Melt–peridotite reactions in upwelling eclogite bodies: Constraints from EM1-type alkaline basalts in Payenia, Argentina.

Soager, Nina and Holm, Paul Martin (2013) Melt–peridotite reactions in upwelling eclogite bodies: Constraints from EM1-type alkaline basalts in Payenia, Argentina. Chemical Geology, 360-361 . pp. 204-219. DOI 10.1016/j.chemgeo.2013.10.024.

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Abstract

The processes of magma generation in upwelling eclogite bodies of recycled lithospheric material are not fully
understood but are important for our understanding and modelling of major and trace element variations in
many ocean island basalts (OIB). The primitive alkaline intraplate basalts from the Payenia volcanic province
(34–38 °S) in Argentina, for which Sr, Nd and double-spike Pb isotope ratios are presented, and from other
north Patagonian volcanic fields may provide details of the eclogite melt–peridotite reactions taking place in
the melting column of an upwelling OIB-type mantle. The isotopic composition of the uncontaminated lavas is
highly restricted but the Payenia basalts fall in two distinct trace element groups termed the high and low
Nb/U groups, which both have EM1-type trace element patterns but with subtle differences that cannot be
explained by contamination, fractionation or simple variations in degrees of mantle melting. The difference is
also clear in major elements where the low Nb/U basalts have markedly higher alkali contents but lower FeO
and Ni than the high Nb/U basalts. Four melt components have been identified based on olivine fractionation
corrected compositions: a low Nb/U pyroxenite melt component which is interpreted as an eclogite melt that
experienced low degrees of melt–peridotite interaction, a high Nb/U pyroxenite melt component which is
interpreted as an eclogite melt that experienced high degrees of melt–peridotite interaction, a low pressure
peridotite melt component which contributes to most high Nb/U, Payún Matrú, Matancilla and Auca Mahuida
basalts and finally, a melt component with similarities to peridotite melts contributing to many low Nb/U
lavas. The high Nb/U type basalts are interpreted to have been formed from mantle with higher temperature
than ambient mantle while the low Nb/U basalts may have been formed from normal temperature mantle.

Document Type: Article
Keywords: Intraplate basalts ; Pyroxenite melting ; Isotopes ; Enriched mantle 1
Research affiliation: OceanRep > GEOMAR > FB4 Dynamics of the Ocean Floor > FB4-MUHS
Refereed: Yes
Open Access Journal?: No
Publisher: Elsevier
Date Deposited: 17 Dec 2013 14:17
Last Modified: 04 Aug 2016 08:50
URI: https://oceanrep.geomar.de/id/eprint/22690

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