Dehydration-melting of solid amphibolite at 10 kbar: Textural development, liquid interconnectivity and applications to the segregation of magmas

1991 ◽  
Vol 44 (3-4) ◽  
pp. 151-179 ◽  
Author(s):  
M. B. Wolf ◽  
P. J. Wyllie
Keyword(s):  
Dehydration Melting ◽  
Textural Development

Dehydration melting at the top of the lower mantle

Science ◽  
2014 ◽  
Vol 344 (6189) ◽  
pp. 1265-1268 ◽  
Author(s):  
B. Schmandt ◽  
S. D. Jacobsen ◽  
T. W. Becker ◽  
Z. Liu ◽  
K. G. Dueker
Keyword(s):  
Lower Mantle ◽  
Dehydration Melting

Textural development in sulfide-matrix ore breccias in the Voisey's Bay Ni-Cu-Co deposit, Labrador, Canada

2017 ◽  
Vol 90 ◽  
pp. 414-438 ◽  
Author(s):  
Stephen J. Barnes ◽  
Margaux Le Vaillant ◽  
Peter C. Lightfoot
Keyword(s):  
Textural Development

Dynamic model of dehydration melting motivated by a natural analogue: applications to the Ivrea–Verbano zone, northern Italy

1996 ◽  
Vol 87 (1-2) ◽  
pp. 23-31 ◽  
Author(s):  
Scott A. Barboza ◽  
George W. Bergantz
Keyword(s):  
Numerical Model ◽  
Mixture Theory ◽  
Mafic Magma ◽  
Northern Italy ◽  
Porous Media Flow ◽  
Theory Approach ◽  
Dehydration Melting ◽  
Porous Flow ◽  
Crustal Rocks ◽  
Switching Functions

ABSTRACT:Dehydration melting of crustal rocks may commonly occur in response to the intrusion of mafic magma in the mid- or lower crust. However, the relative importance of melt buoyancy, shear or dyking in melt generation and extraction under geologically relevant conditions is not well understood. A numerical model of the partial melting of a metapelite is presented and the model results are compared with the Ivrea-Verbano Zone in northern Italy. The numerical model uses the mixture theory approach to modelling simultaneous convection and phase change and includes special ramping and switching functions to accommodate the rheology of crystal-melt mixtures in accordance with the results of deformation experiments. The model explicitly includes both porous media flow and thermally and compositionally driven bulk convection of a restitecharged melt mass. A range of melt viscosity and critical melt fraction models is considered. General agreement was found between predicted positions of isopleths and those from the Ivrea-Verbano Zone. Maximum melt velocities in the region of porous flow are found to be 1 × 10−7 and 1 × 10−1m per year in the region of viscous flow. The results indicate that melt buoyancy alone may not be a sufficient agent for melt extraction and that extensive, vigorous convection of partially molten rocks above mafic bodies is unlikely, in accord with direct geological examples.

scholarly journals Magmatic evolution and textural development of the 1739 CE Pietre Cotte lava flow, Vulcano, Italy

2019 ◽  
Vol 372 ◽  
pp. 1-23 ◽  
Author(s):  
Liam A. Bullock ◽  
Ralf Gertisser ◽  
Brian O'Driscoll ◽  
Sophie Harland
Keyword(s):  
Lava Flow ◽  
Magmatic Evolution ◽  
Textural Development

scholarly journals Fertility of crustal rocks during anatexis

1996 ◽  
Vol 87 (1-2) ◽  
pp. 1-10 ◽  
Author(s):  
Alan Bruce Thompson
Keyword(s):  
Experimental Investigations ◽  
Crustal Rock ◽  
Dehydration Melting ◽  
Specific Pressure ◽  
Crustal Rocks ◽  
Rock Types ◽  
Increasing Temperature ◽  
Low Pressures ◽  
Kbar Pressure ◽  
Melting Relations

ABSTRACT:After many years of systematic experimental investigations, it is now possible to quantify the conditions for optimum fertility to melt production of most common crustal rock types as functions of temperature and to about 30 kbar pressure. Quartzo-feldspathic melting produces steady increases in melt proportion with increasing temperature. The exact melt fraction depends on the mineral mode relative to quartz-feldspar eutectics and the temperatures of mica dehydration melting reactions. Mica melting consumes SiO2 from residual quartz during the formation of refractory Al2SiO5, orthopyroxene, garnet or cordierite.A simple graphical interpretation of experimental results allows a deduction of the proportions of mica and feldspar leading to optimum fertility. In effect, the mica dehydration melting reactions, at specific pressure and are superimposed on quartz-feldspar melting relations projected onto Ab-An-Or. Fertility to melt production varies with the mica to feldspar ratio and pressure. Pelites are more fertile than psammites at low pressures (e.g. 5 kbar), especially if they contain An40 to An50 plagioclase. At higher pressure (e.g. 10-20 kbar) and for rocks containing albitic plagioclase, psammites are more fertile than pelites. For a typical pelite (e.g. with An25 at 20 kbar), the cotectic with muscovite lies at higher (≍·) and XAb (≍0·42) than with biotite :≍0·35; XAb(≍·), thus dehydration melting of muscovite requires 10% more plagioclase for fertility than does biotite.The first melts from dehydration melting of muscovite (with Plg + Qtz) are more sodic and form at lower temperatures than the first melts from Bio + Plg + Qtz. With increasing pressure, to at least 30 kbar, granite minimum and mica dehydration melts become more sodic. This indicates that of such melts is greater than 0·3.

Reactive bulk assimilation: A model for crust-mantle mixing in silicic magmas

Geology ◽  
2005 ◽  
Vol 33 (8) ◽  
pp. 681-684 ◽  
Author(s):  
James S. Beard ◽  
Paul C. Ragland ◽  
Maria Luisa Crawford
Keyword(s):  
Dehydration Melting ◽  
Crustal Rocks ◽  
Host Magma ◽  
Ti Oxides ◽  
Energy Penalty ◽  
Magma Crystallization ◽  
Hydrous Melt ◽  
Silicic Magmas ◽  
Solid Form ◽  
Hydrous Magma

Abstract Bulk assimilation of small (millimeters to ∼1 km) fragments of crust—driven and (ultimately) masked by reactions during xenolith melting and magma crystallization—is an important mechanism for crust-mantle mixing. Xenoliths containing mica or amphibole undergo dehydration melting when incorporated into a host magma, yielding mainly plagioclase, pyroxene, Fe-Ti oxides, and hydrous melt. The xenolith is physically compromised by partial melting and begins to disintegrate; xenolithic melt and crystals are mixed into the host magma. Xenocrystic zircon is liberated at this stage. The cryptic character of assimilation is greatly enhanced in any hydrous magma by hydration crystallization reactions (the reverse of dehydration melting). All pyroxenes and oxides (phenocrysts, xenocrysts, or crystals having a hybrid signature) will be subject to these reactions, producing feldspars, amphiboles, and micas that incorporate material from several sources, a particularly effective mixing mechanism. Implicit in the model is a reduced energy penalty for bulk assimilation—much of the assimilant remains in solid form—compared to melt-assimilation models. A large role for bulk assimilation supports stoping as a credible mechanism for the ascent of magmas. While the assimilation of low-density crust and concomitant fractionation provide the isostatic impetus for ascent, the wholesale incorporation and processing of crustal rocks in the magma chamber helps create the room for ascent.

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