Visualisation and quantification of CV chondrite petrography using micro-tomography

Micro-computed tomography is a non-destructive technique that allows the study of 3D meteorite petrography. The technique produces a unique and instructive visualisation of the meteorite for quantifying its components. We studied the overall petrography of the two CV chondrites Allende and Mokoia to constrain their formation histories. A set of movies and stereographic images detail the 3D petrography. Component modal abundances agree with previous reports and modal abundance differences between Allende and Mokoia support the chondrule-matrix complementarity and that chondrules and matrix formed from the same chemical reservoir. We identified two types of chondrules, a normal type and one where a normal type I or II chondrule is almost completely encapsulated by an opaque-rich layer. This layer was probably acquired during a late stage condensation process. The appearance of opaques in chondrules and matrix is different, not supporting a genetic relationships between these. Low abundances of compound chondrules (1.75 vol% in Allende and 2.50 vol% in Mokoia) indicate low chondrule densities and/or low relative component velocities in chondrule formation regions. Porosities on a scale <10-20 mu m allowed for only local aqueous alteration processes on the meteorite parent bodies. (c) 2012 Elsevier Ltd. All rights reserved.