Magmatic Iron Ores and Associated Mineralisation: Examples from the Chilean High Andes and Coastal Cordillera

The El Laco magnetite-apatite ore deposits in the Andean Cordillera of northern Chile occur as massive, tabular bodies, as stratified, pyroclastic ores, and as crosscutting dykes and vein complexes. The ore deposits and surrounding volcanic rocks, mainly andesites, are Plio-Pleistocene in age and preserve many of their original volcanic textures and structures. All the field and laboratory data are consistent with an origin by eruption and shallow intrusion of a high-temperature, volatile-rich, iron-oxide magma. A number of other iron-oxide-apatite deposits of Cenozoic age in the Andean Cordillera, and a belt of Cretaceous iron deposits in the Coastal Cordillera of Chile also have features that suggest a magmatic origin. Associated with these magmatic ore deposits are economic and sub-economic concentrations of Cu, Au, U, and REE.