Global Fe-O isotope correlation reveals magmatic origin of Kiruna-type apatite-iron-oxide ores.

ABSTRACT: Kiruna-type apatite-iron-oxide ores are key iron sources for modern industry, yet their origin remains controversial. Diverse ore-forming processes have been discussed, comprising low-temperature hydrothermal processes versus a high-temperature origin from magma or magmatic fluids. We present an extensive set of new and combined iron and oxygen isotope data from magnetite of Kiruna-type ores from Sweden, Chile and Iran, and compare them with new global reference data from layered intrusions, active volcanic provinces, and established low-temperature and hydrothermal iron ores. We show that approximately 80% of the magnetite from the investigated Kiruna-type ores exhibit ?⁵⁶Fe and ?¹⁸O ratios that overlap with the volcanic and plutonic reference materials (>?800?°C), whereas ~20%, mainly vein-hosted and disseminated magnetite, match the low-temperature reference samples (?400?°C). Thus, Kiruna-type ores are dominantly magmatic in origin, but may contain late-stage hydrothermal magnetite populations that can locally overprint primary high-temperature magmatic signatures.

SUBMITTER: Troll VR 

PROVIDER: S-EPMC6461606 | biostudies-literature | 2019 Apr

REPOSITORIES: biostudies-literature