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1.
应加拿大滑铁芦大学地质系主任J·P·Greenhouse教授和D·c·Nobes博士的邀请,笔者于1989年12月至1990年12月赴该系进行了为期一年的进修学习与合作研究。其间完成了方向频谱分析及滤波、欧拉反褶积确定南安大略区的构造格架课题的研究工作(研究成果将另文发表)。此课题属于加拿大岩石圈探测计划所属的大湖区深部地质剖面的研究内容。为此有幸接触到这个举世瞩目的国际多学科的深部地质计划的一些情况。仔细了解并研究这个深部探测计划的动向,对开展我国的深部地质研究和大剖面计划无疑会有许多 相似文献
2.
国际岩石圈计划与中国岩石圈委员会于1983年,国际科学联合会岩石圈委员会中国全国委员会,代表我国参加了本世纪80年代地球科学前沿的国际多学科《岩石圈动力学和演化:自然资源和减轻灾害纲要》计划。在这项60多个国家参加的国际合作研究中,我国是最早参加国之一。该计划是60年代国际上地幔计划和70年代地球动力学计划的继续。该计划的中心任务是阐明岩石圈的性质、动力学、成因与演化。作为固体地球石质外壳的岩石圈,既孕育着矿 相似文献
3.
20世纪实施了20年之久的国际岩石圈计划是全球固体地球科学规模最大、持续时间最长的国际合作计划。它是20世纪地学革命的产物和延伸,也是新世纪大陆地球动力学研究的基础和先导。在这一国际大背景下。我国东部大陆岩石圈因其在不同地质时代发育有各类大陆岩石圈地幔的罕见特点,受到了学术界强烈的关注,从而构成了80年代以来我国地球科学前沿领域一个突出的研究热点,吸引了众多的科学家投身其中。 相似文献
4.
本文以国土资源部中国岩石圈三维结构数据库专项计划为依托,利用ESRI公司的ArcIMS作为开发工具,建立了基于WebGIS数据共享平台。文中分析了当今的WebGIS设计思想,详细介绍了该平台的网络结构、系统数据组织、各专业空间数据的发布方式、共享服务功能的实现。通过整个数据共享平台的建立,总结了目前GIS技术和地学研究相互促进共同发展的方向。 相似文献
5.
美国台阵(USArray)是EarthScope计划的主要内容之一。旨在探测北美大陆变形、结构及其演化。USArray主要由平移/滚动台阵和机动台阵两部分构成。滚动台阵由400个宽频带地震台站组成,以向前滚动的方式扫过美国本土和阿拉斯加。利用来自该台阵的数据,科学家能获得地球内部精细图像,藉此考察地震和火山的过程。作为滚动台阵的补充,机动台阵被用于对关键目标进行详细观测和短期测量。美国台阵计划启动5年来,采集的数据已经提供了足以令科学界考虑重新审视地震物理、火山过程、核幔结构、活动变形构造、大陆结构及其演化、地球动力学和地壳流体等基本科学问题的基础资料。 相似文献
6.
本文依据大地构造理论和最新研究资料对中国东南大陆岩石圈演化研究中的有关问题作了探讨,认为地体理论和大地构造相模式理论是相辅相成的;建议扬弃华夏古、特提斯构造域和太平洋构造域等可能束缚研究思路的概念;将板片构造、斜向碰撞与走滑纳入中国东南部碰撞造山带的研究内容。 相似文献
7.
通过对ＥＵＲＯＰＲＯＢＥ计划中５个关键项目的主要研究目标和主要成果的介绍,简述了欧洲大陆岩石圈动力学研究现状及进展。通过研究,人们已以轾芬诺斯堪的亚地盾古元古代、太古代岩石圈演化特征有明显不同;横跨欧洲的缝合带既是前寒武纪地壳显一宙重新活动的结果,也是加里东和华力西地体增生作用的结果,乌拉尔造山带是古生代微大陆碎块进一步裂解、崩解、增生到东欧在陆边缘的结果;侏罗纪到现代的非洲－－阿拉伯板块及其间的 相似文献
8.
探测地球的内部结构和组成是地质学家和地球物理学家的共同目标。欧洲TOPO-EUROPE计划是一个多学科协作的研究项目, 旨在解决欧洲大陆的地球深部与地表过程之间的相互关系及作用。该计划结合数据交互建模研究, 重点针对岩石圈记忆和新构造运动, 板块边界和板内变形的力学机制, 异常沉降和隆起的动力学机制, 以及与地表过程和地形演变间的相互联系。在TOPO-EUROPE天然实验区选取涵盖广泛地球动力学背景的研究区域, 通过地质学、地球物理学、大地测量学和地质工程学等多学科联合, 监测、成像、重建和建模技术等多方法的综合研究, 来恢复欧洲大陆陆内造山带和板内区域的深部结构及地表形态的四维演化。 相似文献
9.
本文把地幔和岩石圈看作统一的动力学系统，分析了岩石圈运动极型场，环型场的激发机制和动力来源，结果表明，岩石圈运动极型场中在岩石圈内部重力，热力，科里奥利力以及应力的作用下产生，又能由地幔自由热运动所激发；而岩石圈运动环型场仅与地球的转动效应和岩石圈不同块体间的旋转剪切运动有关。在岩石圈演化历史上，上述不同性质力源的相对强弱和作用方式，决定了岩石圈运动的的性质及其驱动机制。 相似文献
10.
根据已积累的由多种不同方法所测得的丰富的构造应力资料客观地揭示了驱动构造运动所需和的大上及其窨展布规律。统计分析结果表明，现今不同类型的构造单元，包括构造活动区在内，其构造应力绝大部分者以近水平方向的压应力为主；上地壳最大主应力一般为９１０－３０）ＭＰａ，最小主应力一般为（２－２０）ＭＰａ，最大应力一般为（２－２５）ＭＰａ。在造山带，构造和的大小与造山作用强度呈明显的正相关关系。岩石圈底部构造应力 相似文献
11.
Forward reconstructions of the (mainly) Mesozoic and younger rheological evolution have been made for four basins (Broad Fourteens Basin, Sole Pit Basin, Brittany Basin and the Iberian Basin) in a very consistent way by backstripping and automatic forward modeling of subsidence data, including potentially important effects of heat production, sediment infill and sedimentary blanketing. For default compositional and thermal parameters, the modeling results show strengthening in all basins, and in particular during inversion, with strength increases up to about 2 TN m −1 (20%) relative to their initial values. Given predominantly relatively constant intraplate stresses in continental lithosphere, this is in disagreement with repeated localization of basin deformation. In a thorough sensitivity analysis we explore the possibilities that permissible variations in tectonic history, compositional, rheological and thermal parameters can, in a particular combination, result in slight weakening of the basin, in agreement with reactivation during inversion. However, such a combination reflects an extreme scenario, which is not founded by geological evidence and, statistically, is very unlikely to apply for all basins. A far more likely explanation for relative and permanent weakening of the basins is the presence of pre-existing weak zones, deviating from standard rheological assumptions. At (upper) crustal levels, weakening can be attributed to pre-existing marked faults by a reduced friction angle. This weakening has a pronounced influence on lithospheric strength provided that the reduction in friction angle of pre-existing faults can be extrapolated to the upper mantle. Alternatively, weakening of the upper mantle can be attributed to (1) ductile localization mechanisms, as reflected by the occurrence of upper mantle shear zones, or (2) the occurrence of rheologically weak material, as indicated by upper mantle reflectors. 相似文献
12.
Major- and trace-element analyses of garnets from heavy-mineral concentrates have been used to derive the compositional and thermal structure of the subcontinental lithospheric mantle (SCLM) beneath 16 areas within the core of the ancient Laurentian continent and 11 areas in the craton margin and fringing mobile belts. Results are presented as stratigraphic sections showing variations in the relative proportions of different rock types and metasomatic styles, and the mean Fo content of olivine, with depth. Detailed comparisons with data from mantle xenoliths demonstrate the reliability of the sections. In the Slave Province, the SCLM in most areas shows a two-layer structure with a boundary at 140–160 km depth. The upper layer shows pronounced lateral variations, whereas the lower layer, after accounting for different degrees of melt-related metasomatism, shows marked uniformity. The lower layer is interpreted as a subcreted plume head, added at ca. 3.2 Ga; this boundary between the layers rises to <100 km depth toward the northern and southern edges of the craton. Strongly layered SCLM suggests that plume subcretion may also have played a role in the construction of the lithosphere beneath Michigan and Saskatchewan. Outside the Slave Province, most North American Archon SCLM sections are less depleted than similar sections in southern Africa and Siberia; this may reflect extensive metasomatic modification. In E. Canada, the degree of modification increases toward the craton margin, and the SCLM beneath the Kapuskasing Structural Zone is typical of that beneath Proterozoic to Phanerozoic mobile belts. SCLM sections from several Proterozoic areas around the margin of the Laurentian continental core (W. Greenland, Colorado–Wyoming district, Arkansas) show discontinuities and gaps that are interpreted as the effects of lithosphere stacking during collisional orogeny. Some areas affected by Proterozoic orogenesis (Wyoming Craton, Alberta, W. Greenland) appear to retain buoyant, modified Archean SCLM. Possible juvenile Proterozoic SCLM beneath the Colorado Plateau is significantly less refractory. The SCLM beneath the Kansas kimberlite field is highly melt-metasomatised, reflecting its proximity to the Mid-Continent Rift System. A traverse across the continent shows that the upper part of the cratonic SCLM is highly magnesian; the decrease in mg# with depth is interpreted as the cumulative effect of metasomatic modification through time. The relatively small variations in seismic velocity within the continental core largely reflect the thickness of this depleted layer. The larger drop in seismic velocity in the surrounding Proton and Tecton belts reflects the closely coupled changes in SCLM composition and geotherm. 相似文献
13.
The thermal structure of Archean and Proterozoic lithospheric terranes in southern Africa during the Mesozoic was evaluated by thermobarometry of mantle peridotite xenoliths erupted in alkaline magmas between 180 and 60 Ma. For cratonic xenoliths, the presence of a 150–200 °C isobaric temperature range at 5–6 GPa confirms original interpretations of a conductive geotherm, which is perturbed at depth, and therefore does not record steady state lithospheric mantle structure. Xenoliths from both Archean and Proterozoic terranes record conductive limb temperatures characteristic of a “cratonic” geotherm (40 mW m−2), indicating cooling of Proterozoic mantle following the last major tectonothermal event in the region at 1 Ga and the probability of thick off-craton lithosphere capable of hosting diamond. This inference is supported by U–Pb thermochronology of lower crustal xenoliths [Schmitz and Bowring, 2003. Contrib. Mineral. Petrol. 144, 592–618]. The entire region then suffered a protracted regional heating event in the Mesozoic, affecting both mantle and lower crust. In the mantle, the event is recorded at 150 Ma to the southeast of the craton, propagating to the west by 108–74 Ma, the craton interior by 85–90 Ma and the far southwest and northwest by 65–70 Ma. The heating penetrated to shallower levels in the off-craton areas than on the craton, and is more apparent on the southern margin of the craton than in its western interior. The focus and spatial progression mimic inferred patterns of plume activity and supercontinent breakup 30–100 Ma earlier and are probably connected. Contrasting thermal profiles from Archean and Proterozoic mantle result from penetration to shallower levels of the Proterozoic lithosphere by heat transporting magmas. Extent of penetration is related not to original lithospheric thickness, but to its more fertile character and the presence of structurally weak zones of old tectonism. The present day distribution of surface heat flow in southern Africa is related to this dynamic event and is not a direct reflection of the pre-existing lithospheric architecture. 相似文献
14.
<正>The lithospheric structure of China and its adjacent area is very complex and is marked by several prominent characteristics.Firstly,China's continental crust is thick in the west but thins to the east,and thick in the south but thins to the north.Secondly,the continental crust of the Qinghai—Tibet Plateau has an average thickness of 60—65 km with a maximum thickness of 80 km,whereas in eastern China the average thickness is 30—35 km,with a minimum thickness of only 5 km in the center of the South China Sea.The average thickness of continental crust in China is 47.6 km,which greatly exceeds the global average thickness of 39.2 km.Thirdly,as with the crust,the lithosphere of China and its adjacent areas shows a general pattern of thicker in the west and south,and thinner in the east and north.The lithosphere of the Qinghai—Tibet Plateau and northwestern China has an average thickness of 165 km, with a maximum thickness of 180—200 km in the central and eastern parts of the Tarim Basin,Pamir, and Changdu areas.In contrast,the vast areas to the east of the Da Hinggan Ling—Taihang—Wuling Mountains,including the marginal seas,are characterized by lithospheric thicknesses of only 50—85 km.Fourthly,in western China the lithosphere and asthenosphere behave as a "layered structure", reflecting their dynamic background of plate collision and convergence.The lithosphere and asthenosphere in eastern China display a "block mosaic structure",where the lithosphere is thin and the asthenosphere is very thick,a pattern reflecting the consequences of crustal extension and an upsurge of asthenospheric materials.The latter is responsible for a huge low velocity anomaly at a depth of 85—250 km beneath East Asia and the western Pacific Ocean.Finally,in China there is an age structure of "older in the upper layers and younger in the lower layers" between both the upper and lower crusts and between the crust and the lithospheric mantle. 相似文献
15.
A new tomographic model of the Pyrenean lithosphere is determined down to 200 km depth from teleseismic P and PKP travel times, with a lateral resolution of 0.25°. Compared to previous models, two important improvements are 1) a larger number of stations with a more even distribution, in particular to the west of the range, and 2) the introduction, before inversion, of crustal corrections inferred from previous refraction and reflection experiments. This last point is crucial because a strong Moho jump (up to 20 km) is present at the North Pyrenean Fault, the former boundary between Eurasian and Iberian plates. The comparison of the models obtained with and without crustal corrections reveals the strong contamination of the models by the crust down to 100 km depth. In the uncorrected model, a large strip with negative P-velocity anomalies, previously interpreted as subduction of lower crust, is observed. It disappears in the corrected model. Moreover, the introduction of crustal corrections allows us to reveal short wavelength heterogeneities which were hidden by the crustal signal.An attempt is made to relate the heterogeneities revealed by the tomographic model with the tectonic history of the Pyrenees, in particular with the Alpine orogeny. The Alpine phase includes an extensive episode with generation of the thin continental crust and possibly the opening of an oceanic sea floor, and then a compressive stage. In our model, no signature of an oceanic subducted slab could be detected all along the range, a result which rules out the opening of a large oceanic floor before the compressive stage. A subduction of continental crust is possible but, due to the transformation of lower crust into eclogite at depth, it can not be detected by seismological methods, whereas it was observed from electrical and gravity data. To the East of the range, large heterogeneities with low velocities are ascribable to the Neogene extension related to the rotation of the Corso–Sardo block and the opening of the Gulf of Lion. A prominent high velocity anomaly extending down to 200 km in eastern-central Pyrenees could possibly be interpreted as a detached piece of the Tethys slab. In north of Iberia outside the range, deep (down to 200 km) low velocity structures oriented N130°E are probably related to Hercynian orogeny. 相似文献
16.
Studies of heat flow from Precambrian terrains have demonstrated three empirical relationships; a temporal relationship between heat flow and tectonic age, a spatial pattern between heat flow and the proximity of Archean cratons, and a temporal relationship between heat flow and the age of lithosphere stabilization. In the first relationship, heat flow is inversely related to tectonic age. The second pattern is characterized by low heat flow from Archean cratons and Proterozoic terrains adjacent to cratonic margins (pericratonic terrains), and higher heat flow from Proterozoic terrains that are more than a few hundred kilometers from a craton. In the third pattern, heat flow decreases as the age of stabilization of the lithosphere increases. A number of interpretations of Precambrian heat flow have been offered to explain one or more of these relationships. The simple cooling of a thermal boundary layer predicts essentially no change in heat flow in terrains older than 1.5 Ga, and therefore does not likely provide a comprehensive framework for the interpretation of Precambrian heat flow. By contrast, two other interpretations, (1) thicker lithosphere beneath Archean terrains than beneath Proterozoic terrains, and (2) greater heat production in Proterozoic crust than in Archean crust, when combined with the special structural configuration of sutures, can both contribute to the spatial and temporal heat flow distributions. Xenolith thermobarometry constraints on lithospheric temperatures, however, limit the contribution of age-dependent crustal heat production, and therefore at least part of the heat flow distributions derive from variations in lithosphere thickness. 相似文献
17.
The complicated structural and rheologic properties of Western Carpathian lithosphere reflect the complex geodynamic history of the Carpathian orogen. Based on critical analysis of earlier models, new interpolation of existing geophysical data and results of integrated modelling, a new map of the lithosphere thickness for the Carpathian–Pannonian region has been constructed. The map allows for the distinction of a frontal orogen collision zone in the NE (from increased lithosphere thickness) as well as a zone of oblique collision with the Bohemian Massif in the West, where lithosphere is not significantly thickened. The MOHO discontinuity beneath the Western Carpathian hinterland (Danube and East Slovak Basins), as defined by deep reflection seismic profiling, is relatively shallow. This probably reflects recent crustal extension related to oblique collision between the European plate and the ALCAPA block and an increase of the asthenospheric updoming from the Middle Miocene onward.Crustal thickness reflects the combined effects of deep-seated orogenic processes and mantle thermal evolution beneath the Pannonian Basin system. In this study, we focus particularly the structures of: (1) the Late Alpine collision and Neogene back arc basin development, including deep-seated contacts between colliding plates, a zone of slab detachment, the compressional accretionary wedge of the Outer Western Carpathian Flysch Belt, and extensional structures produced by subduction rollback and asthenosphere upwelling; (2) Early Alpine structures related to Cretaceous thrust-stacking, including subhorizontal reflection packages (interpreted as multi-generational extensional structures), the underplated intra-Penninic (Oravic) continental ribbon, and ophiolite traces of the Meliatic oceanic suture; and (3) north-dipping reflectors interpreted as remnant Hercynian lithotectonic fragments with opposed vergency to the subducted Alpine units. 相似文献
18.
We estimate the lateral variations of the elastic thickness of the Maracaibo block with a 3D numerical approach by using centered finite differences. The calculation is based on solving the fourth-order partial differential equation that governs the bending of a thin plate fixed on its boundaries (zero displacement) with variable thickness (or elastic thickness for this particular case). An initial plate-load model is built and is iteratively modified to fit the general basement configuration and gravity data. The final result is an elastic thickness map that covers the Maracaibo block and the surrounding sections of the South American plate. It shows that the elastic thickness ranges from 30 km to 18 km with a mean value of 23.6 km and a mode of 26 km. The largest elastic thickness values are associated with the location of the Santa Marta Mountains and the Barinas Apure Basin, while the smallest ones with the Mérida Andes-Maracaibo Basin flexural system. The current basement configuration within the Maracaibo basin, formed as a result of its geodynamic evolution, has affected the mechanical properties of the Maracaibo block near the current Mérida Andes position. The load of the Perijá Range is compensated by a complex stress tensor, and that of the Santa Marta Mountains does not have an isostatic root as it is held by a relatively strong lithosphere. 相似文献
19.
High-Mg lavas are characteristic of the mid-Miocene volcanism in Inner Asia.In the Vitim Plateau,small volume high-Mg volcanics erupted at 16-14 Ma.and were followed with voluminous moderate-Mg lavas at 14-13 Ma.In the former unit,we have recorded a sequence of(1) initial basaltic melts,contaminated by crustal material,(2) uncontaminated high-Mg basanites and basalts of transitional(K-Na-K) compositions,and(3) picrobasalts and basalts of K series;in the latter unit a sequence of(1) initial basalts and basaltic andesites of transitional(Na-K-Na) compositions and(2) basalts and trachybasalts of K-Na series.From pressure estimation,we infer that the high-Mg melts were derived from the sublithospheric mantle as deep as 150 km,unlike the moderate-Mg melts that were produced at the shallow mantle.The 14-13 Ma rock sequence shows that initial melts equilibrated in a garnet-free mantle source with subsequently reduced degree of melting garnet-bearing material.No melting of relatively depleted lithospheric material,evidenced by mantle xenoliths,was involved in melting,however.We suggest that the studied transition from high-to moderate-Mg magmatism was due to the mid-Miocene thermal impact on the lithosphere by hot sub-lithospheric mantle material from the Transbaikalian low-velocity(melting) domain that had a potential temperature as high as 1510℃.This thermal impact triggered rifting in the lithosphere of the Baikal Rift Zone. 相似文献
20.
The Rhine Rift System (RRS) forms part of the European Cenozoic Rift System (ECRIS) and transects the Variscan Orogen, Permo-Carboniferous troughs and Late Permian to Mesozoic thermal sag basins. Crustal and lithospheric thicknesses range in the RRS area between 24–36 km and 50–120 km, respectively. We discuss processes controlling the transformation of the orogenically destabilised Variscan lithosphere into an end-Mesozoic stabilised cratonic lithosphere, as well as its renewed destabilisation during the Cenozoic development of ECRIS. By end-Westphalian times, the major sutures of the Variscan Orogen were associated with 45–60 km deep crustal roots. During the Stephanian-Early Permian, regional exhumation of the Variscides was controlled by their wrench deformation, detachment of subducted lithospheric slabs, asthenospheric upwelling and thermal thinning of the mantle-lithosphere. By late Early Permian times, when asthenospheric temperatures returned to ambient levels, lithospheric thicknesses ranged between 40 km and 80 km, whilst the thickness of the crust was reduced to 28–35 km in response to its regional erosional and local tectonic unroofing and the interaction of mantle-derived melts with its basal parts. Re-equilibration of the lithosphere-asthenosphere system governed the subsidence of Late Permian-Mesozoic thermal sag basins that covered much of the RRS area. By end-Cretaceous times, lithospheric thicknesses had increased to 100–120 km. Paleocene mantle plumes caused renewed thermal weakening of the lithosphere. Starting in the late Eocene, ECRIS evolved in the Pyrenean and Alpine foreland by passive rifting under a collision-related north-directed compressional stress field. Following end-Oligocene consolidation of the Pyrenees, west- and northwest-directed stresses originating in the Alps controlled further development of ECRIS. The RRS remained active until the Present, whilst the southern branch of ECRIS aborted in the early Miocene. Extensional strain across ECRIS amounts to some 7 km. Plume-related thermal thinning of the lithosphere underlies uplift of the Rhenish Massif and Massif Central. Lithospheric folding controlled uplift of the Vosges-Black Forest Arch. 相似文献
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