Geochemical Constraints on the Structure of the Earth’s Deep Mantle and the Origin of the LLSVPs

Gleeson, Soderman, Matthews, Cottaar, Gibson, G3, 22, e2021GC009932 (2021). doi: 10.1029/2021GC009932

The Galápagos islands preserve significant geochemical variability in their lavas, which varies consistently with spatial position. It is thought that much of this heterogeneity derives from melting of recycled and primordial mantle components. At the base of the mantle from which the Galápagos plume rises is a large low shear velocity province (LLSVP), however its origin remains enigmatic. LLSVPS have variously been interpreted as primordial mantle heterogeneities or piles of recycled oceanic crust.

If recycled oceanic crust is contributing to the magmatism, we should expect to see evidence for pyroxenite melting, This study demonstrated that the strongest pyroxenite signatures are found in a narrow band offset from the centre of the mantle plume. The lack of evidence for pyroxenite in the centre of the plume, the part most likely to be sampling the LLSVP, could indicate that the LLSVP material is not recycled oceanic crust, but this recycled material might be present on the margins of the LLSVP.

This study made use of the pyMelt mantle melting package (github.com/simonwmatthews/pyMelt) and the THERMOCALC results we published in Soderman et al. (2021).

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