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1.
We present a method based on the combination of elevation and geoid anomaly data together with thermal field to map crustal and lithospheric thickness. The main assumptions are local isostasy and a four-layered model composed of crust, lithospheric mantle, sea water and the asthenosphere. We consider a linear density gradient for the crust and a temperature dependent density for the lithospheric mantle. We perform sensitivity tests to evaluate the effect of the variation of the model parameters and the influence of RMS error of elevation and geoid anomaly databases. The application of this method to the Gibraltar Arc System, Atlas Mountains and adjacent zones reveals the presence of a lithospheric thinning zone, SW–NE oriented. This zone affects the High and Middle Atlas and extends from the Canary Islands to the eastern Alboran Basin and is probably linked with a similarly trending zone of thick lithosphere constituting the western Betics, eastern Rif, Rharb Basin, and Gulf of Cadiz. A number of different, even mutually opposite, geodynamic models have been proposed to explain the origin and evolution of the study area. Our results suggest that a plausible slab-retreating model should incorporate tear and asymmetric roll-back of the subducting slab to fit the present-day observed lithosphere geometry. In this context, the lithospheric thinning would be caused by lateral asthenospheric flow. An alternative mechanism responsible for lithospheric thinning is the presence of a hot magmatic reservoir derived from a deep ancient plume centred in the Canary Island, and extending as far as Central Europe. 相似文献
2.
On the role of heat flow, lithosphere thickness and lithosphere density on gravitational potential stresses 总被引：1，自引：0，他引：1
Gravitational potential stresses (GPSt) are known to play a first-order role in the state of stress of the Earth's lithosphere. Previous studies focussed mainly on crust elevation and structure and little attention has been paid to modelling GPSt using realistic lithospheric structures. The aim of the present contribution is to quantify gravitational potential energies and stresses associated with stable lithospheric domains. In order to model realistic lithosphere structures, a wide variety of data are considered: surface heat flow, chemical depletion of mantle lithosphere, crustal thickness and elevation. A numerical method is presented which involves classical steady-state heat equations to derive lithosphere thickness, geotherm and density distribution, but additionally requires the studied lithosphere to be isostatically compensated at its base. The impact of varying surface and crustal heat flow, topography, Moho depth and crust density on the signs and magnitudes of predicted GPSt is systematically explored. In clear contrast with what is assumed in most previous studies, modelling results show that the density structure of the mantle lithosphere has a significant impact on the value of the predicted GPSt, in particular in the case of thick lithospheres. Using independent information from the literature, the method was applied to get insights in the state of stress of continental domains with contrasting tectono-thermal ages. The modelling results suggest that in the absence of tectonic stresses Phanerozoic and Proterozoic lithospheres are spontaneously submitted to compression whereas Archean lithospheres are in a neutral to slightly tensile stress state. These findings are in general in good agreement with global stress measurements and observed geoid undulations. 相似文献
3.
Assessing subcontinental lithospheric mantle sources for basalts: Neogene volcanism in the Pacific Northwest,USA as a test case 总被引：2，自引：0，他引：2
Many objections have been raised as to the ability of subcontinental lithospheric mantle to produce voluminous amounts of basalt, because this upper part of the mantle is thought to be refractory, and the geotherm is rarely above the peridotite solidus at these depths under continents. However, in the Pacific Northwest of the USA during the Neogene, the subcontinental lithospehric mantle has been proposed as a key source for basalts erupted within the northern Basin and Range, and for the Columbia River flood basalts erupted on the Columbia Plateau. An alternative explanation to melting in the subcontinental lithospheric mantle, which equally well explains the chemical compositions thought to originate there, is that these magmas were contaminated by crust of varying ages. Calc-alkaline lavas, which occupy the Blue Mountains in the center of this region, hold clues to the latter process. Their elevated trace element ratios (e.g., Ba/Zr, K2O/P2O5), coupled with differentiation indicators such as Mg? [molar Mg/(Mg?+?Fe)], and Sr, Nd, and Pb isotopic compositions, can most reasonably be explained by crustal contamination. Appraisal of continental peridotite xenolith data indicates that high trace element ratios such as Ba/Zr in continental basalts cannot result from melting in the subcontinental lithospheric mantle. Instead, as with the calc-alkaline lavas, these high ratios in the tholeiites most likely indicate crustal contamination. Furthermore, the peridotite xenoliths do not have a relative depletion in Nb and Ta that is observed in most of the lavas within the region. Relatively minor volumes of tholeiites erupted in late Neogene times in the northern Basin and Range (Hi-Mg olivine tholeiites) and Columbia Plateau (Saddle Mountains basalts), are the only lavas which have trace element and isotopic compositions consistent with being derived from, or largely interacting with a subcontinental lithospheric mantle in the Pacific Northwest. In contrast to the prior studies, we suggest that the mantle sources for most of the basalts in this region were ultimately beneath the lithospheric mantle. 相似文献
4.
Spinel lherzolite and harzburgite xenoliths from the Basin and Range and Colorado Plateau Provinces in the southwestern United States (SWUS) show a broad range in incompatible element distributions from depleted to enriched, both within and between sites. The most fertile xenoliths occur in the Basin and Range Province and the most refractory in the Colorado Plateau or Transition Zone. Mass balance calculations indicate that up to 80% of the high field strength (Nb, Ta, Zr, Hf, Th, Ti) and rare earth elements (50% for Yb) in these xenoliths occur in phases along grain boundaries (or in microfractures). In lower crustal and eclogite xenoliths, up to 90% of these elements occur in grain-boundary phases. Nb/Ta, Zr/Hf, La/Sm and Nb/Th ratios and Nb-Ta anomalies in both types of xenoliths are also controlled by grain-boundary phases. To interpret these ratios in whole-rock analyses, it is critical to understand the timing and origin of the grain-boundary components in the xenoliths. Most of the enriched mantle xenoliths appear to have been enriched by metasomatic fluids related to silicate magmas and not to carbonatite magmas.Because of a complex multi-event history that affected the composition of the xenoliths, there is no simple geochemical relationship between magmatic or metamorphic history of the lower crust and upper mantle in the SWUS as reflected by the xenolith populations. 相似文献
5.
塔里木盆地及邻区岩石圈拆离解耦与盆山格局关系的天然地震分析 总被引：8，自引：1，他引：7
与洋陆俯冲关系不同,在板内汇聚过程中,大陆岩石圈固有的多圈层、多界面结构的特点,使得地块的俯冲变形伴有多圈层顺层拆离解耦的行为,使变形结构复杂化。虽然多圈层界面拆离解耦所引发的地震点群空间分布不像洋陆俯冲关系那么规则完美,但是依据地震群与破裂位置、破裂与岩石圈分层力学特性的依次控制关系,运用深度/频次、平面密度等统计方法,再以各种地球物理实测手段得到的岩石圈结构构造数据作为界面标定依据,还是能够得出诸如拆离解耦的界面深度、界面归属和区域层间变形范围等重要的几何学信息,这些变形几何学、运动学数据是构建大陆岩石圈板内汇聚造山特别是盆山耦合模式时的关键性的依据。文中通过对塔里木盆地及周缘造山带的相关研究,在岩石圈层拆离解耦状态及其与盆山构造格局之间的关系方面得出以下几点认识:(1)塔里木盆地及周缘造山带岩石圈的主拆离解耦层均发育于中地壳,但随各区中地壳的具体深度位置不同而有所差别;(2)塔西南/西昆仑盆山构造耦合关系是构建于岩石圈尺度上的,塔北/南天山盆山耦合关系是构建于地壳尺度上的;(3)地震活动的密集程度及密集带的展布与天山的变形强度、隆升状态和地貌阶段类型的变化规律有着近乎完美的精确匹配关系;(4)塔北/南天山和塔西南/西昆仑对应于岩石圈的强拆离解耦区,塔东北/东天山和塔东南/阿尔金山之间无耦合关系,其边缘带对应于岩石圈弱拆离解耦和无拆离解耦区;(5)塔里木盆地总体上的弱变形状态与其岩石圈弱或未拆离解耦类型占据总面积90%的情形相适应;(6)塔里木地块以驱动、阻挡约束、平移滚筒约束和克拉通过渡等多重“身份”存在于相邻单元“包围”的力学环境中。 相似文献
6.
Paul E. Damon 《Tectonophysics》1983,99(1):T1-T8
A model for continental uplift at a convergent margin (Damon, 1979) is further developed. The model assumes the necessity of isostatic compensation of the subducted lithospheric plate. It predicts a continental declivity that reaches its maximum uplift and extent at the time of trench-spreading center collision. As a result of the passage of the subducted plate eastward the region of maximum uplift increases and migrates eastward behind the eastward migrating declivity. The “gang plank” from the Front Range to the Mississippi River is the most obvious modern expression of the continental declivity whereas the Great Basin is an expression of the area of maximum uplift lowered somewhat by extension and crustal thinning. Compensation takes place by transfer of asthenosphere to the base of continental lithosphere. At the time of trench-spreading center collision a pressure gradient shunts the asthenospheric current from the quenched spreading center to the channel between the continental lithosphere and the subducted plate. Sinking of the subducted plate causes upwelling of asthenosphere feeding the laminar flow between the two plates. The model is in accord with the physiography of North America and the geologic record. 相似文献
7.
This paper compares the 1.67–1.47 Ga rapakivi granites of Finland and vicinity to the 1.70–1.68 Ga rapakivi granites of the Beijing area in China, the anorogenic 130 Ma granites of western Namibia, and the 20–15 Ma granites of the Colorado River extensional corridor in the Basin and Range Province of southern Nevada. In Finland and China, the tectonic setting was incipient, aborted rifting of Paleoproterozoic or Archean continental crust, in Namibia it was continental rifting and mantle plume activity that led to the opening of southern Atlantic at 130 Ma. The 20–15 Ma granites of southern Nevada were related to rifting that followed the Triassic–Paleogene subduction of the Farallon plate beneath the southwestern United States. In all cases, extension-related magmatism was bimodal and accompanied by swarms of diabase and rhyolite–quartz latite dikes. Rapakivi texture with plagioclase-mantled alkali feldspar megacrysts occurs in varying amounts in the granites, and the latest intrusive phases are commonly topaz-bearing granites or rhyolites that may host tin, tungsten, and beryllium mineralization. The granites are typically ferroan alkali-calcic metaluminous to slightly peraluminous rocks with A-type and within-plate geochemical and mineralogical characteristics. Isotope studies (Nd, Sr) suggest dominant crustal sources for the granites. The preferred genetic model is magmatic underplating involving dehydration melting of intermediate-felsic deep crust. Juvenile mafic magma was incorporated either via magma mingling and mixing, or by remelting of newly hybridized lower crust. In Namibia, partial melting of subcontinental lithospheric mantle was caused by the Tristan mantle plume, in the other cases the origin of the mantle magmatism is controversial. For the Fennoscandian suites, extensive long-time mantle upwelling associated with periodic, migrating melting of the subcontinental lithospheric mantle, governed by heat flow and deep crustal structures, is suggested. 相似文献
8.
龙门山是我国东西构造、地貌分界线的重要组成部分。其两侧的岩石圈结构差异,是形成龙门山造山带的主要原因之一,并对龙门山的构造演化起着持续影响。为了解龙门山两侧壳幔结构差异,本文从重力角度探讨跨龙门山地区的地壳密度结构。我们使用EGM2008模型的重力异常数据,以最新的阿坝-遂宁人工源地震剖面速度模型为基础,得到了龙门山造山带中段及其邻区的精细地壳密度结构。密度结构显示松潘-甘孜地区和四川盆地分别具有软弱和坚硬的下地壳。根据本文所得到的地壳密度结构模型,我们认为龙门山的隆升主要受印度洋板块与欧亚大陆板块的陆-陆碰撞作用影响,强烈的挤压作用使青藏高原物质向东运移,东移物质在青藏高原东缘龙门山地区受到坚硬的四川盆地的阻挡转而向上运移,造成了龙门山的隆升。 相似文献
9.
本文以区域地质、矿产地质为基础,与地球物理和岩石圈深部地质的研究成果相结合,对中国东南陆区的地块、造山带、古板块结合带、隆起带、坳陷带和断陷盆地的地壳厚度变化与物质结构、莫霍面形态、岩石圈地幔的厚度变化与结构进行了研究与构造区划.论述了燕山期陆内造山与喜马拉雅期大陆伸展及其导致的岩石圈物质结构调整作用,建立了隆坳构造分异与壳幔物质结构调整模式,探讨了本区地壳减薄的深部地质过程,分析了燕山期陆内造山的动力机制以及大规模成矿作用与岩石圈物质结构构造的相关关系. 相似文献
10.
中国岩石圈的基本特征 总被引：11，自引：2，他引：9
中国及邻区岩石圈结构构造十分复杂,并具有若干明显的特点:中国大陆地壳西厚东薄、南厚北薄,青藏高原地壳平均厚度为60~65 km,最厚达80 km;东部地区一般为30~35 km,南中国海中央海盆平均只有5 km;中国大陆地壳平均厚度为476 km,大大超过全球地壳392 km的平均厚度。中国大陆及邻区岩石圈亦呈西厚东薄、南厚北薄的变化趋势,青藏高原及西北地区岩石圈平均厚度为165 km,塔里木盆地中东部、帕米尔与昌都地区岩石圈厚度可达180~200 km。大兴安岭-太行山-武陵山以东,包括边缘海为岩石圈减薄区,厚度为50~85 km。西部岩石圈、软流圈“层状结构”明显,反映了板块碰撞汇聚的动力学环境;东部岩石圈、软流圈呈“块状镶嵌结构”,岩石圈薄,软流圈厚,反映了地壳拉张、软流圈物质上涌的特点,并在东亚及西太平洋地区85~250 km深处形成一巨型低速异常体。中国东部上、下地壳及地壳、岩石圈地幔之间普遍存在“上老下新”年龄结构。 相似文献
11.
Tingdong Li 《地学前缘(英文版)》2010,1(1):45-56
<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
12.
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
13.
论燕山运动的深部地球动力学本质 总被引：109，自引：0，他引：109
对中国东部新生代玄武岩及其包体的矿物学、岩 石学和地球化学研究的总结发现,中国东部在燕山期主要表现为岩石圈的减薄,并在其东部 出现软流圈地幔与地壳直接接触的独特地质现象。早先应该存在的古老岩石圈地幔大多由于 拆沉作用而不复存在,现今岩石圈 地幔主体是在燕山晚期及其以后形成的。因此,中国东部燕山运动的本质就是岩石圈的减薄 乃至岩石圈地幔的消失。研究认为,这种岩石圈减薄的触发因素可能与当时东侧大洋板块的 俯冲有关。软流圈地幔与地壳直接接触的动力学效应是产生强烈的岩浆板底垫托作用及相伴 随的深部地壳的高温变质作用和部分熔融作用,形成巨量岩浆的侵位与喷发,并造成新生地 壳的显著增生和原有地壳的重新调整。同时,这种地球动力学过程将携带大量地幔物质（包 括成矿物质）进入地壳,并形成地壳尺度的大规模流体循环,从而产生大面积、突发性的巨 量成矿作用。 相似文献
14.
大陆岩石圈有效弹性厚度与有关地球物理参数的关系--以泉州-黑水地学断面为例 总被引：1，自引：0，他引：1
大陆岩石圈有效弹性厚度(Te)是反映岩石圈综合强度的参数,它反映了岩石圈的整体特征。分析岩石圈有效样性厚度与反映深部地质特征的有关地球物理参数之间的关系,对研究控制Te的因素、各因素之间的关系以及探索大陆构造与大陆动力学等具有重要意义。泉州一黑水地学断面Te与地壳厚度、热岩石圈厚度、均衡重力异常、磁性构造层底面深度、上地幔低速层顶界面深度、上地幔低阻层顶面深度之间的关系研究表明：Te与大地热流关系密切的“热”地球物理参数磁性构造层底面深度、热岩石圈厚度相关性好;与地壳厚度有一定的相关性;上地幔低速层顶界面深度和上地幔低阻层顶面深度与大陆岩石圈Te相关性均较差。 相似文献
15.
A top to bottom lithospheric study of Africa and Arabia 总被引：1，自引：0，他引：1
We study the lithospheric structure of Africa, Arabia and adjacent oceanic regions with fundamental-mode surface waves over a broad period range. Including group velocities with periods shorter than 35 s allows us to examine shallower features than previous studies of the whole continent. In the process, we have developed a crustal thickness map of Africa. Main features include crustal thickness increases under the West African, Congo, and Kalahari cratons. We find crustal thinning under Mesozoic and Cenozoic rifts, including the Benue Trough, Red Sea, and East, Central, and West African rift systems, along with less abrupt crustal thickness changes at passive continental margins. We also find crustal thickness differences in North Africa between the West African Craton and East Saharan Shield. Crustal shear wave velocities are generally faster in oceanic regions and cratons, and slower in more recent crust and in active and remnant orogenic regions. Deeper structure, related to the thickness of cratons and modern rifting, is generally consistent with previous work. Under cratons we find thick lithosphere and fast upper mantle velocities, while under rifts we find thinned lithosphere and slower upper mantle velocities. However, we also find the lack of a thick cratonic keel beneath the central portion of the Congo Craton. There are no consistent effects in areas classified as hotspots, indicating that there seem to be numerous origins for these features. Finally, it appears that the African Superswell, which is responsible for high elevation and uplift over large portions of Africa, has had a significantly different impact (as indicated by features such as temperature, time of influence, etc.) in the north and the south. This is consistent with episodic activity at shallow depths, which is well-expressed in northeastern Africa and Arabia today. 相似文献
16.
A. M. Petrishchevsky 《Geotectonics》2013,47(6):465-484
Structural forms of emplacement of crustal and mantle rigid sheets in collision zones of lithospheric plates in northeastern Asia are analyzed using formalized gravity models reflecting the rheological properties of geological media. Splitting of the lithosphere of moving plates into crustal and mantle constituents is the main feature of collision zones, which is repeated in the structural units irrespective of their location, rank, and age. Formal signs of crustal sheet thrusting over convergent plate boundaries and subduction of the lithospheric mantle beneath these boundaries have been revealed. The deep boundaries and thickness of lithospheric plates and asthenospheric lenses have been traced. A similarity in the deep structure of collision zones of second-order marginal-sea buffer plates differing in age is displayed at the boundaries with the Eurasian, North American, and Pacific plates of the first order. Collision of oceanic crustal segments with the Mesozoic continental margin in the Sikhote-Alin is characterized, as well as collision of the oceanic lithosphere with the Kamchatka composite island arc. A spatiotemporal series of deep-seated Middle Mesozoic, Late Mesosoic, and Cenozoic collision tectonic units having similar structure is displayed in the transitional zone from the Asian continent to the Pacific plate. 相似文献
17.
Effects of mantle upwelling in a compressional setting: the Atlas Mountains of Morocco 总被引：1，自引：0，他引：1
Antonio Teixell Puy Ayarza Hermann Zeyen Manel Fernàndez María-Luisa Arboleya 《地学学报》2005,17(5):456-461
We discuss the implications of a lithospheric model of the Moroccan Atlas Mountains based on topography, heat flow, gravity and geoid anomalies, taking into account the regional geology. The NW African cratonic lithosphere, some 160–180 km thick, thins to c. 80 km beneath the Atlas fold-thrust belts, in contrast with the shortening regime prevailing there since the early Cenozoic. This fact explains several geological and geophysical features as high topography with modest tectonic shortening, the occurrence of alkaline magmatism contemporaneous to compression, the absence of large crustal roots to support elevation, the scarce development of foreland basins, and a marked geoid high. The modelled lithosphere thinning is related to a thermal upwelling constrained between the Iberia–Africa convergent plate boundary and the Saharan craton. 相似文献
18.
Geophysical data illustrate that the Indian continental lithosphere has northward subducted beneath the Tibet Plateau, reaching the Bangong–Nujiang suture in central Tibet. However, when the Indian continental lithosphere started to subduct, and whether the Indian continental crust has injected into the mantle beneath southern Lhasa block, are not clear. Here we report new results from the Quguosha gabbros of southern Lhasa block, southern Tibet. LA-ICP-MS zircon U–Pb dating of two samples gives a ca. 35 Ma formation age (i.e., the latest Eocene) for the Quguosha gabbros. The Quguosha gabbro samples are geochemically characterized by variable SiO2 and MgO contents, strongly negative Nb–Ta–Ti and slightly negative Eu anomalies, and uniform initial 87Sr/86Sr (0.7056–0.7058) and εNd(t) (− 2.2 to − 3.6). They exhibit Sr–Nd isotopic compositions different from those of the Jurassic–Eocene magmatic rocks with depleted Sr–Nd isotopic characteristics, but somewhat similar to those of Oligocene–Miocene K-rich magmatic rocks with enriched Sr–Nd isotopic characteristics. We therefore propose that an enriched Indian crustal component was added into the lithospheric mantle beneath southern Lhasa by continental subduction at least prior to the latest Eocene (ca. 35 Ma). We interpret the Quguosha mafic magmas to have been generated by partial melting of lithospheric mantle metasomatized by subducted continental sediments, which entered continental subduction channel(s) and then probably accreted or underplated into the overlying mantle during the northward subduction of the Indian continent. Continental subduction likely played a key role in the formation of the Tibetan plateau at an earlier date than previously thought. 相似文献
19.
E.V. Artyushkov 《Russian Geology and Geophysics》2012,53(6):566-582
As evidenced by plentiful data, most of the large recent positive topographic features formed as a result of a dramatically accelerated crustal uplift in the Pliocene–Quaternary after a relatively stable period (～100 Myr in most of the regions). The methods used are illustrated by the well-studied large neotectonic crustal uplifts on the Tibetan Plateau and in the Himalayas. Farther north, neotectonic uplifts with amplitudes of several hundred meters to several kilometers spread over a vast area from Central and Northeast China in the south to the Taimyr Peninsula and Northeastern Asia in the north. They are often attributed to the India–Asia plate collision which began ～50 Ma.Most of the uplifts in these regions have formed only during the last few Myr, unaccompanied by significant crustal shortening. Therefore, the large neotectonic crustal uplifts can be explained by a decrease in the lithospheric density. One of the causes was the rapid convective replacement of the lower part of the denser mantle lithosphere by the asthenosphere or mantle plume. This became possible owing to a drastic weakening of the mantle lithosphere under the influence of asthenospheric fluids. In some areas, a considerable asthenospheric top uplift is evidenced by seismic tomography data.The lower mantle lithosphere (～50–100 km thick) was replaced by the asthenosphere underneath the neotectonic crustal uplifts of ～1.0 km in Central Asia. Areas with a thick lithosphere were affected by relatively small neotectonic uplifts, strongly nonuniform in space. They point to metamorphism with mafic-rock expansion in the lower crust upon the infiltration of an asthenospheric fluid. The large crustal uplifts which formed on the continents in the Pliocene and Pleistocene indicate large-scale quasi-synchronic supply of the mantle fluid to their lithosphere. 相似文献
20.
青藏高原隆升三阶段模型的数值模拟 总被引：13，自引：0，他引：13
研究表明 ,青藏高原的隆升不仅是印度板块和欧亚板块碰撞的结果 ,它同时受到高原下部地幔物质运移以及地幔和岩石层之间耦合作用的影响。文中以青藏高原隆升三阶段模式(BCCM )为基本模型 ,对在印度板块向北推移、挤压而导致的高原隆升演化的数值模拟结果进行处理。处理中考虑了与抬升过程相应的剥蚀过程 ,同时还考虑在高原演化的后期大约 8～10Ma时发生的下伏岩石层底部的对流搬离 (convectiveremoval)而导致的隆升作用。结果表明 ,模型描述的青藏高原隆升演化过程和观测资料有较好的吻合 ,同时显示高原下部岩石层的对流搬离可能是最近 8～ 10Ma以来高原整体隆升的主导机制。 相似文献