Oxygen Isotope Signatures of the Apatite-Iron Oxide Ore at Grängesberg

• Main Author: Weis, Franz
• Format: Bachelor Thesis
• Language: English
• Published: Uppsala universitet, Institutionen för geovetenskaper 2011
• Subjects: Grängesberg; Oxygen Isotope; Apatite-Iron Oxide Ore; Solid earth geology and petrology; Berggrundsgeologi och petrologi; Kiruna
• Online Access: http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-173031

The origin of apatite iron oxide ores, like the deposit at Grängesberg in the Bergslagen mining district, has been a subject of much discussion through the years. Some support a formation by hydrothermal fluids while others suggest that the ore is orthomagmatic, i.e. formed directly from a magma as suggested for the iron ore deposits of El Laco in Chile or the deposits in Kiruna, although also these two are still subjected to controversies. In 2009 sampling was done on drillcores through the Grängesberg ore. On these samples an oxygen isotope study on magnetite, quartz and whole rock samples from both the ore and its host rocks was conducted in order to obtain new knowledge about the ore forming processes. The data allowed modeling to simulate a possible origin by different magmas or hydrothermal fluids as well as a possible temperature of formation. In addition, the data set was compared to published oxygen isotope analyses of the possible magmatic iron ores of Kiruna and El Laco. The results of the Grängesberg analysis revealed that the ore in the area seems to have an origin from both magmatic and hydrothermal sources.