Petrogenetic study of the Lonco Trapial volcanism and its comparison with the Early-Middle Jurassic magmatic units from northern Patagonia

CLAUDIA BEATRIZ ZAFFARANA; LAGORIO, SILVIA LEONOR; GLORIA GALLASTEGUI SUÁREZ; GERHARD WORNER; DARIO ORTS; GREGORI, DANIEL; POMA STELLA; ALICIA BUSTEROS; GIACOSA, RAÚL; DIEGO SILVA NIETO; VICTOR RUIZ GONZALEZ; BARBARA BOLTSHAUSER; CARLA G. PUIGDOMENECH NEGRE; MIGUEL HALLER

JOURNAL OF SOUTH AMERICAN EARTH SCIENCES

PERGAMON-ELSEVIER SCIENCE LTD

Lugar: Amsterdam; Año: 2020

0895-9811

One of the largest silicic igneous provinces of the world, the Chon Aike Volcanic Province, is related to an extensional regime developed in Patagonia in Early to Middle Jurassic times. This work presents new geochemical analyses for major and trace elements from different units in the central domain of northern Patagonia, units known as Lonco Trapial and Garamilla formations. Additionally, some samples were analyzed from the Piltriquitrón and Lago La Plata formations in the western domain of northern Patagonia. One new U-Pb age of a rhyolitic dike (177.26 ± 0.96 Ma) and new Rb-Sr and Sm-Nd determinations from the Lonco Trapial Formation are also presented in this work. Results presented here fill a gap in geochemical data for the area with respect to the temporal and spatial coverage of the Chon Aike Volcanic Province in northern Patagonia. Our comparative study shows that all Early-Middle Jurassic igneous rocks from this area have mixed characteristics between slab-derived subduction-related settings and intraplate magmas. Isotopic and whole-rock geochemical data show that the petrogenetic evolution of Lonco Trapial magmas can be explained by a combination of fractional crystallization together with crustal assimilation. Melting of a mantle previously metasomatized by earlier subduction processes can be considered as responsible for the calc-alkaline subduction signature of lavas in the Lonco Trapial Formation. Crustal contamination also played an important role, especially considering the thickened crust that these magmas traversed in their way to the surface.