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Estimating remanent magnetization from aeromagnetic data for geologic applications
Hart, Skye
Hart, Skye
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2024
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Abstract
Magnetic surveys involve measuring the response of the total magnetization in rocks. Total magnetization is the vector sum of induced and remanent magnetization. Induced magnetization is controlled by the inducing field and the rock's magnetic susceptibility. Remanent magnetization is a permanent magnetization in the rock. For the interpretation and modeling of magnetic data, it is common to assume induced magnetization is dominant such that remanent magnetization can be ignored; however, for some specific geologic environments, remanent magnetization is significant and affects the appearance of magnetic anomalies. Additionally, remanent magnetization carries information about the rock composition and formation history.
A remanent magnetization estimation method was tested using aeromagnetic data from the Abitibi greenstone belt to derive remanence directions of ten diabase dike anomalies. The methodology involves separating average remanent magnetization from total magnetization vector inversion models by assuming a magnetic susceptibility distribution. Eight anomalies are interpreted to have significant remanence in a direction different from the inducing field, and for these anomalies, some of the estimated remanence directions align with average paleomagnetic directions. Despite a wide range of estimated directions, the results provide insights for geological interpretation. However, the study emphasizes the inherent ambiguity and non-uniqueness of the remanence estimation methodology, presenting challenges even for isolated, compact, and steeply dipping sources.
Further study involves investigating the association between remanent magnetization and orogenic gold mineralization. Using aeromagnetic, petrophysical, and geologic data from the Timmins gold camp, the study aims to determine the significance of remanent magnetization in interpreting magnetic data from this area. Comparison between magnetization vector inversion models and remotely estimated remanence with petrophysical and geologic data from an orogenic gold deposit site indicates that remanent magnetization may either increase or decrease the total magnetization of certain rock types in the deposit area. These findings contribute to understanding the role of remanent magnetization in geological applications and magnetic modeling.
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