Resource assessment of undiscovered seafloor massive sulfide deposits on an Arctic mid-ocean ridge: Application of grade and tonnage models

摘要

Norway has started ongoing initiatives related to deep sea mining. These include the evaluation of mineral resources within its sovereign territorial waters on the deep ocean floor of the Arctic region, i.e. the Mohns Ridge (71-73 degrees N). Among the variety of possible seabed resources, seafloor massive sulfides (SMS) attract particular interest. Owing to the significant development potential and the general lack of knowledge of the SMS deposits, the present study aims at assessing mineral resources (i.e., Cu, Zn, Au and Ag) from a number of undiscovered sulfide deposits with the help of a revised model for mafic-hosted volcanogenic massive sulfide (VMS) deposits that adequately corresponds to geological settings of slow-spreading ridges. Application of the model requires a priori knowledge of the seafloor terrain to depict favorable geologic environments for the occurrence of SMS deposits. In such context, estimates are conducted for the easily accessible volcanically active parts of the ridge where 11 undiscovered deposits are expected. In these areas, total metal endowments are calculated to be on average 447,000 tonnes using a Monte Carlo simulation that combines the probabilistic estimates of number of undiscovered deposits with the grade and tonnage models. Estimates of in-place metal resources are generated in cumulative distribution form to present expected amount of undiscovered metals at 90% confidence intervals.