Controlled Source Electromagnetic Mapping of Massive Sulfide Deposits with an AUV
Steve Bloomer | Senior Geophysicist (1)
Matthew Kowalczyk* | Chief Executive Officer (1)
Peter Kowalczyk | Chief Technology Officer (1)
Seafloor massive sulfide (SMS) deposits found near seafloor hydrothermal venting sites are of great economic interest because they contain appreciable grades of valuable metals such as gold and copper. Electromagnetic prospecting is one geophysical method that is very useful to map these deposits because copper or gold are highly conductive.
Ocean Floor Geophysics (OFG) in 2008 developed the first EM system to successfully map the limits of conductive mineralization in a survey of a SMS deposit (Kowalczyk, 2008).
Since then, towed coincident loop time domain systems (Nakayama and Saito, 2016) and a deep-tow controlled source electromagnetic (CSEM) array (Murton 2017) have detected anomalies over known sulfide mineralization. Additionally, OFG has partnered with Fukada Salvage and Marine Company Ltd. and the Scripps Institution of Oceanography to successfully map resistive methane hydrate deposits to several hundreds of meters below the seafloor using a towed CSEM system.
However, towed CSEM systems consisting of electrical transmitters and receivers have many shortcomings due to logistic challenges associated with the size of the system and towing the system at constant depths close to hydrothermal vents. To mitigate these problems, and to enable the simultaneous collection of complementary data (e.g. multibeam bathymetry), OFG has modified the Scripps system by integrating a CSEM system on to an AUV with transmitters placed on the seafloor.
The presentation will show the results of two engineering tests performed in 2015 and 2016 by OFG, Fukada, and Scripps to advance the use of CSEM technology on an AUV platform.
(1) Ocean Floor Geophysics, Burnaby, BC, CANADA