<p>Kiruna-type apatite-iron-oxide ores are key iron sources for modern industry. The origin of the Kiruna-type apatite-iron-oxide ores remains ambiguous, however, despite a long history of study and a concurrently intense scientific debate. 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 &#948;<sup>56</sup>Fe and &#948;<sup>18</sup>O ratios that overlap with the volcanic and plutonic reference materials (>&#8201;800&#8201;&#176;C), whereas ~20%, mainly vein-hosted and disseminated magnetite, match the low-temperature reference samples (&#8804;400&#8201;&#176;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 [1] .</p><p>&#160;</p><p>[1] Troll, V.R., Weis, F.A., Jonsson, E.&#160;et al.&#160;Global Fe&#8211;O isotope correlation reveals magmatic origin of Kiruna-type apatite-iron-oxide ores.&#160;Nature Communications&#160;<strong>10,&#160;</strong>1712 (2019) doi:10.1038/s41467-019-09244-4</p>
Toward New High Temperature Reference Materials for Calorimetry and Thermal Analysis
