Estudio aeromagnético del complejo volcánico de Colima, occidente de México – implicaciones tectónicas y estructurales

Abstract

Results of qualitative and quantitative interpretation of aeromagnetic anomalies over the Colima volcanic complex (CVC) and surrounding areas are presented. The area is characterized by magnetic anomalies of distinct amplitude and wavelength associated with volcanic structures and intrusive bodies, including the CVC. We identified 24 aeromagnetic domains in an area of 11,500 km2 around the CVC. We identify, for the first time, new geological structures buried under volcanic products, like faults and intrusive bodies. High amplitude magnetic dipolar anomalies characterize the volcanic structures of Colima and Nevado de Colima volcanoes. CVC deep structure was investigated by using a 2¾ D magnetic model, finding that the source is related to a possible magmatic chamber of elongated shape, >6.8 km long, in north-south strike with maximum thickness of 5.6 km, which is located at 4.8 m depth beneath the Colima volcano. The body extends to 5.6 km south of the Colima volcano, with average thickness of about 0.54 km. Under Nevado de Colima volcano, we interpreted a collapsed magmatic chamber, with elongated shape, >5.6 km long and 1.2 km of maximum thickness at a depth of around 5.2 km below the Nevado summit.

In most of the reduced to the pole magnetic anomaly map, we observed large monopolar anomalies, high amplitude, and long wavelengths associated to the intrusive bodies. Three of these anomalies form a 47 km long belt to the NW of the CVC. There are several magnetic anomalies related to iron-ore deposits, i.e., El Encino mine (48 km SE of CVC) and Sierra de Manantlán (42 km ESE of CVC).