Permian-Triassic volcanic and plutonic records of the Argentine Frontal Cordillera: A review with new U–Pb and Hf-isotope zircon data

Abstract

The Permian-Triassic magmatism of western Argentina and Chile represents one of the most outstanding silicic magmatic events of the southwestern Gondwana margin, notably marked by the development of the Choiyoi Magmatic Province (CMP). We provide a comprehensive review of its volcanic and plutonic record in the Argentine Frontal Cordillera. The volcanic rocks form three distinct sequences. The oldest is depicted by the Las Lozas volcanic sequence of the northern Frontal Cordillera for which new U–Pb zircon data (288 ± 2 Ma and εHft values ranging from −3.97 to +0.73) reassigns these outcrops to the early Cisuralian, aligning with volcanic records of northern Chile (ca. 297-288 Ma). The middle sequence, deposited during the late Cisuralian-late Guadalupian interval, is ascribed to the Choiyoi Group, which is characterised by a transition from andesitic (ca. 280-270 Ma) to rhyolitic compositions (ca. 270-262 Ma), including a remarkable mid-Guadalupian ignimbrite flare-up event (ca. 265 Ma). The upper sequence, composed of andesite-dacite-rhyolite, is associated with the Guanaco Sonso basin situated in the westernmost region, deposited from the late Lopingian to the middle Triassic period (ca. 254-240 Ma). The volcanic successions were developed in an extensional/transtensional setting, with facies and thickness variations controlled by normal faults, some of them active during the eruption of caldera-forming ignimbrites. Regarding the plutonic component, it comprises over sixty granitoid bodies forming the Colangüil and El Portillo batholiths and scattered stocks throughout the Frontal Cordillera. The early-stage plutons (ca. 285-272 Ma) exhibit calc-alkaline tonalite-diorite to granodiorite-monzogranite compositions and overlap in age with the lower andesitic section of the Choiyoi Group, while the late-stage plutons (ca. 265-252 Ma) display syenodiorite and alkali granite compositions and are in most cases younger than the Choiyoi Group succession. Compiled U–Pb zircon geochronological data reveal a distinctive Permian-age phase characterized by a rapid expansion of magmatism from the Gondwana margin towards its interior, followed by a slower westward shift of the main magmatic belt, predominantly recorded in the Frontal Cordillera of Argentina.