Crystallinity, recrystallization, equilibrium, and metamorphism in chondrites
Abstract
The history of the controversial concept of thermal equilibration in chondritic meteorites is reviewed. The physical properties of four H-group chondrites are discussed in order to illustrate the difficulties of classifying chondrites in petrographic types. Analysis of the ultrathin sections of the Allegan (H5) chondrite showed that even apparently 'homogeneous' chondrites did not undergo post-accretionary, secondary recrystallization or equilibration. Analysis of individual chondrules from Allegan (H5), Ochansk (H4) Tieschitz (H3) and the complex breccia Weston (H3, 4, 5, 6, 7 ?) demonstrated the confusion implied by the identifications 'equilibrated' and 'unequilibrated' for chondrites. Photomicrographs of an ultrathin (4 micron) section of the H5 Chondrite Allegan are provided.
- Publication:
-
Chondrules and their Origins
- Pub Date:
- 1983
- Bibcode:
- 1983chto.conf...44F
- Keywords:
-
- Chondrites;
- Crystallinity;
- Metamorphism (Geology);
- Meteoritic Microstructures;
- Petrography;
- Recrystallization;
- Aluminum Oxides;
- Calcium Oxides;
- Chondrule;
- Meteoritic Composition;
- Olivine;
- Photomicrography;
- Lunar and Planetary Exploration