Geochemistry & Geobiology

Magma petrogenesis on the SW Indian Ridge

MSc project of Solveig Lie Onstad

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Project title

Magma plumbing system and MORB petrogenesis along the ultraslow spreading South West Indian Ridge


Cédric Hamelin (main supervisor), Mathilde Cannat (IPGP France)

Project description

Based on proxies such as depth, axial valley relief, and gravity anomalies, the easternmost segment of the South West Indian Ridge (SWIR) appears to be a worldwide end-member in terms of both on-axis plate thickness and low-melt supply. Along this ridge, on-axis colder thermal regime impedes magma generation and intermittent volcanism is occasionally substituted by mantle exhumation along large detachment faults. Recent studies along this regions have been key to an exciting new development concerning basalt generation, showing that mantle melting may be more heterogeneous than previously thought, and that fractional crystallization is not the only process by which parental melts evolve to form the erupted MORBs. These newly emerging questions have a good potential for bringing new concepts on mantle composition and modes of melting, and a non-negligeable potential for breakthrough concerning the global ocean crust geochemical budgets. In this project, basalt samples from the ROVSmooth cruise will be used to confirm preliminary observations made along this ridge in terms of field relations between lithologies and magma petrogenesis.