Banalasta Monzogranite

The Banalasta Monzogranite is large pluton at the southern end of the Bundarra Supersuite of S-type granites in the Southern New England Orogen, NSW, Australia. This sample is taken from ~5 km north of Bendemeer is typical of rocks from across the intrusion. Typical of S-type granites, hornblende is absent, but magmatic cordierite up to 1 cm in size occurs in most samples in addition to ubiquitous aluminous biotite (siderophyllite). Abundant quartz tyically occurs as glomerocrysts, and displays evidence of mild deformation in thin section. The feldspars present are relatively sodic plagioclase and microcline perthite (bluish white). Remnant carlsbad twinning is present but the abundant tartan twins show that the original igneous orthoclase has been largely converted to microcline - a process that is also the result of mild deformation. Accessory phases include ilmenite (the sole opaque phase), apatite, monazite, xenotime and zircon. Zircons from the sample yield and age of ~282 Ma (early Permian).