From Basalt Chemistry to Mantle Mineralogy: Understanding Magmatism from Intraplate Volcanism to Continental Breakup

Basaltic rocks provide a window into the Earth's mantle, recording information about the rocks that melt at depth and the processes that bring magma to the surface. But how much can we really learn about the mantle from basalt chemistry? In this seminar, I will first introduce BaSIC (Basalt Source Investigation and Characterization), a new open-source tool that uses the chemical composition of basalts to estimate the mineralogy of their mantle sources . Applying BaSIC to ocean island basalts reveals how tectonic setting and lithospheric thickness influence which mantle components contribute to melting. I will then show how we can use such tool to investigate the cause of magmatism during continental breakup, focusing on the opening of the Northeast Atlantic around 56 million years ago. Our results show that changes in mantle source mineralogy accompanied variations in magmatic activity, and suggest that thinning of the lithosphere, rather than high mantle temperatures alone, was a major driver of this magmatism. 

Speaker: Sarah Lambart, University of Utah