交代作用の伝播機構 (故坪井誠太郎先生追悼講演会要旨)

概要

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After a brief retrospect on the developement since middle 1950's of studies on metasomatic process, the paper deals with some recent results of experiments aimed to observe the mechanism of propagation of the metasomatic material tranfer in silicates. It is shown that "relict" minerals often participate in the metasomatic reaction. The situation was demonstrated in natural pyroxene skarn transforming into garnet skarn, by a iteration experiments of alkali feldspars and of rhyolitic rock. It is pointed out that the glass phase in rhyolite remained as glass at experimental temperatures as low as 200°300°C and change its composition by Na-K exchange reaction with aqueous solution.<BR>Another experimets showed that the metasomatic reaction propagate to the interior of the crystal through the infiltration of the fluide through cleavage and dislocation lines. The observed reaction rate is about 1000 times greater than that estimated according to a model in which the exotic element is fixed on the surface layer by ion exchange and then by solid state diffusion in the crystal.
公益社団法人東京地学協会の論文