EVIDENCIAS DE DEFORMACIÓN FRÁGIL DURANTE EL EMPLAZAMIENTO DE UN LACOLITO: EL CASO DEL CERRO BAYO DE CHACHAHUÉN, SUR DE MENDOZA, ARGENTINA

BURCHARDT, STEFFI; LEANZA, HÉCTOR A.; GALLAND, OLIVIER; PALMA, OCTAVIO; MAIR, KAREN

San Miguel de Tucumán

Congreso; XX Congreso Geológico Argentino; 2017

Asociación Geológica Argentina

EVIDENCES OF BRITTLE DEFORMATIONDURING EMPLACEMENT OF A LACCOLITH: THE CERRO BAYO OF CHACHAUÉN CASE STUDY,SOUTHERN MENDOZA, ARGENTINA. -Laccoliths are dome-shaped igneous intrusions that grow from the inflation ofsills, which are emplaced at shallow depths in the upper crust. During theinflation process, stresses are concentrated on the sill tips, producing domingand faulting of the host rocks. This was thought to be the only mechanisms fordissipating stress. New field observations on a well preserved laccolith insouthern Mendoza, Argentina, show evidences of brittle deformation duringemplacement. This is the case of the Cerro Bayo laccolith, emplaced in aneroded Miocene caldera termed Sierra of Chachauén. This laccolith shows a widebreccia, approximately 200 m width, composed of igneous rock and fault gauge.The breccia is located inside the laccolith, on the western margin, opposed tothe main igneous conduct, which is identified by its clear flow banding. Themeasurements of the flow banding and the anisotropy of magnetic susceptibility(AMS) allow us to model the emplacement of the laccolith. Also we tested therobustness of the AMS technique for modelling magma flow. Our observationssuggests a co-existence of brittle and ductile deformation during theemplacement of a laccolith.