雅鲁藏布江缝合带的双陆内俯冲构造与部分熔融层特征──INDEPTH项目结果的初步综合   总被引：11，自引：2，他引：9       下载免费PDF全文

赵文津 Nels.  KD 《地球物理学报》1997,40(3):325-336

根据中、美两国合作开展的西藏深反射地震结果,提出雅鲁藏布江缝合带（YZS）的"双陆内俯冲"构造模式和缝合带南、北分别存在着不同特征的、规模不一的部分熔融层;提出YZS处断裂向深部延深有限,认为YZS处地壳增厚有4种机制：①地壳规模的大的俯冲增厚;②上部地壳内的俯冲和背冲增厚;③下地壳内的底部垫托增厚和挤压增厚;④深部熔融体的向上挤入而引起的地壳增厚.提出可能存在两条大的伸展性断裂,造成江孜南、北地块间出现了大升降.  相似文献   

The Institutional Architecture of Extractive Reserves in Rondônia, Brazil     

KATRINA BROWN  SERGIO ROSENDO 《The Geographical journal》2000,166(1):35-48

This paper examines the evolution and development of institutions involved in the establishment of extractive reserves. It focuses on the different actors, organizations and projects concerned with extractive reserves in Rondônia in western Amazonia, Brazil. Extractive reserves are widely seen as a means of integrating forest conservation and local socio-economic development. As such, they have gained the support of the international environmental movement, multilateral and state development organizations, and grassroots community and producer organizations. These institutions represent a vast array of diverse interests which range from conservation of biodiversity, economic and social cohesion, and regional and national development. Whilst the various actors and institutions claim mutual and complementary interests, they form shifting alliances and coalitions in order to further their interests. This paper maps these institutions and interests and describes how alliances have been formed and broken, and how this has contributed to the currently observed implementation of extractive reserves. The paper argues that extractive reserves are constrained by the dissonance or misfit in discourses and underlying worldviews, reflected by the aims and objectives, of the institutions which promote, oppose and lose and benefit from their implementation. This misfit is overcome, in part, by alliances formed between the different institutions, and in part by the creation of new institutions and projects.  相似文献   

AN INTEGRATED APPROACH TO MODELLING HYDROLOGY AND WATER QUALITY IN GLACIERIZED CATCHMENTS     

KEITH RICHARDS  MARTIN SHARP  NEIL ARNOLD  ANGELA GURNELL  MICHAEL CLARK  MARTIN TRANTER  PETER NIENOW  GILES BROWN  IAN WILLIS  WENDY LAWSON 《水文研究》1996,10(4):479-508

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Palaeomagnetic chronostratigraphy of Holocene sediments,Niagara basin,Lake Ontario,Canada     

ROLF GEORGE PIPPERT  G. R. BROWN  W. A. MORRIS 《第四纪科学杂志》1996,11(3):217-231

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The orbit,atmospheric dynamics,and initial mass of the Park Forest meteorite     

P. BROWN  D. PACK  W. N. EDWARDS  D. O. REVELLE  B. B. YOO  R. E. SPALDING  E. TAGLIAFERRI 《Meteoritics & planetary science》2004,39(11):1781-1796

Abstract— The fireball accompanying the Park Forest meteorite fall (L5) was recorded by ground‐based videographers, satellite systems, infrasound, seismic, and acoustic instruments. This meteorite shower produced at least 18 kg of recovered fragments on the ground (Simon et al. 2004). By combining the satellite trajectory solution with precise ground‐based video recording from a single site, we have measured the original entry velocity for the meteoroid to be 19.5 ± 0.3 km/s. The earliest video recording of the fireball was made near the altitude of 82 km. The slope of the trajectory was 29° from the vertical, with a radiant azimuth (astronomical) of 21° and a terminal height measured by infrared satellite systems of 18 km. The meteoroid's orbit has a relatively large semi‐major axis of 2.53 ± 0.19 AU, large aphelion of 4.26 ± 0.38 AU, and low inclination. The fireball reached a peak absolute visual magnitude of ?22, with three major framentation episodes at the altitudes of 37, 29, and 22 km. Acoustic recordings of the fireball airwave suggest that fragmentation was a dominant process in production of sound and that some major fragments from the fireball remained supersonic to heights as low as ?10 km. Seismic and acoustic recordings show evidence of fragmentation at 42, 36, 29, and 17 km. Examination of implied energies/initial masses from all techniques (satellite optical, infrasound, seismic, modeling) leads us to conclude that the most probable initial mass was (11 ± 3) × 10³ kg, corresponding to an original energy of ?0.5 kt TNT (2.1 times 10¹² J) and a diameter of 1.8 m. These values correspond to an integral bolometric efficiency of 7 ± 2%. Early fragmentation ram pressures of <1 MPa and major fragmentations occurring with ram pressures of 2–5 MPa suggest that meter‐class stony near‐Earth asteroids (NEAs) have tensile strengths more than an order of magnitude lower than have been measured for ordinary chondrites. One implication of this observation is that the rotation period for small, fast‐rotating NEAs is likely to be >30 seconds.  相似文献   

THE CORE OF THE QUADRANTID METEOROID STREAM IS TWO HUNDRED YEARS OLD     

PAUL WIEGERT  PETER BROWN 《Earth, Moon, and Planets》2004,95(1-4):81-88

The Quadrantids are one of the most active annual meteor showers and have a number of unusual features. One is a sharp brief maximum, 12–14 h in length. A second is the Quadrantids, relatively recent appearance in our skies, the first observation having likely been made in 1835. Until recently no likely parent with a similar orbit had been observed and previous investigators concluded that the stream was quite old, with the stream’s recent appearance and sharp peak attributed to a recent fortuitous convergence of meteoroid orbits. The recent discovery of the near-Earth asteroid 2003 EH1 on an orbit very similar to that of the Quadrantids has almost certainly uncovered the parent body of this stream. From the simulations of the orbit of this body and of meteoroids released at intervals from it in the past, we find that both the sharp peak and recent appearance of the Quadrantids can most easily be explained assuming meteoroids were ejected in substantial numbers near 1800 AD.  相似文献   

Multiple Genesis of Fluid and Melt during Exhumation of Deeply-Subducted UHP Eclogite     

WANG Lu  WANG Songjie  FENG Peng  WANG Zhuocheng  Michael BROWN  Tim JOHNSON 《《地质学报》英文版》2021,95(Z1):65-67

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Mud diapirism: the origin of melanges in accretionary complexes?     

TONY BARBER  KEVIN BROWN 《Geology Today》1988,4(3):89-94

Chaotic melange deposits, a mixture of blocks in a clay matrix, have commonly been attributed to the mechanism of submarine slumping. In the oceans at the present day slumping does not occur on a sufficiently large scale to produce the quantities of melange seen in ancient accretionary complexes. In modern accretionary complexes, massive shale diapirism produces large volumes of melange, and is an entirely adequate mechanism to account for melanges in ancient complexes.  相似文献   

深反射地震揭示喜马拉雅地区地壳上地幔的复杂结构   总被引：12，自引：5，他引：12       下载免费PDF全文

赵文泽 Nels.  KD 《地球物理学报》1996,39(5):615-628

报告了中、美两国在喜马拉雅山区进行的第一次深反射地震试验的结果．试验剖面南起喜马拉雅山山脊南亚东县的帕里镇，向北穿过喜马拉雅山脊的荡拉，到达康马南的萨马达．剖面长约１００ｋｍ．共中心点（ＣＭＰ）叠加剖面上显示出：１．在地壳中部有一强反射带，向北缓倾斜下去，延长达１００ｋｍ以上．它可能代表了一个活动的逆冲断裂或是一条巨大的拆离带，印度地壳整体或下地壳沿此拆离层俯冲到藏南之下．２．上部地壳的反射很丰富，显示了上地壳存在着大规模的叠瓦状结构．３．下地壳的反射同相轴呈现短而有规律的分布，显示了塑性流变特征．４．在测线南部莫霍反射明显，深度达７２－７５ｋｍ．发现南部有双莫霍层的存在．５．试验中还取得莫霍层下面３２，３８，４８ｓ等双程走时的多条反射，向北倾斜，反射同相轴延续较长，信息丰富，反映了上地幔的成层结构和变形特征．这些结果对印度大陆地壳整体或其下地壳俯冲到藏南特提斯喜马拉雅地壳之下，并导致西藏南端地壳增厚的观点，给予了实质性的支持．  相似文献   

Characterization and P-T Evolution of Melt-bearing Ultrahigh-temperature Granulites: an Example from the Anapolis-Itaucu Complex of the Brasilia Fold Belt, Brazil     

MORAES  R.; BROWN  M.; FUCK  R. A.; CAMARGO  M. A.; LIMA  T. M. 《Journal of Petrology》2002,43(9):1673-1705

Sapphirine–quartz occurs in orthopyroxene–garnetgranulites in two areas  相似文献