Geochemical evidence for melting of carbonated peridotite on Santa Maria Island, Azores.

Beier, Christoph, Mata, J., Stöckhert, F., Mattielli, N., Brandl, Philipp A. , Madureira, P., Genske, F. S., Martins, S., Madeira, J. and Haase, K. M. (2013) Geochemical evidence for melting of carbonated peridotite on Santa Maria Island, Azores. Contributions to Mineralogy and Petrology, 165 (5). pp. 823-841. DOI 10.1007/s00410-012-0837-2.

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Abstract

The islands of the Azores archipelago emerge from an oceanic plateau built on lithosphere increasing in age with distance from the Mid-Atlantic Ridge from 10 to 45 Ma. Here, we present the first comprehensive major and trace element and Sr–Nd–Pb isotope data from Santa Maria, the easternmost island of the archipelago, along with published data from the other Azores islands situated much closer to the Mid-Atlantic Ridge axis. We can show that the distinctively more variable and more enriched trace element ratios at Santa Maria combined with a relatively small range in Sr–Nd–Pb isotope ratios are the result of low degrees of partial melting of a common Azores mantle plume source underneath thicker lithosphere. This implies that melt extraction processes and melting dynamics may be able to better preserve the trace element mantle source variability underneath thicker lithosphere. These conclusions may apply widely for oceanic melts erupted on relatively thick lithosphere. In addition, lower Ti/Sm and K/La ratios and SiO2 contents of Santa Maria lavas imply melting of a carbonated peridotite source. Mixing of variable portions of deep small-degree carbonated peridotite melts and shallow volatile-free garnet peridotite could explain the geochemical variability underneath Santa Maria in agreement with the volatile-rich nature of the Azores mantle source. However, Santa Maria is the Azores island where the CO2-rich nature of the mantle source is more evident, reflecting a combination of a smaller extent of partial melting and the positioning at the edge of the tilted Azores mantle plume.

Document Type: Article
Keywords: Ocean Island Basalts, Azores, Lithosphere thickness, Melting dynamics, Carbonated peridotite
Research affiliation: OceanRep > The Future Ocean - Cluster of Excellence > FO-R07
OceanRep > The Future Ocean - Cluster of Excellence > FO-R09
OceanRep > The Future Ocean - Cluster of Excellence
OceanRep > The Future Ocean - Cluster of Excellence > FO-R03
OceanRep > The Future Ocean - Cluster of Excellence > FO-R10
OceanRep > The Future Ocean - Cluster of Excellence > FO-R06
Kiel University
Refereed: Yes
DOI etc.: 10.1007/s00410-012-0837-2
ISSN: 0010-7999
Projects: Future Ocean
Date Deposited: 09 Aug 2017 09:25
Last Modified: 14 Dec 2017 04:46
URI: http://oceanrep.geomar.de/id/eprint/39059

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