How to Find Buried and Inactive Seafloor Massive Sulfides Using Transient EM - A Case Study from the Palinuro Seamount

Abstract

At present, the investigation of seafloor massive sulfides (SMS) is currently strongly limited by the available technology to the detection of actively forming sites. This is due to the fact that the detection of SMS deposits mainly relies on plume detection of active hydrothermal venting in the water column and seafloor morphological observations. While these methods have proven to be valuable tools for the detection of actively forming SMS, they do not allow the detection of deposits which are no longer connected to hydrothermal activity and which are possibly covered by sediments or lava. Therefore, to broaden the scope of investigations on SMS it is necessary to develop new technologies allowing for the detection of SMS deposits which have finished their active phase. In land-based exploration it has been common practice for several decades to use electromagnetic methods to detect and characterize massive sulphide deposits. However, when turning to marine investigations only a few electromagnetic experiments have ever been conducted on SMS (e.g. by Cairns et al., 1997; Kowalczyk, 2008). In a recent publication our workgroup has proposed to use the transient electromagnetic (TEM) method (Swidinsky et al., 2012). There, we have shown that the TEM method would in principle not only be useful for the detection of a deposit under a sediment cover, but could also yield valuable information about it's depth and potentially also it's thickness. Here, we will give a proof of principle by showing results of the – to our knowledge – first successful experiment, in which the TEM method was used to find a buried SMS deposit at the Palinuro Seamount in the Tyrrhenian Sea.