Low- 18 O Scourie dike magmas from the Lewisian complex, northwestern Scotland

I. Cartwright, J. W. Valley

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Abstract

The Scourie dike swarm of the Lewisian complex, northwestern Scotland, comprises a dominant suite of quartz tholeiites and lesser volumes of norites, olivine gabbros, and bronzite picrites that were emplaced at depths of > 14 km in two episodes at 2.0 and 2.4 Ga. Unaltered quartz tholeiite dikes have low and homogeneous whole-rock δ 18 O values and concordant mineral δ 18 O values. The dikes intrude granulite facies gneisses that have heterogeneous δ 18 O whole-rock values and show no evidence of 18 O depletion. Low-δ 18 O intrusive igneous rocks are generally believed to have exchanged with high-temperature meteoric or oceanic fluids after emplacement. The heterogeneous high δ 18 O values of the country rocks suggest that the Lewisian complex has not been pervasively infiltrated by such fluids. It is more likely that these dikes were emplaced as primary low-δ 18 O magmas derived from the subcontinental lithosphere. -from Authors

Original languageEnglish
Pages (from-to)578-581
Number of pages4
JournalGeology
Volume19
Issue number6
DOIs
Publication statusPublished - 1 Jan 1991

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