School of BEES - Deformation of Granites Research

RESEARCH BY DR PAUL LENNOX

Many granites are spatially and temporally related to known mineral deposits and hence it is crucial to understand the various methods by which they are emplaced (stoping, dyking, ballooning, fault-filling...) and subsequently deformed. Structural studies in weakly deformed granites and their surrounding country rocks provide important clues towards understanding the deformation history of an area.

Schematic illustration of the shape of the Carcoar Granodiorite and surrounding faults

A research team led by Dr Paul Lennox in the School of Biological, Earth and Environmental Sciences, in association with Dr Robert Trzebski, and funded by DeutscheForschungsgemeinschaft, Germany and Hargraves Resources has determined the three dimensional shape of the granites near Blayney, NSW. This area is part of an Ordovician volcanic arc which has been intruded by granites, deformed and probably re-worked along basement weaknesses. Studies by collaborators on zircon dating, the cathodoluminescence of quartz grains within these granites and the anisotropy of magnetic susceptibility have further constrained the likely timing, path to emplacement of these granites and their subsequent deformation. These studies have been complemented by comprehensive regional analysis of all brittle and ductile structures both in the granites and surrounding country rocks.

Different scenarios for the emplacement and subsequent deformation of the Carcoar Granodiorite (CGd), Barry Granodiorite (BGd) and Sunset Hills Granite (SHG).

This study has important implications for:

determination of the timing of mineralisation and its relationship to these granites
development of better tectonic models for this region
elucidating upper crustal architecture
characterising the role of faults in granite intrusion
the role and effects of basement weaknesses on the deformation history of this area
comparing and contrasting ancient and modern volcanic arc development