Micro textures of type-II TCIs in CM carbonaceous chondrites

Abstract

We report microtexture of tochilinite-cronstedtite intergrowths (TCIs) in CM chondrites. In QUE97990 and Murchison, less altered CM meteorites, the TCIs showed the texture with thin tochilinite veins inside cronstedtite, suggesting that tochilinite formed after the formation of cronstedtite. In Nogoya, the fibrous TCIs continuously changed to serpentine aggregates. This suggests that fluid compositions had varied during the course of alteration.