Abstract
An Upper Cambrian-Ordovician (490-460 Ma) batholith crop out along the Cordón de Lila and Sierra de Almeida, in the Antofagasta region, northern Chile, which belongs to the Famatinian arc. Two plutonic rock types can be distinguished: granodiorites and monzogranites. The first lithology is positioned along an occidental fringe in as much the second is located along an oriental part of the batholith. The main geochemical difference between the two lithologies is the enrichment in silica and K of the second with respect of the first one. Most of the granodiorites are metaluminous or are located between the metaluminous and peraluminous fields. The monzogranites are mostly peraluminous. The chemical composition of the plutons (mayor and trace elements and rare earth elements) allow to infer a common origin for both groups, from a mafic magma that evolved by fractional crystallization. The difference in composition between both lithologies, specially the meta or peraluminous character, can be explained by means a different degree of interaction of the original magma with the felsic crustal rocks.
Highlights
Cordón de Lila-Sierra de Almeyda Cambro-Ordovicic batholith: geochemistry of the plutonic rocks
An Upper Cambrian-Ordovician (490-460 Ma) batholith crop out along the Cordón de Lila and Sierra de Almeida, in the Antofagasta region, northern Chile, which belongs to the Famatinian arc
The first lithology is positioned along an occidental fringe in as much the second is located along an oriental part of the batholith
Summary
El orógeno famatiniano representa un evento mayor desarrollado en el borde occidental de Gondwana en el Paleozoico temprano. El arco magmático emplazado durante este evento se extiende desde las sierras pampeanas en Argentina hasta el norte de los Andes en Venezuela (Ramos, 2018). En el área que comprende el Cordón de Lila (CL) y la Sierra de Almeida (SA), ubicada inmediatamente al sur del salar de Atacama, en el norte de Chile (Fig. 1), afloran rocas plutónicas graníticas pertenecientes a un batolito que forma parte del arco magmático famatiniano (Ducea et al, 2015), localmente denominado en Argentina Faja Eruptiva de la Puna Occidental (Palma et al, 1986), de orientación general noroeste. Este arco magmático se desarrolló sobre la corteza continental por subducción dirigida hacia el noreste (Bahlburg y Hervé, 1997), a lo largo del borde occidental de Gondwana durante el Cámbrico superior (Furongiano) a Ordovícico Medio (Zimmermann et al, 2010; Niemeyer et al, 2018), y abarcó un lapso de ca. El objetivo de la presente nota es dar a conocer el carácter geoquímico de los plutones que conforman dicho batolito, a la vez que sugerir ideas acerca de su origen
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