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Barry Murphy
Director, Fractore Pty Ltd, Victoria
Tuesday 9th April, 2019
Nibbles 6.30pm, Presentation 6.50pm (approx.)
Basement on View
50 View St, Bendigo VIC 3550
A unique occurrence of a world class Proterozoic ore deposit, Century, affected by an Ordovician meteorite impact, the Lawn Hill Impact Structure, is described. The meteorite excavated a complex crater with a Proterozoic core surrounded by an annulus filled with Cambrian carbonates. The Century deposit is located at the southwestern edge of the crater and is bounded by post-ore faults that indicate an originally larger orebody. It is overlain by breccias which contain evidence of impact related textures that we interpret as fallback suevite. Above the suevite are slumped Cambrian carbonate and Proterozoic shale, including a million-tonne block of Century ore detached from the main orebody and contained in the carbonate breccias. The Cambrian rocks were partially consolidated prior to impact, became fluidized on impact, and then re-surged into the crater from surroundings areas. The resurge process resulted in a five-fold thickening of carbonates in the annulus, preserved to 600m depth.
Beneath the suevite, in the more competent orebody, fracturing and slab formation were the dominant responses to the impact. A restoration of the displacements on the impact-related faults that moved the orebody towards the crater is proposed. The inference is that, prior to impact, the deposit continued for several hundred meters beyond the current faulted northern boundary of the orebody, and that this missing segment was displaced and may be buried within the annulus.
Based on work by Terry Lees, Barry Murphy, Andy Tomkins and Damian O’Donohue; paper submitted and in review. Supported by New Century Resources Ltd.
Consultant structural geologist in mineral exploration sector with a wide exposure to gold and base metal exploration in Australia and overseas. On-going role as Chief Geologist to ASX-listed Predictive Discovery Ltd, exploring for gold in west Africa. Previous roles in terrain scale research programs with the pmd*CRC in Mt Isa and the Tasmanides, and in global zinc exploration (Pasminco). Has published several papers on Australian (and Irish) geological, geophysical, mineral prospectivity and 3D modelling topics.
To support our Victorian Branch and ongoing future events we kindly ask for a small admission fee from our attendees:
AIG & AusIMM Members $10
Non-Members $15
Students Free
AIG Victoria will supply refreshments and nibblies.
Ben Jupp – bjupp@srk.com.au
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