Surface distributed acoustic sensing for mineral exploration

As a receiver array for active-source seismic studies, the use of distributed acoustic sensing (DAS) technology is well established for vertical seismic profiling. However, given the sensitivity of fiber-optic cables, successful and cost-effective surface array studies in reflection seismology and for mineral exploration are still missing. In a feasibility study, we investigate the performance of surface DAS technology for mineral exploration in a hardrock environment. The target is an iron-oxide deposit located in the Bergslagen district in central Sweden. The fiber-optic cable was laid on the surface above the dipping mineralization and covered with a few centimeters of gravel to increase its ground coupling. The data quality varies significantly along the fiber cable. Nonetheless, it is possible to delineate the mineralization in several raw receiver gathers, justifying the development of this technology as a surface array for deep targeting. The adopted processing workflow handles noise issues inherent to DAS data and allows us to image the mineralization and surrounding host geological structures including a fault system thought to have played a role in the termination of the deposits at about 1000 m depth.