Review of magmatic iron-ore mineralization in central-western Mexico: Rock-magnetism and magnetic anomaly modelling of Las Truchas, case study

Las Truchas deposits formed by contact metasomatism in a Mesozoic volcano-sedimentary sequence intruded by a batholith. Later, post-mineralization hydrothermal alteration affected minerals and magnetic properties. For this study, we sampled the host rocks and iron ores. The mineralogy and magnetic domain states of oxide minerals were characterized by reflected light and scanning electron microscopy together with rock magnetic experiments such as thermomagnetic measurements, frequency dependence of magnetic susceptibility, hysteresis, first-order-reversal-curves and UnMix curves. Qualitative and quantitative forward modelling of the subsurface structure was inferred by processing of magnetic anomaly maps. Induced and remanent magnetization (intensity and direction) and the Konigsberger ratio were used as input parameters for the quantitative modelling process to adjust our calculated anomaly with the observed magnetic anomalies. We attempt to understand the geological factors that control the magnetic signatures, which can be used to improve the geological interpretation of magnetic studies.