Continental Flood Basalts

Question 1

What is a continental flood basalt?

Answer 1

A type of large igneous province, develops over 1 million years

Question 2

Name, give age and locality of 5 continental flood basalts

Answer 2

CRB, NW USA - Miocene
Keeweenawan, Superior Area - Precambrian
Deccan, India - Cretaceous to Eocene
Parana, Brazil - Early Cretaceous (biggest over 10^6 km3)
Karroo, S. Africa - Early Jurassic

Question 3

What kind of eruption forms a flood basalt, where does it come from and what is it composed of?

Answer 3

Short-lived intense periods of basaltic volcanism associated with the rifting/disruption of continental lithospheres.
Erupted from fissures
MORB type composition, isotopic evidence of crustal contamination
Associated with sill complex

Question 4

What happens during the eruption?

Answer 4

10-1000km3 magma erupted daily, repose periods of 1000 years.

Question 5

What kind of deposits are left?

Answer 5

Sequences several km thick, subsidence kept up with accumulation, probably due to flow in crust.

Question 6

Name 5 provinces and there age

Answer 6

Columbia River - 16 mya
Ethiopia - 31 mya
Deccan - 66 mya
Karroo - 183 mya
Siberian - 249 mya

Question 7

When do they develop?

Answer 7

Initial stages of continental rifting

Question 8

What do Sm/Yb tell us about amount of melting at depth within a volcanic sequence?

Answer 8

High Sm/Yb ratios show small amount of melting at greater depth