The Deep Lead Mines of BALLARAT
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And this?
Section 500 million years ago Under the sea
Map 500 million years ago Flat layers of sand and mud on the sea floor
Section 490 – 450 million years ago Squeezing and folding - mountain building
Section million years ago
Section 350 – 65 million years ago Erosion
Map 65 million years ago - Hills of 500 million year old rocks Flat plain
- drained by rivers
Section 65 – 3 million years Lava flows Vulcanism
Map 3 million years ago – west covered by lava
Todays river system Where is the ancient river system?
WHERES THE GOLD In the youngest river system (Yarrowee River etc) In the quartz veins in the oldest rocks (Whitehorse Range, Black Hill) and buried under the lava flows of Ballarat West Widely spread in the old plains gravels (Golden Point, Poverty Point, Newington Gravels) Highly concentrated in the ancient river beds
LEAD Any mineral deposit formed by mechanical concentration in the bed of a stream by water action
SHALLOW LEAD Any lead that is:- Not buried by younger rocks (sediment or lava) The course of the lead can be determined by the present topography
DEEP LEAD Any lead that is:- Buried by younger rocks (sediment or lava) The course of the lead cannot be determined by the present topography NOTE. There is no qualification of depth
30 metres 90 metres 40 metres 60 metres 110 metres 75 metres 95 metres Canadian Lead Inkerman Lead Golden Point Lead Eureka Lead Cosmopolitan Band and Albion No 2
Section across the Ballarat goldfield Golden Point Lead Canadian Lead Lava flows Sovereign Hill Yarrowee River
Consols Lode Drainage Direction
Ballarat Leads – Regional Context
The Deep Lead Mines of Ballarat
The Pleasant Street Group of Mines
Section through typical deep lead Drill hole GutterDrift Basalt Bedrock
Sketch Plan and Long Section of Typical Deep Lead Mine
Sketch Section across Lead Showing Mine Workings
Plan of Deep Lead Working Method
Timbering of Wash Dirt Drives Bedrock
Challenges to Deep Lead Mining Much water – extensive pumping necessary Basalts very hard – required blasting Deep sinking to reach lead Lead direction varied unpredictably Unstable ground in the wash dirt
More Challenges Very long drives – ventilation often poor Very long drives – haulage issues Mines needed to be highly mechanised Large Capital Investment required Poor legislative environment Resource is finite, unlike quartz vein mining
Deep Lead Mining Issues The Frontage Claim System
Advantages of Deep Lead Mining Gold concentration much higher per unit volume Wash Dirt required less processing than quartz ores to release the gold