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Leif Johansson

Leif Johansson

Professor

Leif Johansson

The Finnefjeld domain, Maniitsoq structure, West Greenland: Differential rheological features and mechanical homogenisation in response to impacting?

Author

  • Adam A. Garde
  • Brendan Dyck
  • Kim H. Esbensen
  • Leif Johansson
  • Charlotte Möller

Summary, in English

The 35 by 50 km large, Mesoarchaean Finnefjeld domain near Maniitsoq in the North Atlantic craton of southern West Greenland constitutes the central part of the previously proposed, deeply eroded Maniitsoq impact structure with an age of 3.0 Ga. The Finnefjeld domain is an exceedingly homogeneous, quartzo-feldspathic rock mass which superficially appears to be a late-orogenic, deep-crustal, intrusive granitoid pluton, and which was described as such for decades. However, new observations confirm and qualify the first observations from 1962 of these rocks as 'cataclastic'. The Finnefjeld domain is characterised by a highly unusual, mixed rheological behaviour. Plagioclase displays brittle behaviour with cataclasis, quartz was ductilely deformed, and K-feldspar was melted. The deformation and homogenisation of the Finnefjeld domain was caused by an intense event of heating and deformation, which was coseismic in nature and comprised numerous increments of pure shear strain. This type of intense, brittle, regional deformation and concomitant direct mineral melting in the deep crust is unknown from endogenic orogenic events and is ascribed to deep-crustal effects of impacting. (C) 2014 Elsevier B.V. All rights reserved.

Department/s

  • Lithosphere and Biosphere Science

Publishing year

2014

Language

English

Pages

791-808

Publication/Series

Precambrian Research

Volume

255

Document type

Journal article

Publisher

Elsevier

Topic

  • Geology

Keywords

  • Mixed theological behaviour
  • Maniitsoq impact structure
  • Cataclasis
  • Direct mineral melting

Status

Published

ISBN/ISSN/Other

  • ISSN: 0301-9268