Trace elements in magnetite from massive iron oxide-apatite deposits indicate a combined formation by igneous and magmatic-hydrothermal processes

Abstract

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Mineral chemistry of magnetite from magnetite-apatite mineralization and their host rocks: examples from Kiruna, Sweden, and El Laco, Chile

“…10. Cr vs. V plot discriminating Kiruna-type from other ore deposit proposed by Knipping et al (2015). Many of the magnetite grains from the Kiruna and El Laco magnetite-apatite ores in this study contain higher Cr concentrations than suggested in this diagram.…”

“…In a broad sense, there are two genetic models to describe how magnetite-apatite deposits formed in favor today, with a third model that involves a combination of the first two models: 1) Originating from immiscible iron-rich melts that separated from a silicate melt and were emplaced at subvolcanic levels or erupted and cooled at the surface (e.g., Henríquez and Martin, 1978;Nyström and Henríquez, 1994;Naslund et al, 2002;Nyström et al, 2008;Martinsson, 2016); 2) Metasomatic replacement of the host rocks by hydrothermal fluids (e.g., Hitzman et al, 1992;Rhodes and Oreskes, 1999;Sillitoe and Burrows, 2002;Edfelt et al, 2005;Groves et al, 2010;Valley et al, 2011;Dare et al, 2015;Westhues et al, in press); and 3) a magmatic-hydrothermal combination of these two models (e.g., Knipping et al, 2015;Tornos et al, 2016). A sedimentaryexhalative origin was suggested by Parák (1975) but was not widely accepted (Frietsch, 1978;Nyström et al, 2008).…”

“…There are two genetic models, and a third that is a combination of the first two, for the formation of magnetite-apatite deposits today: 1) Crystallization from iron-rich melts that were immiscible from a parental silicate melt and were emplaced at different depths or erupted and crystallized at the surface (e.g., Henríquez and Martin, 1978;Nyström and Henríquez, 1994;Naslund et al, 2002;Alva-Valdivia et al, 2003;Nyström et al, 2008;Martinsson, 2016); crystallization was accompanied by the exsolution of large amounts of magmatic-hydrothermal fluids (Tornos et al, 2016); 2) Replacement of the host rocks by iron-rich hydrothermal fluids (e.g., Hitzman et al, 1992;Rhodes and Oreskes, 1999;Hitzman, 2000;Sillitoe and Burrows, 2002;Edfelt et al, 2005;Groves et al, 2010;Valley et al, 2011;Dare et al, 2015); and 3) a magmatic-hydrothermal genesis with an early generation of phenocrysts of magnetite that separated and floated from a crystallizing andesite melt and later were overgrown by hydrothermal magnetite (e.g., Knipping et al, 2015). A sedimentary-exhalative origin was suggested by Parák (1975) but was not widely accepted (Frietsch, 1978;Nyström et al, 2008) and will not be discussed further.…”

Multiple Stage Ore Formation in the Chadormalu Iron Deposit, Bafq Metallogenic Province, Central Iran: Evidence from BSE Imaging and Apatite EPMA and LA-ICP-MS U-Pb Geochronology

“…Alteration of apatite, as documented for Chadormalu, appears to be a common feature in IOA type ore deposits (e.g., Kiirunavaara magnetite-apatite ore [53], Los Colorados iron oxide-apatite [83], and Se-Chahun magnetite-apatite deposit [36]). Such reequilibration and modification in Chadormalu ore was already documented for magnetite by Heidarian et al [21].…”

Trace Element Analysis of Minerals in Magmatic-Hydrothermal Ores by Laser Ablation Inductively-Coupled Plasma Mass Spectrometry: Approaches and Opportunities

“…The authors propose a model involving sedimentary carbonates and subsequent metasomatism by REE-rich hydrothermal fluids. Magnetite chemistry has proven critical for understanding the transition from magmatic to hydrothermal conditions in Kiruna-type iron oxide-apatite (IOA) deposits [119].…”