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Anders Scherstén

Anders Scherstén

Universitetslektor

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

Författare

  • 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.

Avdelning/ar

  • Berggrundsgeologi

Publiceringsår

2014

Språk

Engelska

Sidor

36-58

Publikation/Tidskrift/Serie

Precambrian Research

Volym

254

Dokumenttyp

Artikel i tidskrift

Förlag

Elsevier

Ämne

  • Geology

Nyckelord

  • 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/Övrigt

  • ISSN: 0301-9268