Structure of the Mantle Wedge and Volcanic Activities in the Island Arcs
- Murli H. Manghnani and
- Yasuhiko Syono
Published Online: 21 MAR 2013
Copyright © 1987 by Terra Scientific Publishing Company (TERRAPUB), Tokyo.
High-Pressure Research in Mineral Physics: A Volume in Honor of Syun-iti Akimoto
How to Cite
Ida, Y. (1987) Structure of the Mantle Wedge and Volcanic Activities in the Island Arcs, in High-Pressure Research in Mineral Physics: A Volume in Honor of Syun-iti Akimoto (eds M. H. Manghnani and Y. Syono), American Geophysical Union, Washington, D. C.. doi: 10.1029/GM039p0473
- Published Online: 21 MAR 2013
- Published Print: 1 JAN 1987
Print ISBN: 9780875900667
Online ISBN: 9781118664124
- Mineralogy and Crystal Chemistry;
- Phase transformations;
- High Pressure-High Temperature Research
The origin of arc volcanism has not yet been sufficiently investigated to yield a reasonable model of the physical and chemical processes of such volcanism. Seismological observations have revealed that a hot mantle wedge is adjacent to the cool subducting slab in island arcs. Volcanic material and heat flow are largely concentrated near the volcanic front (i.e., the seaward boundary of the volcanic belt) and asymmetrically distributed across the front. There is a systematic variation in the chemical composition of volcanic rocks across the arc, such as the enrichment of incompatible elements in the backarc. All of these observations can not be explained by an interpretation of arc volcanism in which convection is mechanically induced by the slab motion. A mantle diapir containing magma does not meet both the kinematic requirement of a sufficiently high ascending speed and the thermal requirement for sufficient heating of magma. A new model with an ascending continuous flow of mantle material beneath the volcanic belt is proposed to explain the observations mentioned above and the mechanism of magma generation. According to this model, incoming hot material follows the ascending flow and constitutes an upwelling current from the deeper mantle. The subducting slab supplies voltaile components that facilitate partial melting. The convection is maintained by the high temperature state of the incoming flow and by internal partial melting. The flow that has passed the top of the mantle moves out toward the backarc. This outgoing flow is gradually cooled so that the magma partly solidifies. In this way, incompatible elements are concentrated in the backarc.