Abstract
The Grandjean Fjord – Bessel Fjord region (75°–76°N) contains the northernmost occurrences of Caledonian granites in North-East Greenland. Most of them have been emplaced along the margins of a sequence of late Proterozoic sediments, the Eleonore Bay Supergroup, or occur within middle Proterozoic metasediments of the Smallefjord sequence. Most granites are undeformed, but granite sheets within the Smallefjord sequence may be foliated. Zircon U-Pb dates indicate that they were emplaced about 400 Ma ago. Sm-Nd, Rb-Sr, and major and trace element analyses suggest that the granites are of mixed origin. Components of crustal origin and juvenile mantle-derived material are present, and occur in variable proportions. Under these circumstances precise dating of the rocks is difficult: Rb-Sr whole-rock errorchrons yield erroneous 'ages' and zircon U-Pb data are not always easily interpreted.
Highlights
The Grandjean Fjord - Bessel Fjord region (75°-76°N) contains the northernmost occurrences of Caledonian granites in North-East Greenland
Caledonian intrusions are found in the crystalline basement complexes of metasediments and gneisses whieh oeeur strueturally below the Eleonore Bay Supergroup; they can usual!y be distinguished from older, pre-Caledonian, granitie rocks by their lack of deformation and foliation
HlggllL', fered high-grade migmatisation and metamorphism about 950 Ma ago (Strachan et al, in press); (3) the late Proterozoic Eleonore Bay Supergroup (Sønderholm & Tirsgaard, 1993), a thick sedimentary sequence occupying a graben-like depression, which exhibits Caledonian deformation and metamorphism, Iocally reaching amphiboJite facies; (4) Caledonian intrusions, mainly leucocratic granites emplaced into sediments of the Eleonore Bay Supergroup and the adjacent middle Proterozoic Smallefjord sequence
Summary
Within the Grandjean Fjord - Bessel Fjord region four main rock units are present (Fig. l): (l) early Proterozoic basement gneisses and granites whieh have given isotopie ages of c. 2000-1750 Ma (Friderichsen et al, 1994; Kalsbeek et al, 1993); (2) amiddle Proterozoic metasedimentary sequenee, the Smallefjord sequence, whieh suf-. Within the Grandjean Fjord - Bessel Fjord region four main rock units are present (Fig. l): (l) early Proterozoic basement gneisses and granites whieh have given isotopie ages of c. 2000-1750 Ma (Friderichsen et al, 1994; Kalsbeek et al, 1993); (2) amiddle Proterozoic metasedimentary sequenee, the Smallefjord sequence, whieh suf-. Tbe mounlajn :11 Ine left l~ IJ(X) m high. K. HlggllL', fered high-grade migmatisation and metamorphism about 950 Ma ago (Strachan et al, in press); (3) the late Proterozoic Eleonore Bay Supergroup (Sønderholm & Tirsgaard, 1993), a thick sedimentary sequence occupying a graben-like depression, which exhibits Caledonian deformation and metamorphism, Iocally reaching amphiboJite facies; (4) Caledonian intrusions, mainly leucocratic granites emplaced into sediments of the Eleonore Bay Supergroup and the adjacent middle Proterozoic Smallefjord sequence
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