Mineralization along Early and Late Stage Continental Rifting
When a continent comes to rest over a hotspot regional uplift and doming usually result as huge volumes of magma rise to the surface. With continued updoming extensional failure of the lithopheric crust may occur triggering the development of a triple junction, a three armed rift system. Typically, one arm of the rift fails remaining as a fissure in the crust known as an aulacogen, while the remaining two arms open to form an ocean basin. The prevalence of three armed rifts is revealed by reassembling the continents surrounding the Atlantic Ocean to their positions before Pangea split up. In most cases two of the arms were incorporated into the Atlantic, while the third remained as a blind rift extending into the continent.
A more recent example can be observed where the Arabian Peninsula is breaking away from the African continent. The Red Sea and the Gulf of Aden both represent arms of a three-armed rift. The third arm strikes into Ethiopia from the Afar Triangle.
Aulacogens become important sites for sediment accumulation and for ore deposition. Mineralisation commonly consists of copper and other base metals normally deposited syngenetically as sulphides in volcanic deposits or sediments. They are also important sites for hydrocarbon accumulation, and many younger aulacogens have yet to be explored for their hydrocarbon potential.
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Department of Geology
Aligarh Muslim University, Aligarh - 202 002 (India)