Human Interaction with the Rock Cycle

Tara Lead and Zinc Mines

Learning Outcome

Identify the ways humans use rocks in Tara Mines

Discuss the impact this has on the Rock Cycle

Mining in Ireland

• Important economic activity• Employs 6000 people• Generates over 1 billion euro annually

Lead

• Valuable• Widely used• 60% of all lead is used in lead acid batteries• Has many other uses;– Plumbing– X-ray gowns– Ammunition– TV & Computer screens (blocks radiation)

Zinc

• Galvanising steel (prevents rust)• Zinc dust & compounds used in;– Cosmetics– Plastics– Paints– Ink

Tara Mines

• Navan, Co Meath

Formation of Lead & Zinc

• Rock containing metal is called ore• Carboniferous limestone• Formation of ore linked to movement of groundwater

through the rock• Seawater seeped into the rock• This was heated by geothermal energy from inside earth• As the hot seawater (brine) moved through the planes

and joints, it dissolved small amounts of lead and zinc out of the rocks

• The rich layers of ores within the rocks are called veins

Human Interaction with Rock Cycle in Tara

• Construct shaft mines• Extract ore• Disposal of waste products• Transport systems

General Info

• Shaft Mine• Europes largest zinc mine• 5th largest zinc mine in the world• Uses state of the art, remote control

technology and computerised systems• Local economy in Navan has benefitted

financially

Employment

• 700 Jobs– Chemists– Environmental Scientists– Miners– Geologists

Mining in Tara

• Output transported to Norway, Finland & other European countries

• Lead and zinc ores formed in faulted limestone in Navan, over 350 million years ago

• Lie 50 – 900 metres below the surface

Extraction

• Stope and Pillar• Large areas (stopes) blasted out and pillars left

standing to support them• Modern computerised machinery used to

bring the ore to the surface

On the Surface

• Rock crushed into powder• Chemically treated• Dried to form metal concentrate• Then transported to Dublin Port

Further process details

• Water used is recirculated and reused• Sediment is extracted and stored• Backfill may be needed in the stopes, cement

and water pumped through the boreholes

Process Mill

• Operates continously• 12 hour shifts• Highly computerised• On-site laboratory –analysis tests on rock

samples

Environmental Protection

• Landscaping to reduce visual impact• Wetland areas to treat water• Sheep grazing areas• Noise and Dust levels constantly monitored• Regular reports to the EPA

Spin-Off Effects

• For every one job in Tara, three indirect jobs are supported.– Eg; Caterers, Accountants, Truck Drivers, Safety

Consultants, Metallurgists

Future

• 2009; Threatened with closure– Demand for zinc to galvanise car bodies fell

• However continued demand for zinc from China and India

• Mine life extends past 2015

Keywords

• Mining• Ore• Extraction• System• Environmental Protection

Exam Question

• ‘People interact with the rock cycle in various ways.’ Examine this statement using an example you have studied.