Publication: Ultramafic rocks in the north patagonian andes: Is their emplacement associated with the neogene tectonics of the liquiñe-ofqui fault zone?
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Servicio Nacional de Geología y Minería
Abstract
En la vertiente occidental de los Andes norpatagonicos de Chiloé continental (41°44’-42°12’ S) afloran serpentinitas y harzburgitas frescas o parcialmente serpentinizadas. Estas rocas están espacialmente asociadas con rocas metamórficas de bajo grado que contienen circones detríticos Cenozoicos. Estas rocas metamórficas, junto a metasedimentos Devónicos, han sido mapeados previamente como del Paleozoico superior-Triásico, una edad que no es sostenible para al menos una parte de ellos. El emplazamiento tectónico transpresivo del o de los cuerpos ultramáficos, se supone relacionado a la actividad de la Zona de Fallas Liquiñe-Ofqui, después de una fase extensional del Oligoceno tardío-Mioceno temprano en la región de antearco de los Andes actuales. La mencionada zona de fallas aparece inmediatamente al este de los afloramientos de rocas ultramáficas, y ha sido previamente interpretada como causante de una estructura de flor o hemiflor.
Serpentinites and fresh or partially serpentinized harzburgite crop out in the western slope of the North Patagonian Andes of continental Chiloé (41°44’-42°12’S). These rocks are spatially associated with low-grade metamorphic rocks containing Cenozoic detrital zircons. The metamorphic rocks, together with Devonian metasediments, have been mapped previously as Late Paleozoic-Triassic metamorfic complex, an age no longer tenable for at least part of the complex. Transpressional tectonic emplacement of the ultramafic body or bodies is thought to have been related to activity on the Liquiñe-Ofqui Fault Zone, following a late Oligocene-Early Miocene extensional phase in the forearc region of the present Andes. This fault zone occurs immediately east of the outcrops of the ultramafic rocks and has been interpreted previously as generating a hemi-flower or flower structure.
Serpentinites and fresh or partially serpentinized harzburgite crop out in the western slope of the North Patagonian Andes of continental Chiloé (41°44’-42°12’S). These rocks are spatially associated with low-grade metamorphic rocks containing Cenozoic detrital zircons. The metamorphic rocks, together with Devonian metasediments, have been mapped previously as Late Paleozoic-Triassic metamorfic complex, an age no longer tenable for at least part of the complex. Transpressional tectonic emplacement of the ultramafic body or bodies is thought to have been related to activity on the Liquiñe-Ofqui Fault Zone, following a late Oligocene-Early Miocene extensional phase in the forearc region of the present Andes. This fault zone occurs immediately east of the outcrops of the ultramafic rocks and has been interpreted previously as generating a hemi-flower or flower structure.