Very high-pressure orogenic garnet peridotites

doi:10.1073/pnas.0607300104

Very high-pressure orogenic garnet peridotites

Department of Geological and Environmental Sciences, Stanford University, Stanford, CA 94305

Edited by Russell J. Hemley, Carnegie Institution of Washington, Washington, DC, and approved January 4, 2007 (received for review August 23, 2006)

Abstract

Mantle-derived garnet peridotites are a minor component in many very high-pressure metamorphic terranes that formed during continental subduction and collision. Some of these mantle rocks contain trace amounts of zircon and micrometer-sized inclusions. The constituent minerals exhibit pre- and postsubduction microstructures, including polymorphic transformation and mineral exsolution. Experimental, mineralogical, petrochemical, and geochronological characterizations using novel techniques with high spatial, temporal, and energy resolutions are resulting in unexpected discoveries of new phases, providing better constraints on deep mantle processes.

Footnotes

*To whom correspondence should be addressed. E-mail: liou{at}pangea.stanford.edu
Author contributions: J.G.L. and R.Y.Z. designed research; J.G.L. and R.Y.Z. performed research; W.G.E. analyzed data; and J.G.L., R.Y.Z., and W.G.E. wrote the paper.
The authors declare no conflict of interest.
This article is a PNAS Direct Submission.
Abbreviations:

DHMS,

dense hydrous magnesian silicates;

P–T,

pressure–temperature;

REE,

rare earth element;

SHRIMP,

sensitive high-resolution ion microprobe;

TEM,

transmission electron microscopy;

VHP,

very high pressure.