Abstract
Studies of drill cores from the Pasos Blancos area at El Laco in the central Andes, northern Chile, give evidence of an intense and extensive subvolcanic contact-metasomatic process. This process resulted from shallow-level emplacement of very volatile-rich iron-oxide magma, with discharge of volatiles that resulted in extensive fracturing of overlying volcanic rocks. The brecciated rocks were altered (mainly extensive scapolitization and formation of pyroxene) by hot magmatic fluids emitted from the cooling intrusion, and accompanied by magnetite deposition. With time and decreasing temperature, the metasomatic fluids evolved to fluids of hydrothermal character, and a final recent geothermal event took place that deposited superficial gypsum over a large part of the El Laco Volcanic Complex.
Highlights
Since their discovery in the early 1960 ́s (Park, 1961), the iron-oxide ore bodies at El Laco have been suggested to have formed from a volatile-rich, iron-rich magma which intruded a Plio-Pleistocene volcanic complex at shallow depth and at places erupted onto the surface (Naslund et al, 2002, and references therein; Henríquez et al, 2003, 2004; Naranjo et al, 2004; Nyström et al, 2008)
With time and decreasing temperature, the metasomatic fluids evolved to fluids of hydrothermal character, and a final recent geothermal event took place that deposited superficial gypsum over a large part of the El Laco Volcanic Complex
Naranjo et al./ Andean Geology 37 (1): 110-120, 2010
Summary
Since their discovery in the early 1960 ́s (Park, 1961), the iron-oxide ore bodies at El Laco have been suggested to have formed from a volatile-rich, iron-rich magma which intruded a Plio-Pleistocene volcanic complex at shallow depth and at places erupted onto the surface (Naslund et al, 2002, and references therein; Henríquez et al, 2003, 2004; Naranjo et al, 2004; Nyström et al, 2008). The owner of the iron deposits, Compañía Minera del Pacífico (CMP), has carried out an extensive program of drilling at El Laco in recent years (2007-2008).
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