The browser you are using is not supported by this website. All versions of Internet Explorer are no longer supported, either by us or Microsoft (read more here: https://www.microsoft.com/en-us/microsoft-365/windows/end-of-ie-support).

Please use a modern browser to fully experience our website, such as the newest versions of Edge, Chrome, Firefox or Safari etc.

Anders Scherstén

Anders Scherstén

Senior lecturer

Anders Scherstén

Meso- and Neoarchaean geological history of the Bjornesund and Ravns Storo Supracrustal Belts, southern West Greenland: Settings for gold enrichment and corundum formation

Author

  • Nynke Keulen
  • John C. Schumacher
  • Tomas Naeraa
  • Thomas F. Kokfelt
  • Anders Scherstén
  • Kristoffer Szilas
  • Vincent J. van Hinsberg
  • Denis M. Schlatter
  • Brian F. Windley

Summary, in English

To understand the Mesa- and Neoarchaean geological history of the Bjornesund region, southern West Greenland (ca. 62-63 degrees N), we have undertaken an integrated study combining field observations with U-Pb zircon geochronology by LA-ICP-MS, metamorphic petrology, and microstructural analyses. The Bjornesund region links the southern part of the Fiskenaesset anorthosite complex to the well-preserved metavolcanic rocks of the Ravn Story Supracrustal Belt and the Bjornesund Supracrustal Belt, so the development of this region is of key interest to unravelling the Archaean geology of the entire region. In this study, we couple the observed phases of gold-enrichment and corundum formation to the geological history. The leucogabbroic rocks of the Bjornesund region, which are part of the Fiskenaesset complex, intruded at ca. 2.95 Ga into the tholeiitic and calc-alkaline metavolcanic rocks of the two studied belts. Following isoclinal folding, the rocks were intruded by diorite (2.92 Ga) and granodiorite (2.91 and 2.88 Ga), which are now texturally orthogneisses. The area was affected by three major phases of folding; F1 (undated), F2 at 2.85-2.83 Ga, and F3 at 2.71-2.70 Ga. The former deformation event is associated with the gold-enrichment in alteration zones in shear folds in metavolcanic amphibolite near the contact with the orthogneiss. Intrusion of granitic sheets during the F3 deformation triggered the formation of corundum, which is locally of gem quality, at the contact between leucogabbroic and ultramafic rocks. Peak metamorphic conditions were calculated as 580-630 degrees C and 6-4 kbar at 2.85-2.83 Ga. Later retrogression in the southern part of the area at ca. 500-450 degrees C and 4.5-3 kbar, and extensional fault reactivation overprinted some of the older structures. (C) 2014 Elsevier B.V. All rights reserved.

Department/s

  • Lithosphere and Biosphere Science

Publishing year

2014

Language

English

Pages

36-58

Publication/Series

Precambrian Research

Volume

254

Document type

Journal article

Publisher

Elsevier

Topic

  • Geology

Keywords

  • Ravns Storo (Ikattoq Nunaa) and
  • Bjornesund Supracrustal Belt
  • Ruby and
  • pink sapphire corundum
  • Fiskenaesset complex
  • Gold
  • Zircon U-Pb
  • LA-ICP-MS geochronology
  • Metamorphic petrology

Status

Published

ISBN/ISSN/Other

  • ISSN: 0301-9268