First results regarding the influence of mineralogy on the mechanical properties of seafloor massive sulfide samples

• 12 seafloor massive sulfide (SMS) samples have undergone geomechanical tests.
• Mineralogical investigations were also performed.
• For the black smoker, porosity decreases with increasing UCS values.
• The porosity of pyrite and melnikovite is partly interconnected (high strength).
• The geotechnical properties influence the energy consumption during the excavation.

Seafloor Massive Sulfides (SMS) are increasingly accepted as important marine raw material resources for the future, in particular because of their polymetallic character. Many industrial nations are researching not only on the scientific importance of these deposits but also on their economic value. Regarding the current state of the international exploration, mainly two-dimensional surface-close observations are accessible, whereas only some core data and measurements are publicly available to date. In fact, there are few successful drilling campaigns containing information about the size and shape, which also give information on the structure and content of modern massive sulfide ore bodies in their third dimension. Regarding the mechanical properties of SMS samples, only few data are available. Geotechnical data of these deposits are important in order to develop an efficient mining technology for exploitation. In this research, 12 SMS samples from two different locations were investigated. Based on the mineralogical characterization of the studied samples the geotechnical properties were preliminary correlated with the mineralogical results. The comparative study indicates how far the geotechnical data are controlled by mineral type and composition, including the porosity. A regression relation between compressive strength and the porosity based on the mineralogy shows a distinct relation between these parameters. Therefore, the geomechanical and mineralogical features have a strong importance for deep-sea mining applications and this should be kept in mind considering the hyperbaric effects on the rock cutting.

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