Showing papers in "Earth and Planetary Science Letters in 1994"

TL;DR: In this paper, a high-resolution oxygen isotope record from giant piston core MD900963 (Maldives area, tropical Indian Ocean) was studied, in which precession-related oscillations in δ18O were particularly well expressed, owing to the superimposition of a local salinity signal on the global ice volume signal.

TL;DR: The conditions under which partial melting of subducting oceanic crust occurs can be determined by combining a partial melting model for basaltic compositions with two-dimensional thermal models of subduction zones as discussed by the authors.

TL;DR: In this article, it was shown that most variations in composition among primitive basalts from the Mariana back-arc trough can be explained by melting mixtures of an NMORB-type mantle source and an H 2O-rich component, provided the degree of melting is positively and approximately linearly correlated with the proportion of the H 2 O-rich components in the mixture.

TL;DR: The oxygen isotopic composition of 76 samples of olivine in spinel, garnet and diamond-facies peridotites, and as syngenetic inclusions within diamond has been determined by laser fluorination (LF) as mentioned in this paper.

TL;DR: In this article, a method for detecting multiple components in a population of analytical observations for zircon and other ages is presented, which uses an approach known as mixture modeling, in order to estimate the most likely ages, proportions and number of distinct components.

TL;DR: In this article, the authors measured the anisotropy of a natural 40Ar diffusion gradient, parallel and perpendicular to a single euhedral muscovite phenocryst.

TL;DR: Pollen and lake records from West Asia (Western Tibet and Rajasthan), East Africa (Ethiopia) and West Africa (Western Sahara, Sahel and subequatorial Africa) were selected on the basis of chronological control, sensitivity of both site and environmental indicators to climate change, the continuity of the record, and interdisciplinary control of the palaeoclimatic interpretation.

TL;DR: A detailed Ar Ar study of the Parana-Etendeka continental flood basalts (CFB) has been undertaken using laser spot analysis as discussed by the authors, which provides information not only on the age of the samples but also on the variability of the non-radiogenic Ar component and state of alteration.

TL;DR: In this article, the authors measured rutile/aqueous fluid partition coefficients (Drutfl) for Nb, Ta, Hf, Zr, U and Th at 1-2 GPa and 900-1100°C and concluded that only small amounts of residual rutiles are required to prevent HFSE enrichment of the mantle wedge by fluids derived from either pelagic sediments or the basaltic portion of the subducting slab.

TL;DR: In this article, a model of the melting under oceanic spreading centers is presented, which reproduces the observed variations with spreading rate of crustal thickness and the main geochemical changes observed in basalts.

TL;DR: In this article, the authors measured the 14C difference between the atmosphere and the North Atlantic surface during a prominent climatic period of the last deglaciation, the Younger Dryas event (YD).

TL;DR: The influence of surface topography on the form of steady-state isotherms during erosion-driven denudation is investigated in this paper, where it is shown that, for realistic geothermal gradients and a topography amplitude of H = 3 km and wavelength of w = 20 km, the 100°C isotherm may be perturbed to an amplitude of 1000 m/Ma.

TL;DR: In this paper, the first detailed study of oxygen isotope ratios in zircon has been carried out and the results show that high-magnetism zircons are up to 2 ǫ lower in δ18O than low magnetism zirons from the same rock, consistent with the hypothesis that they represent nearly pristine samples of the parent magma.

TL;DR: In this article, a new quantitative approach is proposed for estimating palaeoprecipitation across the Chinese Loess Plateau, where the concentration of ferrimagnetic iron oxide minerals in nine modern soil types (represented by 37 individual soil profiles) is strongly correlated with this contemporary rainfall gradient.

TL;DR: In this paper, the first measurement of bubble nucleation in hydrated rhyolitic melts in response to pressure release was reported, and the results demonstrate the importance of heterogeneous nucleation.

TL;DR: In this paper, spinel peridotite, pyroxenite and glimmerite xenoliths from Eocene minette dikes from the Highwood Mountains and Eagle Buttes, Montana, U.S.A., reveal a prolonged, yet episodic, history of melt removal and addition within the shallow lithospheric mantle of the Archean Wyoming Craton or its modified margin.

TL;DR: The Pb/Pb model ages for these phosphates range from 4.563 to 4.502 Ga, with an analytical precision of 106 y and the UPb system is apparently concordant as discussed by the authors.

TL;DR: In this article, the authors derived an activation energy of 2.44(+2.85/−1.26) × 105 J/mol and a frequency factor of 3.2 × 107 cm2/s, taking account of uncertainties of ±15°C in the temperatures and of ±20% in the diffusion coefficients.

TL;DR: In this paper, phase equilibria in a composition similar to that of average upper continental crust, over the pressure interval 6-24 GPa, have been tested via an experimental study of phase equilibrium, with major roles played by K-hollandite, garnet, Na-clinopyroxene and stishovite.

TL;DR: In this paper, 60 four size fractions of zircon, monazite, xenotime and titanite were used to temporally and spatially constrain left-lateral movements in the Red River shear zone between the depths of 15 and 20 km.

TL;DR: In this article, the authors used the 4°Ar-39Ar data for Pagalu basalts, combined with published K-Ar ages for Principe and S~to TomE, indicate that all three volcanic islands have been active in the past 5 Ma.

TL;DR: Geochemical and Nd isotopic studies are reported for widespread Late Proterozoic (approximately 800 Ma) mafic dyke swarms and volcanics in central-southern Australia as discussed by the authors.

TL;DR: A 6-year-long (1978-1984) δ 18 O and δ 13 C record from a Great Barrier Reef (Pandora Reef) Porites lutea coral based on near-weekly sample intervals is presented in this paper.

TL;DR: In this paper, the authors combine eigen analysis and parameter estimation techniques for a newly constituted, more versatile fold test, which is automatic, requiring no assumptions about the polarity or distribution of data, and gives confidence limits on the degree of unfolding required to produce the tightest grouping of data.

TL;DR: In this paper, Fe Mossbauer spectroscopy was employed to estimate Fe3+ΣFe ratios and the Fe2O3 content of 28 well characterized pyroxenite and peridotite xenoliths from central France, southeastern Australia, northern Tanzania, southern Africa and Siberia.

TL;DR: Isotopic patterns of Nd, Sr, and Pb are remarkably coherent along the super-fast spreading portion of the East Pacific Rise from 13°S to 23°S as discussed by the authors.

TL;DR: In this article, the boron content and δ11B values of 40 oceanic basalt glasses (N-MORB, E-MorB, BABB, OIB and OIB) were determined at ±10% relative, with values ranging from 0.34 to 0.74 ppm.

TL;DR: In this article, a suite of well-preserved sedimentary carbonates from Lower Cambrian strata of the Lena River region of Siberia were used to identify potentially unaltered samples for Sr isotopic measurements.

TL;DR: In this article, two carbonate-dominated bulk compositions (fertile and refractory with respect to Al content and Fe Mg ratio) were used to approximate carbonatite melt compositions in equilibrium with oceanic and subcontinental lithospheric peridotites.