Abstract
Zircon U-Pb and Rb-Sr whole-rock isotope data show that the crystalline rocks at the head of Victoria Fjord, North Greenland, have Archaean ages (c. 3000 Ma), but that strong disturbance of the isotope systems has taken place later. K-Ar analyses on hornblende show that the area underwent a phase of high-grade metamorphism during the Proterozoic, probably around 1850 Ma.
Highlights
Zircon U-Pb and Rb-Sr whole-rock isotope data show that the crystalline rocks at the head of Victoria Fjord, North Greenland, have Archaean ages (c. 3000 Ma), but that strong disturbance of the isotope systems has taken place later
In North Greenland the crystalline basement is only exposed at the head of Victoria Fjord along the margin of the Inland Ice; elsewhere icetransported boulders of basement rocks are common in glacial deposits, and indicate the presence of crystalline rocks beneath the northem sector of the Inland Ice and probably underlying the Middle Proterozoic to Lower Palaeozoic platform throughout North Greenland
The zircon U-Pb data show beyond doubt that the rocks in question have Archaean ages
Summary
Zircon U-Pb and Rb-Sr whole-rock isotope data show that the crystalline rocks at the head of Victoria Fjord, North Greenland, have Archaean ages (c. 3000 Ma), but that strong disturbance of the isotope systems has taken place later. Zircon U-Pb and Rb-Sr whole-rock isotope data show that the crystalline rocks at the head of Victoria Fjord, North Greenland, have Archaean ages F. K., Grønlands Geologiske Undersøgelse, øster Voldgade IO, DK-1350 Copenhagen K, Denmark. H., Institut for Petrologi, Københavns Universitet, øster Voldgade IO, DK-I350 Copenhagen K, Denmark. This report presents the results of U-Pb age determinations on zircons f~om two samples, Rb-Sr whole-rock isotope data on two sample sets, and K-Ar measurements on three hornblende concentrates, all from the basement rocks at the head of Victoria Fjord. Supracrustal rocks have been observed at a number of localities within the orthogneisses. They are dominated by foliated amphibolite bands together with biotite-rich mica schists and, at one 10-
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