New U-Pb ages in the Diablillos Intrusive Complex, Southern Puna, Argentina: A long magmatic event in the Lower Paleozoic Arc, SW Gondwana

ORTIZ YAÑEZ, AGUSTIN; HAUSER, NATALIA; RAUL BECCHIO; SUZAÑO, NESTOR; NIEVES, A.

Brasilia

Congreso; XV Congresso Brasileiro de Geoquímica. Geoquímica Isotópica,; 2015

Sociedad Brasilera de Geologìa.

Three samples were selected to study and register the magmatic event on theDiablillos Intrusive Complex. Each sample corresponds to the Diorite, Granodiorite and Monzogranite facies units of this complex. Zircon grains from the Monzogranite (Sample D-13-01) gave a weighted average U/Pb age of 517.1±3.5 Ma (Fig.2a). The U/Pb analyses of the Diorite (Sample D-13-40) displayed a weighted average age of 514.9±5.8 Ma (Fig.2b). And zircon grains from the Granodiorite (Sample D-13-02) yielded a Concordia age of 520.6±4.5 Ma (Fig.2c). Since the ages in all three samples overlap with each other within error, we cannot define a unique emplacement age for the complex.After the reduction of the data, Pb loss was disregarded because there was not an evident loss. Since we can see a continuous age distribution in the Concordia diagrams (from ~540 Ma to 490 Ma, Fig.2) where there is not a marked age difference between core and rims single grain analyses and single spot grain analyses; a combination of Pb-loss and inheritance is possible. To confirm or disregard accurately the unseen Pb loss in this complex, a more precise analyses method should be use. We propose that the Diablillos Intrusive Complex was emplaced between the 540-490 Ma (~50Ma magmatic event). Where the CID would represent early stages of the Lower Paleozoic arc, formed in a long lived magmatic event. Supporting the idea presented by Lucassen et al. (2000), where they proposed for the Central Andean basement, an evolution in a mobile belt, where the Pampean and Famatinian cycles are not distinct events but, they are one single, non-differentiable event from 600 to 400 Ma