Abstract
Since the first discovery of coesite (Chopin, 1984; Smith, 1984) and microdiamond (Sobolev & Shatsky, 1990) within eclogite-bearing metamorphic belts, extensive progress has been achieved in understanding the origin of ultrahigh-pressure metamorphic (UHPM) rocks in the context of global tectonics operating through continental subduction, collision, exhumation, mantlelithospheric slab interactions, and geochemical recycling of subducted/exhumed rocks. Comprehensive review articles and special issues related to UHP metamorphism and plate tectonics are published almost every year (Ernst & Liou, 2000, 2008; Chopin, 2003; Liou et al., 2004; Green, 2005; Ernst et al., 2007; Zhang et al., 2007; Guillot et al., 2008; Liou et al., 2009a; Beltrando et al., 2010).
They provide valuable summaries of existing knowledge, outline future directions, and discuss controversial concepts. These papers also summarized recent progress in experimental determination of PT stability fields of new phases, phase transformations of those minerals which were known before to be stable only at shallow depths of the continental crust, and they reported that the exsolution products of UHPM minerals indicate that continental rocks were subducted to depths exceeding 100250 km.
Extensive research in UHP metamorphic rocks led to new constraints and the improvement of many geotectonic models developed for very deep subduction of continental rocks and their exhumation within many well-known orogenic belts. Numerical geodynamic modeling of subduction and exhumation became a powerful tool for understanding mantle dynamics and global continental subduction (Gerya, 2010).