Bimodal magmatism produced by progressively inhibited crustal assimilation

• Published in: Nature Communications
• Main Authors: Meade, F., Troll, V., Ellam, R. M., Freda, C., Font, L., Donaldson, C. H., Klonowska, I.
• Other Authors: Meade, F.; Department of Earth Sciences, CEMPEG, Uppsala University, Villava¨gen 16, 752 36 Uppsala, Sweden, Troll, V.; Department of Earth Sciences, CEMPEG, Uppsala University, Villava¨gen 16, 752 36 Uppsala, Sweden, Ellam, R. M.; Scottish Universities Environmental Research Centre, Rankine Avenue, East Kilbride, G75 0QF Scotland, UK., Freda, C.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia, Font, L.; Department of Petrology, Vrije Universiteit Amsterdam, De Boelelaan 1085, 1081 HV Amsterdam, Netherlands, Donaldson, C. H.; School of Geography and Geosciences, University of St Andrews, North Street, St Andrews, KY16 9AL Scotland, UK., Klonowska, I.; Department of Earth Sciences, CEMPEG, Uppsala University, Villava¨gen 16, 752 36 Uppsala, Sweden, Department of Earth Sciences, CEMPEG, Uppsala University, Villava¨gen 16, 752 36 Uppsala, Sweden, Scottish Universities Environmental Research Centre, Rankine Avenue, East Kilbride, G75 0QF Scotland, UK., Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia, Department of Petrology, Vrije Universiteit Amsterdam, De Boelelaan 1085, 1081 HV Amsterdam, Netherlands, School of Geography and Geosciences, University of St Andrews, North Street, St Andrews, KY16 9AL Scotland, UK.
• Format: Article in Journal/Newspaper
• Language: English
• Published: 2014 Macmillan Publishers Limited 2014
• Subjects: Bimodal magmatism; crustal contamination; isotope geochemistry; experimental petrology; 04. Solid Earth::04.04. Geology::04.04.07. Rock geochemistry; North Atlantic
• Online Access: http://hdl.handle.net/2122/9048; https://doi.org/10.1038/ncomms5199

The origin of bimodal (mafic–felsic) rock suites is a fundamental question in volcanology. Here we use major and trace elements, high-resolution Sr, Nd and Pb isotope analyses, experimental petrology and thermodynamic modelling to investigate bimodal magmatism at the iconic Carlingford Igneous Centre, Ireland. We show that early microgranites are the result of extensive assimilation of trace element-enriched partial melts of local metasiltstones into mafic parent magmas. Melting experiments reveal the crust is very fusible, but thermodynamic modelling indicates repeated heating events rapidly lower its melt-production capacity. Granite generation ceased once enriched partial melts could no longer form and subsequent magmatism incorporated less fertile restite compositions only, producing mafic intrusions and a pronounced compositional gap. Considering the frequency of bimodal magma suites in the North Atlantic Igneous Province, and the ubiquity of suitable crustal compositions, we propose ‘progressively inhibited crustal assimilation’ (PICA) as a major cause of bimodality in continental volcanism. Irish Research Council for Science, Engineering and Technology (IRCSET) Science Foundation Ireland basic research Published 4199 1V. Storia e struttura dei sistemi vulcanici JCR Journal restricted