TheThe Deep Lead MinesDeep Lead Minesof of

BALLARATBALLARAT

What does this image represent to you?

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 450-350 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

Lava flows

Vulcanism

Map 3 million years ago – west covered by lava

Today’s river system

Where is the ancient river system?

WHERE’S 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 metres75 metres

95 metres

Can

adia

n L

ead

Inkerman Lead

Golden Point Lead

Eureka LeadCosmopolitan

Cosmopolitan

Band and Albion No 2

Section across the Ballarat goldfield

Golden Point Lead Canadian Lead

Lava flowsSovereign 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 holeGutter Drift

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