AGM

Join the Central VIC Branch for their 2021 Annual General Meeting.

About this event

Register now to join the Central VIC Branch for their 2021 Annual General Meeting.

From 6pm there will be a BBQ followed by a technical presentation at 7pm by Rob Duncan, GSV. 

Title: Understanding gold mobility, enrichment and preservation in the crust of central Victoria

Overview: Over the last few years a compelling gold exploration story has developed across central Victoria driven largely by the ultra-high gold grades at depth in the Fosterville deposit in the Bendigo Zone.

This means that mineral exploration expenditure in Victoria has been increasing at unprecedented rates compared with other Australian jurisdictions. Our understanding of how orogenic gold systems formed in the Bendigo Zone has evolved through research efforts by The Geological Survey of Victoria, Geoscience Australia, industry, and academia, particularly over the past decade.

There is geological evidence to demonstrate that gold was mobile and became concentrated in economic quantities during three main orogenic events at ~440, ~415, and ~380 Ma associated with transient shortening in a back-arc setting. Geological interpretations from large-scale government-funded seismic survey acquisition allowed both major and smaller-scale crustal structural characteristics to be mapped, these are significant because they permitted the circulation of large quantities of metamorphic fluid that had the potential to transport gold from source to sink across the crust.

Controversy exists around the most likely gold source, it is likely to be from pre-existing sulfides in a combination of basalts (specifically boninites) and finer-grained portions of Bouma sequences. Specific structural geometries where faults become relatively flat in gold hinges appear to be preferential sites for high grade gold mineralisation.

In these sites there is geological evidence for rapid changes in physio-chemical conditions that drive gold precipitation that results in different deportment of gold mineralisation (free gold versus sulfide-hosted). In terms of preservation, the Bendigo Zone has been geologically stable between 400 and 80 Ma.

After that time uplift and erosion brought the orogenic gold systems relatively closer to the surface. Some orogenic deposits were partially reworked into the alluvial gold systems that generated the Victoria gold rush era.

This comprehensive understanding of controls on mineralisation is unique and is significant because it provides a predictive framework for the gold exploration industry to discovery high quality deposits in central Victoria, including those that are covered by post-mineral cover of the Murray Basin.

 

Call for committee nominations

If you are interested in joining the Branch Committee, please send an email to centralvic@ausimm.com.