UAV magnetometry for chromite exploration in the Samail ophiolite sequence, Oman

Chromite occurrences in ophiolite complexes present valuable natural resources and require sophisticated geophysical exploration methods. As chromite does not exhibit significant geophysical anomalies, we propose an indirect method of detection by surveying for magnetic anomalies caused by the serpentinization of the chromite host rock, which contains magnetite developed through petrogenesis. An unmanned airborne vehicle (UAV) magnetometry test survey revealed a known chromite deposit. The results show that mapping for serpentinite is a viable option to find chromite provided the survey is conducted at low flight elevations (<60 m above ground). The survey results reveal the location of a known chromite deposit and indicate that the magnetic susceptibility contrast between chromite and the surrounding serpentinite is low. It further indicates a low-grade serpentinization in the area, which requires very sensitive magnetometry surveys in close proximity to the targets provided by terrestrial and UAV platforms. The ability of UAV surveys to acquire observations of the magnetic field in 3D enables the calculation of magnetic gradients, which show higher sensitivity than classical gradient estimation from 2D observations.