2007:17 DOCTORAL T H E SI S The Tjårrojåkka Apatite-Iron and Cu (-Au) Deposits, Northern Sweden - Products of One Ore Forming Event Åsa Edfelt Luleå University of Technology Department of Chemical Engineering and Geosciences Division of Ore Geology and Applied Geophysics 2007:17|: 102-1544|: - -- 07⁄17 -- Thesis for the Degree of Doctor of Philosophy The Tjårrojåkka Apatite-Iron and Cu (-Au) Deposits, Northern Sweden – Products of One Ore Forming Event Åsa Edfelt Division of Ore Geology and Applied Geophysics Luleå University of Technology SE-971 87 Luleå, Sweden Phone: +46-920-492029 E-mail:
[email protected] May 2007 For Lionel and Adina with love Abstract The Tjårrojåkka area is located about 50 km WSW of Kiruna, northern Sweden, and hosts one of the best examples of spatially related apatite-iron (Kiruna type) and Cu (-Au) deposits in Sweden. The results from this project show that the two deposits are genetically related and indicate the presence of a younger, previously unknown, 1780 Ma generation of apatite-iron ores in northern Sweden. The bedrock in the Tjårrojåkka area is dominated by intermediate and basic extrusive and intrusive rocks. The 1880 Ma intermediate volcanic rocks, belonging to the Porphyrite Group, formed in association with subduction- related magmatism in a volcanic arc environment close to the Archaean continental margin. The overlying basalts and related feeder dykes formed through extrusion of mantle derived magma during a local extensional event in a subaquatic back arc setting. The area was metamorphosed at epidote- amphibolite facies and deformed during at least three stages, creating NE-SW, E-W, and NNW-SSE striking structures.