Geochronological and thermochronological constraints on porphyry copper mineralization in the Domeyko alteration zone, northern Chile

At Domeyko, 40 km south of Vallenar in northern Chile (28°57'S-70°53'W), the Dos Amigos and Tricolor porphyry copper centers are located within a north-south-elongated hydrothermal alteration zone 6x1.5 km of surface dimensions. The centers are related to tonalite to granodiorite porphyry...

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Autores principales:	Maksaev,Víctor, Almonacid,Tomás A, Munizaga,Francisco, Valencia,Víctor, McWilliams,Michael, Barra,Fernando
Lenguaje:	English
Publicado:	Servicio Nacional de Geología y Minería (SERNAGEOMIN) 2010
Materias:	Porphyry copper Andes Chile Geochronology Thermochronology Coastal Cordillera
Acceso en línea:	http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0718-71062010000100007
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spelling	oai:scielo:S0718-710620100001000072010-04-14Geochronological and thermochronological constraints on porphyry copper mineralization in the Domeyko alteration zone, northern ChileMaksaev,VíctorAlmonacid,Tomás AMunizaga,FranciscoValencia,VíctorMcWilliams,MichaelBarra,Fernando Porphyry copper Andes Chile Geochronology Thermochronology Coastal Cordillera At Domeyko, 40 km south of Vallenar in northern Chile (28°57'S-70°53'W), the Dos Amigos and Tricolor porphyry copper centers are located within a north-south-elongated hydrothermal alteration zone 6x1.5 km of surface dimensions. The centers are related to tonalite to granodiorite porphyry stocks displaying potassic alteration, which are surrounded by Lower Cretaceous andesitic volcanic rocks with sericitic, kaolinite-illite and propylitic alteration zones. The western boundary of the alteration zone is marked by the post-mineralization Cachiyuyo Batholith of granodioritic to dioritic composition. U-Pb zircon ages for the Dos Amigos porphyry are of 106.Ü3.5 and 104.0±3.5 Ma; and 108.5±3.4 for the nearby Tricolor porphyry. The Cachiyuyo Batholith yielded U-Pb zircon ages of 99.6±1.8 and 99.1±1.9 Ma; and 40Ar/39Ar ages for biotite of 96.9±3.9 and 94.8±0.9 Ma. These dates indicate that batholith emplacement postdated the Dos Amigos and Tricolor porphyries, in agreement with geological relationships. Although copper mineralization is spatially and genetically related to the Lower Cretaceous (Albian) porphyry stocks, most of the dated hydrothermal micas from the Dos Amigos and Tricolor porphyries yielded 40Ar/39Ar ages between 97.1±2.5 and 96.0±1.4 Ma, which overlap within error with the cooling ages obtained for the neighboring batholith. 40Ar/39Ar dating of micas revealed significant disturbance of their K-Ar isotopic systematics that complicates accurate determination of the timing of hydrothermal activity at Domeyko. Nevertheless, the 40Ar/39Ar data establish a minimum Late Cretaceous age for this activity. A fission track age of 59.8±9.8 Ma of apatite from the Dos Amigos porphyry indicates cooling through the temperature range of the apatite partial annealing zone (~125-60°C) during the Paleocene; and an (U-Th)/He age of 44.7±3.7 Ma of apatite from the same porphyry sample shows cooling through the temperature range of the apatite He partial retention zone (~85-40°C) during the Eocene. These ages correspond to the exhumation of the porphyry, and the latter provides a maximum age for the supergene enrichment processes that formed the chalcocite blanket currently mined at Dos Amigos.info:eu-repo/semantics/openAccessServicio Nacional de Geología y Minería (SERNAGEOMIN)Andean geology v.37 n.1 20102010-01-01text/htmlhttp://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0718-71062010000100007en10.4067/S0718-71062010000100007
institution	Scielo Chile
collection	Scielo Chile
language	English
topic	Porphyry copper Andes Chile Geochronology Thermochronology Coastal Cordillera
spellingShingle	Porphyry copper Andes Chile Geochronology Thermochronology Coastal Cordillera Maksaev,Víctor Almonacid,Tomás A Munizaga,Francisco Valencia,Víctor McWilliams,Michael Barra,Fernando Geochronological and thermochronological constraints on porphyry copper mineralization in the Domeyko alteration zone, northern Chile
description	At Domeyko, 40 km south of Vallenar in northern Chile (28°57'S-70°53'W), the Dos Amigos and Tricolor porphyry copper centers are located within a north-south-elongated hydrothermal alteration zone 6x1.5 km of surface dimensions. The centers are related to tonalite to granodiorite porphyry stocks displaying potassic alteration, which are surrounded by Lower Cretaceous andesitic volcanic rocks with sericitic, kaolinite-illite and propylitic alteration zones. The western boundary of the alteration zone is marked by the post-mineralization Cachiyuyo Batholith of granodioritic to dioritic composition. U-Pb zircon ages for the Dos Amigos porphyry are of 106.Ü3.5 and 104.0±3.5 Ma; and 108.5±3.4 for the nearby Tricolor porphyry. The Cachiyuyo Batholith yielded U-Pb zircon ages of 99.6±1.8 and 99.1±1.9 Ma; and 40Ar/39Ar ages for biotite of 96.9±3.9 and 94.8±0.9 Ma. These dates indicate that batholith emplacement postdated the Dos Amigos and Tricolor porphyries, in agreement with geological relationships. Although copper mineralization is spatially and genetically related to the Lower Cretaceous (Albian) porphyry stocks, most of the dated hydrothermal micas from the Dos Amigos and Tricolor porphyries yielded 40Ar/39Ar ages between 97.1±2.5 and 96.0±1.4 Ma, which overlap within error with the cooling ages obtained for the neighboring batholith. 40Ar/39Ar dating of micas revealed significant disturbance of their K-Ar isotopic systematics that complicates accurate determination of the timing of hydrothermal activity at Domeyko. Nevertheless, the 40Ar/39Ar data establish a minimum Late Cretaceous age for this activity. A fission track age of 59.8±9.8 Ma of apatite from the Dos Amigos porphyry indicates cooling through the temperature range of the apatite partial annealing zone (~125-60°C) during the Paleocene; and an (U-Th)/He age of 44.7±3.7 Ma of apatite from the same porphyry sample shows cooling through the temperature range of the apatite He partial retention zone (~85-40°C) during the Eocene. These ages correspond to the exhumation of the porphyry, and the latter provides a maximum age for the supergene enrichment processes that formed the chalcocite blanket currently mined at Dos Amigos.
author	Maksaev,Víctor Almonacid,Tomás A Munizaga,Francisco Valencia,Víctor McWilliams,Michael Barra,Fernando
author_facet	Maksaev,Víctor Almonacid,Tomás A Munizaga,Francisco Valencia,Víctor McWilliams,Michael Barra,Fernando
author_sort	Maksaev,Víctor
title	Geochronological and thermochronological constraints on porphyry copper mineralization in the Domeyko alteration zone, northern Chile
title_short	Geochronological and thermochronological constraints on porphyry copper mineralization in the Domeyko alteration zone, northern Chile
title_full	Geochronological and thermochronological constraints on porphyry copper mineralization in the Domeyko alteration zone, northern Chile
title_fullStr	Geochronological and thermochronological constraints on porphyry copper mineralization in the Domeyko alteration zone, northern Chile
title_full_unstemmed	Geochronological and thermochronological constraints on porphyry copper mineralization in the Domeyko alteration zone, northern Chile
title_sort	geochronological and thermochronological constraints on porphyry copper mineralization in the domeyko alteration zone, northern chile
publisher	Servicio Nacional de Geología y Minería (SERNAGEOMIN)
publishDate	2010
url	http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0718-71062010000100007
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Geochronological and thermochronological constraints on porphyry copper mineralization in the Domeyko alteration zone, northern Chile

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