MODELLO

An analysis of crustal structure and major tectonic features derived from interpretation of country-wide regional aeromagnetic anomalies is presented. As part of long-term exploration programs of the National Oil Company (PEMEX), aeromagnetic surveys have been completed for most of the country. Recently the Petroleum Research Institute has completed the integration of the available aeromagnetic data. In this study, we present a new aeromagnetic anomaly map of Mexico at a scale 1:2000 000, based on data integration and reduction at a reference level of 3500 m above sea level. Aeromagnetic data collected for small scale prospect areas at different times in the past decades have been re-processed to take into account the secular variation field and global reference field (IGRF), and continued upwards to a uniform level of 3500 m. Different smoothing and contouring techniques were then applied to the data set to generate a country-scale aeromagnetic anomaly map. Zones that were not surveyed include the ignimbritic volcanic province of the Sierra Madre Occidental, the area around Mexico City within the Trans-Mexican volcanic belt (TMVB) and smaller areas in southern Mexico. Major geologic provinces can be delineated in the aeromagnetic anomaly map, such as the batholithic belt in the Gulf of Mexico coastal plain that follows the trend of the fold and thrust belt of the Sierra Madre Oriental, and major NW-SE lineaments in northern Mexico. Arcute anomalies mark the Jalisco block in westernmost Mexico and also a major trend across central and southern Mexico that defines a Michoacan-Guerrero block. Major volcanic provinces and a few isolated volcanic centers such as the Chichonal volcano in Chiapas are marked by high amplitude high frequency anomalies and large dipolar anomalies, respectively.