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Magma composition is interpreted from the composition of igneous rocks exposed at the surface and while they have a wide range of compositions they are ultimately derived by melting in the Earth's mantle or the crust. Those derived from the mantle are dominantly basalts, whereas those from the crust are granites.
The latest stages of the lunar magma ocean (LMO) crystallization led to the formation of ilmenite-bearing cumulates and urKREEP, residual melts enriched in K, rare earth elements (REEs), P, and other incompatible elements. Those highly evolved lithologies had major impacts on the petrogenesis of lunar volcanic rocks and the compositional diversity of post-LMO magmatism resulting from mantle ...
The existence of magma reservoirs beneath the WVF remains contentious, thus we calculated the ascent rates of mantle fluids under two scenarios. (1) Assuming no magma reservoir exists or magma is located at the base of the crust, with the crust thickness in the WVF (30 km) as the ascent distance for mantle fluids.
1 janv. 2015 · Magmas contain dissolved gases-volatiles-when they are at depth in the Earth. When magma ascends to the Earth's surface, the volatiles can no longer remain dissolved because of the decrease of pressure, and this causes the formation and expansion of gas bubbles, creating a magmatic froth that can erupt explosively, depending on the gas content.
1 sept. 2024 · However, for a granitic pluton that crystallized from a single batch of magma, evolution via rapid and large-scale gravitational settling of minerals is hindered given the high viscosity of high-silica felsic magmas (Davis and Acrivos, 1985, Bergantz and Ni, 1999) and the similarity in density of fractionating phases (e.g., feldspar and quartz ...
1 mars 2024 · In turn, the large Nb/Ta fractionation during magma evolution is particularly important for understanding partial melting, melt segregation and crystallization processes of granitic magma. This paper presents a combined study of whole-rock geochemistry and microbeam analysis of titanite, including major and trace elements, U Pb ages and Nd isotopes, for Late Triassic granites in the Sulu orogen.
1 sept. 2012 · While active, a magma chamber acts as a sink for magma from the deeper reservoir, and as a source for magma injections (dykes, sheets, sills) into the surrounding crust and the associated volcano. Some magma chambers, particularly small sill-like chambers during their early stages of development, may be totally molten.
1 mai 2024 · A transient melt-rich layer can form at the top of the lower mantle during late-stage crystallization in a mushy magma ocean when melt percolation dominates. When crystallization exceeds ∼98%, hydrous melts (>25 mol% H 2 O) become buoyant and can percolate into and hydrate the mantle transition zone. Previous. Magma ocean.
1 nov. 2014 · Download: Download full-size image. Fig. 1. The Standard Model of caldera formation. (A) Stably stratified magma chamber forms over thousands of years by crystal settling and upward migration of volatiles. (B) Eruption starts with Plinian activity through a single vent, driven primarily by volatile exsolution.
1 déc. 2019 · Magma from the VEI 3 eruption of 1992 decompressed at a rate of ∼0.0073 MPa/s (∼0.3 m/s), while magma from the VEI 2 1995 eruption record decompression rates of ∼0.0014 MPa/s (∼0.05 m/s). These decompression rates fit within the general trend of mass eruption rate (MER) versus decompression rate based on embayment studies for other volcanoes ( Fig. 14 ).
