Subduction factory 1. Theoretical mineralogy, densities, seismic wave speeds, and H2O contents
Article first published online: 18 JAN 2003
Copyright 2003 by the American Geophysical Union.
Journal of Geophysical Research: Solid Earth (1978–2012)
Volume 108, Issue B1, January 2003
How to Cite
2003), Subduction factory 1. Theoretical mineralogy, densities, seismic wave speeds, and H2O contents, J. Geophys. Res., 108, 2029, doi:10.1029/2001JB001127, B1., , and (
- Issue published online: 18 JAN 2003
- Article first published online: 18 JAN 2003
- Manuscript Accepted: 18 JUL 2002
- Manuscript Revised: 11 JUN 2002
- Manuscript Received: 27 AUG 2001
- seismic velocities;
- mineral physics;
 We present a new compilation of physical properties of minerals relevant to subduction zones and new phase diagrams for mid-ocean ridge basalt, lherzolite, depleted lherzolite, harzburgite, and serpentinite. We use these data to calculate H2O content, density and seismic wave speeds of subduction zone rocks. These calculations provide a new basis for evaluating the subduction factory, including (1) the presence of hydrous phases and the distribution of H2O within a subduction zone; (2) the densification of the subducting slab and resultant effects on measured gravity and slab shape; and (3) the variations in seismic wave speeds resulting from thermal and metamorphic processes at depth. In considering specific examples, we find that for ocean basins worldwide the lower oceanic crust is partially hydrated (<1.3 wt % H2O), and the uppermost mantle ranges from unhydrated to ∼20% serpentinized (∼2.4 wt % H2O). Anhydrous eclogite cannot be distinguished from harzburgite on the basis of wave speeds, but its ∼6% greater density may render it detectable through gravity measurements. Subducted hydrous crust in cold slabs can persist to several gigapascals at seismic velocities that are several percent slower than the surrounding mantle. Seismic velocities and VP/VS ratios indicate that mantle wedges locally reach 60–80% hydration.