Mantle-derived volatiles in continental crust: the Massif Central of France   总被引：1，自引：0，他引：1  

A. Matthews  C. Fouillac  R. Hill  R.K. O'Nions  E.R. Oxburgh 《Earth and Planetary Science Letters》1987,85(1-3)

CO₂-rich gases and groundwaters from springs and boreholes originating within the basement of the Massif Central have variable³He/⁴He ratios with correspondingR/R_a values ranging from 0.8 to 5.5 and 0.3 to 2.8 respectively, indicating the presence of a significant component of mantle helium. Molar concentrations of rare gases in the CO₂-rich gases are approximately 5 orders of magnitude greater than in the waters and suggest that a near-surface Henry's Law fractionation has occurred between exsolving CO₂ and water.δ¹³C values of the CO₂-rich gases are in the range −4.2 to −6.1‰, i.e. in that range normally attributed to mantle carbon, but which could also represent an average crustal composition and therefore do not discriminate between mantle and crustal sources.C/³He ratios show 4 orders of magnitude variation from 1.4 × 10¹² to 5 × 10⁸ and, compared to a mantleC/³He ratio of 10⁹, indicate that either a complex fractionation has occurred between mantle helium and mantle CO₂ or more likely that mantle rare gases have been diluted by large quantities of CO₂ with an average crustal carbon isotope composition. The regional distribution of³He and C does not show any obvious relationship to age or proximity of volcanic centres or major faults, suggesting that mantle-derived C and He components decoupled from their silicate melt sources at some depth.The results from this area of active fluid circulation suggest that C-isotope data derived from metamorphic terrains should be interpreted with great caution, but that input of some mantle-derived carbon is expected to accompany crustal extension.  相似文献   

Evidence for sea-floor spreading in the Cayman Trough     

T.L. Holcombe  P.R. Vogt  J.E. Matthews  R.R. Murchison 《Earth and Planetary Science Letters》1973,20(3):357-371

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Nitrogen dioxide column content measurements made from an aircraft between 5° and 82°N     

W. A. Matthews 《Journal of Atmospheric Chemistry》1984,2(2):125-132

In the first two weeks of May 1981, the research jet of the German Aerospace Research Establishment (DFVLR) was charted to fly a meridional section between 5° and 82°N. A scanning filter photometer, developed at the Max Planck Institut für Aeronomie to measure column content values of atmospheric ozone and nitrogen dioxide, using ultra violet and visible absorption techniques, constituted part of the experimental payload for this campaign that was called SIMOC. The vertical NO₂ column content above the aircraft, flying at approximately 10 km, was found to decrease rapidly from 6.9×10¹⁵ molecules cm^-2 to 2.5×10¹⁵ molecules cm^-2 around 50°N and then to increase again north of 75°N. A sharp rise in the NO₂ content was observed south of the subtropical jet but this could possibly be due to the increased depth of the troposphere above the aircraft in these regions.  相似文献   

Characterization of floating and sinking tar balls in the marine environment     

T.I. Balkas  I. Salihoǧlu  A.F. Gaines  M. Sunay  J. Matthews 《Marine pollution bulletin》1982,13(6):202-205

Tar balls, according to their densities, the prevailing temperature and their degree of weathering, are observed as floating, sinking, or are washed onto the beaches in the marine environment. To characterize the differences between floating and sunken tar balls, samples were analysed by IR, H-nmr, GC and GC/MS techniques. Hexane, benzene and methanol solubilities as well as densities were measured. The degree of weathering of the tar balls was investigated in terms of the losses of $\text{n-}\text{paraffinic/aromatic}$ hydrocarbons. The ratio of paraffinic/aromatic hydrocarbon concentrations was calculated by IR and H-nmr whereas pristane/phytane ratios were estimated from GC measurements. The comparison of some high molecular weight, but minor, components between the major $\text{n-}\text{paraffins}$ was obtained from GC/MS measurements.  相似文献   

Delineating generalized species boundaries from species distribution data and a species distribution model     

Matthew P. Peters  Stephen N. Matthews  Louis R. Iverson  Anantha M. Prasad 《International journal of geographical information science》2014,28(8):1547-1560

Species distribution models (SDM) are commonly used to provide information about species ranges or extents, and often are intended to represent the entire area of potential occupancy or suitable habitat in which individuals occur. While SDMs can provide results over various geographic extents, they normally operate within a grid and cannot delimit distinct, smooth boundaries. Additionally, there are instances where a zone of primary occupancy (i.e., a mostly continuous region where species exists, excluding outliers) is better suited for particular analyses, such as when examining source/sink population dynamics or modeling movement into new habitats. We present a semi-automated method to delineate a generalized species boundary (GSB) from SDM output, which provides a practical alternative to digitizing. This preliminary boundary is then manually updated based on inventory data and historical ranges. We used the method to generate contemporary boundaries for 132 tree species of the eastern United States, which are complementary to the ranges generated by Elbert Little for North America during the 1970s, but are not replacements. The methods we present can broadly be applied to other grid-based SDM to generate GSBs.  相似文献   

Benchmarking Climate-Carbon Model Simulations against Forest FACE Data     

Andrew J. Pinsonneault  H. Damon Matthews  Zavareh Kothavala 《大气与海洋》2013,51(1):41-50

Terrestrial carbon fluxes are an important factor in regulating concentrations of atmospheric carbon dioxide (CO₂). In this study, we use a coupled climate model with interactive biogeochemistry to benchmark the simulation of net primary productivity (NPP) and its response to elevated atmospheric CO₂. Short-term field experiments such as Free-Air Carbon Dioxide Enrichment (FACE) studies have examined this phenomenon but it is difficult to infer trends from only a few years of field data. Here, we employ the University of Victoria's Earth System Climate Model (UVic ESCM) version 2.8 to compare simulated changes in NPP due to an elevated atmospheric CO₂ concentration of 550 ppm to observed increases in NPP of 23% ±2% from four temperate forest FACE studies between 1997 and 2002. We further compare two scenarios: elevated CO₂ with climate change, and elevated CO₂ without climate change, the latter being consistent with FACE methodology. In the climate change scenario global terrestrial and forest-only NPP increased by 24.5% and 27.9%, respectively, while these increases were 21.0% and 17.2%, respectively, in the latitude band most representative of the location of the FACE studies. In the scenario without climate change, terrestrial and forest-only NPP increased instead by 28.3% and 30.6%, respectively, while these increases were 24.3% and 14.4%, respectively, in the FACE latitudes. This suggests that the model may underestimate temperate forest NPP increases when compared to results from temperate forest FACE studies and highlights the need for both increased experimental study of other forest biomes and further model development.  相似文献   

A transition from CMIP3 to CMIP5 for climate information providers: the case of surface temperature over eastern North America     

Marko Markovic  Ramón de Elía  Anne Frigon  H. Damon Matthews 《Climatic change》2013,120(1-2):197-210

The release of new data constituting the Coupled Model Intercomparison Project—Phase 5 (CMIP5) database is an important event in both climate science and climate services issues. Although users’ eagerness for a fast transition from CMIP3 to CMIP5 is expected, this change implies some challenges for climate information providers. The main reason is that the two sets of experiments were performed in different ways regarding radiative forcing and hence continuity between both datasets is partially lost. The objective of this research is to evaluate a metric that is independent of the amount and the evolution of radiative forcing, hence facilitating comparison between the two sets for surface temperature over eastern North America. The link between CMIP3 and CMIP5 data sets is explored spatially and locally (using the ratio of local to global temperatures) through the use of regional warming patterns, a relationship between the grid-box and the global mean temperature change for a certain time frame. Here, we show that local to global ratios are effective tools in making climate change information between the two sets comparable. As a response to the global mean temperature change, both CMIP experiments show very similar warming patterns, trends, and climate change uncertainty for both winter and summer. Sensitivity of the models to radiative forcing is not assessed. Real inter-model differences remain the largest source of uncertainty when calculating warming patterns as well as spatially-based patterns for the pattern scaling approach. This relationship between the datasets, which may escape users when they are provided with a single radiative forcing pathway, needs to be stressed by climate information providers.  相似文献   

A Practical Approach for Collecting Large‐n Detrital Zircon U‐Pb Data sets by Quadrupole LA‐ICP‐MS          下载免费PDF全文

William A. Matthews  Bernard Guest 《Geostandards and Geoanalytical Research》2017,41(2):161-180

A measurement procedure for the rapid acquisition of U‐Pb dates for detrital zircons by quadrupole LA‐ICP‐MS was developed. The procedure achieves a threefold increase in measurement efficiency compared with the most commonly used methods. Utilising reduced background counting times and a shortened ablation period, a throughput of ~ 130 measurements/h can be achieved. The measurement procedure was characterised and validated using data from thirty‐nine sessions acquired over a twelve‐month period. Systematic measurement error in ²⁰⁶Pb/²³⁸U dates for reference materials used for quality control with ages between 28.2 and 2672 Ma was < 1.5%. Average measurement uncertainty, including both random and systematic components, was 1–4% (2s). Interrogation of time‐resolved calculated dates and signal intensities for each measurement allows for the detection and elimination of portions of measurements exhibiting age heterogeneities, zoning, lead loss and contamination by common lead. The measurement procedure diminishes the need to acquire cathodoluminescence imagery for routine detrital zircon applications further increasing throughput and reducing cost. The utility of the measurement procedure is demonstrated by the measurement of samples previously characterised by LA‐MC‐ICP‐MS.  相似文献   

Glacial activity and paraglacial landsliding in the Devensian Lateglacial: evidence from Craig Cerrig-gleisiad and Fan Dringarth,Fforest Fawr (Brecon Beacons), South Wales     

Richard A. Shakesby  John A. Matthews 《Geological Journal》1996,31(2):143-157

The tongue-shaped mass of debris and associated ridges on the cirque floor below Craig Cerrig-gleisiad, Brecon Beacons National Park is important and controversial because it has been attributed to more than one glacier advance during the Late Devensian. A new origin is proposed involving landslide development from the collapse of part of the western headwall followed by a single phase of glacier development in the Loch Lomond Stadial (Younger Dryas), which reworked the landslide sediments. Evidence for this landslide, which provides useful criteria for differentiating moraines formed by small glaciers from landslides, lies in tension cracks, backward-tilted blocks and bedrock joints dipping out of the western headwall, together with lateral levées, upstanding termini and angular clasts with only occasional, indistinct striae on the tongue-shaped mass, which is interpreted as a flowslide. Glacier reworking of debris in the upper part of the Cwm Cerrig-gleisiad landslide is indicated by subparallel ridges rising to 20 m above the cirque floor containing abraded clasts (16-32% striated). This interpretation is supported by a comparison with the morphological and sedimentary characteristics of a neighbouring landslide at Fan Dringarth, where no glacier developed in the Loch Lomond Stadial. The existence of paraglacial landsliding has significant palaeoenvironmental implications leading to: (1) erroneously large estimates of equilibrium line depression ($Δ$ELA) in the Loch Lomond Stadial; (2) consequent underestimates of summer palaeotemperatures and/or overestimates of the contribution of wind-drifted snow to glacier accumulation; and (3) larger moraines than usual and overestimation of the efficacy of glacial erosion because of antecedent processes.  相似文献