NUEVOS ESTUDIOS GEOQUÍMICOS DE LAS FORMACIONES LONCO TRAPIAL Y GARAMILLA Y SU INTERPRETACION EN EL CONTEXTO DE PATAGONIA SEPTENTRIONAL

GLORIA GALLASTEGUI; GREGORI, DANIEL; RAUL GIACOSA; BARBARA BOLTSHAUSER; MIGUEL HALLER; LAGORIO, S. L.; DARIO ORTS; ALICIA BUSTEROS; VÍCTOR RUIZ GONZALEZ; RUBEN SOMOZA; CLAUDIA BEATRIZ ZAFFARANA; GERHARD WORNER; POMA STELLA; DIEGO SILVA NIETO; CARLA G. PUIGDOMENECH NEGRE

Córdoba

Congreso; XIII MinMet - IV PIMMA; 2019

In Early to Middle Jurassic times, the Chon Aike Volcanic Province was erupted in Patagonia during the Gondwana breakup stage. New geochemical analyses were obtained from Lonco Trapial and Garamilla Formations, volcanic rocks which belong to this magmatic province. Their geochemical features are typical of subduction environments, but some trace elements ratios and mineral compositions are compatible with intraplate magmas as well. Intermediate rocks are moderately enriched in LREE, are almost devoid of negative Eu anomalies and show a moderate fractionation in their HREE ([La/Sm]N=2.21-5.04, Eu/Eu*=0.81-1.32 and [Gd/Yb]N=1.40-3.06). The acidic rocks, in turn, are more enriched in LREE, whereas the HREE are almost unfractionated ([La/Sm]N=3.26-6.51, [Gd/Yb]N=1.27-1.79). The andesites from Lonco Trapial Formation have 87Sr/86Sr initial relationships between 0.7056 and 0.7064, negative initial ɛNd (average -3.78), and TDM of 1.3 Ga. Isotopic data point out to reworking of crustal rocks of mesoproterozoic age in the genesis of the central volcanic belt of Northern Patagonia.