Summary of the new zircon U-Pb SHRIMP radiometric dating of Cordilleran granitoids from the Bariloche region. Age ranges of the silicic volcanism in Patagonia (V1, V2 and V3 eruption events) and the Subcordilleran plutonic belt are shown for comparison. Individual bars represent the age range from statistical analyses of the analyzed zircon populations.

Interpretative sketch of emplacement of the northern part of the Northern Patagonian batholith during the Middle Jurassic, according to the data presented in this work. (a) Middle Jurassic reconstruction of the South American margin of Gondwana. The large red arrow marks the supposed convergence vector for this time period. LOFS: Liquiñe-Ofqui fault system. GFS: Gastre fault system. AFFZ: Agulhas-Falkland fracture zone. The block diagram above the map illustrates the proposed mechanism of emplacement in the upper crust of the Cordilleran granitoids in the Bariloche area during the Middle Jurassic. (b) Schematic map and interpretative block diagram of the oblique subduction of the Phoenix plate under the South American margin of Gondwana during the Jurassic.

Sr/Y vs Y (a) and Sr/Y vs LaN/YbN (b) diagrams plotting representative intrusive rocks from the Bariloche region. Diorites, Qtz-diortes and their fractionates (i.e.: granodiorites and tonalites) define a possible “trend of pulses” as supported by age-composition relations. Granites are plotted defining a parallel trend possibly related by fluid migration fractionation. Arrows mark the possible low-pressure (i.e. subvolcanic) evolution from individual pulses of magma at late stages of fractionation. Samples from the Patagonian batholith and from the Peninsular Ranges batholith in North America are plotted in the background for comparisons.