Results from the Captains Flat and Braidwood mapping projects

1. Exploration Data WorkshopGeological Survey Technical Talks
1st June 2016, Orange
Results from the Captains
Flat and Braidwood mapping
projects

2. Exploration Data WorkshopGeological Survey Technical Talks
1st June 2016, Orange
Where are we?

3. Exploration Data WorkshopGeological Survey Technical Talks
1st June 2016, Orange
Captains Flat
• Release due mid 2016
Braidwood
• Release due late 2016

4. Exploration Data WorkshopGeological Survey Technical Talks
1st June 2016, Orange
Goulburn Basin

5. Exploration Data WorkshopGeological Survey Technical Talks
1st June 2016, Orange
Goulburn Basin
• late Silurian sequences hosts VAMS
mineralisation (e.g. Woodlawn)
• Intrusion-related mineralisation in
the Early Devonian Braidwood
Granodiorite (e.g. Dargues Reef)
• Skarns in the late Silurian
limestones resulting from the Early
Devonian plutons (e.g. Mayfield)

6. Exploration Data WorkshopGeological Survey Technical Talks
1st June 2016, Orange
Goulburn Basin
• late Silurian sequences hosts VAMS
mineralisation (e.g. Woodlawn)
• Intrusion-related mineralisation in
the Early Devonian Braidwood
Granodiorite (e.g. Dargues Reef)
• Skarns in the late Silurian
limestones resulting from the Early
Devonian plutons (e.g. Mayfield)

7. Exploration Data WorkshopGeological Survey Technical Talks
1st June 2016, Orange
Stratigraphic
Correlations
• Historical
correlations very
simple
• Based on a ‘layer
cake’ stratigraphy
Modified after Davis 1990

8. Exploration Data WorkshopGeological Survey Technical Talks
1st June 2016, Orange

9. Exploration Data WorkshopGeological Survey Technical Talks
1st June 2016, Orange

10. Exploration Data WorkshopGeological Survey Technical Talks
1st June 2016, Orange

11. Exploration Data WorkshopGeological Survey Technical Talks
1st June 2016, Orange

12. Exploration Data WorkshopGeological Survey Technical Talks
1st June 2016, Orange

13. Exploration Data WorkshopGeological Survey Technical Talks
1st June 2016, Orange

14. Exploration Data WorkshopGeological Survey Technical Talks
1st June 2016, Orange
Why do only some
centres appear to
be mineralised?

15. Exploration Data WorkshopGeological Survey Technical Talks
1st June 2016, Orange
Why do only some
centres appear to
be mineralised?
large volumes of
subsurface gabbro
and granites?

16. Exploration Data WorkshopGeological Survey Technical Talks
1st June 2016, Orange
Late Silurian Intrusions
• Evidence of mixing the
gabbro and the granites
• Geochemically the
gabbros match the
erupted basalts
• Potential heat source for
the VAMS mineralising
systems?

17. Exploration Data WorkshopGeological Survey Technical Talks
1st June 2016, Orange
Late Silurian
Basin
Architecture

18. Exploration Data WorkshopGeological Survey Technical Talks
1st June 2016, Orange
Mapping Outcomes
• Basin-wide events can be correlated across the basin,
despite complex lateral changes
• SHRIMP age dating
• Confirms the Late Silurian age of the volcanics and
comagmatic igneous rocks at Woodlawn and Captains
Flat, aiding the correlation of this volcanic events
across the basin
• Shows that not all rhyolitic volcanics are Late Silurian
• A coincidence between mineralisation and high-level
bimodal intrusive complexes

19. Exploration Data WorkshopGeological Survey Technical Talks
1st June 2016, Orange
Outcomes for Exploration
• Refining prospective areas
• Previously targeted areas include areas now
recognised as Ordovician sediments and as Early
Devonian sub-aerial volcanics
• Understanding the stratigraphy allows the targeting of
specific horizons
• Identifying possible heat sources to VAMS systems,
may explain why not all volcanic centers are
mineralised and refine targeting
• Coeval mafic rocks in the sequence may help find
‘hotter’ parts of the system

20. Exploration Data WorkshopGeological Survey Technical Talks
1st June 2016, Orange
Thank You