Calculated greenschist facies mineral equilibria in the system CaO−FeO−MgO−Al2O3−SiO2−CO2−H2O     

Thomas M. Will  Roger Powell  Tim Holland  Michel Guiraud 《Contributions to Mineralogy and Petrology》1990,104(3):353-368

The kinetic problems associated with the experimental determination of reactions among complex solidsolution phases at low temperatures have hindered our understanding of the phase relations in greenschist facies rocks. In the absence of reliable experimental data, we have used the new, expanded internally-consistent thermodynamic dataset of Holland and Powell (1990), to present calculated phase equilibria for the system CaO–FeO–MgO–Al₂O₃–SiO₂–H₂O–CO₂ (CaFMASCH) with quartz in eccess, in the range 400°–500°C at low to intermediate pressures, involving the minerals amphibole, chlorite, anorthite, clinozoisite, dolomite, chloritoid, garnet, margarite, andalusite, and calcite. By solving independent sets of non-linear equations formed from equilibrium relationships, we calculate not only the loci of reactions in pressuretemperature-x(CO₂) space, but also the compositions of coexisting minerals in terms of the substitutions, FeMg_-1 and (Fe,Mg)SiAl_-1Al_-1. Invariant, univariant and divariant equilibria are calculated and discussed in relation to naturally-occurring greenschist facies metabasic and siliceous dolomitic mineral assemblages. We thus avoid the use of activity-corrected curves so commonly presented in the literature as a substitute for genuine univariant phase diagram boundaries.  相似文献   

A time varying AR coefficient model for modelling and simulating earthquake ground motion     

Will Gersch  Genshiro Kitagawa 《地震工程与结构动力学》1985,13(2):243-254

A smoothness priors-time varying autoregressive (AR) coefficient model method for the modelling of earthquake ground motion is shown. The method yields the instantaneous smoothed values of the AR coefficients and the instantaneous smoothed values of the innovations variance. These results in turn yield estimates of the instantaneous spectral density, the time varying covariance function and a simulation model for the ground motion data. An example of the application of the method to the analysis of an accelogram from the February 1971 San Fernando, California earthquake is shown.  相似文献   

Stratigraphic and structural controls on groundwater salinity variations in the Poso Creek Oil Field,Kern County,California, USA     

Stephens  Michael J.  Shimabukuro  David H.  Chang  Will  Gillespie  Janice M.  Levinson  Zack 《Hydrogeology Journal》2021,29(8):2803-2820

Hydrogeology Journal - Groundwater total dissolved solids (TDS) distribution was mapped with a three-dimensional (3D) model, and it was found that TDS variability is largely controlled by...  相似文献   

Thermal properties of Pluto’s and Charon’s surfaces from Spitzer observations     

Emmanuel Lellouch  John Stansberry  Will Grundy 《Icarus》2011,214(2):701-716

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Deep learning for dune pattern mapping with the AW3D30 global surface model     

Samuel Shumack  Paul Hesse  Will Farebrother 《地球表面变化过程与地形》2020,45(11):2417-2431

In this paper we present a deep learning (U-Net)-based workflow for classifying linear dune landforms based on the discrete Laplacian convolution of a new global elevation dataset, the AW3D30 digital surface model. Crest vectors were then derived for landscape pattern analysis. The U-Net crest classification model was trained and evaluated on sample data from dunefields across the Australian continent. The resulting crest vectors and dune defect placement were then evaluated in typical semi-arid and arid dune landscapes in eastern central Australia where high-resolution (5 m horizontal) digital elevation models are available (for three out of our four study sites) as a reference dataset. The method was applied to quantify dune pattern metrics for the entire Simpson Desert dunefield, Australia. The U-Net does a very good job of segmenting dune crests, even where dunes are less clear in the Laplacian map (intersection over union score ≈ 0.68). When crest vectors and dune defects (network nodes) were derived, the defect predictions were typically correct (0.4 to 0.79 correctness) but incomplete (0.02 to 0.64 completeness). Much of the residual error was traced to the resolution of the input data. Through the application to the Simpson Desert, we nevertheless demonstrated that our method can effectively be used for regional-scale dune pattern analysis. Furthermore, we suggest that the combination of morphological filtering and a convolutional neural network could readily be adapted to target other geomorphic features, such as channel networks or geological lineaments. © 2020 John Wiley & Sons, Ltd.  相似文献   

Understanding the spatial distribution and physical attributes of upland swamps in the Sydney Basin as a template for their conservation and management     

Kirstie A. Fryirs  Will Farebrother  Grant C. Hose 《The Australian geographer》2019,50(1):91-110

Temperate Highland Peat Swamps on Sandstone (THPSS) and Coastal Upland Swamps in the Sydney Basin (CUSSB) are listed as endangered ecological communities under Australia's national and state legislation. They are threatened by a range of human and climate impacts. Across the region there are 3208 individual, valley-bottom, elongate-shaped, upland swamps that drain first- or second-order drainage lines and small catchment areas (mean?=?0.25?km²). They occur at a median distance of 57?km from the coast in areas with an average annual rainfall of 1505?mm/year and average annual temperature of 15°C. Those closer to the coast occur on elevations as low as 160?m a.s.l., and those further from the coast, on plateau country, occur up to 1172?m a.s.l. (median 634?m a.s.l.). The valleys that contain these swamps terminate downstream at a valley constriction or bedrock step, behind which alluvial materials have accumulated, and peat has formed to produce relatively steep swamps (median slope 6.2 per cent). Understanding the spatial distribution and physical attributes of these systems, and having the accompanying maps as a resource, is critical for development of sound, well-informed conservation, rehabilitation and monitoring programs, and for analysing the ecosystem services they provide.  相似文献   

Patterns and Meanings of Housing: Residential Mobility and Homeownership among Former Refugees     

Will Poppe 《Urban geography》2013,34(2):218-241

Abstract

This article explores the patterns of residential mobility and homeownership, and in particular the meanings that former refugees attach to housing and neighborhood. While there are numerous studies on housing among voluntary migrants, studies that focus exclusively on refugees are rare. This multi-method study is based on interviews and a questionnaire survey with participants from Burma and the African Great Lakes Region in Buffalo, New York, who had arrived in the United States since 1995. Residential mobility patterns and meanings of housing indicate substantial differences between households in the two groups. The central argument of the paper is that the patterns and the meanings of housing are shaped by: (1) current socio-economic characteristics and resources, including educational attainment, employment status, and income; (2) current housing market conditions, including housing prices and racial discrimination; and (3) pre-migration experiences, including socio-economic status, socialization, and the corresponding internalized structures of meanings with respect to residential and housing patterns.  相似文献   

The 2dF Galaxy Redshift Survey: the bias of galaxies and the density of the Universe   总被引：1，自引：0，他引：1  

Licia Verde  Alan F. Heavens  Will J. Percival  Sabino Matarrese  Carlton M. Baugh  Joss Bland-Hawthorn  Terry Bridges  Russell Cannon  Shaun Cole  Matthew Colless  Chris Collins  Warrick Couch  Gavin Dalton  Roberto De Propris  Simon P. Driver  George Efstathiou  Richard S. Ellis  Carlos S. Frenk  Karl Glazebrook  Carole Jackson  Ofer Lahav  Ian Lewis  Stuart Lumsden  Steve Maddox  Darren Madgwick  Peder Norberg  John A. Peacock  Bruce A. Peterson  Will Sutherland  Keith Taylor 《Monthly notices of the Royal Astronomical Society》2002,335(2):432-440

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The 2dF Galaxy Redshift Survey: a targeted study of catalogued clusters of galaxies     

Roberto De Propris  Warrick J. Couch  Matthew Colless  Gavin B. Dalton  Chris Collins  Carlton M. Baugh  Joss Bland-Hawthorn  Terry Bridges  Russell Cannon  Shaun Cole  Nicholas Cross  Kathryn Deeley  Simon P. Driver  George Efstathiou  Richard S. Ellis  Carlos S. Frenk  Karl Glazebrook  Carole Jackson  Ofer Lahav  Ian Lewis  Stuart Lumsden  Steve Maddox  Darren Madgwick  Stephen Moody  Peder Norberg  John A. Peacock  Will Percival  Bruce A. Peterson  Will Sutherland  Keith Taylor 《Monthly notices of the Royal Astronomical Society》2002,329(1):87-101

We have carried out a study of known clusters within the 2dF Galaxy Redshift Survey (2dFGRS) observed areas and have identified 431 Abell, 173 APM and 343 EDCC clusters. Precise redshifts, velocity dispersions and new centroids have been measured for the majority of these objects, and this information is used to study the completeness of these catalogues, the level of contamination from foreground and background structures along the cluster's line of sight, the space density of the clusters as a function of redshift, and their velocity dispersion distributions. We find that the Abell and EDCC catalogues are contaminated at the level of about 10 per cent, whereas the APM catalogue suffers only 5 per cent contamination. If we use the original catalogue centroids, the level of contamination rises to approximately 15 per cent for the Abell and EDCC catalogues, showing that the presence of foreground and background groups may alter the richness of clusters in these catalogues. There is a deficiency of clusters at     that may correspond to a large underdensity in the Southern hemisphere. From the cumulative distribution of velocity dispersions for these clusters, we derive a space density of     clusters of     This result is used to constrain models for structure formation; our data favour low-density cosmologies, subject to the usual assumptions concerning the shape and normalization of the power spectrum.  相似文献   

P–T evolution of glaucophane–omphacite bearing HP–LT rocks in the western Tianshan Orogen, NW China:new evidence for 'Alpine-type' tectonics     

R. Klemd  F. C. Schröter  T. M. Will  J. Gao 《Journal of Metamorphic Geology》2002,20(2):239-254

The late Palaeozoic western Tianshan high‐pressure /low‐temperature belt extends for about 200 km along the south‐central Tianshan suture zone and is composed mainly of blueschist, eclogite and epidote amphibolite/greenschist facies rocks. P–T conditions of mafic garnet omphacite and garnet–omphacite blueschist, which are interlayered with eclogite, were investigated in order to establish an exhumation path for these high‐pressure rocks. Maximum pressure conditions are represented by the assemblage garnet–omphacite–paragonite–phengite–glaucophane–quartz–rutile. Estimated maximum pressures range between 18 and 21 kbar at temperatures between 490 and 570 °C. Decompression caused the destabilization of omphacite, garnet and glaucophane to albite, Ca‐amphibole and chlorite. The post‐eclogite facies metamorphic conditions between 9 and 14 kbar at 480–570 °C suggest an almost isothermal decompression from eclogite to epidote–amphibolite facies conditions. Prograde growth zoning and mineral inclusions in garnet as well as post‐eclogite facies conditions are evidence for a clockwise P–T path. Analysis of phase diagrams constrains the P–T path to more or less isothermal cooling which is well corroborated by the results of geothermobarometry and mineral textures. This implies that the high‐pressure rocks from the western Tianshan Orogen formed in a tectonic regime similar to ‘Alpine‐type’ tectonics. This contradicts previous models which favour ‘Franciscan‐type’ tectonics for the southern Tianshan high‐pressure rocks.  相似文献