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A geochemical and Sr-Nd-O isotopic study of the Proterozoic Eriksfjord Basalts, Gardar Province, South Greenland: Reconstruction of an OIB signature in crustally contaminated rift-related basalts

Published online by Cambridge University Press:  05 July 2018

R. Halama ,
T. Wenzel ,
B. G. J. Upton ,
W. Siebel  and
G. Markl
R. Halama
Affiliation:
Universität Tübingen, Institut für Geowissenschaften, Wilhelmstr. 56, D-72074 Tübingen, Germany
T. Wenzel
Affiliation:
Universität Tübingen, Institut für Geowissenschaften, Wilhelmstr. 56, D-72074 Tübingen, Germany
B. G. J. Upton
Affiliation:
Department of Geology and Geophysics, The University of Edinburgh, West Mains Road, Edinburgh EH9 3JW, UK
W. Siebel
Affiliation:
Universität Tübingen, Institut für Geowissenschaften, Wilhelmstr. 56, D-72074 Tübingen, Germany
G. Markl*
Affiliation:
Universität Tübingen, Institut für Geowissenschaften, Wilhelmstr. 56, D-72074 Tübingen, Germany
*
* E-mail: markl@uni-tuebingen.de
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Abstract

Basalts from the volcano-sedimentary Eriksfjord Formation (Gardar Province, South Greenland) were erupted at around 1.2 Ga into rift-related graben structures. The basalts have compositions transitional between tholeiite and alkaline basalt with MgO contents <7 wt.% and they display LREE-enrichment relative to a chondritic source. Most of the trace element and REE characteristics are similar to those of basalts derived from OIB-like mantle sources. Initial 87Sr/86Sr ratios of clinopyroxene separates range from 0.70278 to 0.70383 and initial ϵNd values vary from –3.2 to +2.1. The most unradiogenic samples overlap with the field defined by carbonatites of similar age and can be explained by mixing of isotopically depleted and enriched mantle components. Using AFC modelling equations, the Sr-Nd isotope data of the more radiogenic basalts can successfully be modelled by addition of <5% lower crustal granulite-facies gneisses as contaminants. δ18Ov-smow values of separated clinopyroxene range from +5.2 to +6.0% and fall within the range of typical mantle-derived rocks. However, up to 10% mixing with an average lower crustal component are permitted by the data.

Keywords

geochemistrySr-Nd-O isotopesGardar ProvincebasaltGreenland.
Type
Research Article
Information
Mineralogical Magazine , Volume 67 , Issue 5 , October 2003 , pp. 831 - 853
Copyright
Copyright © The Mineralogical Society of Great Britain and Ireland 2003

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