The influence of H2O on mantle wedge melting

被引：400

作者：

Grove, Timothy L. ^{[1
]}

Chatterjee, Nilanjan ^{[1
]}

Parman, Stephen W. ^{[1
]}

Medard, Etienne ^{[1
]}

机构：

[1] MIT, Dept Earth Atmospher & Planetary Sci, Cambridge, MA 02139 USA

来源：

EARTH AND PLANETARY SCIENCE LETTERS | 2006年 / 249卷 / 1-2期

基金：

美国国家科学基金会;

关键词：

subduction zone melting; vapor saturated peridotite melting; mantle wedge melting; arc magma generation; water in magmas;

D O I：

10.1016/j.epsl.2006.06.043

中图分类号：

P3 [地球物理学]; P59 [地球化学];

学科分类号：

0708 ; 070902 ;

摘要：

The solidus and near-solidus melting behavior of a primitive undepleted peridotite composition has been determined over a pressure range of 1.2-3.2 GPa at H2O saturated conditions. Vapor-saturated melting (melting in the presence of an H2O-rich supercritical fluid) begins at 940 degrees C at 1.2 GPa and the solidus temperature decreases continuously to 860 degrees C at 2 GPa and 800 degrees C at 3.2 GPa. This solidus is similar to the lower temperature results of previous investigations. The temperature discrepancies found in earlier studies could be a result of short run times used in several studies and the slower kinetics of olivine vs. diopside melting. The solidus phases include olivine, orthopyroxene, high-Ca clinopyroxene and Al-rich phases that change from spinel + amphibole (1.2-1.8 GPa) to spinel + chlorite over the pressure range of 2-2.4 GPa. Above 2.4 GPa garnet + chlorite + ilmenite are present along with olivine + orthopyroxene + clinopyroxene on the solidus. Chlorite may be a stable phase at the base of the mantle wedge and it may play a role in the onset of flux melting. Ilmenite might play a role in the development of HFSE depletions in are magmas, Flux melting of the mantle wedge above the subducting oceanic lithosphere begins when an H2O-rich component (either fluid or melt) released from the stab ascends within the overlying mantle. As it ascends into the mantle wedge the H2O triggers melting at the vapor-saturated solidus at a depth shallower than the wedge-slab interface. Melting continues as the melt ascends into shallower, hotter overlying mantle. Melting in this part of the wedge occurs at vapor-undersaturated conditions because the H2O content of the melt is continually diluted as the melt ascends through the wedge, dissolving and re-equilibrating with shallower, hotter mantle. Final equilibration with the mantle wedge occurs at shallow depths near the top of the wedge. A model of this process is developed using the vapor-saturated phase relations as a starting point. (c) 2006 Elsevier B.V All rights reserved.

引用

页码：74 / 89

页数：16

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