Serpentine Stability to Mantle Depths and Subduction-Related Magmatism

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Science  12 May 1995:
Vol. 268, Issue 5212, pp. 858-861
DOI: 10.1126/science.268.5212.858


Results of high-pressure experiments on samples of hydrated mantle rocks show that the serpentine mineral antigorite is stable to ∼720°C at 2 gigapascals, to ∼690°C at 3 gigapascals, and to ∼620°C at 5 gigapascals. The breakdown of antigorite to forsterite plus enstatite under these conditions produces 13 percent H2O by weight to depths of 150 to 200 kilometers in subduction zones. This H2O is in an ideal position for ascent into the hotter, overlying mantle where it can cause partial melting in the source region for calc-alkaline magmas at a depth of 100 to 130 kilometers and a temperature of ∼1300°C. The breakdown of antigorite in hydrated mantle produces an order of magnitude more H2O than does the dehydration of altered oceanic crust.

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