Abstract
Lamprophyres represent hydrous alkaline mantle melts that are a unique source of information about the composition of continental lithosphere. Throughout southwest Britain, post-Variscan lamprophyres are (ultra)potassic with strong incompatible element enrichments. Here we show that they form two distinct groups in terms of their Sr and Nd isotopic compositions, occurring on either side of a postulated, hitherto unrecognized terrane boundary. Lamprophyres emplaced north of the boundary fall on the mantle array with eNd -1 to +1.6. Those south of the boundary are enriched in radiogenic Sr, have initial eNd values of -0.3 to -3.5, and are isotopically indistinguishable from similar-aged lamprophyres in Armorican massifs in Europe. We conclude that an Armorican terrane was juxtaposed against Avalonia well before the closure of the Variscan oceans and the formation of Pangea. The giant Cornubian Tin-Tungsten Ore Province and associated batholith can be accounted for by the fertility of Armorican lower crust and mantle lithosphere.
DOI
10.1038/s41467-018-06253-7
Publication Date
2018-09-14
Publication Title
Nature Communications
Volume
9
Issue
1
Publisher
Nature Research (part of Springer Nature)
ISSN
2041-1723
Embargo Period
2024-11-25
Recommended Citation
Dijkstra, A., & Hatch, C. (2018) 'Mapping a hidden terrane boundary in the mantle lithosphere with lamprophyres', Nature Communications, 9(1). Nature Research (part of Springer Nature): Available at: https://doi.org/10.1038/s41467-018-06253-7
Comments
No embargo required.