A company is prospecting for Pb on Middleton Moor (250555). A geologist estimate

Question

A company is prospecting for Pb on Middleton Moor (250555). A geologist estimates that the limestone ore contains, on average, 10% galena and 6% sphalerite by volume. If the quarry goes ahead and extracts100000 tonnes of ore per annum over a 15 year period: 5. H8IING Introductory Geology S H Marsh a) How many tonnes of lead will the mine produce in a year? If the footprint of the quarry is 200 x 200 m calculate the final depth and the volume available for landfill once the quarry is abandoned. b) Comment on the quality of the underlying strata as a barrier to the migration of landfill leachate c)

Explanation / Answer

a) The average amount of lead that we get from galena is about 86%.

The mine extracts 100,000 tonnes of ore per year.

Galena content in 100,000 tonnes of ore = 10% of 100,000 = (10/100) x 100,000 = 10,000tonnes

Lead present in 10,000 tonnes = (86/100) x 10,000 = 8,600 tonnes

b) We know that 1 cubic meter (m3) = 2.41 tonnes (t)

Total material excavated = 100,000 x 15 = 1,500,000 tonnes

Foot print of quarry = 200 x 200 m2

Let the depth be "d" meters

200 x 200 x d = 2.41 x 1,500,000

d = (2.41 x 1,500,000) / (200 x 200)

Therefore depth of the landfill, d = 90.375 meters

Total volume of landfill = 200 x 200 x 90.375 = 3,615,000 mt3

c) Since there are limestone rocks present and they possess a serious case of leaching and dissolution and hence the quality of underlying strata as a barrier to the migration is poor.

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