The evolution of the hydrothermal IOCG system in the Mantoverde district,northern Chile: new evidence from microthermometry and stable isotope geochemistry |
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Authors: | Email author" target="_blank">Ana?A?RiegerEmail author Robert?Marschik Manuel?Díaz |
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Institution: | 1.Resource Geology Research Group, Department of Earth and Environmental Sciences,Ludwig-Maximilians-Universit?t,Munich,Germany;2.Los Bonces Division,AngloAmerican Chile,Santiago de Chile,Chile;3.Ebersberg,Germany |
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Abstract: | New microthermometric data combined with stable isotope geochemistry and paragenetic relationships support a previously suggested
cooling–mixing model for the iron oxide–copper–gold mineralization in the Mantoverde district. Fluid inclusions show characteristics
of a CO2-bearing aqueous NaCl ± CaCl2 salt system. The evolution of the Mantoverde hydrothermal system is characterized by (1) an early hypersaline, high to moderate
temperature fluid; (2) a moderate saline, moderate temperature fluid; and (3) a low saline, moderate to low temperature fluid.
Early magnetite formation took place at median temperatures of 435.0°C, whereas hematite formed at median temperatures of
334.4°C. The main sulfide mineralization texturally post-dates the iron oxides and occurred before late-stage calcite, which
developed at a median temperature of 244.8°C. Boiling occurs only locally and is of no relevance for the ore formation. The
microthermometric and stable isotope data are supportive for a fluid cooling and mixing model, and suggestive for a predominantly
magmatic–hydrothermal fluid component during the iron oxide and main sulfide mineralization. Thereafter, the incursion of
a nonmagmatic fluid of ultimately meteoric or seawater gains more importance. |
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