نتایج جستجو برای: peridotite
تعداد نتایج: 891 فیلتر نتایج به سال:
Tabular dunites in the Josephine peridotite of southwestern Oregon represent conduits for melt extraction from the upper mantle. The amount of melt trapped within these channels during cooling and exhumation of the peridotite massif was calculated using a mass-balance approach. These calculations suggest that no more than 0·1^0·2 vol. % melt could have been trapped within these dunites after cr...
Plate tectonic processes introduce basaltic crust (as eclogite) into the peridotitic mantle. The proportions of these two sources in mantle melts are poorly understood. Silica-rich melts formed from eclogite react with peridotite, converting it to olivine-free pyroxenite. Partial melts of this hybrid pyroxenite are higher in nickel and silicon but poorer in manganese, calcium, and magnesium tha...
s of 33rd International Geological Congress, 6–14 August 2008, Oslo. Coltorti, M., Bonadiman, C., O’Reilly, S. Y., Griffin, W. L. & Pearson, N. J. 2010. Buoyant ancient continental mantle embedded in oceanic lithospheric (Sal Island, Cape Verde Archipelago). Lithos, doi: 10.1016/j.lithos.2009.11.005. Davies, G. R., Nixon, P. H., Pearson, D. G. & Obata, M. 1993. Tectonic implications of graphiti...
The Trinity peridotite (northern CA) contains numerous lithologic sequences consisting of dunite to harzburgite to spinel lherzolite to plagioclase lherzolite. Previous workers have documented geochemical gradients in these sequences consistent with melt-rock reaction processes occurring around dunites, interpreted to reflect conduits for melt ascent. We have undertaken a study of Li isotope co...
This dissertation discusses the experimental results designed to constrain the processes of MORB generation. The main focus of this study is to investigate the location and the related processes of the transformation boundary from spinel to garnet peridotite facies at subsolidus conditions, because the presence of garnet in melting residues has significant influence to the conclusion drawn from...
Near-solidus Melting of the Shallow Upper Mantle: Partial Melting Experiments on Depleted Peridotite
We present the results of melting experiments on a moderately depleted peridotite composition (DMM1) at 10 kbar and 1250±1390 C. Specially designed experiments demonstrate that liquids extracted into aggregates of vitreous carbon spheres maintained chemical contact with the bulk charge down to melt fractions of 0 02±0 04 and approached equilibrium closely. With increasing melt fraction, SiO2, F...
Subducted Carbonates And Their Role In The Metasomatism Of Mantle Wedges: An Example From California
We investigated calcite veins in two spinel-garnet peridotite xenoliths from the sub-Sierra Nevada mantle. These peridotites represent samples of the lithospheric mantle wedge beneath the Mesozoic California magmatic arc, as indicated by radiogenic isotopic ratios measured on clinopyroxenes separates (Sr/Sr8 Ma= 0.7058-0.7061, Nd/Nd8 Ma= 0.512538-0.512601). Mineral chemistry of the peridotite m...
O are claimed to be pieces of ocean crust and upper mantle that have been thrust up onto continental crust and are now found in mountains, mainly along continental margins.1,2 An ideal ophiolite suite consists from bottom to top of peridotite, gabbro, sheeted dikes, basalt with pillow lavas and sedimentary rocks. The peridotite is considered to be an upper mantle rock, while the remainder of th...
The available experimental data and steady-state calculations make it difficult to explain the M discontinuity beneath both oceans and continents on the basis of the same phase change. The oceanic M discontinuity may be a chemical discontinuity between basalt and peridotite , and a similar chemical discontinuity ma,y thus be expected b�neath the conti nents. Since ayailable experimental data p...
[1] Convergent margin magmas typically have geochemical signatures that include elevated concentrations of large-ion lithophile elements; depleted heavy rare earth elements and high field strength elements; and variously radiogenic Sr, Pb, and Nd isotopic compositions. These have been attributed to the melting of depleted mantle peridotite by the fluxing of fluids or melts derived from subducti...
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