陨石中林伍德石的形成条件对寻找地球产状林伍德石的启示

橄榄石高压多形林伍德石被认为是地幔过渡带的主要矿物。天然产状林伍德石主要在发生强烈冲击变质的球粒陨石冲击脉体中出现。目前还没有在地球岩石中发现林伍德石的报告。陨石冲击脉体的温度压力历史和矿物组合特征研究表明,林伍德石形成后,高压下淬火是使林伍德石不发生退变作用的重要条件。陨石中有利于林伍德石保存的淬火时间仅为数秒到十多秒。在地球上任何地质事件中,均难以实现在如此短的时问内使位于地幔过渡带的林伍德石被带往地球表层。寻找地球产状的林伍德石,关键是要在岩石和矿物中存在有利于林伍德石保存的条件,特别是当这些岩石和矿物仍处于高温的环境时。     

Earthlearningidea—ideas for the International Year of Planet Earth

'Earthlearningidea' will be putting up a new idea for learning about the Earth every week during 2008—the International Year of Planet Earth. The ideas are aimed at teacher trainers in science and geography who will be training teachers in the teaching of Earth science—but we hope they will be widely used by classroom teachers who have access to the internet too. A blog runs alongside them aiming to build up a worldwide discussion network of Earth science educators. Help us circulate Earthlearningideas around the globe!     

大地构造理论假说争论的历史及地质哲学的贫困

地球科学中大地构造理论假说争论的历史经历了山脉臆说的“实在论”与“唯名论”的探索、“塌陷说”与“隆起说”对立时期以及受“形而上学”和“自然哲学”的影响这一过程。“收缩说”统治时期,“机械唯物主义”阻碍了“自然辩证法”的指导;“活动论”兴起后,并未找到先进的地学哲学武器。中国古代有机论自然观蕴藏了丰富的地学哲学思想－有机论辩证唯物主义的天地生整体自然观。“立地之道,曰柔与刚”,“合乎谓之坤,辟乎谓之乾,一合一辟谓之变”,“刚柔相摩,八卦相摩,八卦相荡”等精辟论述。早已从地质哲学高度,把“威尔逊旋回”、“开合运动”等大地构造假说涵蓄其内。大地构造理论的未来发展必然由此获得新的启迪。     

浅议学科交叉与地球系统科学

以整体系统的观念认识地球 ,强化学科间的交叉与渗透 ,是 2 1世纪初地球科学发展的主题。各国都十分重视推动学科交叉研究 ,并将学科交叉分为Modidisciplinary、Interdisciplinary、Transdiscipli nary三个层次。地球系统科学的两大前沿为“地球系统的联系”和“地球系统的演化” ,2 1世纪地球科学的突破在于地球系统变化理论的形成。笔者指出 :目前 ,我们的观念还跟不上地球科学的发展 ,尤其是“学科交叉”的理念不强 ,缺乏地球系统科学的思维 ,但我们有开展地球系统科学研究的有利条件     

SinoProbe——中国深部探测实验

在人类向太空发展,实施新一轮太空计划,中国“神舟7号”载人航天飞船、“嫦娥”探月工程圆满成功之时,中国地球科学家不得不面对这样一个现实：对人类赖以生存的地球内部了解的太少,直接钻探深度只有12 km,涉及的仅仅是地球的表皮。可谓上天不易,“入地”更难。地球是人类居住的唯一场所,为人类提供了生命必需的粮食、水,和生活必须能源和矿产资源;同时也常给人类带来诸如火山、地震、海啸等灾难。通过深部探测,了解地下的物质、结构和动力学过程,不仅是人类探求自然奥秘的追求,更是人类汲取资源、保障自身安全的基本需要。近百年来,各国的地球科学家一直不断地进行探索,我国科学家也意识到必须开展中国的地球深部探测计划,才能解决面临的重大资源环境问题,才能全面实现地球科学的创新和发展。最近,国家启动“深部探测技术与实验研究”专项（英文简写SinoProbe）,标志了我国地球科学的深部探测计划拉开帷幕。该专项（2008~2012）年总体任务是,为全面开展我国地壳探测工程做好关键技术准备,解决关键探测技术难点与核心技术集成,形成对固体地球层圈立体探测技术体系;在不同自然景观、复杂矿集区、含油气盆地深层、重大地质灾害区等关键地带进行试验、示范,形成若干深部探测实验基地;解决急迫的重大地质科学难题,部署实验任务;实现深部数据融合与共享,建立深部数据管理系统;积聚、培养优秀人才,形成若干技术体系的研究团队。     

The Heat Balance in the Earth

Doklady Earth Sciences - The observed heat flux from the Earth is created mainly by the heat released due to radioactive decay, secular cooling of the Earth, and solidification of the growing inner...     

The oceans and the physics of the Earth

The Earth is the only terrestrial planet to have seas, by which it is covered to the extent of seventy percent. The oceans determine the climate of the Earth and it is through them that life and civilization have evolved, but they also have major influence on physical processes in the solid Earth. Tidal friction leads to the Earth's spin slowing down with a consequent recession of the Moon from the Earth, while the presence of the oceans controls the tectonic evolution of the Earth through the formation of oceanic crust, the erosion of land and the accumulation of sediment, the formation of mountains and the establishment of isostatic balance.     

The Deep Velocity Structure of the Central Kola Peninsula Obtained using the Receiver Function Technique

Doklady Earth Sciences - New results are presented on the features of the deep velocity structure of two of the three main tectonic blocks that make up the Kola region—Murmansk and...     

The composition of the Earth

Compositional models of the Earth are critically dependent on three main sources of information: the seismic profile of the Earth and its interpretation, comparisons between primitive meteorites and the solar nebula composition, and chemical and petrological models of peridotite-basalt melting relationships. Whereas a family of compositional models for the Earth are permissible based on these methods, the model that is most consistent with the seismological and geodynamic structure of the Earth comprises an upper and lower mantle of similar composition, an Fe---Ni core having between 5% and 15% of a low-atomic-weight element, and a mantle which, when compared to CI carbonaceous chondrites, is depleted in Mg and Si relative to the refractory lithophile elements.The absolute and relative abundances of the refractory elements in carbonaceous, ordinary, and enstatite chondritic meteorites are compared. The bulk composition of an average CI carbonaceous chondrite is defined from previous compilations and from the refractory element compositions of different groups of chondrites. The absolute uncertainties in their refractory element compositions are evaluated by comparing ratios of these elements. These data are then used to evaluate existing models of the composition of the Silicate Earth.The systematic behavior of major and trace elements during differentiation of the mantle is used to constrain the Silicate Earth composition. Seemingly fertile peridotites have experienced a previous melting event that must be accounted for when developing these models. The approach taken here avoids unnecessary assumptions inherent in several existing models, and results in an internally consistent Silicate Earth composition having chondritic proportions of the refractory lithophile elements at 2.75 times that in CI carbonaceous chondrites. Element ratios in peridotites, komatiites, basalts and various crustal rocks are used to assess the abundances of both non-lithophile and non-refractory elements in the Silicate Earth. These data provide insights into the accretion processes of the Earth, the chemical evolution of the Earth's mantle, the effect of core formation, and indicate negligible exchange between the core and mantle throughout the geologic record (the last 3.5 Ga).The composition of the Earth's core is poorly constrained beyond its major constituents (i.e. an Fe---Ni alloy). Density contrasts between the inner and outer core boundary are used to suggest the presence ( 10 ± 5%) of a light element or a combination of elements (e.g., O, S, Si) in the outer core. The core is the dominant repository of siderophile elements in the Earth. The limits of our understanding of the core's composition (including the light-element component) depend on models of core formation and the class of chondritic meteorites we have chosen when constructing models of the bulk Earth's composition.The Earth has a bulk Fe/Al of 20 ± 2, established by assuming that the Earth's budget of Al is stored entirely within the Silicate Earth and Fe is partitioned between the Silicate Earth ( 14%) and the core ( 86%). Chondritic meteorites display a range of Fe/Al ratios, with many having a value close to 20. A comparison of the bulk composition of the Earth and chondritic meteorites reveals both similarities and differences, with the Earth being more strongly depleted in the more volatile elements. There is no group of meteorites that has a bulk composition matching that of the Earth's.     

Earth tide effects on kinematic/static GPS positioning in Denmark and Greenland

A detailed study of the Earth tide effects on the GPS kinematic/static positioning is presented in this paper by using theoretical Earth tide computation and practical GPS data processing. Tidal effects could reach up to 30 cm in Denmark and Greenland depending on the measuring time and the position of reference station. With a baseline less than 80 km, the difference of the Earth tide effects could reach more than 5 mm. So, in precise applications of GPS positioning, the Earth tide effect has to be taken into account even for a relative small local GPS network. Several examples are given for demonstrating that the Earth tide effects can be viewed by GPS surveying. They are given through static GPS data static processing, static GPS data kinematic processing, and airborne kinematic GPS data processing. In these cases, the Earth tide effects can be subtracted from the GPS results. The determination of tidal parameter through static GPS data kinematic processing has also been tested.     

The Radionuclide 60Co as a Marker for Estimating the Scale of Transfer of Bottom Sediments in the Yenisei River during the Flood of 2006

Doklady Earth Sciences - The studies of bottom sediments of the Yenisei River from 2006 to 2016 near the Mining and Chemical Combine (MCC) and at a distance of up to 250 km from it downriver...     

核幔成矿物质(流体)的反重力迁移——地幔热柱多级演化成矿作用

地壳中矿床分布极不均匀 ,这与地球的形成与演化密切相关。在地球演化的早期 ,由于在引力收缩和热力膨胀的统一作用支配下 ,放射性、卤族、稀有、稀土元素及碱金属向上迁移 ,而贵金属、有色、铁族、铂族等密度较大的元素则有逐渐向地核聚集的趋势 ,以至于铁、镍、金等元素主要聚集在地核之中。但是 ,在地球形成圈层结构的同时 ,由于地球内外温度差、压力差、粘度差等的存在 ,导致地球发生以地幔热柱多级演化为主要形式的垂向物质运动 ,两者互为依存 ,并构成幔壳运动的原动力。地幔热柱多级演化沟通了深部矿质的迁移通道 ,聚集在地核及核幔界面上的气态金等重元素得以作为地幔热柱的热物质流 ,呈反重力迁移至岩石圈 ,并进而以气 液态向近地表迁移 ,在有利的构造扩容带中聚集成矿。这可能是金银铜铅锌等多种元素的重要成矿作用方式。     

统一构造理论初探

以地球系统科学为指导思想,提出统一构造理论的新观点和理论基础,初步建立了理论体系框架。提出统一引力场表示理论,用Ｎｅｗｔｏｎ位算子将地球内、外扰动引力场统一。通过对地球不同圈层水平速度矢量场的对比分析,提出不同圈层的水平运动速度矢量场具有高度的相似性和统一性,且与地球自转密切相关的认识。根据观测数据,探讨板块的统一动力源。研究了幔柱构造特征,提出地幔热柱构造的动力学模型。利用积分关系法求出地表热流与岩石圈厚度的关系,提出大陆岩石圈的统一热模式和大陆地表热流经验关系式。     

软流层的地球膨胀成因及其形成时间

地球的软流层(圈)堪称全球构造、岩浆与成矿作用动力之源。以往人们虽然认识到软流层的重要作用,但其形成机制的定量研究还不够。最近20多年来,对地球半径变化的检验研究结果表明,地球膨胀已经有了较多的直接证据。而且,即使按照地球膨胀晚期0.1 mm/a的半径增长率计算,所产生的地球膨胀构造动力事件,也将是一个全球性超级构造动力事件。根据地球的非线性有限膨胀演化,所提出的软流层成因是:源于原始地球深部的膨胀内压,推挤原始地幔顶部物质做功并转化为原始岩石圈球壳围限下的地幔顶部物质的压缩能A,当压缩能的积累超过原始地幔顶部物质局部熔融所需要的热能Ω时,地幔顶部物质便开始熔融并逐渐形成地球的原始软流层。据此,按照地球非线性膨胀演化初期的半径增长率1.08 mm/a、原始地幔顶部物质以15%的局部熔融和绝热等压过程估算,地球开始膨胀后仅19.2 Ma,地球的原始软流层(圈)便可形成。     

美国国家大气研究中心优先研究领域新特点

美国国家大气研究中心于2005年11月提出了新的战略计划。该计划突出的新特点在于无论科学研究活动还是教育、观测设施等方面的战略目标和优先领域,都是以地球系统研究为中心。如在科学研究方面的战略目标确定为：认识地球系统的作用、准确预报地球系统的演变。相应的优先研究领域则为：研究和了解地球和太阳的自然变率;地球系统各分量的相互作用;地球系统预报;人类活动与地球系统的演变等。鉴于NCAR在国际大气科学界的地位,这种以地球系统为中心的优先研究领域对我国大气科学及地球科学研究有一定的借鉴意义,同时也将促使大气科学工作者摆脱传统天气、气候概念的束缚,站在更高的高度来科学审视学科的发展。     

论地球科学

地球科学的基本任务是认识地球,并为矿产资源勘查、环境保护和灾害防治服务。国民经济建设对地球科学有广泛的需求。它需要在地球科学取得规律性认识的指导下,解决大量微观的实际问题,而这些实际问题的解决,又将积累起丰富的资料,推动地球科学的进展。地球科学包括地质、地球物理、地球化学以及其它有关学科。无论是认识地球,还是为国民经济建设服务,都要求对各种地球科学资料进行综合研究,以期获得比较全面的认识。地球是一个处于运动中的巨系统,它不仅体积庞大,结构和成分复杂,而且有漫长的演化历史。因此,对地球的研究必须分层次进行,而宏观认识将具体指导微观调查。整个２０世纪的重大成就是对地球的认识经历了大陆漂移、海底扩张和岩石层板块大地构造的发展,基本上建立起以活动论为内涵的全球构造观。在板块构造的宏观指导下,地质、地球物理与地球化学的系统总结,已经建立起中国大地构造格架及其演化史,尽管还有许多问题有待于深入解决,但它毕竟说明沉积盆地与矿产资源分布的大地构造环境。在宏观认识的基础上,还必须对区域地质作中观分析,例如通过详细的地质、地球物理和地球化学综合研究,进一步了解造山带、盆地及其间的关系。应该指出,只有深刻地认识区域地质特色,才能?     

The Earth’s tungsten budget during mantle melting and crust formation

During silicate melting on Earth, W is one of the most incompatible trace elements, similar to Th, Ba or U. As W is also moderately siderophile during metal segregation, ratios of W and the lithophile Th and U in silicate rocks have therefore been used to constrain the W abundance of the Earth’s mantle and the Hf-W age of core formation. This study presents high-precision W concentration data obtained by isotope dilution for samples covering important silicate reservoirs on Earth. The data reveal significant fractionations of W from other highly incompatible lithophile elements such as Th, U, and Ta. Many arc lavas exhibit a selective enrichment of W relative to Th, U, and Nb-Ta, reflecting W enrichment in the sub-arc mantle via fluid-like components derived from subducting plates. In contrast, during enrichment by melt-like subduction components, W is generally slightly depleted relative to Th and U, but is still enriched relative to Ta. Hence, all arc rocks and the continental crust exhibit uniformly low Ta/W (ca. 1), whereas W/Th and W/U may show opposite fractionation trends, depending on the role of fluid- and melt-like subduction components. Further high-precision W data for OIBs and MORBs reveal a systematic depletion of W in both rock types relative to other HFSE, resulting in high Ta/W that are complementary to the low Ta/W observed in arc rocks and the continental crust. Similar to previous interpretations based on Nb/U and Ce/Pb systematics, our Ta/W data confirm a depletion of the depleted upper mantle (DM) in fluid mobile elements relative to the primitive mantle (PRIMA). The abundance of W in the depleted upper mantle relative to other immobile and highly incompatible elements such as Nb and Ta is therefore not representative of the bulk silicate Earth. Based on mass balance calculations using Ta-W systematics in the major silicate reservoirs, the W abundance of the Earth’s primitive mantle can be constrained to 12 ppb, resulting in revised ratios of W-U and W-Th of 0.53 and 0.14, respectively. The newly constrained Hf-W ratio of the silicate Earth is 25.8, significantly higher than previously estimated (18.7) and overlaps within error the Hf-W ratio proposed for the Moon (ca. 24.9). The ¹⁸²Hf-¹⁸²W model age for the formation of the Earth’s core that is inferred from the ¹⁸²W abundance and the Hf/W of the silicate Earth is therefore younger than previously calculated, by up to 5 Myrs after solar system formation depending on the accretion models used. The similar Hf/W ratios and ¹⁸²W compositions of the Earth and the silicate Moon suggest a strong link between the Moon forming giant impact and final metal-silicate equilibration on the Earth.     

数字地球及其应用前景

介绍了数字地球的有关概念,探讨了数字地球的有关技术基础,并就数字地球应用进行了展望.     

地球磁极倒转的星地碰撞成因

地球磁场多次发生南北(正负)磁极位置的变换, 即极性倒转, 这已为大家所公认; 但造成这种极性倒转的原因, 则是迄今未能很好解答的一个难题.基于地球磁场的发电机效应理论和星地碰撞的动力效应研究, 探讨了外星撞击地球造成地磁场极性倒转的可能性.研究表明, 当外星沿与地球自转的正逆不同方向撞击地球时引起的地球转速快慢变化, 可导致地球内部核、幔圈层之间的转速相对快慢关系(相对运动方向)发生改变, 从而受其控制的液核涡旋方向及相应的地磁场方向也会随之改变, 于是就形成地磁极性倒转.这是一个新的思路, 它给地磁极性倒转提出了一个简明的动力机制解释.      

The preventive destruction of a hazardous asteroid

One means of countering a hazardous asteroid is discussed: destruction of the object using a nuclear charge. Explosion of such an asteroid shortly before its predicted collision would have catastrophic consequences, with numerous highly radioactive fragments falling onto the Earth. The possibility of exploding the asteroid several years before its impact is also considered. Such an approach is made feasible because the vast majority of hazardous objects pass by the Earth several times before colliding with it. Computations show that, in the 10 years following the explosion, only a negligible number of fragments fall onto the Earth, whose radioactivity has substantially reduced during this time. In most cases, none of these fragments collides with the Earth. Thus, this proposed method for eliminating a threat from space is reasonable in at least two cases: when it is not possible to undergo a soft removal of the object from the collisional path, and to destroy objects that are continually returning to near-Earth space and require multiple removals from hazardous orbits.