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

Abstract

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 (<60m 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 3-D enables the calculation of magnetic gradients, which show higher sensitivity compared to classical gradient estimation from 2-D observations.

Cooperative digital magnetic‐elevation maps by small autonomous aerial robots

“…Despite some meteorological challenges, the data acquired compared favorably to the high-resolution low-altitude airplane data available from the same site. Parvar et al (2017) have described a magnetic survey conducted over chromite deposits in Oman as an example of initial exploration for magnetic anomalies. Due to the low susceptibilities of this mineral, its localization with a magnetometer is not feasible for flights at altitudes above 60 m, they observe that UAV magnetometry enables the surveying of chromite deposits through closer proximity with the terrain and to the targets enabled by these aircrafts as well as the ability to conduct magnetic surveys in 3D.…”

Real‐time compensation of magnetic data acquired by a single‐rotor unmanned aircraft system

“…; Parvar et al . ). This can prove problematic as this design can introduce directional and positional errors and increase the risk of impact to the magnetometer (Kaneko et al .…”

“…; Parvar et al . ) and offer faster data collection at lower cost per kilometer than ground surveys (Parshin et al . ).…”

“…Unmanned aircraft systems (UAS) are increasingly used for small-scale (<10 km 2 ) high-resolution magnetic surveys in part because they offer reduced mobilization time and operating costs compared to traditional manned airborne surveys (Funaki and Hirasawa 2008;Eck and Imbach 2012;Koyama et al 2013;Hashimoto et al 2014;Macharet et al 2016;Wood et al 2016;Malehmir et al 2017;Cunningham et al 2018;Parshin et al 2018;Parvar et al 2018) and offer faster * E-mail: loughlin.tuck@carleton.ca data collection at lower cost per kilometer than ground surveys (Parshin et al 2018). The interference generated by the UAS on the recorded magnetic data is a major impediment for further penetration into the commercial market.…”

“…A simple method to mitigate magnetic interference effects is to increase the distance between the magnetometer and the sources of interference by suspending it on a long cable beneath the UAS (Kaneko et al 2011;Koyama et al 2013;Malehmir et al 2017;Parvar et al 2018). This can prove problematic as this design can introduce directional and positional errors and increase the risk of impact to the magnetometer (Kaneko et al 2011).…”