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1.
ZHANG Yuquan XIE Yingwen LI Xianhua QIU Huaning LIANG Huaying LI Jianping ZHAO Zhenhua DENG Wanming CHUNG Sunlin 《中国科学D辑(英文版)》2001,44(1)
The Cenozoic magmatic rocks of shoshonitic series in the easternQinghai-Tibet Plateau include potassic alkaline plutonic rocks, volcanic rocks, lamprophyres and acidic porphyries. Analytical results show that these different lithological rocks are extremely similar in Sr, Nd and Pb isotopic compositions with the range of 0.705 187-0.707 254 for 87Sr/86Sr, 0.512 305-0.512 630 for 143Nd/144Nd, 18.53-18.97 for 206Pb/204Pb, 15.51-15.72 for 207Pb/204Pb and 38.38-39.24 for 208Pb/204Pb. They are isotopically similar to the EMII end-member. This indicates that mantle metasomatism must have taken place in their source region. The formation of these particular rocks is related to crustal thinning and mantle upwelling in a large-scale strike-slip and pull-apart fault zone at about 40 Ma in northern and eastern Qinghai-Tibet Plateau. 相似文献
2.
Teleseismic receiver functions and travel-time residuals along the north Hi-Climb broadband seismic array in the central-southern Qinghai-Tibet Plateau show that the lithosphere structures in the central and western Qinghai-Tibet Plateau are different. In the central Qinghai-Tibet Plateau, the Indian Plate is northward subducted beneath the Qiangtang block and arrives at the greatest depth beneath the central-southern Qiangtang block. The delaminated Indian lithospheric slab remains beneath the central Lhasa block to a depth possibly greater than that of the upper interface of the mantle transform zone. In the western Qinghai-Tibet Plateau, the Indian lithospheric plate is gently northward subducted and may have arrived to the south of Tarim plate. Due to the resistance from the gently northward subduction of the Indian mantle lithosphere in the western Qinghai-Tibet Plateau, the upwelling mantle material be-neath the Qiangtang block moves mostly toward the east to bring about the lateral eastward flow of the deep mantle hot material in the central Qinghai-Tibet Plateau. 相似文献
3.
利用中国西部地震台网的数据,通过体波层析成像反演了青藏高原及邻域的三维P波速度结构.根据地壳和上地幔的速度变化和构造特征,重点讨论了下地壳流动、地幔上涌、岩石圈减薄以及与藏北新生代火山岩和藏南裂谷系的关系等问题.分析表明,青藏高原中、下地壳平均速度偏低,低速区主要分布在拉萨和羌塘块体内部,随着深度的增加逐渐扩大到松潘—甘孜块体.上述低速区之间多被高速带分隔,暗示地壳中、下部的韧性变形被限制在特定的区域,不太适于产生贯穿整个青藏高原的大规模横向流动.此外,地幔上涌也并非普遍发生于整个青藏高原,而是集中在羌塘、松潘—甘孜以及喜马拉雅东构造结附近,导致上述区域的岩石圈地幔较薄,并且伴生火山活动和岩浆作用.此外,由于印度大陆岩石圈在向北俯冲,板片下沉过程中引起地幔上涌,热流物质有可能上升进入地壳,这一作用对藏北新生代火山岩和藏南裂谷系的形成以及中、下地壳的韧性变形产生了明显的影响. 相似文献
4.
Quaternary volcanic rocks of Stromboli (Italy) can be divided into older calc-alkaline and younger shoshonitic series. The SiO2 contents of the rocks range from 50% to 61% but the majority of them are basalts. The rocks show systematic variations in chemical composition which correlate with the volcanic stratigraphy, such that, at a given SiO2 content, K and other incompatible elements such as REE increase with decreasing age. In addition, the La/Yb ratio increases while the K/Rb, K/Ba, Zr/Ce and Zr/Nb ratios decrease towards the top of the volcanic pile. On the other hand, the abundances of transition elements, V, Co, Sc and Zn, like most major elements are broadly similar in comparable rocks of different ages. It is suggested that the parent magmas were derived by partial melting from upper mantle peridotite enriched in incompatible elements by fluids released from the descending oceanic lithosphere. The temporal chemical variations may probably be related to the lengths of time during which fluids were in contact with the upper mantle source. 相似文献
5.
藏北高原地震活动性特征及其大地构造意义 总被引：1，自引：0，他引：1
藏北高原自新生代以来不仅发生了强烈的火山作用,而且现今的地震活动性仍然强烈.本文收集了2011年前藏北高原区发生的地震事件(源自NEIC)及相应的震源机制解数据(源自GCMT),结合地质与地球物理等相关资料,初步分析表明藏北高原地壳整体上处于伸展应力状态.然而,因区域构造应力场及构造环境差异,将藏北高原地震活动区分为两个地震活动区,即西昆仑地震活动区和藏北中部火山岩区.西昆仑区的地壳应力状态呈东西向伸展,而岩石圈地幔部分主要以南北汇聚为主,表明西昆仑区域下的地壳与岩石圈地幔应力状态是解耦的,而这种解耦机制需要更进一步的研究.而在藏北中部火山岩区的地壳的主张应力场为NNE-SSW的走滑和正断层性质的伸展,尽管缺乏该区域下的岩石圈结构特征认识,但是依据幔源性质的钾质和超钾质火山岩成因模式,认为其下的岩石圈地幔也处于伸展状态,该区域下的地壳与岩石圈地幔同处于伸展应力环境中,表明藏北火山岩区下的结构特征更加复杂,亟待开展相关探测与研究. 相似文献
6.
Deep structure and lithospheric shear faults in the East Kunlun-Qiangtang region,northern Tibetan Plateau 总被引：1，自引：0，他引：1
Xu Zhiqin Yang Jingsui Jiang Mei Li Haibing Xue Guangqi Yuan Xuecheng Qian Hui 《中国科学D辑(英文版)》2001,44(1):1-6
The Cenozoic magmatic rocks of shoshonitic series in the eastern Qinghai-Tibet Plateau include potassic alkaline plutonic
rocks, volcanic rocks, lamprophyres and acidic porphyries. Analytical results show that these different lithological rocks
are extremely similar in Sr, Nd and Pb isotopic compositions with the range of 0.705 187– 0.707 254 for87Sr/86Sr, 0.512 305–0.512 630 for143Nd/144Nd, 18.53–18.97 for206Pb/204Pb, 15.51–15.72 for207Pb/204Pb and 38.38–39.24 for208Pb/204Pb. They are isotopically similar to the EMII end-member. This indicates that mantle metasomatism must have taken place in
their source region. The formation of these particular rocks is related to crustal thinning and mantle upwelling in a large-scale
strike-slip and pull-apart fault zone at about 40 Ma in northern and eastern Qinghai-Tibet Plateau 相似文献
7.
利用远震接收函数偏移成像方法获得青藏高原西部Hi-Climb项目剖面北段地壳结构转换波成像。结果显示班公-怒江缝合带下方拉萨地体上地壳向N仰冲,下地壳向N俯冲,而羌塘地块上地壳向S仰冲,下地壳向S俯冲,可能意味着青藏高原西部拉萨地块和羌塘地块具有复杂的拼合过程。结合前人的岩石学研究成果,建立了新特提斯北洋盆洋壳S向俯冲、距今60～50Ma印度板块与欧亚板块碰撞后,拉萨地块的下地壳向羌塘地块下俯冲,而后印度板块俯冲到羌塘地块下方的地块拼合模式 相似文献
8.
利用地震层析成像结果分析了中国西部地区的上地幔速度结构,发现青藏高原北部至东南边缘上地幔顶部速度普遍偏低;随着深度的增加,低速区主要分布在羌塘、松潘—甘孜和云南西部地区,而印度大陆、塔里木、柴达木、鄂尔多斯和四川盆地均显示出较高的速度.上述速度分布与青藏高原及周边地区的岩石层结构和深部动力性质密切相关:其中羌塘地区的低速异常反映了青藏北部的地幔上涌和局部熔融,起因于印度大陆岩石层的向北俯冲;松潘—甘孜地区的低速异常与青藏东部的深层物质流动及四川盆地刚性岩石层的阻挡有关;而滇西地区的低速异常可能受到印缅块体向东俯冲作用的影响.以上三个区域构成青藏高原和周边地区的主要地幔异常区.相比之下,印度大陆、塔里木、柴达木、鄂尔多斯和四川盆地的高速异常反映了大陆构造稳定地区的岩石层地幔特点.根据速度变化推测,地幔上涌和韧性变形并非贯穿整个青藏高原,而是主要集中在羌塘、松潘—甘孜和滇西地区,上述构造效应不仅导致岩石层厚度减薄且引发了火山和岩浆活动. 相似文献
9.
M. Cortini 《Bulletin of Volcanology》1981,44(4):711-722
Historical volcanic rocks of the Aeolian islands range in composition from shoshonitic basalts to rhyolites, which might reflect fractional crystallization of a shoshonitic parent magma. However Sr and Pb isotopic data indicate a more complex history. The shoshonitic basalts at present erupted at Stromboli, although chemically similar to the postulated parent magma, are genetically unrelated to the other studied rocks. Sr isotopes indicate that Vulcano, Vulcanello and Lipari had independent magma sources. It is proposed that crustal contamination raised the Sr isotopic composition of the Lipari rhyolites. The rocks of these island are related by a common very steep trend of207Pb/204Pbvs. 206Pb/204Pb. Such a trend is a common feature of orogenic magmas and shows that Pb was derived by mixing of at least two components. Presently it is impossible to constrain precisely either the timing or the physical meaning of the Pb end members. The Pb isotopic trend in the Eolian island is very distinct from those recorded in volcanic rocks both from behind the arc (Etna, Iblean Mts.) and from Central and Southern Italy. 相似文献
10.
The Cenozoic volcanic rocks of eastern China are subalkalic to alkalic basalts erupted in an early Tertiary back-arc rift environment and from scattered late Tertiary and Quaternary volcanic centers in a continental area crossed by active faults, driven by subduction of the Pacific plate and the collision of India and Eurasia. Immobile trace elements and major elements conform very well to each other in classification of the 59 rocks for which complete data are reported and they correctly identify the tectonic setting. LIL-element enrichments of the basalts lie between those of P-MORB and ocean island alkalic basalts, and show a secular increase.87Sr/86Sr ratios of basalts vary from 0.7029 to 0.7048. Alkalic basalts are systematically less radiogenic than geographically coextensive and contemporaneous tholeiitic basalts. Increase of radiogenic Sr with increasing crustal thickness and crustal age and with silica enrichment of the magmas suggests crustal contamination but this is inadequate to explain the LIL-element enrichment patterns and variable LIL-element enrichments. The preferred hypothesis is that the alkalic magmas come from a deeper source, with long-term LIL-element depletion and low Rb/Sr ratio but relatively recent LIL-element enrichment. Conversely the tholeiitic magmas are melts of subcontinental mantle lithosphere that is more LIL-element depleted than the alkalic source, at the time of magma genesis, but has had an elevated Rb/Sr ratio for much of its post-consolidation history. 相似文献
11.
本文报道通过综合大地电磁调查数据研究青藏高原岩石圈三维电阻率模型的初步成果.大地电磁法调查区域已经覆盖了高原大部分面积,为全区三维电阻率成像研究打下了可靠的基础.对多个测区大地电磁数据进行精细的同化处理和反演成像,取得了青藏高原可靠的岩石圈三维电阻率结构图像.成像的区域为28°N—35°N,80°E—104°E.三维反演计算时采用的网格尺寸为20km×20km,垂直方向不等间距剖分为26层.结果表明,青藏高原现今岩石圈电阻率扰动主要反映印度克拉通对亚欧大陆板块俯冲引起的热流体运动和大陆碰撞和拆离产生的构造.在岩石圈地幔,察隅地块、喜马拉雅地块和拉萨地块东部联成统一的高电阻率地块,它们反映了向北东俯冲的印度克拉通.雅鲁藏布江、班公—怒江和金沙江缝合带都有明显的低电阻率异常,表明岩石圈深处有热流体活动.雅鲁藏布江、班公—怒江和金沙江缝合带都有明显的低电阻率异常,也表明它们的岩石圈还有流体活动.青藏高原东部的低阻区沿100°E向地幔下方扩大,反映了金沙江断裂带有切穿岩石圈的趋势.地幔电阻率平面扰动的模式显示,青藏高原东西部的地体碰撞拼合形式和方向是不同的.在青藏高原西部,羌塘、拉萨和喜马拉雅等地体从北到南碰撞拼合.在青藏高原东部,羌塘—拉萨、察隅、印支、雅安和扬子等地体多方向拆离拼合,在地壳造成不正交的拆离带和压扭构造系.从高阻-低阻区的分布看,东部的地体拼合有地幔的根源,今后还会进一步发展.察隅地块岩石圈对青藏高原东部的楔入,使其北部和东部地块的岩石圈发生拆离撕裂,也造成热流体上涌的低电阻率异常. 相似文献
12.
47个腾冲火山岩样品的K-Ar年龄值域在0.09和17.84Ma之间。4条火山岩的40Ar/36Ar-40K/36Ar等时线年龄分别为2.93、0.81、0.31和0.13Ma。火山喷发的时代从中新世到更新世,喷发的高潮在晚更新世。腾冲火山目前还不是死火山,而腾冲及其邻区的热事件（侵入-热变质-喷发）又是连续发生的。20个样品的Rb和Sr含量、稳定Sr同位素初始比（0.70578-0.71437）以及其它地球化学资料还表明,这些火山岩是属于板块碰撞带生成的高钾钙碱性岩浆系列。火山岩的母岩浆来源于地幔的玄武岩浆,但在上升过程中受到过富含放射性成因Sr的地壳物质的强烈渐进混染。 相似文献
13.
利用PASSCAL、INDEPTH Ⅱ、INDEPTH Ⅲ、HIMNT等研究计划，及中国新疆地学断面和国家973项目在青藏高原布设的流动台站记录的到时数据，以及自1990年1月到2004年2月全球地震事件的震相报告，作者对覆盖印度大陆的恒河平原和整个青藏高原的305个地震台站记录的9649个远震事件，共139021条P波初至到时资料进行了层析成像反演．结果表明：印度岩石圈地幔在不同的位置向北俯冲的形态不同，但俯冲前缘都到达羌塘地体之下．沿88°E剖面显示，厚约100 km的印度岩石圈地幔从南部的恒河平原向北一直俯冲到青藏高原之下．在主边界逆冲断裂之下100 km深度处以约22°角度开始向北俯冲，俯冲最前缘到达羌塘地体的中部地区约34°N，之后进入上地幔深处．而沿北东方向的剖面则显示，印度岩石圈地幔以近水平的角度俯冲到青藏高原之下，向北越过班公－怒江缝合带，到达33°N附近，然后以大角度近乎垂直地向下俯冲断离，并引起地幔热物质的上涌，形成羌塘地体之下大规模的低速带． 相似文献
14.
塔里木南缘位于塔里木块体同青藏高原碰撞的前缘,是认识青藏高原同周围块体相互作用的重要位置.横波分裂方法可以获得岩石圈及软流圈地幔的介质各向异性特征,进而探讨岩石圈变形和地幔流动.本文利用横波分裂方法对中国科学院地质与地球物理研究所、北京大学和南方科技大学联合布设在塔里木盆地南部的8个宽频带流动地震台站记录的SKS和SKKS震相进行分析,获得了塔里木盆地南部上地幔各向异性参数.分析结果显示,研究区快波偏振方向总体比较一致呈近东西向,但存在盆地边缘到盆地内部变化,而慢波延迟时间分布在0.3~1.5 s,差异较大.综合前人对青藏高原北缘和阿尔金断裂周边的横波分裂研究结果,研究区内大部分地区地幔流动方向和绝对板块运动方向保持一致,推测青藏高原北缘同塔里木盆地接触带,青藏高原北缘软流圈南东东向流动对塔里木块体下方地幔流动造成扰动,随着深入到塔里木块体内部,干扰越来越弱;同时青藏高原北部软流圈物质可能对塔里木盆地岩石圈产生影响,随着地幔软流圈物质持续向北运动逐渐冷却,对盆地内部岩石圈的影响程度减弱. 相似文献
15.
Research on the 3—D Seismic Structures in Qinghai—Xizang Plateau 总被引：1，自引：0，他引：1
Based on the recording data from the analogue and broadband digital seismic stations in and around Qinghai-Xizang (Tibet)Platean,the three dimensiomal 3-D) seismic velocity stroctures in Qinghai-Xizang Plateau were obtained by using the regional body wave tomography and surface wave tomography.The results from these two tomography methods have similar characteristics for P-and S-wave velocity structures in crust and upper mantle.They show that there are remarkahle low velocity zones in the upper crust of L hasa block in the southern Qinghai-Xizang Plateau and the lower crust and upper mantle of Qiangtang block in the northern Qinghai-Xizang Plateau.These phenomena may be related to the different steps of collision process in southern and northern Qinghai-Xizang Plateau. 相似文献
16.
本文利用三维有限差分方法,基于EIGEN6C4布格重力异常和SIO V15.1地形数据,计算了青藏高原东南缘岩石圈有效弹性厚度.结果表明:青藏高原东南缘岩石圈有效弹性厚度为0~100 km,四川盆地和喜马拉雅东构造结岩石圈有效弹性厚度最大,达50~100 km;巴颜喀拉块体东部、川滇菱形块体大部、滇西等地区岩石圈强度弱,有效弹性厚度一般小于15 km;羌塘块体东部的玉树—德格附近地区岩石圈有效弹性厚度大于40 km;滇南地区岩石圈有效弹性厚度为10~30 km,大于云南北部地区.研究区域有效弹性厚度分布特征与岩石圈结构关系密切.四川盆地、喜马拉雅东构造结地区内部结构稳定,因而岩石圈强度大.川滇菱形块体等岩石圈有效弹性厚度小的地区与壳内低速、低阻/高导层分布有很好的对应关系,推测壳内岩石的部分熔融软化可能是造成高原东南缘岩石圈强度较弱的重要原因.羌塘块体东部的局部高力学强度岩石圈则可能是高原形成过程中的残留克拉通.根据本文计算的岩石圈有效弹性厚度特征,结合地震学、大地电磁等研究成果,认为青藏高原物质向东南缘挤出后受四川盆地等阻挡,造成下地壳软弱物质在理塘—稻城—丽江一带堆积,少部分物质可能穿过鲜水河断裂带的康定—道孚地区向北运动,但大部分物质向南运动,在受到滇南块体阻挡后一支流向西南的腾冲方向,另一支流向东南的攀枝花—东川方向. 相似文献
17.
The Madang Cenozoic sodic alkaline basalt occurred in the eastern margin of the Tibetan Plateau, where is a key tectonic transform region of Tibet, North China, and Yangtze blocks. The basalts are characterized by the variation in SiO2=42%–51%, Na2O/K2O>4, belonging to the sodic alkaline basalt series. The rocks are enriched in Ba, Th, Nb, Ta, relative to a slight depletion in K, Rb in the trace and rare earth element (REE) spider diagrams that are similar to the typical oceanic island alkaline basalt. The Sr-Nd-Pb isotopic compositions suggest that they are derived from a mixed mantle reservoir. The western Qinling-Songpan tectonic region was controlled by Tibet, North China and Yangtze blocks since Cenozoic, therefore, the region was in the stage of the substance converge from the mantle to upper crust, producing a mixed mantle reservoir in the studied area. The Madang basalts occurred in the specific tectonic background, they result from partial melting of a mixed asthenospheric mantle reservoir in the western Qinling-Songpan tectonic node.
相似文献18.
19.
对INDEPTH Ⅲ台站的接收函数进行扫描，利用Moho界面产生的转换波和多次波的走时信息，估计台站下方的地壳平均波速比VP/VS和地壳厚度.结果显示：（1）沿着INDEPTH Ⅲ剖面，地壳厚度整体变化不大，均为65±5km，其中拉萨地块Moho界面埋深较羌塘地体要深约5～6km.结合其他研究资料，我们推断，在整个班公-怒江缝合带存在约10km的Moho错断，为拉萨地体北缘的地幔盖层向北俯冲到羌塘地体之下所致.（2）青藏高原地壳平均波速比整体都较高，可能与青藏高原地壳广泛存在的流体/部分熔融岩浆有关.拉萨地体北部异常高的地壳VP/VS可能与嘉黎-崩错右旋走滑断裂相关；而另一个泊松比异常区位于羌塘中北部（st36～st40），它可能是由热的地幔引起的壳内部分熔融所致. 相似文献
20.
The Early Permian mafic-ultramafic concentrically zoned Gaositai intrusion at Chengde, on the northern margin of the North China Craton (NCC), is a cumulative complex emplaced along a giant fracture that penetrates deeply into the continental lithosphere. Melt inclusions are present in chromite crystals from the inner dunite and chromitite zones of the Gaositai complex. The melt inclusions have experienced post-trap crystallization and resulted in multiple mineral phases, including melilite, garnet, phlogopite, magnesite and apatite, which can indicate the liquidus minerals of the primitive magma. The characteristics of the melilite+melanite+clinopyxene assemblage indicate that the primary parental magma was highly undersaturated and derived from an alkali-rich mantle source. The crystallization of phlogopite, magnesite and apatite suggests a primary magma rich in K, H2O and CO2. When compared with experimental data, the primary magma of the Gaositai intrusion is concordant with a kamafugite magma originating from partial melting of enriched mantle with H2O and CO2 at pressures greater than 2.7 GPa. This magmatic process would have been related to extensional thinning of the continental lithosphere. The Gaositai primary magmas have high Nb/La ratios, which are similar to those of ocean island basalts, but different from arc-related magmas. This suggests that the northern margin of the NCC was not an active continental margin of the Paleo-Asian Ocean subduction zone during the Early Permian: an extensional tectonic setting during the emplacement of the Gaositai intrusion is more likely. 相似文献