Geochemistry of the Palaeoproterozoic Bangenhuk granitoids, Ny Friesland, Svalbard

Abstract

Old Red Sandstones and younger strata overlie a variety of Early Palaeozoic and Precambrian rocks on Svalbard, referred to as the Hecla Hoek Complex, which were deformed and metamorphosed during the Caledonian orogeny. At least three different Caledonian terranes are recognized, occurring in the eastern, northwestern and southwestern parts of Svalbard. The Eastern Terrane is exposed on the island of Nordaustlandet and on the Ny Friesland peninsula of northeast Spitsbergen. In the latter area, c. 1750 Ma old granites and gneissic granites, mainly from the Bangenhuk Formation in the Lower Hecla Hoek, have been studied. They have previously been interpreted by most authors to be of metavolcanic and/or metasomatic origin. Petrographical and geochemical data and field relationships indicate that these are plutonic rocks; they can be classified as granites or granodiorites and plot as A‐type granites in tectonic discrimination diagrams, being characterized by high alkali contents, high Fe2O₃∗/(Fe2O₃∗+MgO) ratios and high contents of Zr, Zn, Y, Nb, Ga, and REE (except Eu). They show slightly negative initial ε_Nd‐values of ‐2 to ‐3, while the Rb‐Sr system has been disturbed. However, Caledonian deformation and metamorphism have, in general, not influenced the element distribution significantly. High trace and rare earth element abundances, fractionated REE patterns, and low initial ε_Nd‐values are all suggestive of some crustal precursor or crustal contribution to their magmas, and preclude direct mantle derivation.

Carlsson, P., Johansson, Å. & Gee, D.G., 1995: Geochemistry of the Palaeoproterozoic Bangenhuk granitoids, Ny Friesland, Svalbard. GFF, Vol. 117 (Pt. 2, June), pp. 107–119. Stockholm. ISSN 1103–5897.

Keywords:

• Svalbard
• Hecla Hoek
• Bangenhuk
• Palaeoproterozoic
• geochemistry
• A‐type granites
• REE