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New SEDEX and MVT Provinces discovered under shallow cover in the Southern Georgina Basin

Mathew Davies, Christopher Woodfull, Peter Stuart-Smith
Wednesday, September 30, 2015
First presented: 
SEG Conference, September 2015

SK Networks Resources Ltd (SK) is currently exploring beneath shallow cover sequences within greenfield mineral tenure in the Southern Georgina Basin. A geological model has been developed of the Mt Whelan area highlighting two distinct geological domains separated by the Pippagitta Fault: 1) a western domain with the potential to be a new MVT province based on widespread elevated levels of Pb, Zn and Ag in drill assays; and 2) an eastern domain, which based on current interpretations has identified potential Mesoproterozoic sequences with SEDEX potential. These potential Mesoproterozoic sequences have not been previously identified and based on geophysical responses could be analogous to McArthur Basin or Lawn Hill sequences.

Initial reconnaissance drilling in 2011/2012 identified MVT-style (Pb, Zn and Ag) mineralisation and elevated phosphate within Middle Cambrian limestones of the Georgina Basin to the west of the Pippagita Fault along a basement high. The limestone units were tentatively correlated with the Thorntonia Limestone or equivalent e.g., Beetle Creek Formation and are considered to be prime host rocks for MVT-style mineralisation and/or phosphate in the right structural and palaeogeographic settings. While preliminary evaluation has highlighted a number of MVT-style drilling targets and a corridor for phosphate testing, the large extent of the tenure holding necessitates further exploration to assess its mineralisation potential.

A geological model was initially constructed using drilling, geological mapping and structural interpretations based on regional and highresolution airborne magnetic datasets. An updated stratigraphic and structural interpretation and model was produced using additional 2D seismic data made available by a 2013 data exchange between SK and Central Petroleum who are exploring for unconventional oil and gas in the area.

The updated model maps the Thorntonia Limestone at depth with moderate to high confidence over a laterally continuous area of ~1,500 km². The interpretation and modelling has helped identify sub-cropping limestone within favourable structural (trap) settings both near surface and at depth over a broad elongated basement high to the west of the Pippagita Fault. Nearly all drill holes have encountered elevated Pb, Zn ± Ag; maximum values encountered were 0.34%, 1.41% and 17 g/t respectively.

The drilling results are highly suggestive of a fertile MVT-style system and reminiscent of early exploration results reported in other MVT provinces such as the Lennard Shelf. Drill testing to the east of the Pippagita Fault has provided valuable stratigraphic information confirming a thick sequence of Neoproterozoic tillite the Yardida Tillite (previously the Field River Beds); which was previously unknown in the area. Unconformably (?) underlying the tillite sequence is a prominent sequence of seismic reflectors, which are potentially analogous to less deformed Mesoproterozoic-aged sequences found in the McArthur Basin and Lawn Hill region. The seismic profiles identify this prominent sequence of reflectors at shallow depths (<500 m) in some areas within SK’s tenure amenable to drill testing.

The seismic data has also helped identify major, steeply dipping growth fault zones with multiple movement history. The discovery of new potentially Mesoproterozoic stratigraphy at shallow depths has positive exploration implications given the base metal mineral endowment of similar provinces of the North Australian Craton.

Feature Author

Mathew Davies

Mathew Davies is a geologist with eight years’ experience in the Australian mining industry. His experience includes over five years’ experience working as a consultant for SRK and three years’ experience working as an exploration geologist in the Hunter Valley of NSW. Since joining SRK in 2011, he has been involved in a range of coal and mineral focused work including; coal and mineral exploration programs; including project management and legislative compliance, management, planning and execution of field drilling and mapping programs, development of 3D geological models for coal and mineral Resource evaluations and coal and mineral asset valuations.

Senior Consultant (Geology)
BSc Hons (Exploration and Resource Geology)
SRK Newcastle
Chris Woodfull

Chris Woodfull is a geologist with over 27 years’ experience in exploration, mining geology and environmental management, in industry or as a consultant.  He is an experienced project director and manager in a range of areas including: geological risk, exploration and independent technical reviews for the resource sector.  Chris has worked on numerous exploration targeting/ assessment and structural geological risk studies for minerals and coal exploration and mining companies.  In recent years, he has managed a number of major geological and multi-disciplinary projects including two multi-client, basin-scale structural framework and risk studies to assist coal, coal seam gas and minerals companies operating and exploring in the Sydney-Gunnedah Basin in New South Wales and the Bowen, Surat and Drummond Basins in Queensland.

Managing Director and Principal Consultant (Geology)
MSc (Geology), MAIG, MAusIMM
SRK Newcastle
SRK Africa