Do we really need mantle components to define mantle composition?

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doi: 10.1093/petrology/eg1078
Authors:Armienti, Pietro; Gasperini, Daniela
Author Affiliations:Primary:
Universita di Pisa, Diaprtimento di Scienze della Terra, Pisa, Italy
Volume Title:Journal of Petrology
Source:Journal of Petrology, 48(4), p.693-709. Publisher: Oxford University Press, Oxford, United Kingdom. ISSN: 0022-3530
Publication Date:2007
Note:In English. 76 refs.; illus., incl. 3 tables
Summary:We discuss the concept of components in the Earth's mantle starting from a petrological and geochemical approach, but adopting a new method of projection of geochemical and isotopic data. This allows the compositional variability of magmatic associations to be evaluated in multi-dimensional space, thus simultaneously accounting for a large number of compositional variables. We demonstrate that ocean island basalts (OIB) and mid-ocean ridge basalts (MORB) are derived from a marble-cake mantle, in which different degrees of partial melting or recycled lithosphere, which are heterogeneous in age and composition, contribute to the magma genesis. This view is supported by the variability in the geochemical and isotopic signatures of OIB that are observed on the scale of a single ocean island as well as on that of an ocean, mostly varying between two extreme compositions, that are not strictly related to the commonly accepted mantle components (DMM, EMI, EMII, HIMU). Rather they are a distinctive feature of the mantle source sampled at each ocean island and are strongly dependent on the Pb isotope system. We recommend a change in perspective in studies of MORB-OIB geochemistry from one based on physically distinct mantle components to a model based on the existence of a marble-cake-like upper mantle. Although resembling the statistical upper mantle, this model implies that geochemical homogenization can be attained only within the limits of local mantle composition, so that a world-wide uniform depleted reservoir cannot be sampled by simply extending the volume of the region undergoing partial melting.
Sections:Petrology
Subsections:Igneous petrology
Subjects:Basalts; Chemical ratios; Geochemistry; HIMU; Igneous rocks; Lithogeochemistry; Mantle; Mid-ocean ridge basalts; Ocean-island basalts; Partial melting; Upper mantle; Volcanic rocks
Abstract Numbers:07M/2233
Record ID:2007113874
Copyright Information:GeoRef, Copyright 2019 American Geosciences Institute.
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