1. Max-Planck-Institut für Chemie, Postfach 3060, 55020 Mainz, Germany
2. Vernadsky Institute of Geochemistry, Russian Academy of Sciences, Kosygin street 19, 117975 Moscow, Russia
3. GeoForschungsZentrum, Telegrafenberg E, D-14473, Potsdam, Germany
4. Institute of Physics of the Earth, Russian Academy of Sciences, B. Gruzinskaya street 10, 123995 Moscow, Russia
5. Faculty of Geosciences, Department of Petrology, Utrecht University, Budapestlaan 4, 3584 CD Utrecht, The Netherlands
6. Faculty of Earth and Life Sciences Department of Petrology, Vrije Universiteit, De Boelelaan 1085, 1081 HV, Amsterdam, The Netherlands

Correspondence to: Alexander V. Sobolev^1,2 Correspondence and requests for materials should be addressed to A.V.S. (Email: asobolev@mpch-mainz.mpg.de).

Abstract

More than 50 per cent of the Earth's upper mantle consists of olivine and it is generally thought that mantle-derived melts are generated in equilibrium with this mineral. Here, however, we show that the unusually high nickel and silicon contents of most parental Hawaiian magmas are inconsistent with a deep olivine-bearing source, because this mineral together with pyroxene buffers both nickel and silicon at lower levels. This can be resolved if the olivine of the mantle peridotite is consumed by reaction with melts derived from recycled oceanic crust, to form a secondary pyroxenitic source. Our modelling shows that more than half of Hawaiian magmas formed during the past 1 Myr came from this source. In addition, we estimate that the proportion of recycled (oceanic) crust varies from 30 per cent near the plume centre to insignificant levels at the plume edge. These results are also consistent with volcano volumes, magma volume flux and seismological observations.

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