Partial Melting of Metapelitic Rocks Beneath the Bushveld Complex, South Africa   总被引：6，自引：5，他引：6  

JOHNSON  TIM E.; GIBSON  ROGER L.; BROWN  MICHAEL; BUICK  IAN S.; CARTWRIGHT  IAN 《Journal of Petrology》2003,44(5):789-813

Metapelitic rocks in the aureole beneath the Bushveld Complexpreserve evidence for both high- and low-a_H2O anatexis. Theaureole is characterized by an inverted thermal structure inwhich suprasolidus rocks potentially interacted with an H₂O-richvolatile phase derived from underlying, dehydrating rocks. Atlower grade (T < 700°C) the rocks contain fibrolite matsand seams that record local redistribution of volatiles. Incongruentreactions consuming biotite produced small quantities (<1mol %) of liquid and peritectic cordierite that remained trappedwithin the mesosome. Larger volumes of melt (3–4%), preservedas coarse-grained discordant leucosomes, were produced by congruentmelting following a structurally focused influx of H₂O. Subhorizontalvolatile-phase flow was concentrated within thin (  相似文献   

The fate of coral reefs in the Andaman Sea, eastern Indian Ocean following the Sumatran earthquake and tsunami, 26 December 2004     

BARBARA E BROWN 《The Geographical journal》2005,171(4):372-374

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Spatial and temporal variation of gravity field in the capital region   总被引：1，自引：0，他引：1  

华昌才  果勇  刘瑞法  肖钢 《地震学报(英文版)》1995,8(3):427-433

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SEISMIC INTERPRETATION OF UPPER ELK POINT (GIVETIAN) CARBONATE RESERVOIRS OF WESTERN CANADA1     

R. J. BROWN  N. L. ANDERSON  L. V. HILLS 《Geophysical Prospecting》1990,38(7):719-736

The seismic signatures of three reefs of the Upper Elk Point Subgroup (Givetian Stage) of the Western Canada Sedimentary Basin are documented and analysed on the basis of variations in seismic image of particular lithologic units, lateral amplitude and/or phase changes, structural relief and velocity-generated relief, as rendered by the reflection data. The effects on seismic signatures of spatial geological variations resulting from such phenomena as differential compaction, reef-focused salt dissolution, palaeotopography, lateral and vertical facies variations, regional dip, and reservoir morphology are discussed. The usefulness of seismic data in clarifying relationships between reefs and their adjacent sedimentary sections, particularly in cases where well control is sparse, is also considered. Such documentation of seismic signatures from known reefs using geophysical and geological analysis can establish criteria to enable recognition of similar buildups elsewhere. Three example reefs are presented, each typical of a particular area and environment of W. Canada. The first is from the Winnipegosis Formation of SE Saskatchewan, the second and third from the Rainbow Member and Upper Keg River Reef Member, respectively, of the Keg River Formation of NW Alberta. All three of these carbonate buildups developed in the evaporitic Elk Point Basin. However, the degree of salt encasement and subsequent dissolution varied greatly, as do the resulting seismic effects. For these three reef types, the typical elements of their seismic signatures have been compiled and are here summarized.  相似文献   

An Anorthosite Suite in a Ring-Complex: Crystallization and Emplacement of an Anorogenic Type from Abontorok, A?r, Niger     

BROWN  WILLIAM L.; MOREAU  CHRISTIAN; DEMAIFFE  DANIEL 《Journal of Petrology》1989,30(6):1501-1540

Laminated anorthosite grading outwards into leucogabbro, gabbro,and monzogabbro occurs in a 2.6-km-diameter funnel-shaped intrusion,cut by a quartz alkali syenite plug and concentric syenite andgranite ring-dykes. The anorthosite-gabbro series is laminatedbut not modally or otherwise texturally layered. The lamination,defined by large tabular plagioclase crystals, forms a set ofinwarddipping cones, the dips of which decrease from 60–45?in the central anorthosite to < 25? in the outer gabbros.Rocks close to the outer contact are medium-grained isotropicgabbros. Plagioclase, forming >80% of the series, generallyhas homogeneous labradorite cores (An_62–58 in the wholeseries) and thin strongly zoned rims, which follow progressivelylonger solidus paths from the anorthosites to the gabbros. Allrocks contain a late-magmatic alkali feldspar. Plagioclase isthe main or only cumulus phase, the anorthosites being ad- tomesocumulates and the gabbros orthocumulates. Olivine (FO_49–41)is more abundant than clinopyroxene in most of the series. Dependingon quartz content, the syenites and granites are hypersolvusor subsolvus and the depth of crystallization was calculatedto be 5 ? 2 km. A Rb/Sr isochron for the syenites and granites gave an age of399 ? 10 Ma with an initial strontium isotopic ratio of 0.7084? 0.0005. Ten samples from the anorthosite-gabbro scries havean average calculated initial ratio of 0.70582 ? 0-00004 at– 400 Ma, showing that the two series are not comagmatic.The anorthosite-gabbro series has parallel REE trends (La_N/Yb_N{small tilde} 7–10) with decreasing positive Eu anomaliesand increasing total REE contents from anorthosite to gabbro;two monzogabbros have almost no Eu anomaly. The liquid calculatedto be in equilibrium with the lowest anorthosite has almostno Eu anomaly and its normalized REE pattern lies just abovethose for the monzogabbros. The syenites and granites have complementaryREE patterns with negative Eu anomalies. The inferred parental magma was alkalic and leucotroctoliticwith high TiO₂ P₂O₅, Sr and K/Rb and with low MgO, very similarto parental magmas in the Gardar province, South Greenland.It was probably produced at depth by settling of olivine andclinopyroxene but not of plagioclase, which accumulated by flotation.It is suggested that plagioclase crystals from this lower chamberwere progressively entrained (from 0% in the gabbros to 30–40%in the anorthosites), giving rise to the flow lamination inthe upper chamber. The magma in the lower chamber may have beenlayered, because the plagioclase cores in the anorthosite areconsiderably richer in Or than those in the leucogabbros orgabbros. Overall convection did not occur in the upper chamber,whereas compositional convection occurred in the more slowlycooled central anorthositic adcumulates.  相似文献   

Widespread transport of pyroclastic density currents from a large silicic tuff ring: the Glaramara tuff, Scafell caldera, English Lake District, UK   总被引：4，自引：0，他引：4  

R. J. BROWN  B. P. KOKELAAR†  M. J. BRANNEY 《Sedimentology》2007,54(5):1163-1190

The Glaramara tuff presents extensive exposures of the medial and distal deposits of a large tuff ring (original area >800 km²) that grew within an alluvial to lacustrine caldera basin. Detailed analysis and correlation of 21 sections through the tuff show that the eruption involved phreatomagmatic to magmatic explosions resulting from the interaction of dacitic magma and shallow-aquifer water. As the eruption developed to peak intensity, numerous, powerful single-surge pyroclastic density currents reached beyond 8 km from the vent, probably >12 km. The currents were strongly depletive and deposited coarse lapilli (>5 cm in diameter) up to 5 km from source, with only fine ash and accretionary lapilli deposited beyond this. As the eruption intensity waned, currents deposited fine ash and accretionary lapilli across both distal and medial regions. The simple wax–wane cycle of the eruption produced an overall upward coarsening to fining sequence of the vertical lithofacies succession together with a corresponding progradational to retrogradational succession of lithofacies relative to the vent. Various downcurrent facies transitions record transformations of the depositional flow-boundary zones as the depletive currents evolved with distance, in some cases transforming from granular fluid-based to fully dilute currents primarily as a result of loss of granular fluid by deposition. The tuff-ring deposits share several characteristics with (larger) ignimbrite sheets formed during Plinian eruptions and this underscores some overall similarities between pyroclastic density currents that form tuff rings and those that deposit large-volume ignimbrites. Tuff-ring explosive activity with such a wide area of impact is not commonly recognized, but it records the possibility of such currents and this should be factored into hazard assessments.  相似文献   

EXPERIMENTAL INVESTIGATIONS OF THE WEATHERING OF SUSPENDED SEDIMENT BY ALPINE GLACIAL MELTWATER     

GILES H. BROWN  M. TRANTER  M. J. SHARP 《水文研究》1996,10(4):579-597

The magnitude and processes of solute acquisition by dilute meltwater in contact with suspended sediment in the channelized component of the hydroglacial system have been investigated through a suite of controlled laboratory experiments. Constrained by field data from Haut Glacier d'Arolla, Valais, Switzerland the effects of the water to rock ratio, particle size, crushing, repeated wetting and the availability of protons on the rate of solute acquisition are demonstrated. These ‘free-drift’ experiments suggest that the rock flour is extremely geochemically reactive and that dilute quickflow waters are certain to acquire solute from suspended sediment. These data have important implications for hydrological interpretations based on the solute content of glacial meltwater, mixing model calculations, geochemical denudation rates and solute provenance studies.  相似文献   

Jason Microwave Radiometer Performance and On-Orbit Calibration     

SHANNON BROWN  CHRIS RUF  STEVE KEIHM  AMI KITIYAKARA 《Marine Geodesy》2013,36(1-2):199-220

Results are presented from the on-orbit calibration of the Jason Microwave Radiometer (JMR). The JMR brightness temperatures (TBs) are calibrated at the hottest and coldest ends of the instrument's dynamic range, using Amazon rain forest and vicarious cold on-Earth theoretical brightness temperature references. The retrieved path delay values are validated using collocated TOPEX Microwave Radiometer and Radiosonde Observation path delay (PD) values. Offsets of 1–4 K in the JMR TBs and 8–12 mm in the JMR PDs, relative to TMR measurements, were initially observed. There were also initial TB offsets of 2 K between the satellite's yaw state. The calibration was adjusted by tuning coefficients in the antenna temperature calibration algorithm and the antenna pattern correction algorithm. The calibrated path delay values are demonstrated to have no significant bias or scale errors with consistent performance in all nonprecipitating weather conditions. The uncertainty of the individual path delay measurements is estimated to be 0.74 cm ± 0.15, which exceeds the mission goal of 1.2 cm RMS.  相似文献   

A Deep Seismic Reflection Profile Spanning the Tibetan Plateau: INDEPTH and SINOPROBE     

Larry D. BROWN  ZHAO Wenjin  GAO Rui  CHEN Chen  LU Zhanwu  WU Zhenhan  INDEPTH  SINOPROBE Teams 《《地质学报》英文版》2013,87(Z1):39-39

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Calcium Isotope Constraints on Global Carbon Cycle Dynamics during the End-Permian Mass Extinction     

Jonathan L. PAYNE  Juan Carlos SILVA TAMAYO  Katharine MAHER  Jessica L. HINOJOSA  Adam B.JOST  Alexandra V. TURCHYN  Shaun T. BROWN  CHEN Jun  Adina PAYTAN  SHEN Shu-zhong  Donald J. DEPAOLO  Anton EISENHAUER  Daniel J. LEHRMANN  Demir ALTINER  YU Meiyi 《《地质学报》英文版》2013,87(Z1):902-902

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