570 Ma in the Northern Norwegian Caledonides: U–Pb Zircon
Geol. Mag. 143 (6),2006,pp.887–903. c 2006 Cambridge University Press ! 887 doi:10.1017/S0016756806002512 Printed in the United Kingdom Short-lived mafic magmatism at 560–570 Ma in the northern Norwegian Caledonides: U–Pb zircon ages from the Seiland Igneous Province R. J. ROBERTS∗ ,F.CORFU,T.H.TORSVIK,L.D.ASHWAL∗ &D.M.RAMSAY † ‡ § ¶ ∗School of Geosciences, Private Bag 3, University of the Witwatersrand, Johannesburg 2050, Republic of South Africa Department of Geology, University of Oslo, Oslo, Norway Geodynamic Centre, Geological‡ Survey of Norway, Leiv Erikssonsvei 39, N-7491 Trondheim, Norway; and Institute § for Petroleum Technology and Applied Geophysics, NTNU, N-7491 NTNU, Norway 27 Marlee Road, Dundee, Scotland, UK ¶ (Received 2February2005; accepted 13 March 2006) Abstract – The Seiland Igneous Province (SIP) of northern Norway comprises a suite of mainly gabbroic plutons, with subordinate ultramafic, syenitic and felsic intrusions. Several intrusions from the Seiland Igneous Province have been dated by ID-TIMS U–Pb zircon and monazite analyses. The Hasvik Gabbro on the island of Sørøy, previously assigned an age of 700 33 Ma by Sm–Nd, yields a U–Pb zircon age of 562 6 Ma, within error of the Storelv Gabbro± (569 5Ma)anda diorite associated with the Breivikbotn± Gabbro (571 4 Ma). Various intrusions on± the Øksfjord peninsula give nearly identical ages of 565 9Ma(gabbro),566± 4 Ma (monzonite), 565 5Ma (monzodiorite), 570 9 Ma (norite), and 566± 1 Ma (orthopyroxenite).± These ages overlap with± those from Sørøy, and define± a single and short-lived± period of gabbroic (to felsic) magmatism for the region between 570 and 560 Ma, pre-dating a subordinate episode of alkalic magmatism at 530–520 Ma.
[Show full text]