Geochemistry of Precambrian basal gneisses in Lofoten—Vesterålen,northern Norway |
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Authors: | IK Iden |
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Institution: | Mineralogisk-Geologisk Museum, Sarsgt. 1, Oslo 5 Norway |
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Abstract: | The basal gneiss complex of Lofoten—Vesterålen consists of an older (ca. 2.7 Ga) migmatite complex, believed to be largely supracrustal in origin, and a younger (ca. 1.8 Ga) cover complex of clearly supracrustal origin. The major-element geochemistry of both groups is that of an igneous suite of generally calc-alkaline character. Similarities with the volcanic rocks of modern continental-margin environments extend to trace-element contents and REE patterns. A complex multistage evolution is inferred.An orthopyroxene isograd bisects the area. Element fractionation between amphibolitefacies and granulite-facies rocks appears to be limited to some trace elements; REE patterns are not affected by the metamorphism. |
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