Title

Late Neoproterozoic Amphibolite-Facies Metamorphism of a Pre-Caledonian Basement Block in Southwest Wedel Jarlsberg Land, Spitsbergen: New Evidence from U–Th–Pb Dating of Monazite

Publication Title

Geological Magazine

Publication Date

11-2008

Document Type

Article

DOI

10.1017/S001675680800530X

Keywords

svalbard, caledonides, terranes, geochronology, tectonics

Disciplines

Geology

Abstract

Abstract Southwest Spitsbergen, Wedel Jarlsberg Land, consists of two Proterozoic crustal blocks with differing metamorphic histories. Both blocks experienced Caledonian greenschist-facies metamorphism, but only the southern block records an earlier pervasive M1 amphibolite-facies metamorphism and strong deformational fabric. In situ EMPA total-Pb monazite geochronology from both matrix and porphyroblast inclusion results indicate that the older M1 metamorphism occurred at 643 ± 9 Ma, consistent with published cooling ages of c. 620 Ma (hornblende) and 580 Ma (mica) obtained from these same rocks. This region thus contains a lithostratigraphic profile and metamorphic history which are unique within the Svalbard Archipelago. Documentation of a pervasive late Neoproterozoic Barrovian metamorphism is difficult to reconcile with a quiescent non-tectonic regime typically inferred for this region, based on the occurrence of rift-drift sequences on the Baltic and Laurentian passive margins. Instead, our new metamorphic age implies an exotic origin of the pre-Devonian basement exposed in SW Spitsbergen and supports models of terrane assembly postulated for the Svalbard Archipelago.

Publisher

Cambridge University Press

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