Plagioclase archives of depleted melts in the oceanic crust

This is a Preprint and has not been peer reviewed. This is version 1 of this Preprint.


Download Preprint


David Axford Neave, Olivier Namur


Mid-ocean ridge and ocean island basalts provide vital but incomplete insights into the chemical structure of Earth’s mantle. For example, high-anorthite plagioclase carried by these basalts is generally too primitive and incompatible-element depleted to have crystallized from them. Moreover, erupted basalts rarely preserve the strong isotopic and incompatible-element depletions found in some melt inclusions and mantle residua represented by abyssal peridotites. By integrating experimental observations with published analyses of natural crystals and glasses, we demonstrate that high-anorthite plagioclase is in equilibrium with melts generated by high-degree melting of depleted mantle sources. Although such melts seldom erupt, their imprints on crystal and melt inclusion records nonetheless suggest that high-anorthite plagioclase grows from endmember but essentially unexotic magmas. The widespread occurrence of high-anorthite plagioclase in both oceanic basalts and the oceanic crust hence indicates that depleted melts are pervasive in the upper mantle and lower crust despite rarely reaching the surface. Plagioclase archives therefore imply that depleted melts play much a greater role in lower crustal accretion than typically recognized and that the upper mantle may also be more depleted than previously thought.



Geochemistry, Geology



Published: 2021-11-15 11:46

Last Updated: 2021-11-15 16:46


CC BY Attribution 4.0 International

Add a Comment

You must log in to post a comment.


There are no comments or no comments have been made public for this article.