Journal
EARTH AND PLANETARY SCIENCE LETTERS
Volume 308, Issue 3-4, Pages 380-390Publisher
ELSEVIER SCIENCE BV
DOI: 10.1016/j.epsl.2011.06.008
Keywords
experimental petrology; ocean island basalt; partial melting; garnet peridotite
Categories
Funding
- NSF [EAR0609967, EAR1019744]
- Division Of Earth Sciences
- Directorate For Geosciences [1019744] Funding Source: National Science Foundation
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We determined experimentally the composition of an incipient partial melt of a garnet Iherzolite similar to KLB-1 peridotite at 3 GPa using modified iterative sandwich experiments (MISE). The MISE method enables microbeam analyses of quenched liquids that are in equilibrium at the onset of melting (nominally, 0% melt fraction) with a specified peridotite bulk composition. The equilibrium incipient partial melt is a TiO2-enriched (2.5 +/- 0.2 wt.%) alkali olivine basalt with 44.8 +/- 0.2 wt.% SiO2 and 15.8 +/- 0.1 wt% MgO. Therefore, it has some compositional characteristics similar to a plausible parent to many alkalic oceanic island basalts. But in detail, several key components of this melt are different from parental liquids of typical primitive alkalic OIB, including lower FeO* (9.7 +/- 0.1 wt.%) and higher Al2O3 (12.7 +/- 0.2 wt.%). It is also distinct from basalts derived from the EM and HIMU mantle end-members. We conclude that the vast majority of alkalic OIB cannot originate from volatile-poor partial melting of garnet peridotite at the base of the oceanic lithosphere unless there are contributions from non-peridotitic lithologies and/or enrichment in volatiles, iron, or other metasomatic components, and that such lithologic heterogeneities are intrinsic features of the HIMU and EM mantle reservoirs. (C) 2011 Elsevier B.V. All rights reserved.
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