boundary is characterized as a stable sliding fault plain. In case of earthquakes, this zone may be tsunamigenic. 3) Below forearc crust where P-wave velocity is almost 6 km/s and larger: this zone is the seismogenic zone below inner trench slope, which is a plate boundary between the forearc and oceanic crusts. 4) Below mantle wedge: the rupture zones of thrust large earthquakes near land (e.g. 1978 off Miyagi earthquake) are located beneath the mantle wedge. The depth of the rupture zones is 30–50 km below sea level. From the comparison, the rupture zones of large earthquakes off Miyagi are limited in two parts: plate boundary between the forearc and oceanic crusts and below mantle wedge. This limitation is a rare case for subduction zone. Although the seismogenic process beneath the mantle wedge is not fully clarified, our observation suggests the two possibilities: earthquake generation at the plate boundary overridden by the mantle wedge without serpentinization or that in the subducting slab. 相似文献