Journal Article

Magmatic origin of giant ‘Kiruna-type’ apatite-iron-oxide ores in Central Sweden

Skelton, Alasdair, Högdahl, Karin, Jonsson, Erik, Harris, Chris, Troll, Valentin R., Weis, Franz, Nilsson, Katarina P.

2013

Overview

Iron is the most important metal for modern industry and Sweden is by far the largest iron-producer in Europe, yet the genesis of Sweden's main iron-source, the ‘Kiruna-type’ apatite-iron-oxide ores, remains enigmatic. We show that magnetites from the largest central Swedish ‘Kiruna-type’ deposit at Grängesberg have δ 18 O values between −0.4 and +3.7‰, while the 1.90−1.88 Ga meta-volcanic host rocks have δ 18 O values between +4.9 and +9‰. Over 90% of the magnetite data are consistent with direct precipitation from intermediate to felsic magmas or magmatic fluids at high-temperature (δ 18 O mgt > +0.9‰, i.e. ortho-magmatic). A smaller group of magnetites (δ 18 O mgt ≤ +0.9‰), in turn, equilibrated with high-δ 18 O, likely meteoric, hydrothermal fluids at low temperatures. The central Swedish ‘Kiruna-type’ ores thus formed dominantly through magmatic iron-oxide precipitation within a larger volcanic superstructure, while local hydrothermal activity resulted from low-temperature fluid circulation in the shallower parts of this system.

• Publisher: Nature Publishing Group UK,Nature Publishing Group
• Subject: 704/2151/209 / 704/2151/330 / 704/2151/431 / 704/2151/598 / Apatite / Earth Science with specialization in Mineral Chemistry, Petrology and Tectonics / Geovetenskap med inriktning mot mineralogi, petrologi och tektonik / High temperature / Humanities and Social Sciences / Iron / Low temperature / Magma / Magnetite / multidisciplinary / Ores / Science / Temperature effects