Aeromagnetic anomalies and paleomagnetism in Jalisco and Michoacan, southern Mexico continental margin

Along the southern Mexico continental margin, there are several calc-alkaline batholiths and volcanics emplaced in a complex sedimentary and metamorphic terrane. As part of a long-term project to study the evolution of the margin and its mineral deposits, we have conducted paleomagnetic and aeromagnetic studies in several areas. Attention is concentrated on the correlation of paleomagnetic and rock-magnetic results and the aeromagnetic anomaly responses of intrusive bodies and iron-ore deposits. It is shown that the remanent magnetization data are necessary for adequate quantitative modeling of anomalies, particularly for dipolar anomalies which are not oriented N-S. Rock-magnetic data also permit characterization of the units: intrusives, volcanics, sedimentary, metamorphics and iron ores. The dipolar aeromagnetic anomalies are related to large, deep, prismatic bodies of apparent Late Cretaceous-early Tertiary age. The aeromagnetic response of granitic bodies provides a simple criterion for distinguishing granite type and tectonic environment. The intrusive bodies are magnetite rich with large associated magnetometric anomalies and correspond to the I-type granites of a magmatic arc environment.