Granitic magmatism,basement ages,and provenance indicators in the Malay Peninsula: Insights from detrital zircon U–Pb and Hf-isotope data     

Inga Sevastjanova  Benjamin Clements  Robert Hall  Elena A. Belousova  William L. Griffin  Norman Pearson 《Gondwana Research》2011,19(4):1024-1039

The Malay Peninsula lies on two continental blocks, Sibumasu and East Malaya, which are intruded by granitoids in two provinces: the Main Range and Eastern. Previous models propose that Permian–Triassic granitoids are subduction-related and syn-to post-collisional. We present 752 U–Pb analyses that were carried out on zircons from river sands in the Malay Peninsula; of these, 243 grains were selected for Hf-isotope analyses. Our data suggest a more complex Sibumasu–East Malaya collision history. ¹⁷⁶Hf/¹⁷⁷Hf_i ratios reveal that Permian–Triassic zircons were sourced from three magmatic suites: (a) Permian crustally-derived granitoids, (b) Early-Middle Triassic granitoids with mixed mantle–crust sources, and (c) Late Triassic crustally-derived granitoids. This suggests three Permian–Triassic episodes of magmatism in the Malay Peninsula, two of which occurred in the Eastern Province. Although the exact timing of the Sibumasu–East Malaya collision remains unresolved, current data suggest that it occurred before the Late Triassic, probably in Late Permian–Early Triassic. Our data also indicate that Sibumasu and East Malaya basements are chronologically heterogeneous, but predominantly of Proterozoic age. Some basement may be Neoarchaean but there is no evidence for basement older than 2.8 Ga. Finally, we show that Hf-isotope signatures of Triassic zircons can be used as provenance indicators.  相似文献   

Uranium and Thorium Concentration and Isotopic Composition in Five Glass (BHVO‐2G,BCR‐2G,NKT‐1G,T1‐G,ATHO‐G) and Two Powder (BHVO‐2, BCR‐2) Reference Materials     

Kathryn A. Matthews  Michael T. Murrell  Steven J. Goldstein  Andrew J. Nunn  Deborah E. Norman 《Geostandards and Geoanalytical Research》2011,35(2):227-234

Here we report uranium and thorium isotopic ratios and elemental concentrations measured in solid reference materials from the USGS (BHVO‐2G, BCR‐2G, NKT‐1G), as well as those from the MPI‐DING series (T1‐G, ATHO‐G). Specifically created for microanalysis, these naturally‐sourced glasses were fused from rock powders. They cover a range of compositions, elemental concentrations and expected isotopic ratios. The U‐Th isotopic ratios of two powdered source materials (BCR‐2, BHVO‐2) were also characterised. These new measurements via multi‐collector thermal ionisation mass spectrometry and multi‐collector inductively coupled plasma‐mass spectrometry can now be used to assess the relative performance of techniques and facilitate comparison of U‐Th data amongst laboratories in the geoscience community for in situ and bulk analyses.  相似文献   

A lacustrine GDGT-temperature calibration from the Scandinavian Arctic to Antarctic: Renewed potential for the application of GDGT-paleothermometry in lakes   总被引：2，自引：0，他引：2  

Emma J. Pearson  Steve Juggins  Jan Weckström  David B. Ryves  Roland Schmidt 《Geochimica et cosmochimica acta》2011,75(20):6225-6238

Quantitative climate reconstructions are fundamental to understand long-term trends in natural climate variability and to test climate models used to predict future climate change. Recent advances in molecular geochemistry have led to calibrations using glycerol dialkyl glycerol tetraethers (GDGTs), a group of temperature-sensitive membrane lipids found in Archaea and bacteria. GDGTs have been used to construct temperature indices for oceans (TEX₈₆ index) and soils (MBT/CBT index). The aim of this study is to examine GDGT-temperature relationships and assess the potential of constructing a GDGT-based palaeo-thermometer for lakes. We examine GDGT-temperature relationships using core top sediments from 90 lakes across a north-south transect from the Scandinavian Arctic to Antarctica including sites from Finland, Sweden, Siberia, the UK, Austria, Turkey, Ethiopia, Uganda, Chile, South Georgia and the Antarctic Peninsula. We examine a suite of 15 GDGTs, including compounds used in the TEX₈₆ and MBT/CBT indices and reflecting the broad range of GDGT inputs to small lake systems.GDGTs are present in varying proportions in all lakes examined. The TEX₈₆ index is not applicable to our sites because of the large relative proportions of soil derived and methanogenic components. Similarly, the MBT/CBT index is also not applicable and predicts temperatures considerably lower than those measured. We examine relationships between individual GDGT compounds and temperature, pH, conductivity and water depth. Temperature accounts for a large and statistically independent fraction of variation in branched GDGT composition. We propose a GDGT-temperature regression model with high accuracy and precision (R² = 0.88; RMSE = 2.0 °C; RMSEP = 2.1 °C) for use in lakes based on a subset of branched GDGT compounds and highlight the potential of this new method for reconstructing past temperatures using lake sediments.  相似文献   

Biogeochemical processes in a clay formation in situ experiment: Part E - Equilibrium controls on chemistry of pore water from the Opalinus Clay, Mont Terri Underground Research Laboratory, Switzerland     

F.J. Pearson  Christophe TournassatEric C. Gaucher 《Applied Geochemistry》2011,26(6):990-1008

The chemistry of pore water (particularly pH and ionic strength) is an important property of clay rocks being considered as host rocks for long-term storage of radioactive waste. Pore waters in clay-rich rocks generally cannot be sampled directly. Instead, their chemistry must be found using laboratory-measured properties of core samples and geochemical modelling. Many such measurements have been made on samples from the Opalinus Clay from the Mont Terri Underground Research Laboratory (URL). Several boreholes in that URL yielded water samples against which pore water models have been calibrated. Following a first synthesis report published in 2003, this paper presents the evolution of the modelling approaches developed within Mont Terri URL scientific programs through the last decade (1997-2009). Models are compared to the composition of waters sampled during dedicated borehole experiments. Reanalysis of the models, parameters and database enabled the principal shortcomings of the previous modelling efforts to be overcome. The inability to model the K concentrations correctly with the measured cation exchange properties was found to be due to the use of an inappropriate selectivity coefficient for Na-K exchange; the inability to reproduce the measured carbonate chemistry and pH of the pore waters using mineral-water reactions alone was corrected by considering clay mineral equilibria. Re-examination of the measured Ca/Mg activity ratios and consideration of the mineralogical composition of the Opalinus Clay suggested that Ca/Mg cation exchange rather than dolomite saturation may control the ratio of these ions in solution. This re-examination also suggests that the Ca/Mg ratio decreases with increasing pore-water salinity. Several possible reasons for this are proposed. Moreover, it is demonstrated that feldspar equilibria must not be included in Opalinus Clay modelling because feldspars are present only in very small quantities in the formation and because Na/K ratios measured in pore water samples are inconsistent with feldspar saturation. The principal need to improve future modelling is additional or better data on rock properties, in particular: (i) a more detailed identification of phases in the Opalinus Clay that include redox-sensitive elements together with evaluation of their thermodynamic properties; (ii) an improved understanding of the distribution of celestite throughout the Opalinus Clay for Sr/SO₄ concentrations control; (iii) improvements in analytic and thermodynamic data for Ca-Mg rock cation exchange and mineral chemical properties and (iv) the measurement of composition and stability constants of clay minerals actually present in the formation.  相似文献   

The effect of sideband ratio on line intensity for Herschel/HIFI     

Ronan Higgins  David Teyssier  Colin Borys  Jonathan Braine  Claudia Comito  Bertrand Delforge  Frank Helmich  Michael Olberg  Volker Ossenkopf  John Pearson  Russell Shipman 《Experimental Astronomy》2014,37(2):433-452

The Heterodyne Instrument for the Far Infrared (HIFI) on board the Herschel Space Observatory is composed of a set of fourteen double sideband mixers. We discuss the general problem of the sideband ratio (SBR) determination and the impact of an imbalanced sideband ratio on the line calibration in double sideband heterodyne receivers. The HIFI SBR is determined from a combination of data taken during pre-launch gas cell tests and in-flight. The results and some of the calibration artefacts discovered in the gas cell test data are presented here along with some examples of how these effects appear in science data taken in orbit.  相似文献   

SCALES FOR DETERMINING SLOPE FROM TOPOGRAPHIC MAPS     

Norman J. W. Thrower  Ronald U. Cooke 《The Professional geographer》1968,20(3):181-186

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Breaking wave loads at vertical seawalls and breakwaters     

Giovanni Cuomo  William Allsop  Tom Bruce  Jonathan Pearson 《Coastal Engineering》2010

This paper presents recent advances in knowledge on wave loads, based on experimental work carried out in the CIEM/LIM large flume at Barcelona within the framework of the VOWS (Violent Overtopping by Waves at Seawalls) project. Both quasi-static and impact wave forces from the new data set have been compared with predictions by empirical and analytical methods. The scatter in impact forces has been found to be large over the whole range of measurements, with no existing method giving especially good predictions. Based on general considerations, a simple and intuitive set of prediction formulae has been introduced for quasi-static and impact forces, and overturning moments, giving good agreement with the new measurements. New prediction formulae have been compared with previous measurements from physical model tests at small and large scale, giving satisfactory results over a relatively wide range of test conditions. The time variation of wave impacts is discussed, together with pressure distribution up the wall, which shows that within experimental limitations the measured pressures are within existing limits of previous study.  相似文献   

The dissociation constants of carbonic acid in seawater at salinities 5 to 45 and temperatures 0 to 45°C     

Rabindra N Roy  Lakshimi N Roy  Kathleen M Vogel  C Porter-Moore  Tara Pearson  Catherine E Good  Frank J Millero  Douglas M Campbell 《Marine Chemistry》1993,44(2-4)

The pK₁^* and pK₂^* for the dissociation of carbonic acid in seawater have been determined from 0 to 45°C and S = 5 to 45. The values of pK₁^* have been determined from emf measurements for the cell: where X is the mole fraction of CO₂ in the gas. The values of pK₂^* have been determined from emf measurements on the cell: The results have been fitted to the equations: where T is the temperature in K, S is the salinity, and the standard deviations of the fits are σ = 0.0048 in lnK₁^* and σ = 0.0070 in lnK₂^*.Our new results are in good agreement at S = 35 (±0.002 in pK₁^*and ±0.005 in pK₂^*) from 0 to 45°C with the earlier results of Goyet and Poisson (1989). Since our measurements are more precise than the earlier measurements due to the use of the Pt, H₂|AgCl, Ag electrode system, we feel that our equations should be used to calculate the components of the carbonate system in seawater.  相似文献   

Sublethal effects of oiled sediment on the sand worm, Nereis (neanthes) virens: Induced changes in burrowing and emergence     

Bori L. Olla  Allen J. Bejda  Anne L. Studholme  Walter H. Pearson 《Marine environmental research》1984,13(2):121-139

The burrowing and emergence behavior of sand worms, Nereis (Neanthes) virens Sars, in sediment contaminated with sublethal concentrations of Prudhoe Bay crude oil ranging from 74 to 5222 ppm, was studied in the laboratory. Initial burrowing in oiled sediment did not differ from that observed in unoiled sediment. Emergence of exposed worms was related to the oil concentration and the extent of weathering of oiled sediment. Sand worms buried in unoiled sediment did not emerge. Worms dug from oiled sediment after 12 hours' exposure and placed on unoiled sediment were impaired, resulting in a significant increase in time to burrow. However, after 12h, they recovered and burrowed at normal rates. Worms held in oiled sediment for 96 h also recovered. Possible causes for recovery are discussed. Results suggest that oil-induced aberrations may increase vulnerability to predation.  相似文献   

Processes involved in the uptake and elimination of organic micropollutants in bivalve molluscs     

M. Boryslawskj  A.C. Garrood  J.T. Pearson  D. Woodhead 《Marine environmental research》1985,17(2-4)

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