Constructing geochemical analogues of the asthenosphere: Earth’s largest geochemical reservoir

"It is becoming increasingly clear that the study of basalt composition does not always lead to an accurate assessment of the isotopic and chemical composition of its mantle source. Therefore, in order to understand mantle composition better, it is more prudent to collect direct evidence from the mantle itself. However, obtaining representative samples of the modern-day convecting mantle is problematic because it is overlain by the lithosphere, yet lithospheric mantle samples are the only examples of the mantle available. Oceanic lithospheric mantle collected as dredged or drilled abyssal peridotites is often heavily altered by interaction with seawater and hydrothermal fluids. On the other hand, peridotite xenoliths, while exposed at the surface of the Earth, are often affected by metasomatism, melt-rock interaction and / or refertilization processes.
This project will examine the various processes that have affected the composition of peridotites recovered from the Mid-Atlantic ridge, the Iberian continental passive margin and the Cape Verde Islands in order to (i) better understand the processes that can overprint the chemical and isotopic signatures preserved in the oceanic mantle at different tectonic settings, and (ii) assess peridotite from each of these provinces for its suitability as a chemical and isotopic proxy for the more voluminous, yet unreachable, asthenospheric mantle "

http://www.nercdtp.leeds.ac.uk/projects/index.php?id=497