Gneiss complex of the Skærfjorden region (76°-78°N), North-East Greenland

J.M Hull,J.A Gilotti,N Henriksen,F Kalsbeek,A.K Higgins,J.D Friderichsen

doi:10.34194/rapggu.v162.8247

Abstract

The crystalline rocks of the Skærfjorden region are dominated by grey migmatitic orthogneisses with smaller bodies of ultramafic, mafic and metasedimentary lithologies. Archaean rocks (c. 3.0 Ga) have been documented, but crustal additions were predominantly Early Proterozoic (2.0–1.75 Ga) in age, reflecting subduction zone magmatism. FolIowing Early Proterozoic orogenesis and migmatisation, granitic sheets (c. 1.7 Ga) and dolerite dykes were intruded. These intrusive rocks were subsequently deformed and metamorphosed in the Caledonian orogeny (c. 400 Ma). The Skærfjorden region is located in the Caledonian hinterland, where orogen parallel stretching and extension followed an early nappe stage.

Highlights

Dove BugtOne polyphase gneiss sample near the Danmarkshavn weather station has yielded an Archaean (- 3.0 Ga), U-Pb age (upper intercept) on zircon separates (Steiger et al, 1976), recently confirmed by new SHRIMP analyses (Nutman & Kalsbeek, 1994)
The crystalline rocks of tbe Skærfjorden region are dominated by grey migmatitic orthogneisses with smaller bodies of ultramafic, mafic and metasedimentaI)' lithologies
The Skærfjorden region is located in the Caledonian hinterland, where Drogen parallel stretching and extension followed an early nappe stage

Summary

Dove Bugt

One polyphase gneiss sample near the Danmarkshavn weather station has yielded an Archaean (- 3.0 Ga), U-Pb age (upper intercept) on zircon separates (Steiger et al, 1976), recently confirmed by new SHRIMP analyses (Nutman & Kalsbeek, 1994). This age has been interpreted as the crystallisation of the igneous protolith. A malic dyke swarm cuts gneissosity and associaled tight to isoclinal folds in this area (Fig. 3), and was in turn deformed and metamorphosed in the amphibolite facies, probably during the Caledonian orogeny (Steiger et al, 1976). The only nolable difference is lhe greater abundance of mafic dykes around Danmarkshavn, compared with most other areas

EARLY PROTEROZOIC

Zr er

Structure and metamorphism

HINGE LINES ISOCLlNES

SECOND SCHISTOSITY

Deformation zones