Date(s) - Thursday, 18/10/2018
7:00 pm - 8:30 pm
Ballarat Technical Talk – October 2018
Central Victorian Goldfield Indicators
Thursday 18th October 2017, 7:00pm
Mallow Hotel, 20 Skipton Street – upstairs
In the eighteen seventies Ballarat hard rock miners discovered that certain persistent “favourable beds” with distinctive features, if followed were likely to lead to appreciably higher gold occurrences when intersected by or were found in association with quartz reef systems. These favourable beds or structures were termed “Indicators”. Some were correlated for some distance across the Ballarat goldfields and given often descriptive names; “The Pencil Mark”, “The Double Indicator”, “The Black Seam” and “The Red Steak”. Most Indicators are thin (1-20mm), generally bedding parallel carbon and or sulphide rich laminae hosted in or are part of the general slate sequences. Indicators were subsequently also recognised at other central Victorian goldfields.
Considerable differences in the interpretation of the nature of these structures exist in the historical records but also in more recent accounts.
A summary of the historical records and a progress report will be made of a research project commenced on around twenty samples of Ballarat and other goldfields Indicator samples obtained from Museum Victoria and Ballarat School of Mines historical collections.
Results so far show some significant common characteristics and some differences in mineralogy and other characteristics, as was mentioned in the old reports. Several examples will be described in detail, including a puzzling common feature of Ballarat Indicators to date not reported.
No satisfactory explanation as to how such nearly insignificant lithologies or structures could lead to the gold endowments claimed, there are in fact recorded doubts of the claims. Several proposals on how Indicators could lead to or be associated with enhanced gold deposition will be presented for discussion.
Stafford is a long-time lecturer in mineralogy, petrology and structural geology at Federation University. His main interests are in the application of x-ray diffraction and transmission electron microscopy techniques to mineralogy in general. His current research projects include lithium-tantalum-niobium (LCT) pegmatites of eastern Victoria and of course central Victorian goldfield historical “Indicators”
Stafford is an active consultant to the Australian mineral and ceramic industries.
It’s free entry. All welcome. Cash bar and meals available.
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