Petrogenesis of late stage magmatism at Hold with Hope, East Greenland
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The Myggbukta caldera complex and a swarm of basic dykes constitute the latest Tertiary magmatism in the Hold with Hope region, East Greenland. The Sr and Nd isotope ratios of these rocks show coherent variations which extend to high 87Sr/86Sr and low 143Nd/144Nd values and require a contribution from continental lithosphere. Broad correlations with major element differentiation indices suggest that the continental component was incorporated during magmatic differentiation thereby favouring a crustal contamination process. Trace element concentrations are strongly correlated with isotopic compositions but display ranges for many incompatible elements which extend beyond likely crustal contaminant compositions. This is readily modelled by AFC processes in which the dominant cause of trace element enrichment is the concentration effect of fractional crystallisation rather than the composition of the contaminant. The simplest such models still require unrealistically high degrees of fractional crystallisation to explain the ten-fold enrichment of some trace elements. This can be overcome if the primary magmas entering the crust already had highly variable trace element compositions. Such variability is readily achieved if melts from different parts of the melting column escape without thorough homogenization. An AFC model which incorporates variability in parental magma composition is then able to simulate the range of compositions observed at Hold with Hope. This carries the implication that the variations observed are more readily attributed to changes in uncontaminated parental magma than to variations in the composition or amount of contaminant.
- Petrogenesis of late stage magmatism at Hold with Hope, East Greenland
Contributions to Mineralogy and Petrology
Volume 133, Issue 1-2 , pp 51-59
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- A1. Isotope Geosciences Unit, Scottish Universities Research and Reactor Centre, East Kilbride, G75 0QF, Scotland, UK Tel.: +44 (0) 1355 223332; Fax: +44 (0) 1355 229898; e-mail: email@example.com, GB
- A2. Department of Geology and Geophysics, University of Edinburgh, West Mains Road, Edinburgh, EH9 3JW, Scotland, UK, GB