The Geological Survey of NSW is undertaking a detailed study into the 3-dimensional architecture of the eastern Lachlan Orogen. These rocks record prolonged development and evolution of a now fragmented oceanic arc and proximal back-arc system that was punctuated by a series of tectonic and mineralising episodes throughout the early Palaeozoic. The terrain now comprises a multi-phase arc-system (the Macquarie Arc) intercalated with early- to mid-Palaeozoic quartz-rich turbidites and Siluro-Devonian sedimentary and volcanic rocks.

By building on and integrating available datasets (including, but not limited to, potential field, geochemical, palaeontological, petrological, geochronological and structural datasets) we are developing and refining our understanding of the architecture of mineralised system that is incorporated into the Lachlan Orogen and the deformation events that have lead to its current geometry.

The project encompasses detailed studies of:

• Extent of, and correlations between, fragmental oceanic arc-related high- and low-K calc-alkaline basalt sequences, arc or back-arc-related tholeiites and mid-ocean ridge basalts to test potential reconstructions
• The extent and significance of Siluro-Devonian sequences
• The application of thermodynamic models to test the veracity of granite-source models and genetic classification schemes (e.g., I- and S-type) as well as investigate pertinent metamorphic processes.

This work is leading to a better understanding of the architecture and kinematics of the orogen and a series of model representations, expressed in three spatial dimensions, that will encompass the range of internally-consistent solutions.

For more information please contact the Geological Mapping Team.

(Last updated on 24/02/2009)