Remnants of arc-related Mesoarchaean oceanic crust in the Tartoq Group of SW Greenland

Kristoffer Szilas, Vincent J. van Hinsberg, Alex. F.M. Kisters, J. Elis Hoffmann, Brian F. Windley, Thomas F. Kokfelt, Anders Scherstén, Robert Frei, Minik T. Rosing, Carsten Münker

Research output: Contribution to journalArticleResearchpeer-review

49 Citations (Scopus)

Abstract

The Tartoq Group, located in SW Greenland, consists of supracrustal rocks of mainly tholeiitic basaltic composition, including pillow lavas, sills/dykes and gabbros, as well as ultramafic rocks. Metamorphic grade ranges from greenschist facies to granulite facies. The Tartoq Group crops out as a series of blocks and slivers that are imbricated with originally intrusive Mesoarchaean TTG orthogneisses. The supracrustal rocks form part of a SE vergent fold and thrust belt consistent with the imbrication of TTG gneisses and supracrustal rocks along a convergent margin. LA-ICP-MS U-Pb zircon dating of an intrusive TTG sheet yields a minimum age of 2986±4Ma for the Tartoq Group. This age is consistent with MC-ICP-MS Lu-Hf and Sm-Nd isotopic whole-rock data for mafic samples from different blocks of the Tartoq Group, which yield errorchron ages of 3189±65Ma and 3068±220Ma, respectively. The mafic supracrustal rocks of the Tartoq Group have chondrite-normalized REE patterns with La CN/Sm CN of 0.67-1.96 and rather flat primitive mantle-normalized multi-element patterns, except for scattered LILE contents, and generally negative Nb-anomalies with Nb/Nb* of 0.26-1.31. Th/Yb varies between 0.06 and 0.47 and Nb/Yb between 0.45 and 4.4 indicative of an arc affinity when compared to rocks from modern settings. The similar geochemistry of the different lithological units, together with their coeval formation, as evident from trace element geochemical trends, supports a co-magmatic origin for the rock assemblage and their formation as imbricated relics of oceanic crust. Accordingly, we propose that the Tartoq Group represents remnants of Mesoarchaean oceanic crust, which formed in a suprasubduction zone geodynamic environment.

Original languageEnglish
Pages (from-to)436-451
Number of pages16
JournalGondwana Research
Volume23
Issue number2
DOIs
Publication statusPublished - Mar 2013

Keywords

  • Archaean
  • Geochronology
  • Greenland
  • Oceanic crust
  • Supracrustal belt
  • Tartoq Group

Programme Area

  • Programme Area 4: Mineral Resources

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