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 δ56Fe and δ18O 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.

The origin of giant Kiruna-type iron ores has been debated for nearly 100 years. This study employs extensive stable isotope data from Kiruna-type ores worldwide and magmatic and hydrothermal reference materials to show that iconic Kiruna-type ores originate primarily from ortho-magmatic processes.

Details

Title
Global Fe–O isotope correlation reveals magmatic origin of Kiruna-type apatite-iron-oxide ores
Author
Troll, Valentin R 1 ; Weis, Franz A 2 ; Jonsson, Erik 3 ; Andersson, Ulf B 4 ; Majidi Seyed Afshin 5 ; Högdahl Karin 6 ; Harris, Chris 7 ; Marc-Alban, Millet 8 ; Chinnasamy Sakthi Saravanan 9 ; Kooijman, Ellen 10 ; Nilsson, Katarina P 11 

 Uppsala University, Section for Mineralogy, Petrology and Tectonics, Department of Earth Sciences, Uppsala, Sweden (GRID:grid.8993.b) (ISNI:0000 0004 1936 9457) 
 Uppsala University, Section for Mineralogy, Petrology and Tectonics, Department of Earth Sciences, Uppsala, Sweden (GRID:grid.8993.b) (ISNI:0000 0004 1936 9457); Swedish Museum of Natural History, Dept. of Geosciences, Stockholm, Sweden (GRID:grid.425591.e) (ISNI:0000 0004 0605 2864) 
 Uppsala University, Section for Mineralogy, Petrology and Tectonics, Department of Earth Sciences, Uppsala, Sweden (GRID:grid.8993.b) (ISNI:0000 0004 1936 9457); Geological Survey of Sweden, Department of Mineral Resources, Uppsala, Sweden (GRID:grid.426025.7) (ISNI:0000 0001 2179 2375) 
 Uppsala University, Section for Mineralogy, Petrology and Tectonics, Department of Earth Sciences, Uppsala, Sweden (GRID:grid.8993.b) (ISNI:0000 0004 1936 9457); Luossavaara-Kiirunavaara AB, Research & Development, Kiruna, Sweden (GRID:grid.8993.b) 
 Geological Survey of Iran, Meraj St, Azadi Sq, Tehran, Iran (GRID:grid.484159.5) (ISNI:0000 0001 2243 211X) 
 Uppsala University, Section for Mineralogy, Petrology and Tectonics, Department of Earth Sciences, Uppsala, Sweden (GRID:grid.8993.b) (ISNI:0000 0004 1936 9457); Geology and Mineralogy, Åbo Akademi University, Turku, Finland (GRID:grid.13797.3b) (ISNI:0000 0001 2235 8415) 
 University of Cape Town, Department of Geological Sciences, Rondebosch, South Africa (GRID:grid.7836.a) (ISNI:0000 0004 1937 1151) 
 School of Earth and Ocean Sciences, Cardiff University, Park Place, Cardiff, UK (GRID:grid.5600.3) (ISNI:0000 0001 0807 5670) 
 Uppsala University, Section for Mineralogy, Petrology and Tectonics, Department of Earth Sciences, Uppsala, Sweden (GRID:grid.8993.b) (ISNI:0000 0004 1936 9457); National Institute of Technology Rourkela, Department of Earth & Atmospheric Sciences, NIT Rourkela, Odisha, India (GRID:grid.444703.0) (ISNI:0000 0001 0744 7946); Department of Earth Sciences, Powai, Indian Institute of Technology (IIT) Bombay, Mumbai, India (GRID:grid.417971.d) (ISNI:0000 0001 2198 7527) 
10  Swedish Museum of Natural History, Dept. of Geosciences, Stockholm, Sweden (GRID:grid.425591.e) (ISNI:0000 0004 0605 2864) 
11  Geological Survey of Sweden, Department of Mineral Resources, Uppsala, Sweden (GRID:grid.426025.7) (ISNI:0000 0001 2179 2375); Swedish Ministry of Enterprise and Innovation, Division for Business, Stockholm, Sweden (GRID:grid.426025.7) 
Publication year
2019
Publication date
2019
Publisher
Nature Publishing Group
e-ISSN
20411723
Source type
Scholarly Journal
Language of publication
English
ProQuest document ID
2208721221
Copyright
© The Author(s) 2019. This work is published under http://creativecommons.org/licenses/by/4.0/ (the “License”). Notwithstanding the ProQuest Terms and Conditions, you may use this content in accordance with the terms of the License.