Geophysical Exploration Tools for Deep Sea Mineral Resources

Abstract

The two types of Deep Sea Mineral resources which we are exploring at the moment (Polymetallic Nodules and Seafloor Massive Sulfides, SMS) are being found in very different settings and hence require different approaches for exploration with geophysical methods. In both cases, exploration begins with overview measurements of multibeam bathymetry, magnetics, and gravity over large areas carried out at the sea surface with research vessels. In the case of Polymetallic Nodules, especially the acoustic backscatter data have proven to be highly useful and reliable for classification of the seafloor according to the abundance and size of the Nodules. Further investigations mainly involve geologic sampling. The occurrence of SMS is connected to active or inactive seafloor hydrothermalism for which indications can be found in morphological structures and magnetic anomalies observed from the sea surface. Since the SMS are confined to very small spots at the seafloor and in some cases buried by sediments, extensive near bottom observations with high resolution bathymetry, magnetic, and electromagnetic methods are required for ground-truthing in prospective areas.