The Faja Eruptiva of the Eastern Puna and the Sierra de Calalaste, NW Argentina: U-Pb zircon chronology of the early Famatinan orogeny

CASQUET, C.; ALASINO, P.; GALINDO, C.; PANKHURST, R.; DAHLQUIST, J.; BALDO, E.; RAMACCIOTTI, C.; VERDECCHIA, SEBASTIÁN O.; LARROVERE, M.; RAPELA, C.; RECIO, C.

JOURNAL OF IBERIAN GEOLOGY

SERVICIO PUBLICACIONES

Lugar: Madrid; Año: 2021

1698-6180

We present geochemistry and U-Pb geochronology of igneous and metamorphic rocks from the Central Famatinian Domain in the northern Sierras Pampeanas and the southern Puna of North West Argentina. The Famatinian is a segment of the Ordovician Terra Australis accretionary orogen that stretched along the SW Margin of Gondwana from Australia to Colombia. New U-Pb SHRIMP zircon dating is presented for six samples of igneous rocks (peraluminous granitoids, mafic and felsic rocks, volcanic/subvolcanic rocks) and six samples of associated meta-sedimentary rocks, all from the Puna. The results indicate that the Central Famatinian Domain is an internally composite domain that includes a Cordilleran-type magmatic arc (ca. 470 Ma) and a fault-bounded older terrain formed in an extensional setting at the very start of the Famatinian orogeny, between 480 and 485 Ma, i.e., shortly after the SW Gondwana margin switched from passive to active. This short period of extension with related sedimentation, volcanism and mainly granitoid plutonism has not been previously recognised. It occurred before the Cordilleran-type magmatic arc that resulted from a magmatic flare-up between ca. 473 and 468 Ma, coincident with a contractional phase. This evidence confirms that accretionary orogeny results from tectonic switching (pull-push orogeny) and that the extensional and contractional phases are of relatively short duration.