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 language | English (US) |
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Pages (from-to) | 109-118 |
Number of pages | 10 |
Journal | GFF |
Volume | 106 |
Issue number | 2 |
DOIs | |
State | Published - Jun 1984 |
Keywords
- Boudinage
- Diapirism
- E1957
- E2035
- Extension
- Greenstone belt
- Kiruna iron district
- Lappland
- N6745
- N6757
- Northern Norrbotten
- Proterozoic
- Structure
- Svecokarelian
- Tectonics