Departmental Bulletin Paper 冷却する海洋リソスフェア中の単斜輝石の化学反応と元素拡散
Chemical reaction and diffusion in a clinopyroxene in a cooling oceanic lithosphere

西村, 光史  ,  山本, 順司  ,  石橋, 秀巳

Calcium diffusion profiles in clinopyroxene adjacent to orthopyroxene are calculatednumerically under P-T conditions of a cooling oceanic lithosphere. The compositions oftwo pyroxenes at a contact surface are determined based on a thermodynamic modelassuming instantaneous interfacial equilibrium. The compositional difference betweenthe core and rim of crystals induces the diffusion of cations within the crystals. At a distance of 2000 km from a ridge, the clinopyroxene in the shallower part of theoceanic lithosphere (e.g., 30 km depth) has a high-Ca rim, whereas that in the deeperpart (e.g., 60 km depth) are homogenized by annealing because of lower cooling rate.

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