Nils Roar

Senior lecturer Jennifer S. Collier, Imperial College, will Tuesday March 23 at 11:15 give a lecture with the title:

Beyond hotspots: the importance of rift history for volcanic margin formation

Auditorium I, Geology Building. All are welcome!

Abstract:
Rifting and magmatism are fundamental geological processes that shape the surface of our planet. A relationship between the two is widely acknowledged but its precise nature has eluded geoscientists and remained controversial. Two decades ago, largely based on detailed observations from the North Atlantic, a paradigm was established that identified mantle temperature as the primary factor. This idea has dominated our understanding with most authors seeking to explain observed variations in volcanic activity at rifted margins in terms of the mantle temperature at the time of breakup.

Recently we generated a new model of the conjugate Indian-Seychelles continental margins from marine geophysical observations. These margins have been widely cited as a classic example of rifting in association with a continental flood basalt province, the Deccan Traps. However our study did not find the typical set of geophysical characteristics reported at other margins linked to continental flood basalts, such as those of the north Atlantic. Instead our work showed that that rifting of India from the Seychelles was characterised by modest magmatism. These observations, together with those of others that question the “hotspot-volcanic margin” relationship, led us to revisit the primary factors that control continental break-up.

We developed a series of numerical models that explicitly account for the effects of earlier episodes of extension. Our work showed that the volume of rift-related magmatism generated, both at the Northwest Indian Ocean and North Atlantic margins, depends not only on the mantle temperature but, to a similar degree, on the rift history. We conclude that the inherited extensional history can either suppress or enhance melt generation, and mantle temperature alone is not the primary factor controlling continental break-up.