GEOCHEMICAL CHARACTERIZATION AND EMPLACEMENT OF THE EARLY TRIASSIC FELSIC DYKE SWARMS, MENUCOS- LA ESPERANZA, NORTH PATAGONIAN MASSIF

MARTÍNEZ DOPICO, CARMEN; LÓPEZ DE LUCHI, MÓNICA; MARQUEZ, EMILIA; FRANCESCHINIS, PABLO REINALDO; RAPALINI, AUGUSTO ERNESTO; MIGUEZ, MAXIMILIANO; COLAVITTO, BRUNO

Puerto Madryn

Congreso; XXI Congreso Geológico Argentino; 2022

Asociación Geológica Argentina

Acidic dyke swarms are an exceptional expression of crustal extension as feeding channels for silicarich magmas in their way from the magmatic reservoirs throughout the upper crust. Evidence of extensional conditions from the Late Permian to Late Triassic can be tracked in the centre of the North Patagonian Massif, such as large shallow plutonic-volcanic complexes and volcanoclastic deposits (i.e. La Esperanza plutonic- volcanic complex, Martínez Dopico et al. 2019, Los Menucos basin, Luppo et al. 2018) and large W-E dextral strike-slip fault systems with kilometric displacements (i.e. Giacosa et al. 2007 Luppo et al. 2018). In the area of Estancia Cerro Piche, 45 km to the NW of Los Menucos (40º51´S, 68º5´E), three sets of rhyolitic dyke swarms (10-50 m-length; 0.5 to 3 m-width) were recognized, mainly W-E to WNW-ESE and NW-SE, and minor NE-SW. The distribution of dykes is parallel to the Jurassic (?) E-W-trending transcurrentfaults (Giacosa et al. 2007). In Los Menucos area, the dyke swarm crosscuts Palaeozoic units, such as the Cambrian metaclastic Colo Niyeu Formation (Martínez Dopico et al. 2017b), the andesitic and dacitic couleescorrelated with the Collinao Dacite (Luppo et al. 2019), and sections of the rhyolitic to andesitic volcanic and volcaniclastic sequences of the Los Menucos Complex (Lema et al. 2008) which were dated at 257 ± 2and 252 ± 2 Ma, respectively (Luppo et al. 2018). Similarly, 20 km to the north, in La Esperanza area, another E-W to minor SW-NE rhyolite dyke swarm intrudes the Collinao Dacite (253 ± 2 Ma; Luppo et al. 2019) andthe epizonal leucogranites of the Calvo Granite (250 ± 2 Ma; Pankhurst et al. 2006) and older units of the La Esperanza plutonic-volcanic Complex (Martínez Dopico et al. 2019). The rhyolite dyke swarm was datedin La Esperanza area at 246 ± 2 and 244 ± 2 Ma (Pankhurst et al. 2006; Luppo et al. 2019).