Tuesday, April 07, 2009

Cyclicity in Cordilleran orogenic systems

Peter DeCelles and colleagues from the UA Geosciences Dept have a recent paper in Nature Geoscience on cyclicity in Cordilleran orogenic systems. As a former tectonics geek before becoming a full time paper pusher, I found this an intriguing explanation for some problematic issues.

A key element of their findings is that "the western American Cordilleras display a 25–50 million year cycle of linked upper-plate processes. In a typical cycle, as the two plates converge and a magmatic arc forms, most of the continental crust shortens by thrusting behind the arc, whereas the lowermost continental lithosphere is shoved beneath the arc — a process that fuels episodic high-flux magmatism in the arc and simultaneously generates dense melt residues. On reaching a critical mass, these residues sink into the mantle, creating space beneath the arc and setting the stage for renewal of the cycle. This alternative model explains key features of Cordilleran systems, such as cyclical trends in the flux and composition of magma supplied to the upper plate, and the foundering of arc roots."

Ref: Nature Geoscience 2, 251 - 257 (2009)
Published online: 15 March 2009 | doi:10.1038/ngeo469

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