نتایج جستجو برای: earth mantle
تعداد نتایج: 108664 فیلتر نتایج به سال:
The earth dynamic system is one of the key scientific questions on the earth science. The thermodynamic behavior and gravity force of the earth and the rheology nature of the mantle prove that mantle convection is the main power source leading the lithosphere to break and move. Yet the directivity of both the structures in the crust and plate movement reminds of the earth rotation. Here we demo...
[1] Reconstructing the thermal history of the Earth, consistent with the low concentration of heat-producing elements in convecting mantle as well as with modest secular cooling required by geological records, has been a major challenge in geophysics and geochemistry. By developing the self-consistent energetics of plate-tectonic mantle convection, we show that the low Urey ratio of convecting ...
The possibility of a hidden geochemical reservoir in the deep mantle has long been debated in geophysics and geochemistry, because of its bearings on the structure of the core–mantle boundary region, the origin of hotspots, the style of mantle convection, the history of the geomagnetic field, and the thermal evolution of Earth. The presence of such hidden reservoir, however, may invalidate exis...
Experimental metal-silicate partitioning data for Ni, Co, V, Cr, Nb, Mn, Si and W were used to investigate the geochemical consequences of a range of models for accretion and core formation on Earth. The starting assumptions were chondritic ratios of refractory elements in the Earth and the segregation of metal at the bottom of a magma ocean, which deepened as the planet grew and which had, at ...
New measurements of Nd/Nd in kimberlites, carbonatites, komatiites, ocean island basalts from Pitcairn, and mid-ocean ridge basalts from the Pacific and Indian Oceans show no deviation from the terrestrial Nd standard within an external reproducibility of 8 ppm. Measurements of mafic rocks from Isua Greenland confirm previous discoveries of an excess of between 0 and 17 ppm in the Nd/Nd of thes...
Introduction. Diverse origins of terrestrial planet atmospheres are inferred from differences in the noble gas abundances and isotope ratios observed on Venus, Earth, and Mars [e.g., 1, 2]. Models for the origin of terrestrial atmospheres typically require an intricate sequence of events, including substantial loss and isotopic fractionation of solar nebula gases, outgassed mantle volatiles, an...
Starting with Kelvin there have been many controversies and paradoxes associated with the evolution of the Earth. These are not faith-based controversies, in the ordinary sense; they are based on calculations and assumptions which are a form of faith . Present-day heat flow is determined by the amount and distribution of radioactive elements, their secular decline with time, the delay between h...
We have previously presented a model for the distribution and transport of rare gases within the Earth [1,2,3,4] which explains the available observational data for mantle He, Ne, Ar, and Xe isotope compositions and provides specific prdctions regarding the rare gas isotopic compositions of the lower mantle, interactions between rare gas reservoirs, and mantle rare gas concentrations. Here we d...
We investigate the influence on mantle convection of the negative Clapeyron slope ringwoodite to perovskite and ferro-periclase mantle phase transition, which is correlated with the seismic discontinuity at 660 km depth. In particular, we focus on understanding the influence of the magnitude of the Clapeyron slope (as measured by the Phase Buoyancy parameter, P ) and the vigour of convection (a...
Based on a pyrolitic compositional model, the lower mantle is mainly made of ferropericlase, aluminous silicate perovskite, and calcium perovskite. Silicate perovskite transforms into silicate post-perovskite structure just above the core-mantle region, the D" layer. The existence of iron in the lower-mantle minerals can affect a broad spectrum of the minerals’ physical and chemical properties....
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