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Thermochronological evidence for late Proterozoic (Vendian) cooling in southwest Wedel Jarlsberg Land, Spitsbergen

Published online by Cambridge University Press:  01 January 1998

M. MANECKI
Affiliation:
Department of Geology, Kent State University, Kent, Ohio 44242, USA
D. K. HOLM
Affiliation:
Department of Geology, Kent State University, Kent, Ohio 44242, USA
J. CZERNY
Affiliation:
Faculty of Geology, Geophysics and Env. Protection, Univ. of Mining and Metallurgy, 30-059 Krakow, Poland
D. LUX
Affiliation:
Department of Geological Sciences, University of Maine, Orono, Maine 04469, USA

Abstract

Two Proterozoic terranes with different metamorphic histories are distinguished from geological mapping in southwestern Wedel Jarlsberg Land: a northern greenschist facies terrane and a southern amphibolite facies terrane which has been overprinted by greenschist facies metamorphism. To better characterize the tectonothermal history of these terranes we have obtained new 40Ar/39Ar mineral dates from this area. A muscovite separate from the northern terrane yielded a Caledonian plateau age of 432±7 Ma. The southern terrane yielded significantly older 40Ar/39Ar ages with three muscovite plateau dates of 584±14 Ma, 575±15 Ma, and 459±9 Ma, a 484±5 Ma biotite plateau date, and a 616±17 Ma hornblende plateau date. The oldest thermochronological dates are over 300 Ma younger than the age of amphibolite facies metamorphism and therefore probably do not represent uplift-related cooling. Instead, the Vendian dates correlate well with a regionally widespread magmatic and metamorphic/thermal resetting event recognized within Caledonian complexes of northwestern Spitsbergen and Nordaustlandet. The apparent Ordovician dates are interpreted to represent partial resetting, suggesting that late Caledonian greenschist facies overprinting of the southern terrane was of variable intensity.

Type
Research Article
Copyright
© 1998 Cambridge University Press

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