Using Field-Portable XRF to Assess Geochemical Variations Within and Between Dolerite Outcrops of Preseli, South Wales   总被引：1，自引：0，他引：1  

Michael C. Jones  Olwen Williams-Thorpe  Philip J. Potts  Peter C. Webb 《Geostandards and Geoanalytical Research》2005,29(3):251-269

Eight dolerite outcrops in Preseli, south Wales were measured in situ using field-portable XRF analysis, in order to compare two different analysis ("sampling") strategies, and to investigate geochemical variability within and between outcrops. A sampling strategy of two (neighbouring but independent) measurements at each of a maximal number of locations dispersed over an outcrop was the more effective in indicating the overall chemical variance of that outcrop. Analysis of variance indicated that much of the observed variance within individual outcrops stems from real geochemical variability rather than from sampling and analytical factors. Standard ANOVA F tests showed that several of the studied outcrops are heterogeneous at the 5% significance level for one or more elements. Geochemical distinctions between some outcrops were demonstrated using discriminant analysis. PXRF analysis offers an alternative approach to conventional characterisation of outcrops, which is often based on laboratory analysis of small numbers of samples. However, PXRF data are affected by rock weathering and may require correction for this if they are to be compared with analyses of fresh rock.  相似文献   

Analysis and interpretation of the aftershock sequence of the August 17, 1999, Izmit (Turkey) earthquake     

O. Polat  H. Eyidogan  H. Haessler  A. Cisternas  H. Philip 《Journal of Seismology》2002,6(3):287-306

A micro-seismic field experiment has been carried out in the Marmara Searegion. The analysis of the events before and after the August 17, 1999Izmit (Turkey) earthquake has been completed. 1446 events have beenwell located out of a total of 3165 recorded within the period from July15 to November 2, 1999. 67% of the aftershocks with magnitudegreater than 4 have occurred within the first 6 days after the main-shock. Earthquakes of the Izmit sequence are distributed in the first 15 km of theearth crust, but major events are located in between 5 km and 15 kmdepth. The seismicity pattern defines a rupture plane extending for about150 km in an E-W direction. The rupture is extremely linear butsegmented, and its complexity increases towards the western endmanifesting bifurcation. A stress analysis has been carried out both at thewestern end and all along the aftershock zone. 96 selected aftershocks,registered between August 21 and October 22, were chosen in order tocompute their focal mechanisms and obtain information about the stressregime after the Izmit earthquake. Strike-slip and normal faultingmechanisms are dominant. The numerous strike-slip mechanisms arecompatible with a dextral motion on an EW oriented vertical fault plane. The best stress tensor solution shows a regime in extension with awell-defined ₃ axis oriented approximately N35^°.  相似文献   

Prediction of diffusion coefficients in porous media using tortuosity factors based on interfacial areas   总被引：1，自引：0，他引：1  

Saripall KP  Serne RJ  Meyer PD  McGrail BP 《Ground water》2002,40(4):346-352

Determination of aqueous phase diffusion coefficients of solutes through porous media is essential for understanding and modeling contaminant transport. Prediction of diffusion coefficients in both saturated and unsaturated zones requires knowledge of tortuosity and constrictivity factors. No methods are available for the direct measurement of these factors, which are empirical in their definition. In this paper, a new definition for the tortuosity factor is proposed, as the real to ideal interfacial area ratio. We define the tortuosity factor for saturated porous media (tau5) as the ratio S/S(o) (specific surface of real porous medium to that of an idealized capillary bundle). For unsaturated media, tortuosity factor (tau(a)) is defined as a(aw)/a(aw),o (ratio of the specific air-water interfacial area of real and the corresponding idealized porous medium). This tortuosity factor is suitably measured using sorptive tracers (e.g., nitrogen adsorption method) for saturated media and interfacial tracers for unsaturated media. A model based on this new definition of tortuosity factors, termed the interfacial area ratio (IAR) model, is presented for the prediction of diffusion coefficients as a function of the degree of water saturation. Diffusion coefficients and diffusive resistances measured in a number of saturated and unsaturated granular porous media, for solutes in dilute aqueous solutions, agree well with the predictions of the IAR model. A comparison of permeability of saturated sands estimated based on tau(s) and the same based on the Kozeny-Carman equation confirm the usefulness of the tau(s) parameter as a measure of tortuosity.  相似文献   

International viewpoint and news     

Philip E. LaMoreaux 《Environmental Geology》2007,53(1):229-230

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Reviews on books,internet and scientific media     

Anne Marie de Grosbois  Anna Grazia Chiodetti  Philip E. LaMoreaux  Fakhry A. Assaad 《Environmental Geology》2007,53(4):923-926

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中国中部寄生虫病的景观控制     

F. Mark Danson  Patrick Giraudoux  David Pleydell  Philip S. Craig 《遥感学报》2007,11(5):727-730

多房棘球绦虫（Echinococcus multilocularis）的幼虫期导致罕见而致命的肝病即人类的泡型包虫病（HAE）。绦虫在狐狸（或狗类）与一些小型哺乳类动物之间以寄生虫-寄主的方式进行循环传播。中国中部一些地区的人类泡型包虫病属于地方流行病,在部分乡村的发生概率达到15%。本文研究如何利用遥感数据并基于地区景观特性获取该流行病清晰地空间危害分布图。遥感数据分析的结果显示,人类居住地附近的草地或灌木是HAE传播的一个主要危险区域,从空间分布上看,这些区域是小型哺乳动物等中间寄主的聚集处。  相似文献   

Laboratory measurement of hydrodynamic saline dispersion within a micro-fracture network induced in granite     

Nicholas W.A. Odling  Stephen C. Elphick  Philip Meredith  Ian Main  Bryne T. Ngwenya   《Earth and Planetary Science Letters》2007,260(3-4):407-418

We report the first measurements of hydrodynamic dispersion in a microfractured granite using a combination of novel techniques. A fracture network was induced in a cylindrical plug of Ailsa Craig micro-granite by thermal stressing, to produce an isotropic network of fractures with an average aperture of  0.3 μm, a density of approximately 4 × 10⁴ fractures/mm³ and a permeability of 5.5 × 10^− 17 m². After saturating the cores with 0.01 M NaCl solution a step in the concentration profile to 1 M was advected into the plug at flow rates of 0.07 to 2.13 cm³ h^− 1. The longitudinal electrical impedance of the plug was measured continuously as the solute front advected through its length until the plug was saturated with the concentrated electrolyte. Analysis of the impedance versus time relationships allows the derivation of the longitudinal dispersion coefficient, D_L, and hydrodynamic retardation, R_H. The Peclet number–dispersion relationship for the micro-fracture network is very similar to that predicted for other, radically different, fracture networks. Thus dispersion may be more dependent on fracture connectivity and length than fracture density and display a relationship similar to that shown by particle beds and clastic sandstones. The high retardation values observed (2.2–4.9) reflect flow behaviour within a fracture network with a proportion of ‘blind’ sections, and demonstrates how such networks can slow the advance of conservative solute components.  相似文献   

Small towns as ‘sub-poles’ in English rural development: Investigating rural–urban linkages using sub-regional social accounting matrices     

Paul Courtney  Lucy Mayfield  Richard Tranter  Philip Jones  Andrew Errington   《Geoforum》2007,38(6):1219-1232

This paper uses spatial economic data from four small English towns to measure the strength of economic integration between town and hinterland and to estimate the magnitude of town–hinterland spill-over effects. Following estimation of local integration indicators and inter-locale flows, sub-regional social accounting matrices (SAMs) are developed to estimate the strength of local employment and output multipliers for various economic sectors. The potential value of a town as a ‘sub-pole’ in local economic development is shown to be dependent on structural differences in the local economy, such as the particular mix of firms within towns. Although the multipliers are generally small, indicating a low level of local linkages, some sectors, particularly financial services and banking, show consistently higher multipliers for both output and employment.  相似文献   

Reply to Comment on “The Misorientation index: Development of a new method for calculating the strength of lattice-preferred orientation”     

Philip Skemer  Shun-ichiro Karato 《Tectonophysics》2007,441(1-4):119-120

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Iron isotope, major and trace element characterization of early Archean supracrustal rocks from SW Greenland: Protolith identification and metamorphic overprint   总被引：3，自引：0，他引：3  

Nicolas Dauphas  Mark van Zuilen  Aivo Lepland  Philip E. Janney 《Geochimica et cosmochimica acta》2007,71(19):4745-4770

The iron isotope, trace and major element compositions of Eoarchean supracrustal rocks from southern West Greenland (Isua Supracrustal Belt, the islands of Akilia and Innersuartuut) were analyzed in order to identify protoliths and characterize the imprints of metamorphism and metasomatism. Banded iron formations (BIFs) from the Isua Supracrustal Belt (ISB) have trace element characteristics that are consistent with seawater derivation, including high Y/Ho ratios, positive Eu/Eu^∗ anomalies, positive La/La^∗ anomalies, and concave upward REE patterns. These rocks also have heavy Fe isotopic compositions relative to surrounding igneous rocks (∼+0.4‰/amu). The most likely interpretation is that this signature was inherited from partial oxidation in a marine setting of Fe emanating from a source similar to modern mid-ocean ridge hydrothermal vents (∼−0.15‰/amu).Banded quartz-rich rocks from the island of Akilia with high Fe/Ti ratios share many similarities with bona fide BIFs from Isua (heavy Fe isotopic compositions up to +0.4‰/amu, elevated Y/Ho ratios compared to igneous rocks, sometimes positive Eu/Eu^∗ anomalies) suggesting a chemical sedimentary origin.Iron-poor metacarbonates from the southwestern part of the ISB have light Fe isotopic compositions (∼−0.4‰/amu). This is consistent with derivation of these rocks by fluid flow through surrounding ultramafic rocks and deposition as metasomatic carbonates. Iron-rich metacarbonates from the northwest and northeast parts of the ISB have Fe isotopic compositions (from +0.1 to +0.4‰/amu) and trace element patterns (high Y/Ho ratios, positive Eu/Eu^∗ and La/La^∗ anomalies, and concave upward REE) similar to associated BIFs. The most likely interpretation is that these iron-rich metacarbonates were derived from mobilization of Fe in BIFs by metasomatic fluids.  相似文献