New hornblende and muscovite 40Ar/39Ar cooling ages in the central Rinkian fold belt, West Greenland

Authors

  • Ann-Sofie Sidgren Department of Geolog y, Geobiosphere Science Center, Lund University, Sölvegatan 12, S-223 62 Lund, Sweden
  • Laurence Page Department of Geolog y, Geobiosphere Science Center, Lund University, Sölvegatan 12, S-223 62 Lund, Sweden
  • Adam A. Garde Geological Survey of Denmark and Greenland, Øster Voldgade 10, DK-1350 Copenhagen K, Denmark

DOI:

https://doi.org/10.34194/geusb.v11.4920

Keywords:

Ar-Ar, geochronology, Rinkian, Palaeoproterozoic, West Greenland

Abstract

The Palaeoproterozoic Rinkian fold belt in West Greenland consists of reworked Archaean basement, mainly orthogneiss, and the unconformably overlying Palaeoproterozoic Karrat Group. Both parts were intensely deformed and metamorphosed at around 1.87 Ga, at which time the crustal anatectic Prøven igneous complex was emplaced into the northern part of the belt. Seven new hornblende and muscovite 40Ar/39Ar cooling ages are presented from the central–northern parts of the Rinkian fold belt. Four 40Ar/39Ar hornblende ages ranging from 1795 ± 3 to 1782 ± 3 Ma were obtained from amphibolite and hornblendite enclaves in the Archaean orthogneiss, and two from relict dyke fragments in the latter that may be of Palaeoproterozoic age. Three 40Ar/39Ar muscovite ages of 1681 ± 6 Ma, 1686 ± 3 Ma and 1676 ± 3 Ma were obtained from samples of Karrat Group metagreywacke, andalusite schist and metasiltstone. The new 40Ar/39Ar ages, from hornblende and muscovite respectively, are very uniform and probably unrelated to local metamorphic grade and structural history, and are interpreted as regional late orogenic cooling ages. The new hornblende ages are significantly older than those previously obtained from the central and northern parts of the adjacent Nagssugtoqidian orogen to the south, and point to different uplift histories, which may suggest that the orogeny was not synchronous in the two regions.

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Published

2006-12-05

How to Cite

Sidgren, A.-S. ., Page, L. ., & Garde, A. A. . (2006). New hornblende and muscovite 40Ar/39Ar cooling ages in the central Rinkian fold belt, West Greenland. GEUS Bulletin, 11, 115–124. https://doi.org/10.34194/geusb.v11.4920

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