Olivine Major and Trace Element Compositions in Southern Payenia Basalts, Argentina: Evidence for Pyroxenite–Peridotite Melt Mixing in a Back-arc Setting.

Soager, Nina, Portnyagin, Maxim , Hoernle, Kaj , Holm, Paul Martin, Hauff, Folkmar and Garbe-Schönberg, Dieter (2015) Olivine Major and Trace Element Compositions in Southern Payenia Basalts, Argentina: Evidence for Pyroxenite–Peridotite Melt Mixing in a Back-arc Setting. Journal of Petrology, 56 (8). pp. 1495-1518. DOI 10.1093/petrology/egv043.

[thumbnail of Søager.pdf] Text
Søager.pdf - Published Version
Restricted to Registered users only

Download (2MB) | Contact
[thumbnail of egv043_Supplementary_Data.zip] Archive
egv043_Supplementary_Data.zip - Supplemental Material
Restricted to Registered users only

Download (1MB) | Contact

Supplementary data:

Abstract

Olivine major and trace element compositions from 12 basalts from the southern Payenia volcanic province in Argentina have been analyzed by electron microprobe and laser ablation inductively coupled plasma mass spectrometry. The olivines have high Fe/Mn and low Ca/Fe and many fall at the end of the global olivine array, indicating that they were formed from a pyroxene-rich source distinct from typical mantle peridotite. The olivines with the highest Fe/Mn have higher Zn/Fe, Zn and Co and lower Co/Fe than the olivines with lower Fe/Mn, also suggesting contributions from a pyroxene-rich source. Together with whole-rock radiogenic isotopes and elemental concentrations, the samples indicate mixing between two mantle sources: (1) a pyroxene-rich source with EM-1 ocean island basalt type trace element and isotope characteristics; (2) a peridotitic source with more radiogenic Pb that was metasomatized by subduction-zone fluids and/or melts. The increasing contributions from the pyroxene-rich source in the southern Payenia basalts are correlated with an increasing Fe-enrichment, which caused the olivines to have lower forsterite contents at a given Ni content. Al-in-olivine crystallization temperatures measured on olivine–spinel pairs are between 1155 and 1243°C and indicate that the magmas formed at normal upper mantle (asthenospheric) temperatures of ∼1350°C. The pyroxene-rich material is interpreted to have been brought up from the deeper parts of the upper mantle by vigorous asthenospheric upwelling caused by break-off of the Nazca slab south of Payenia during the Pliocene and roll-back of the subducting slab beneath Payenia. The pyroxene-rich mantle mixed with peridotitic metasomatized South Atlantic mantle in the mantle wedge beneath Payenia.

Document Type: Article
Additional Information: WOS:000361838900002
Keywords: back-arc basalts, mantle temperature, olivine, peridotite, pyroxenite
Research affiliation: Kiel University
OceanRep > The Future Ocean - Cluster of Excellence
OceanRep > GEOMAR > FB4 Dynamics of the Ocean Floor > FB4-MUHS
Refereed: Yes
Open Access Journal?: No
Publisher: Oxford Univ. Press
Projects: Future Ocean
Date Deposited: 31 Aug 2015 11:17
Last Modified: 23 Sep 2019 19:34
URI: https://oceanrep.geomar.de/id/eprint/29465

Actions (login required)

View Item View Item