大洋钻探与全球变化(一)——南极地区显生宙晚期气候演变历史及对全球的影响     

茅绍智 《地球科学进展》1995,10(3):263-266

通过介绍Ｊ．Ｐ．Ｋｅｎｎｅｔｔ为代表的“洋流说”阐述了大洋钻探２５年来约１０个航次研究所揭示的南极地区显生宙晚期气候演变的历史。晚白垩世时南极地区和全球一样暖和无冰，末期变冷，古新世开始后不久又转暖，早始新世－中始新世早期达顶峰，以后变冷。渐新世为主要冷却期，南极东部形成冰盖，中，晚中新世为另一重要冷却期，南极西部以至全部南极在中新世晚期－上新世早期最终形成稳定冰盖。德雷克海峡打开，环南极洋流（Ａ  相似文献   

澜沧江—湄公河多目标协同开发研究   总被引：2，自引：2，他引：2  

郭来喜 《云南地理环境研究》1994,6(1):1-10

本文从流域的整体性论述了世界第六大河、亚洲跨国最多的国际河流——澜沧江—湄公河的基本特性，对澜沧江中下游段多目标梯级水利枢纽进行了评估，提出了中近期多国协同开发的优选项目．论证了中老缅泰“黄金四角”次区域合作，必须以开发澜沧江—湄公河航运工程为前提，同时加快中老泰、中缅泰陆上通过、航空港建设，兼论了旅游网络工程、防洪灌溉工程、经济走廊工程等多目标巨系统的国际协同开发问题，提出了“平等协商，友好合作，统一规划，综合利用，协同开发，资源共享，经济互补，利益兼顾，共同繁荣”的开发原则，充分调动流域国及国际组织力量，把澜沧江—湄公河作为南南合作与南北合作的典范，进行跨世纪开发。  相似文献   

青藏高原隆升的主因—大陆板块内的盆-山碰撞作用   总被引：7，自引：0，他引：7  

白文吉  杨经绥 《吉林大学学报(地球科学版)》1987,(2)

在地壳运动中,盆地和山脉的形成机制是不可分割而有联系的。上地幔的波动起伏引起地壳上部物质的分配,在重力均衡作用的支配下,地壳物质由上地幔的隆升区域向拗陷区域蠕动,因而形成大陆板块内的盆地和山脉的分异和盆-山运动。高耸的喜马拉雅山和青藏高原就是塔里木盆地、卡拉库姆盆地和印-恒盆地等巨大盆地的扩张作用挤压而造成的。盆-山运动是真正的造山运动。  相似文献   

大陆碰撞动力学的三维数值模拟   总被引：10，自引：0，他引：10       下载免费PDF全文

高祥林  罗焕炎  H.J.诺依格鲍尔 《地震地质》1987,9(2):65

用三维有限单元模型模拟了印度—亚洲大陆碰撞在板内的力学效应。结果表明,印度板块北东方向的推挤力作用在亚洲大陆内造成逆断层和走滑断层型的应力状态,以及北西走向的平行的弧形应力等值线。岩石圈下伏岩层的塑性变形导致地壳变形范围扩大,垂直位移的水平梯度减小,应力传递的水平距离显著增加。在相对坚硬的地盾型构造区边缘,出现应力梯度较高的特征。对比了刚体水平挤入和低角度俯冲这两种大陆聚合模型,计算结果表明低角度俯冲是较合理的模型  相似文献   

Climatology Comparison Studies of Precipitations Between GPCP and Rain Gauges in China          下载免费PDF全文

ZI Yong  XU Yinlong  FU Yunfei 《Acta Meteorologica Sinica》2006,20(3):322-333

The Global Precipitation Climatology Project (GPCP) monthly rainfall data and the rainfall records observed by 740 rain gauges in the mainland of China are used to analyze similarities and differences of the precipitation in China in the period from January 1980 to December 2000. Results expose significantly consistent rainfall distributions between the both data in multi-year mean, multi-year seasonal mean, and multi-year monthly mean. Departures of monthly rainfall for each dataset also show a high correlation with an over 0.8 correlation coefficient. Analysis indicates small differences of both datasets during autumn, winter, and spring, but relative large ones in summer. Generally, the GPCP has trend of overestimating the rainfall rate. Based on above good relationship of both datasets, the GPCP data are used to represent distributions and variations of precipitation in the Tibetan Plateau and Northwest China. Results indicate positive departures of precipitation in summer in the west part of Tibetan Plateau in the 1980s and negative departures after the 1980s. For the west part of Northwest China, analysis illustrates precipitation decreases a little, but no clear variation tendency.  相似文献   

都江堰市农村"安身工程"防震抗震的讨论     

李伟  郑松林  朱昌保 《四川地震》2006,(4):37-40

“安身工程”是成都市人民政府为民办实事工程,全市每年约修建2千套住房,体现了党和人民政府对农村困难群众的关怀,“安身工程”的防震抗震工作也关系到群众的生命和财产安全。都江堰市人民政府和四川省古建筑设计研究院合作,为“安身工程”提供了造价低廉、有一定抗震性能的川西民居风格的总平面图纸,本文分析和讨论了都江堰农村“安身工程”防震抗震性能与特点。  相似文献   

Extension-related origin of magmas from a garnet-bearing source in the Los Tuxtlas volcanic field, Mexico     

Surendra P. Verma 《International Journal of Earth Sciences》2006,95(5):871-901

The Los Tuxtlas volcanic field (LTVF) of late Miocene to Recent age is a key area to understand the consequences of the current subduction of the Cocos plate beneath the North American plate, as well as the competing effects of the ongoing extension along the Gulf of Mexico coast. Geochemical and radiogenic (Sr, Nd, and Pb) isotope data are used to constrain the origin of these 7 Ma to Recent magmas in this area. The basanitic and alkaline basaltic rocks show highly steep light rare-earth element-enriched patterns implying residual garnet in their mantle source, whereas the evolved alkaline and sub-alkaline rocks have less steep rare-earth element patterns consistent with a contribution from the continental crust. Geochemical and isotope data from the LTVF are compared with those from continental rifts, extension-related areas, continental break-up regions, and island and continental arcs, including the Central American volcanic arc related to the subduction of the same oceanic plate (Cocos plate), as well as with those from the two nearby Mexican provinces [the Eastern Alkaline Province (EAP) and the eastern part of the Mexican Volcanic Belt (E-MVB)]. These data for the LTVF primitive rocks are similar to rifts, extension-related areas and continental break-up regions, including the two Mexican provinces, but different from island and continental arcs, including the northern part of the Central American Volcanic Arc (CAVA). The LTVF rocks show an unusual Th and U enrichment with respect to Ba and Rb, which also renders a distinct negative Nb anomaly (with respect to Th and K) in them. These rocks also show a negative Nb anomaly (with respect to Ba and La) that is similar to numerous rift, extension-related areas, and continental break-up regions, but distinct from all arcs around the world, indicating that the magma genesis processes in the LTVF are similar to those in rifts. The “Sr-shift”, shown to be a typical feature of most, if not all, island and continental arcs including the CAVA, is not present in the LTVF rocks. Numerous discrimination diagrams, including the new discriminant function diagrams, suggest a rift setting for the LTVF. An essentially extension-related origin of the LTVF is, therefore, inferred in this study. Furthermore, in the light of major and trace element data for LTVF primitive rocks and their modelling an incompatible element-enriched garnet-bearing source seems plausible. The LTVF source is likely to reside in the lithosphere rather than the asthenosphere although the asthenospheric contribution cannot be completely ruled out. The evolved alkaline and sub-alkaline rocks might have a lower crustal component. Finally, it appears that the LTVF shows more affinity to the EAP rather than to the Mexican Volcanic Belt (MVB), implying that the LTVF should probably be considered as a part of the EAP.  相似文献   

Petrogenesis of Maobei rutile eclogites from the southern Sulu ultrahigh-pressure metamorphic belt, eastern China   总被引：10，自引：0，他引：10  

Z. M. ZHANG  J. G. LIOU  X. D. ZHAO  C. SHI 《Journal of Metamorphic Geology》2006,24(8):727-741

The Maobei complex in the southern Sulu ultrahigh‐pressure (UHP) metamorphic belt, eastern China, mainly consists of layered eclogites, garnet peridotites and orthogneisses. Based on the modal mineral and whole‐rock compositions, eclogites from the Maobei complex are divided into quartz eclogite, quartz‐rich eclogite, rutile eclogite, rutile‐rich eclogite and eclogite. The distinct spatial changes in the lithology and related chemical compositions indicate that this complex includes 10 rhythmic layers. The rutile eclogites have high TiO₂ (2.4–5.9 wt%), commonly coupled with high P₂O₅ (up to 4.1 wt%) contents; most show fractionated REE patterns with slight positive Eu anomalies. The rutile‐rich eclogites have very high TiO₂ (3.3–5.7 wt%), FeO^T (17.5–25.3 wt%), V (126–1163 ppm) and Co (14–132 ppm), and very low SiO₂ (38.0–42.3 wt%), Zr (24–85 ppm), Nb (0.3–6.9 ppm), Ta (<0.1–0.6 ppm) and total REE (10.7–334.0 ppm) contents, variable degree of LREE depletion, and positive Eu anomalies (Eu/Eu* = 1.1–2.9), and the Ti is decoupled from other high‐field‐strength elements. These characteristics are consistent with Fe‐Ti gabbros of typical layered intrusions, implying a cumulate of plagioclase, clinopyroxene and abundant accessory magnetite in an evolved basaltic magmatic chamber. Based on a normal stratigraphic sequence, the Maobei complex shows an iron‐enrichment trend, followed by alkaline enrichment with increasing fractionated crystallization and stratigraphic height. These facts, together with SHRIMP U‐Pb zircon ages of 773.7 ± 8.0 Ma, indicate that the protolith of the Maobei complex is a Neoproterozoic layered intrusion consisting of a base of peridogabbro, a main body of gabbro and minor granodiorite. Unusually high Ti, V and P contents in three rutile eclogite layers suggest that they are potential economic ore deposits.  相似文献   

苏鲁造山带胶东区段花岗片麻岩类的常量与微量元素地球化学：扬子克拉通北缘新元古代活动大陆边缘的证据   总被引：7，自引：8，他引：7  

薛怀民刘福来  孟繁聪 《岩石学报》2006,22(7):1779-1790

胶东东部地区的基底片麻岩以牟平-海阳断裂为界，两侧在岩性组合和地球化学性质上完全不同，本文认为该断裂应代表苏鲁造山带的西北边界（北段）。断裂西侧岩性包括花岗闪长质、奥长花岗质和花岗质，地球化学上表现为低硅（SiO2：64．16～71．76％）、高铝（Al2O3=15．60-18．51％）、显著的Ba和Sr正异常、强烈的稀土元素分馏程度（LaN／YbN=15．77～68．19）和贫重稀土元素（YbN=2．9-4．4）、Eu异常不明显（δEu=0．86～1．02），具典型的太古代高铝TTG岩石组合的特征。而东侧新元古代的基底片麻岩从地球化学上可分为高钾的Ⅰ型花岗质片麻岩和富钠的A型花岗质片麻岩。前者总体表现为富钾（K2O／Na2O比接近或大于1）和亚铝质，强烈亏损Sr、Nb和Ta，轻稀土元素之间的分馏程度强（LaN／SmN=4．21～5．37），而重稀土元素之间几乎无分馏（GdN／YbN：0．78～1．54），负Eu异常较强（δEu=0．47～0．61），岩石地球化学特征显示它们的原岩类似于活动大陆边缘的Ⅰ型花岗岩类。而后者则以偏碱和富钠（Na2O／K2O=1．06～1.77），高Y（20.4～52．9μg／g）、Zr（218～39μg/g）、Ga（18．8～22．9μg／g）及稀土元素丰度为特征，稀土元素分馏程度强（LaN／YbN=11．30～19．09），弱到中等程度的负Eu异常（δEu=0．94～0．65），强烈亏损Sr为显著特征，Nb和Ta相对于La也强烈亏损，而Ba则表现出明显的正异常。推测Ⅰ型花岗岩是在与俯冲有关的构造环境下，压力0．8～1．0Gpa条件下，由受俯冲板片脱水交代的镁铁质下地壳（26～33km）部分熔融形成的。而A型花岗岩则是在Ⅰ型花岗质岩浆形成后，由脱水的紫苏辉石质残留下地壳在温度大于900℃的条件下再一次部分熔融形成的。相对于Ⅰ型花岗岩，A型花岗岩中可能有更多的大洋岩石圈的组份被卷入。  相似文献   

榴辉岩退变质过程中的微量元素地球化学行为：对CCSD主孔退变质榴辉岩的研究   总被引：2，自引：2，他引：2  

张斌辉刘勇胜  宗克清高山   《岩石学报》2006,22(7):1833-1844

对中国大陆科学钻探工程主孔榴辉岩退变质过程中的微量元素地球化学行为进行了研究。对退变质程度连续变化样品的不同部分的对比研究表明，流体作用下的退变质过程中大离子亲石元素（Cs、Rb、Ba、Sr、K、Th、U）和轻稀土元素表现出较大的活动性，重稀土元素和高场强元素变化相对较小。退变质后大离子亲石元素的显著增加和高场强元素、重稀土元素的轻微变化（甚至相对降低），表明与退变质作用有关的流体中的络阴离子含量很少，并不富集高场强元素和重稀土元素。退变质后总体上表现出的Si、大离子亲石元素和轻稀土元素的明显变化，表明外来流体参与了榴辉岩的退变质过程，带入和带出了一些元素。结合榴辉岩中单矿物微量元素组成以及前人对D^Mineral/Fluid的研究成果，对流体-榴辉岩作用形成的退变质分带（富石英条带→角闪岩→退变质榴辉岩→新鲜榴辉岩）的微量元素组成变化进行了详细研究。结果表明在流体作用下的榴辉岩退变质过程中，大离子亲石元素、轻稀土元素和高场强元素含量的变化除了受退变质流体性质的影响外，更大程度上取决于退变质过程中的矿物相（尤其是副矿物）的变化。  相似文献