Showing papers in "Earth and Planetary Science Letters in 1991"

TL;DR: In this paper, the authors present theoretical estimates of the production rates of isotopes of He, Ne and Ar based on available cross-section data, and discuss the implications of these parameters for single and multiple nuclide studies in terms of the erosion models considered.

TL;DR: In this article, a quantitative model has been developed for IAB petrogenesis with the transfer of trace elements from the slab to the mantle wedge being modelled with empirical slab-fluid partition coefficients whilst the mantlewedge to arc-crust transfer is constrained by melt-solid partitioning.

TL;DR: In this paper, the trace element and isotopic constraints for the three OIB end-members suggest a relatively simple model for their origin, where the dominant component in all OIB is ancient recycled basaltic oceanic crust which has been processed through a subduction zone.

TL;DR: In this paper, a Mediterranean Precession-Related Sapropel (MPRS) coding is introduced according to which sapropels are coded after the correlative peak of the precession index as numbered from the Recent.

TL;DR: In this paper, the authors proposed a model whereby carbonated, undersaturated silicate melts crystallizing pargasitic amphibole at depths of ⩾ 90 km, produce a mobile carbonatite melt which can segregate and ascend at very low melt fractions, and undergo decarbonation reactions with refractory lithosphere at 55-65 km depth.

TL;DR: The early Pleistocene to late Pliocene astronomically calibrated time scale of Shackleton et al. as mentioned in this paper is extended to the Miocene/Pliocene boundary by correlating the detailed record of CaCO3 cycles in the Trubi and the lower part of the overlying Narbone Formation (Rossello composite section; Sicily).

TL;DR: In this article, it was shown that very small pressure fluctuations of the order of one bar in the chamber lead to large changes of gas content at the vent, and this decrease acts to increase the fraction of gas lost to the country rock and hence to reduce the gas content of the erupted material.

TL;DR: In this article, the authors used the near bottom ARGO imaging system to visually and acoustically survey the narrow ( < 200 m wide) axial zone of the fast-spreading East Pacific Rise (EPR) along 83 km of its length (9°09′-54′N), and systematically mapped the distribution of hundreds of hydrothermal features relative to other fine-scale volcanic and tectonic features of the ridge crest.

TL;DR: In this article, the Akademik Boris Petrov sample (sample 2πD43) was reported to have the largest gas content so far reported in MOR basalts, which contained, when erupted, 7.56 cm 3 STP g −1 of gas.

TL;DR: In this paper, it was shown that plumes do not provide the ultimate driving force for continental break-up (these come from the plate-scale motions), but the extra gravitational potential that they impose means that they play an important role in determining both where and when continental breakup does occur.

TL;DR: In this paper, major and rare-earth-element (REE) concentrations and U Th Pb, Sm Nd, and Rb Sr isotope systematics are reported for Cenozoic volcanic rocks from northeastern and eastern China.

TL;DR: In this article, the Ferrar magmatic province was identified as a major province of the Gondwana supercontinent, and the major and trace element compositions of these low-Ti CFB's were compared to those of oceanic basalts.

TL;DR: The authors' data show that the Onverwacht and Fig Tree felsic units have distinctly different ages and therefore do not represent a single, tectonically repeated unit as proposed by others, and indicate the existence of still older units, possibly stratigraphically lower and older portions of the greenstone sequence itself, older granitoid intrusive rocks, or bodies of older, unrelated crustal material.

TL;DR: In this paper, the authors show that dilation, or decompaction, of the porous matrix creates a high-porosity boundary layer, beneath an impermeable cap of cooler, solid mantle.

TL;DR: In this paper, mass spectrometric analyses of Nb, Th, REE and other trace elements in Archaean to Tertiary komatiites and basalts were undertaken to test the model of Hofmann et al.

TL;DR: In this article, the authors suggest that mantle plumes control magnetic reversal frequency by the following sequence of events, which increases core cooling by allowing heat to be conducted more rapidly across the core/mantle boundary.

TL;DR: In this paper, mean erosion rates were calculated for the limiting case of steady-state surface exposure to cosmic rays, and minimum exposure ages, for the limited case of no erosion, and the sampling is believed to be sufficient to generalize this result to exposed bedrock in Antarctica.

TL;DR: In this article, Nd and Hf-isotope data for oceanic volcanics and island arc basalts are presented in order to further examine the correlation between the two isotopic systems, determine 176Hf/177Hf of the mantle components as described by Zindler and Hart (1986) [1], and assess the origin of HFSE depletions in calc-alkaline volcanics.

TL;DR: In this paper, the authors identify a depleted, MORB-like composition of the Nuanetsi-N Lebombo basalts as a mixing line between mantle and mantle lithospheric components, and demonstrate that the latter is similar to lamproitic magmas, which appear to have acted as contaminants to the asthenospheric melts.

TL;DR: In this article, an ICP-MS study of the distributions of trace elements (Fe, Ca, Mg, Al, Mn, Cu, Zn, V, As, Cr, Co, Pb, Y, Mo, Ag, Sn, Cd and Be) was carried out to examine the extent to which fluxes of dissolved trace elements emitted from hydrothermal vent-fluids are balanced by the precipitation of associated particulate phases.

TL;DR: The isotopic composition and abundances of He, Ne and Ar have been measured in a sequence of vertically stacked gas reservoirs at Hajduszoboszlo and Ebes, in the Pannonian Basin of Hungary as discussed by the authors.

TL;DR: In this paper, the authors report the Sr, Nd and Pb isotopic compositions of 66 lava flows and dikes spanning the circa 15 Myr subaerial volcanic history of Gran Canaria and of five Miocene through Cretaceous sediment samples from DSDP site 397.

TL;DR: In this article, the Os isotopic compositions of twelve ultramafic and six mafic layer samples from the Ronda Ultramerafic Complex of southern Spain have been determined.

TL;DR: The South Pacific is anomalous in terms of the Sr, Nd, and Pb isotope ratios of its hot spot basalts, a thermally enhanced lithosphere, and possibly a hotter mantle as discussed by the authors.

TL;DR: In this paper, the authors used a reversing axial dipole to explain the sense of equatorial symmetry exhibited by the Matuyama-Brunhes polarity reversal obtained recently from the northern, equatorial and southern latitudes of the Atlantic sector.

TL;DR: In this paper, a fresh suite of MgO-and SiO 2 -rich lavas from the northern termination of the northern Tonga ridge was dredged from one dredge site, station 21, and their major element chemistry appears to be consistent with production of this suite via crystal fractionation.

TL;DR: In this paper, a geodynamic model for the post-Messinian growth of the Apenninic prism is proposed, based on the interpretation of conventional seismic reflection profiles and exploration wells, combined with geologic field studies (biostratigraphy and structural geology).

TL;DR: In this paper, the authors used plagioclase from dykes from the Taoudenni area (Mali) and two lava flows from Morocco to determine an age of around 200 Ma for this body.

TL;DR: The low-field susceptibility of the loess deposits in the Chinese Loess Plateau is due to both paramagnetic and ferromagnetic minerals as mentioned in this paper, which can be seen in the less-to unweathered loess horizons where superparamagnetic contributions which arise from ultrafine magnetite particles, are not as strongly developed as in the heavily weathered palaeosols.

TL;DR: Igneous rocks from the Philippine tectonic plate recovered on Deep Sea Drilling Project Legs 31, 58 and 59 have been analyzed for Sr, Nd and Pb isotope ratios as discussed by the authors.