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

Keulen, Nynke; Schumacher, John C.; Naeraa, Tomas LU ; Kokfelt, Thomas F.; Scherstén, Anders LU ; Szilas, Kristoffer; van Hinsberg, Vincent J.; Schlatter, Denis M. and Windley, Brian F. (2014) In Precambrian Research 254. p.36-58
Abstract
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... (More)
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. (Less)
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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
in
Precambrian Research
volume
254
pages
36 - 58
publisher
Elsevier
external identifiers
  • wos:000343786400003
  • scopus:84906738235
ISSN
0301-9268
DOI
10.1016/j.precamres.2014.07.023
language
English
LU publication?
yes
id
28fa6158-3970-4040-80bd-63b790dfc50f (old id 4876085)
date added to LUP
2014-12-23 09:26:09
date last changed
2017-11-12 03:12:17
@article{28fa6158-3970-4040-80bd-63b790dfc50f,
  abstract     = {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.},
  author       = {Keulen, Nynke and Schumacher, John C. and Naeraa, Tomas and Kokfelt, Thomas F. and Scherstén, Anders and Szilas, Kristoffer and van Hinsberg, Vincent J. and Schlatter, Denis M. and Windley, Brian F.},
  issn         = {0301-9268},
  keyword      = {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},
  language     = {eng},
  pages        = {36--58},
  publisher    = {Elsevier},
  series       = {Precambrian Research},
  title        = {Meso- and Neoarchaean geological history of the Bjornesund and Ravns Storo Supracrustal Belts, southern West Greenland: Settings for gold enrichment and corundum formation},
  url          = {http://dx.doi.org/10.1016/j.precamres.2014.07.023},
  volume       = {254},
  year         = {2014},
}