Early deformation in the Svecokarelian greenstone belt of the Kiruna iron district, northern Sweden

Frederick W. Vollmer, Stephen F. Wright, Peter J Hudleston

Research output: Contribution to journalArticle

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Abstract

The Proterozoic iron ores of the Kiruna district, northern Sweden, occur as discontinous lenses of magnetite and hematite up to 4 kilometers in length within a sequence of felsic porphyries. The association of low-grade felsic volcanics and sedimentary rocks with basaltic pillow lavas and granitic rocks shows a strong similarity to typical Archean greenstone belts. Primary younging indicators, bedding/cleavage relationships, and minor fold symmetries through the district suggest that the area occupies the eastern limb of a major antiform, cored by granitic rocks to the west. A steep regional cleavage, inhomogeneously developed through the district, suggests one major episode of compressional deformation. The cleavage and associated flattened clasts indicate a compression direction plunging 10°WNW. Elongate clasts, boudins, and fibrous veins indicate a strong extension plunging 60°SSE, parallel to fold hinge lines. Boudinage of the major ore bodies to produce their present distribution is compatible with the estimated strain of a single deformation. Diapirism is suggested as a likely explanation of the observed strain patterns.

Original languageEnglish (US)
Pages (from-to)109-118
Number of pages10
JournalGFF
Volume106
Issue number2
DOIs
StatePublished - Jun 1984

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Keywords

  • Boudinage
  • Diapirism
  • E1957
  • E2035
  • Extension
  • Greenstone belt
  • Kiruna iron district
  • Lappland
  • N6745
  • N6757
  • Northern Norrbotten
  • Proterozoic
  • Structure
  • Svecokarelian
  • Tectonics

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