The zoned Bruinbun granitoid pluton and its aureole |
| |
| Authors: | Roger Bateman |
| |
| Institution: | 1. School of Earth Sciences , Macquarie University , North Ryde, N.S.W.;2. 2113 , Department of Geology , James Cook University of North Queensland, Townsville, Qld, 4811 |
| |
| Abstract: | The Bruinbun pluton is a small, massive, I‐type granitoid intruded into the meta‐sedimentary Hill End Trough, in eastern N.S.W. It is a multiple pluton representing two discrete magma pulses, the granodiorite core intruding the adamellite margin. A weak alignment of orthoclase megacrysts in the granitoids is best developed adjacent to both the internal and external intrusive contacts, and is considered by the writer to be a product of magmatic flow. Part of the northern contact and the southern and western contacts dip inward at moderate angles, whereas the eastern contact is vertical to outward‐dipping. The pluton is inferred to be mushroom‐shaped, and slightly tilted. The intensity of aureole deformation is low. The aureole has been flexed into concordancy with the pluton roof, and a rudimentary rim fold‐zone is present around lower levels of the pluton. Intrusion of the granitoid is inferred to be primarily by uplift of its roof and depression of its floor. The highest‐grade contact metamorphic parageneses developed are: cordierite‐K feldspar‐biotite‐quartzite ± andesine ± epidote in metapelites, and ferrohornblende‐biotite‐muscovite‐andesine‐epidote‐quartz in metavolcarenites. No intrusion‐related foliation or lineation was formed. |
| |
| Keywords: | Multiple pluton fractionation remelting megacryst alignment structural aureole intrusive mechanisms contact metamorphism |
|
|
