 |
 |
Growth and Stabilization of Continental Crust in Circum-Pacific Accretionary Orogens Topical Session 45, GSA Annual Meeting, October 17-21, 2009, Portland, Oregon, USA. http://www.geosociety.org/meetings/2009/ Co-conveners: Christine Siddoway and David Foster Keynote speakers: C. Mark Fanning, Mark Johnston, and Patrice Rey We invite contributions that address the growth and evolution of continental crust during circum-Pacific ocean-continent convergence, including transient extensional, contractional and transcurrent events that affect the overriding plate. Perspectives from diverse disciplines are sought, including geodynamics, tectonics, metamorphism, magmatism and geochemistry/geochronology. Abstracts may be submitted online at http://gsa.confex.com/gsa/2009AM/cfp.epl now and up until the GSA deadline, 11 August 2009. Rationale: Accretionary orogens formed at subduction margins are sites of continental growth attributable to arc magmatism, erosion of the upper plate, and transfer of material from the down-going to the overriding plate. The circum-Pacific regions contain a repository of information about crustal growth by diverse mechanisms. An "accretionary orogen" GSA session will be timely in 2009 due to developments in two subject areas over the past three years. These are 1) isotope geochemistry and geochronology of magmatic/metamorphic belts around the circum-Pacific region that bring into question long-standing interpretations of magmatic arc processes. The recognition of a mantle component in the generation of I-type granites in the Lachlan Orogen signifies that the granites cannot be attributed wholly to fractionation and assimilation. 2) Structural geology and geophysics identify examples of dramatic supra-subduction zone extension, sedimentary infilling, and basin inversion followed by intense contraction events that served to transform primitive oceanic crust with sedimentary cover into continental crust of ordinary thickness. This topical session, devoted to the advances in studies of arc magmatism and of intraplate deformation, will enhance our understanding of the geodynamics of oceanward growth and the fundamental mechanisms responsible for stabilization of continental crust.