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Melt Composition (melt + composition)

Distribution by Scientific Domains
Physics and Astronomy75%

Selected Abstracts

Valence state partitioning of V between pyroxene-melt: Effects of pyroxene and melt composition, and direct determination of V valence states by XANES.

METEORITICS & PLANETARY SCIENCE, Issue 8 2008
Application to Martian basalt QUE 94201 composition
This increase is due to the increased availability of elements for coupled substitution with the V3+ or V4+ ions, namely A1 and Na. For this bulk composition, both A1 and Na are higher in concentration in augite compared with pigeonite; therefore more V can enter augite than pigeonite. Direct valence state determination by XANES shows that the V3+ and V4+ are the main V species in the melt at fO2 conditions of IW-1 to IW+3.5, whereas pyroxene grains at IW-1, IW, and IW+1 contain mostly V3+. This confirms the idea that V3+ is more compatible in pyroxene than V4+. The XANES data also indicates that a small percentage of V2+ may exist in melt and pyroxene at IW-1. The similar valence of V in glass and pyroxene at IW-1 suggests that V2+ and V3+ may have similar compatibilities in pyroxene. [source]

Growth of CuInS2 crystals from melt and their properties

PHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 8 2006
N. Satoh
Abstract CuInS2 crystals are grown from the melt with the typical compositions which are stoichiometric, In2S3 and Cu2S excess ones and the effect of the melt composition on the melt growth is examined. Large grain size crystals are grown for the melt compositions except the case of Cu2S excess one. It is found that a small amount of CuIn5S8 is precipitated in In2S3 excess crystals by forming thin film layers in the bulk. From electrical conductivity and photo-luminescence (PL) spectra of the grown crystals, predominant native point defects characterizing their semi-conducting properties are discussed. As a result, it is suggested that native vacancy and the interstitial Cu play an important roles and a tentative band-diagram is proposed. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

The Cornubian Batholith: an Example of Magmatic Fractionation on a Crustal Scale

RESOURCE GEOLOGY, Issue 3 2006
Bruce W. Chappell
Abstract. The Cornubian Batholith comprises six major and several smaller bodies of S-type granite in southwestern England. These late-Variscan granites comprise two-mica granites, and much less abundant Li-mica granites that are restricted to one of the major bodies (St Austell) and smaller bodies. Some of these intrusive rocks are associated with major Sn mineralization. This paper is concerned with the geochemistry of the two-mica granites, which are felsic, strongly peraluminous, and have a high total alkali content and low Na:K. Rocks with very similar compositions to these granites occur elsewhere, including the Variscan granites of continental Europe, and in southeastern Australia. In detail all of the major plutons of this batholith have distinctive compositions, except for Bodmin Moor and Carnmenellis which cannot be discriminated from each other compositionally. A comparison with experimental data shows that the granites attained their major element composition under conditions of crystal-liquid equilibrium, with the final melt being saturated in H2O, at temperatures close to 770d,C and pressures about 50 MPa. That temperature estimate is in good agreement with values obtained from zircon saturation thermometry. The specific minimum-temperature composition excludes the possibility of widespread transfer of elements during hydrothermal alteration. Minor elements that are relatively very abundant are Li, B, Cs and U, while F, Ga, Ge, Rb, Sn, Ta, W and Tl are quite abundant and P is high for felsic rocks. Sr, Ba, and the trace transition metals Sc to Zn, are low, but not as low as they commonly are in very felsic granites. These trace element abundances, and the EL2O-saturation, resulted from the fractional crystallization of a melt derived by the partial melting of feldspathic greywackes in the crust. The Cornubian granites have compositions very similar to the more felsic rocks of the Koetong Suite of southeastern Australia, where a full range of granites formed at the various stages of magmatic fractionation postulated for the Cornubian granites, can be observed. The operation of fractional crystallization in the Cornubian granites is confirmed by the high P abundances in the feldspars, with P contents of the plagioclase crystals correlating with Ab-con-tent Most of the granites represent solidified melt compositions but within the Dartmoor pluton there is a significant component of granites that are cumulative, shown by their higher Ca contents. The Cornubian plutons define areas of high heat flow, of a magnitude which requires that fractionated magmas were transported laterally from their sources and concentrated in the exposed plutons. The generation of these granite plutons therefore involved magmatic fractionation during the stages of partial melting, removal of unmelted material from that melt, and fractional crystallization. During the later stages of those processes, movement of those magmas occurred on a crustal scale. [source]