Palaeoproterozoic and Archaean gneiss complexes in northern Greenland: Palaeoproterozoic terrane assembly in the High Arctic

• Published in: Precambrian Research
• Main Authors: Nutman, Allen, Dawes, Peter R., Kalsbeek, Feiko, Hamilton, Michael A.
• Format: Article in Journal/Newspaper
• Language: unknown
• Published: Elsevier
• Subjects: Keywords: amphibolite; magmatism; mapping; metamorphism; metasediment; mica; orthogneiss; plutonic rock; Proterozoic; SHRIMP dating; terrane; uranium-lead dating; Arctic; Arctic Ocean; Baffin Bay [Arctic Ocean]; Canada; Greenland; North America Early Precambrian terranes; Inglefield Mobile Belt; Magmatic arc; Metasediments; Northern Greenland; Plutonic rocks; SHRIMP U-Pb zircon dating; Sm-Nd model ages; Baffin Bay; Inglefield Land; Prudhoe Land; Sunrise Pynt; Baffin; East Greenland; Inglefield land; Prudhoe land
• Online Access: http://hdl.handle.net/1885/81917; https://doi.org/10.1016/j.precamres.2007.09.006; https://openresearch-repository.anu.edu.au/bitstream/1885/81917/5/Nutman_A_2008_Palaeoproterozoic.pdf.jpg; https://openresearch-repository.anu.edu.au/bitstream/1885/81917/7/01_Nutman_Palaeoproterozoic_and_Archaean_2008.pdf.jpg

The Precambrian shield of northern Greenland has been investigated by SHRIMP U-Pb zircon dating of 14 orthogneisses and granitoids plus 5 metasediments, integrated with mapping by the Geological Survey of Denmark and Greenland and whole-rock Nd isotopic studies. The Inglefield Mobile Belt is a tract of Palaeoproterozoic sedimentation, plutonism, polyphase deformation and high-grade metamorphism that underlies Inglefield Land and northern Prudhoe Land. In the southern part of the belt at 78°30′N, the E-W-trending Sunrise Pynt Straight Belt is a high-grade, but structurally late, shear zone with contrasts in the geology on either side. South of the Sunrise Pynt Straight Belt, ca. 1980 Ma diorites and tonalites were emplaced into older orthogneisses and metasediments. Detrital zircons from two metaquartzites (deposited on Archaean basement?) yielded complex age spectra from ca. 3250 Ma to 2350 Ma, with 2600-2450 Ma grains dominant. In associated mica schist, low Th/U, 1923 ± 8 Ma zircons date high-grade metamorphism. The most southern orthogneiss investigated (77°45′N) is Neoarchaean (ca. 2600 Ma), in agreement with previously published isotopic data. North of the Sunrise Pynt Straight Belt to 79°10′N an amphibolite-granulite-facies complex with extensive pelitic to psammitic paragneisses are the oldest rocks recognised. Two psammitic paragneisses yielded unrounded zircons with a unimodal detrital age population centred on 2000-1980 Ma. Their source could be ca. 1980 Ma orthogneisses from south of the Sunrise Pynt Straight Belt, or from basement inliers in the North-East Greenland Caledonian fold belt. The metasediments were intruded by tonalites and diorites with dates of 1949 ± 13 Ma and 1943 ± 11 Ma, and then by granitoids (free of zircon inherited from older rocks) with ages of 1924 ± 29 Ma to 1915 ± 19 Ma. The metasediments show development of low Th/U zircon overgrowths at ca. 1920 Ma, coeval with the granitoids. Finally, other granites, some locally transformed into gneisses, have ages of 1783 ± 22 Ma to ...