EOSC 118 - Lesson 10

A and C

they are the only mine producing lamproite-hosting diamonds commercially

• high pressure

• depth: 140km or more

• ‘cool’ temperature region: a region between 950 and 1400 C

Kimberlite magma generates at the base of the craton, at 200-300km depth, and ascends through 140km of crust, picking up diamonds along the way, and brings them to the Earth’s surface through eruptions in special volcanoes

They are rare because they form so deep underground and need special environmental conditions in order for them to be brought to the surface

the main producer is Africa, followed by Russia, Australia and Canada

• historically produced in India and Brazil, but these were alluvial secondary deposits

• late 19th century, discovered diamond-bearing kimberlite in South Africa

• 1957: First significant non-African mine opens in Russia

• 1983: Australian Argyle mine opens, producing diamond-bearing lamproite

• 1998: Canada joins trade with the Ekati mine

kimberlite

Because the conditions at the base of the Archean cratons is a favourable environment for diamond growth (high pressures + relatively ‘cool’ temperatures)

Because as the magma ascends upwards through the crust it moves into regions with less and less confining pressure, which allows for faster and faster propagation of the magma

sourced from upper mantle, Fe- and Mg- rich (aka ultramafic) as well as K rich

another host rock for diamonds, a lot less common, can exist outside Archean cratons