Geology

Alpine Growth Spurts

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Science  09 Apr 2010:
Vol. 328, Issue 5975, pp. 141
DOI: 10.1126/science.328.5975.141-d

Traditionally, the formation of metamorphic rock was thought to occur slowly and steadily, driven by the gradual rates of tectonics or conductive heat flow. However, recent research has shown that more rapid transformation is possible when fluid movement through the crust is involved. Pollington and Baxter show that this probably occurred in the Austrian Alps, where metamorphism broadly reflects gradual continental collision and tectonic exhumation of deep seated rocks. The authors used the Sm-Nd isotopic system to date garnets from old cores to young rims, with improved accuracy. The garnets overall grew during about 8 million years, but the individual dates show that most of the growth actually occurred during two short pulses. The first, which may have lasted less than a few hundred thousand years, seems to reflect the infiltration of fluids during the beginning of exhumation.

Earth Planet. Sci. Lett. 293, 63 (2010).

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