U-series Isotope Data on Lau Basin Glasses: the Role of Subduction-related Fluids during Melt Generation in Back-arc Basins   总被引：6，自引：2，他引：6  

PEATE  DAVID W.; KOKFELT  THOMAS F.; HAWKESWORTH  CHRIS J.; VAN CALSTEREN  PETER W.; HERGT  JANET M.; PEARCE  JULIAN A. 《Journal of Petrology》2001,42(8):1449-1470

New thermal ionization mass spectrometry U-series disequilibriumdata are presented for 24 basaltic to dacitic glasses from activespreading centres in the back-arc Lau Basin (SW Pacific), togetherwith additional inductively coupled plasma mass spectrometrytrace element analyses and Sr–Nd–Pb isotope data.Valu Fa Ridge samples, adjacent to the arc front, have highU/Th and (²³⁰Th/²³⁸U) <1, implying a recent (<<350ka) addition of a U-rich slab-derived fluid. The Valu Fa datacan be combined with existing ²³⁰Th–²³⁸U data for theCentral Tonga arc to infer a fluid addition event at  相似文献   

Theoretical and measured aeolian sand transport on a barrier island, Louisiana, USA     

JOHN R. DINGLER  S. A. HSU†  THOMAS E. REISS 《Sedimentology》1992,39(6):1031-1043

Over the past 100 years, the Isles Dernieres, a low lying barrier island chain along the coast of central Louisiana, Usa , has undergone more than 1 km of northward beach face retreat with the loss of 70% of its surface area. The erosion results from a long term relative sea level rise coupled with day to day wind and wave action that ultimately favours erosion over deposition. At a site in the central Isles Dernieres, 8 days of wind and beach profile measurements during the passage of one winter cold front documented aeolian erosion and deposition patterns under both onshore and offshore winds. For offshore winds, the theoretical erosion rate, based on wind shear velocity, closely matched the measured erosion rate; for onshore winds, the theoretical rate matched the measured rate only after being corrected by a factor that accounted for beach face morphology. In late February 1989, a strong cold front moved into coastal Louisiana. That cold front stalled over the Gulf of Mexico, resulting in 4 days of strong northerly winds at a study site on the Isles Dernieres. During those 4 days, the wind moved sand from the backshore to the upper beach face. When the cold front finally moved out of the area, the wind shifted to the south and decreased in strength. The onshore wind then restored some of the upper beach face sand to the backshore while increased wave activity moved the rest into the nearshore. The theoretical estimate of 1·28 m³ m^?1 for the rate of sand transport by the northerly wind compares well with the measured backshore erosion rate of 1·26 m³ m^?1, which was determined by comparing beach profiles from the start and end of the period of northerly winds. The theoretical estimate of 0·04 m³ m^?1 for the rate of sand transport by the southerly wind, however, is notably less than the measured rate of 0·45 m³ m^?1. The large discrepancy between the two rates can be explained by a difference in the shear velocity of the wind between the beach face, where the erosion occurred, and the backshore, where the wind stress was measured. Using an empirical relationship for the wind shear drag coefficient as a function of coastal environment, the theoretical estimate for the rate of sand transport by the southerly wind becomes 0·44 m³ m^?1  相似文献   

A decade of carbon, water and energy flux measurements of an old spruce forest at the Anchor Station Tharandt   总被引：3，自引：0，他引：3  

THOMAS GRÜNWALD  CHRISTIAN BERNHOFER 《Tellus. Series B, Chemical and physical meteorology》2007,59(3):387-396

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Horizontal homogeneity and vertical extent of new particle formation events   总被引：1，自引：0，他引：1  

BIRGIT WEHNER  HOLGER SIEBERT  FRANK STRATMANN  THOMAS TUCH  ALFRED WIEDENSOHLER  TUUKKA PETÄJÄ  MIIKKA DAL MASO  MARKKU KULMALA 《Tellus. Series B, Chemical and physical meteorology》2007,59(3):362-371

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Fog deposition fluxes of water and ions to a mountainous site in Central Europe   总被引：1，自引：0，他引：1  

OTTO KLEMM  THOMAS WRZESINSKY 《Tellus. Series B, Chemical and physical meteorology》2007,59(4):705-714

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Dominant particle support mechanisms in debris flows at Mt Thomas, New Zealand, and implications for flow mobility   总被引：5，自引：0，他引：5  

THOMAS C. PIERSON 《Sedimentology》1981,28(1):49-60

Within zones of little or no deformation by internal shearing in debris flows at Mt Thomas, about two-thirds of the weight of large particles is supported by buoyancy and about one-third by static grain to-grain contact. In boundary shear zones of low velocity flows and in high velocity, turbulent debris flow, grain-to grain contact is replaced by turbulence and dispersive pressure. Cohesive strength of the clay + silt + water interstitial fluid provides less than 2 % of the force keeping particles larger than 1 cm gravel in suspension. Excess pore pressure is generated in the interstitial fluid by the weight of coarse particles suspended in the slurry. According to Coulomb strength theory, pore pressures measured in these debris-flow slurries reduce the shear strength of the material to less than 10 % of what it is in the unsaturated state. The excess pore pressures are slow to dissipate because of the small connections between pore spaces that result from the extremely poor sorting of the debris and the presence of silt and clay in the pore fluid. Maintenance of sufficient pore space to trap fluid and facilitate flow on low-gradient slopes may be accomplished by dilatancy and subsequent partial liquefaction of the debris during shear.  相似文献   

The Tugtutoq Younger Giant Dyke Complex, South Greenland: Fractional Crystallization of Transitional Olivine Basalt Magma     

UPTON  B. G. J.; THOMAS  J. E. 《Journal of Petrology》1980,21(1):167-198

The Younger Giant Dyke Complex consists of a set of massivecoalescing dykes of Proterozoic age (c. 1170 Ma), resultingfrom intrusion of a suite of transitional olivine basaltic/hawaiiticmagmas in a continental rift setting. The suite, compositionallyrelated by low pressure (< 10 kb) olivine-plagioclase fractionation,is believed to have had a deeper level evolution dominated bypyroxene and possibly garnet fractionation. Slow cooling insitu of the interior parts of the dyke complex produced cumuliticsuites. Those exposed range from gabbroic to syenitic; residualbodies of riebeckite granite and, very subordinate, feldspathoidalsyenite were also generated. The basic magmas had notably lowfO₂ values, leading to delayed magnetite and clinopyroxene precipitation,relatively iron-rich differentiates and some residual liquidsof pantelleritic composition. The basic magmas had high F/Clvalues and are inferred to have had low H₂O contents. They werealso characterized by relatively high K/Rb and low ⁸⁷Sr/⁸⁶Srvalues; these characteristics imply a mantle source with highF/Cl but depleted in Rb relative to K and Sr. Basaltic magmasresponsible for (a) the preceding Older Giant Dyke Complex and(b) a suite of anorthositic xenoliths within the Younger GiantDyke Complex, are inferred to have been derived from separateprimary magma batches independent of those that yielded theYounger Giant Dyke Complex. The giant dykes are the highest-levelrepresentatives of a larger basic complex responsible for theextensive linear gravity ‘high’ in the Tugtutôq-Narssaqarea.  相似文献   

LE MAGNETOMETRE AEROPORTE MP 121 SUD-AVIATION     

J. THOMAS 《Geophysical Prospecting》1965,13(1):22-36

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Pressure image assimilation for atmospheric motion estimation     

THOMAS CORPETTI  PATRICK HÉAS  ETIENNE MÉMIN  NICOLAS PAPADAKIS 《地球，A辑:动力气象学与海洋学》2009,61(1):160-178

The complexity of the laws of dynamics governing 3-D atmospheric flows associated with incomplete and noisy observations make the recovery of atmospheric dynamics from satellite image sequences very difficult. In this paper, we address the challenging problem of estimating physical sound and time-consistent horizontal motion fields at various atmospheric depths for a whole image sequence. Based on a vertical decomposition of the atmosphere, we propose a dynamically consistent atmospheric motion estimator relying on a multilayer dynamic model. This estimator is based on a weak constraint variational data assimilation scheme and is applied on noisy and incomplete pressure difference observations derived from satellite images. The dynamic model is a simplified vorticity-divergence form of a multilayer shallow-water model. Average horizontal motion fields are estimated for each layer. The performance of the proposed technique is assessed using synthetic examples and using real world meteorological satellite image sequences. In particular, it is shown that the estimator enables exploiting fine spatio-temporal image structures and succeeds in characterizing motion at small spatial scales.  相似文献   

Controlling factors of volumetrically important marine carbonate cementation in deep slope settings   总被引：1，自引：0，他引：1  

BRAM VAN DER KOOIJ  ADRIAN IMMENHAUSER  THOMAS STEUBER  JUAN RAMON BAHAMONDE RIONDA  OSCAR MERÍNO TOMÉ 《Sedimentology》2010,57(6):1491-1525

The controlling parameters of early marine carbonate cementation in shoal water and hemipelagic to pelagic domains are well‐studied. In contrast, the mechanisms driving the precipitation of early marine carbonate cements at deeper slope settings have received less attention, despite the fact that considerable volumes of early marine cement are present at recent and fossil carbonate slopes in water depths of several hundreds of metres. In order to better understand the controlling factors of pervasive early marine cementation at greater water depths, marine carbonate cements observed along time‐parallel platform to basin transects of two intact Pennsylvanian carbonate slopes are compared with those present in the slope deposits of the Permian Capitan Reef and Neogene Mururoa Atoll. In all four settings, significant amounts of marine cements occlude primary pore spaces downslope into thermoclinal water depths, i.e. in a bathymetric range between some tens and several hundreds of metres. Radial, radiaxial and fascicular optic fibrous calcites, and radiaxial prismatic calcites are associated with re‐deposited facies, boundstones and rudstones. Botryoidal (formerly) aragonitic precipitates are common in microbially induced limestones. From these case studies, it is tentatively concluded that sea water circulation in an extensive, near‐sea floor pore system is a first‐order control on carbonate ion supply and marine cementation. Coastal upwelling and internal or tidal currents are the most probable mechanisms driving pore water circulation at these depths. Carbonate cements precipitated under conditions of normal to elevated alkalinity, locally elevated nutrient levels and variable sea water temperatures. The implications of these findings and suggestions for future work are discussed.  相似文献