A non-brecciated, relatively coarsely crystalline eucrite was found in 1940 near Moama, southern New South Wales, Australia. The texture and mineralogy (plagioclase 49.1 volume per cent, pyroxene 48.9 per cent, tridymite 0.72 per cent, chromite 1.0 per cent, troilite 0.24 per cent and metallic iron 0.14 per cent) are characteristic of an adcumulate formed in a terrestrial layered igneous intrusion. Its composition and texture most closely resemble the eucrite Serra de Mage. Moama and Serra de Mage are the best approximations to the pyroxene-plagioclase cumulates which McCarthy et al. (1973) propose have separated from a primary magma to produce the eucrite group of achondrites. Primary (coarse) and secondary (fine) augitic exsolution lamellae in the host hypersthene grains indicate a cooling history for the Moama eucrite similar to that of mafic rocks in slowly cooled, large, layered terrestrial intrusions such as Bushveld.
- Pub Date:
- June 1975
- Meteoritic Composition;
- Chemical Composition;
- Lunar and Planetary Exploration;