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本文采用依赖温度的黏度结构以及考虑海洋板块和大陆板块厚度差异等特征,以太平洋板块向欧亚板块会聚速率作为板块速度的主要约束,通过变化海沟后撤速度模型,数值模拟西太平洋板块向中国东北的俯冲过程.结果表明,要产生类似于中国东北之下低角度的板片俯冲,海沟后撤是重要条件;而上下地幔黏度的较大差异是决定俯冲板片不穿透660 km相变面的决定因素;西太平洋板块向欧亚板块的俯冲应早于70 Ma B.P.,海沟后撤速度可能小于一些地质学家估计的45 mm/a, 而且可能是分阶段变化的;速度场表明运动学模型的反过程：大陆岩石圈之下物质的不断水平向东的流动和推挤可能成为海沟后撤的力源之一,地幔物质的这种东向流动可能与印度板块挤压碰撞欧亚板块有关,沿欧亚板块东缘的扩张构造可能是太平洋-欧亚板块运动和印度-欧亚板块运动的综合效应. 相似文献
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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
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印度板块与欧亚板块在60～50Ma的碰撞不仅造成了喜马拉雅造山带的形成,还导致了自印度与欧亚板块缝合带以北2 000km宽的广大地区逐步隆升,形成号称"世界屋脊"的青藏高原。青藏高原的形成对欧亚大陆的构造格局、中亚地区乃至全球的气候变化产生了深远的 相似文献
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在比印度-欧亚碰撞区更广阔的范围最好地察看了青藏高原的地质学演化。在碰撞之后的50Ma,西藏的中部和西部的地壳缩短,而巨大的岩石层块体从碰撞区域向西太平洋和印度尼西亚的海沟俯冲回转区移动。快速的太平洋海沟迁移的停止（大约15～20Ma前）,与该高原远处块体挤出的变慢相一致,而且可能是由于西藏东部快速的地表隆升和地壳变厚导致的。后来出现的深部地壳快速向东流动可能是和西藏东部下面由地震成像的地壳通道有关。这些事件标志着向符合西藏内部形变的现代结构系统的转变。 相似文献
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青藏高原是当今地球上海拔最高、规模最大、时代最为年青的地域.在太平洋板块、印度板块与欧亚板块三大板块错综复杂的远程和近程俯冲、消减、碰撞、挤压与多元力系作用下,使青藏高原成为一盘破碎块体的镶嵌.两个大陆板块的陆 陆碰撞,于55-50 Ma首先在西部弧顶强力碰撞和持续的挤压,东部弧顶相续相衔,最后两板块相连,导致了喜马拉雅弧形山系的形成与崛起.地壳以平均约50mm·a^-1的速率向北推进,使地壳缩短约2000~2500km,增厚达70±5km. 相似文献
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帕米尔构造结是印度板块向欧亚大陆碰撞的两个突出支点之一,是中国大陆受板块动力作用最强烈、强震频发的地区之一,也是揭示青藏高原形成与演化历史的关键地区之一。晚新生代帕米尔构造结北部向北楔入推移了约300km,形成了一陆内深俯冲带和地震带,但对这一变形过程及方式至今未能很好的限定。沿76°E附近横跨帕米尔—天山的最新GPS测量 相似文献
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利用近年来中外几个研究单位在青藏高原的GPS观测结果，根据印度板块向欧亚大陆 俯冲模型，采用二层弹性自重半空间内断层运动的位错模型，对印度板块向欧亚大陆俯冲的 速率进行了反演，给出了在大地测量观测结果约束下的现今印度板块向欧亚大陆俯冲的速率 . 反演结果表明，现今印度板块约以8.1°的倾角、21.8 mm/a的速率向欧亚大陆俯冲. 本文 结果与从地质推断的在过去2～３Ma时期内，印度板块向欧亚大陆俯冲速率平均为18mm/a,有 较好的一致性,表明在较长时间内，印度板块向欧亚大陆俯冲的速率仍然是稳定的. 相似文献
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龙门山作为青藏高原的东边界,是一个从青藏高原到四川盆地的陡直的过渡地带,其新生代的造山运动受到约50 Ma年前印度板块和欧亚板块碰撞的影响.2008汶川地震及其后续的研究证明了其晚更新世以来的活跃性,但是对于龙门山推覆构造带及其邻近地区的新生代的演化过程的认识还较缺乏. 相似文献
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《中国科学:地球科学(英文版)》2014,(12)
正SCIENCE CHINA Earth Sciences,an academic journal cosponsored by the Chinese Academy of Sciences and the National Natural Science Foundation of China,and published by Science China Press and Springer,is committed to publishing high-quality,original results in both basic and applied research. 相似文献
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《中国科学:地球科学(英文版)》2014,(9)
正SCIENCE CHINA Earth Sciences,an academic journal cosponsored by the Chinese Academy of Sciences and the National Natural Science Foundation of China,and published by Science China Press and Springer,is committed to publishing high-quality,original results in 相似文献
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In natural waters arsenic concentrations up to a few milligrams per litre were measured. The natural content of arsenic found in soils varies between 0.01 mg/kg and a few hundred milligrams per kilogram. Anthropogenic sources of arsenic in the environment are the smelting of ores, the burning of coal, and the use of arsenic compounds in many products and production processes in the past. A lot of arsenic compounds are toxic and cause acute and chronic poisoning. In aqueous environment the inorganic arsenic species arsenite (As(III)) and arsenate (As(V)) are the most abundant species. The mobility of these species is influenced by the pH value, the redox potential, and the presence of adsorbents such as oxides and hydroxides of Fe(III), Al(III), Mn(III/IV), humic substances, and clay minerals. 相似文献
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《中国科学:地球科学(英文版)》2014,(3)
正SCIENCE CHINA Earth Sciences,an academic journal cosponsored by the Chinese Academy of Sciences and the National Natural Science Foundation of China,and published by Science China Press and Springer,is committed to publishing high-quality,original results in both basic and applied research. 相似文献
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《国际泥沙研究》2014,(4)
正Director:Shangfu Kuang,China Vice-directors:Chunhong Hu,China Duihu Ning,China Guangquan Liu,China The International Research and Training Center on Erosion and Sedimentation(IRTCES)was jointly set up by the Government of China and UNESCO on July 21,1984.It aims at the promotion of international exchange of knowledge and cooperation in the studies of erosion and 相似文献
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Richard D. Hey 《地球表面变化过程与地形》1979,4(1):59-72
Feedback mechanisms, which operate upstream through drawdown and backwater effects and downstream through sediment discharge are responsible for channel evolution. By combining these mechanisms with channel processes it euables a dynamic process-response model to be developed to simulate the initial evolution of straight gravel-bed channels. When erosion commences on a land surface, sediment entrained in the headwater reach by hydraulic action is selectively transported, deposited and reworked. This produces a damped oscillation between degradation and aggradation as the channel and valley respond to spatial and temporal variations in sediment calibre and hydraulic conditions. The initial cut and fill phases are responsible for valley incision and floodplain development while secondary and subsequent activity can produce river terraces. Eventually sediment entrainment in the headwaters declines as slopes are reduced. Subsequent channel evolution is relatively insignificant because it is dependent on local weathering activity producing material that can be transported on declining slopes. Therefore landforms produced during the initial phase of development, when local weathering was non-limiting, dominate the landscape. 相似文献