Olivine orientation in the ALIIA77005 achondrite

erna77fi)5, a unique achondrite found in the Allan Hills area, Antarctica, contains cumulus olivine and chromite phenocyrsts poikiliticaily enclosed by pyroxene and maskelynite. Petrofabric analysis on olivine shows a weak preferred orientaticin primarity consisting of a YZ foliation plane containing a weak [001] lineation. Secondary maxima are attributed to the development of exaggerated {ll0} forms in some olivine grains. Olivine microstructures suggest an approach to equilibrium grain orientation in response to laminar flow lines in a fluid medium.. Orientation effects caused by grain-to-grain contact are probably of minimal importance. else77005 is an example of a cumulate rock solidified in the act of flow and accumulation. Olivine orientations closely mimic patterns in porphyritic, tabular bodies (dikes, sills, flows).