ABSTRACT:The northern part of the roughly north-south trending Loei suture zone has been investigated extensively by several geoscientists for more than five decades not only for its complex geology but also for mineral exploration. In this study, we have reprocessed existing detailed aeromagnetic data for interpreting the continuity of geological units and structures where most of the pre-Cenozoic rock units are overlain by regolith cover comprised of recent soils, alluvial deposits, and colluvium surrounding hills and mountains. The aeromagnetic data were run through a series of filter routines to highlight deep and shallow magnetic features. These include analytic signal, reduction to the pole, first vertical derivative, directional cosine filtering, and upward continuation. Interpretation of all the processed geophysical data has been carried out by integration of aeromagnetic data with electromagnetic data, radiometric data, enhanced Landsat images and GIS geological information. Three geological domains (eastern, central, and western) were interpreted from the geophysical data to correspond to assemblages of contrasting rock types, as well as different regional structures identified in this study. These three domains are interpreted to be markedly separated by thrusts and sub-vertical shear zones. The magnetic data were also used to model the geometry of mafic units and granitic intrusions in 3 dimensions. Magnetic mafic bodies in the Loei suture zone were found to display their dip direction to the east. Magnetic units running along the eastern side of the Loei suture zone correspond fairly well to folded and thrust faulted basalt flows of Devonian age. Moreover, some PermoTriassic granitoid intrusions have a strong magnetic fabric, and a few have surrounding magnetic rings are likely caused by magnetic minerals in hornfels. The others turn out to be a single smaller magnetic rings at depths suggesting only one feeding magma chamber. A few Permo-Triassic felsic to intermediate lava flows are identified by their hummocky magnetic texture. Northeast-southwest trending faults observed in the magnetic data cross-cut Triassic granite intrusions and pre-Jurassic stratigraphy, mostly producing more than 1 km of sinistral offsets. Our new interpretation agrees with the existing geological bedrock mapping in a broad sense, but shows differences in the continuity of features and extent of granitoid intrusions, and contains more large-scale structural detail. Our interpretation overlain onto the mineral occurrences map with GIS application will help to improve subsurface exploration and will help mineral explorers by highlighting new mineral target areas under thin Quaternary regolith cover. List of abbr List of abbr List of abbr List of abbr List of abbreviations: eviations: eviations:
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