In situ observation of the formation of 10 A phase from talc + H(2)O at mantle pressures and temperatures

Development of an x-ray-transparent capsule that is suitable for water-saturated experiments has allowed the high-pressure and high-temperature synthesis of 10 angstrom phase from talc + H(2)O to be observed in situ in a multianvil apparatus with synchrotron radiation. The reaction talc + H(2)O = 10 angstrom phase was observed within 20 minutes at 6 gigapascals and 500 degrees C. The higher pressure vapor-absent reaction talc = 10 angstrom phase + enstatite + coesite was also observed. The 10 angstrom phase is therefore a good candidate for transporting water into Earth's mantle at subduction zones. The in situ technique may allow the hydration of other high-pressure mantle phases to be observed under dynamic conditions.

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