Parameter and Index for Delineation and Evaluation of Co-Rich Crust Resources

Marine Co-riched crusts are important as potential mineral resources for Co, Ni, Pt, Mn, and other metals, as well as for the paleoenvironment signals stored in their stratigraphic layers.The higher Co, Ni and Pt content of crusts relative to abyssal polymetallic nodules and hydrothermal deposits have made seamount crusts a potential target for commercial exploitation and has thus led to a surge of interest in their genesis and geochemistry.Twenty-six seamounts and guyots in the Western Pacific (Maggellan Seamounts, Marcus-Wake Mountains, Marshall Islands, Mid-Pacific Mountains, Line Islands) were sampled in detail, environmentally surveyed, and photographed by bottom cameras in order to better understand the distribution, origin, and evolution of marine Co-enriched crusts by Second Institute of Oceanography of SOA and Guangzhou Marine Geological Survey of MLR in the last decade.The major purpose of exploiting Co-riched crusts is to delineate and mine the deposits.Unfortunately, the parameter and index for delineating and evaluating the crust resources are not available so far.Based on the various data collected from the twenty-six seamounts and guyots, together with marine environment information of the Pacific, we have analyzed the changes of crust thickness, abundance, grade, coverage, resource amount, seamount slope and water depth by the quantitative method.We determined the mine area, studied the distribution characteristics of crust resources, delineated and evaluated the crust resources of thirteen typical seamounts and guyots.Accordingly proposed eight important parameters and indexes for delineating and evaluating Co-enriched crust deposits: (1) crust thickness ≥3 cm or ≥4 cm, depending on the different seamount locations; (2) water depth ≤2 500 m or ≤3 000 m; (3) Co content ≥0.50% or ≥0.60%; (4) abundance ≥ 60 kg/m² or ≥70 kg/m²; (5) seamount slope ≤15°; (6) crust coverage ≥30%; (7) application area 17 000-20 000 km²; (8) reservation area 5 000-6 000 km².The parameters and indexes we present here will promote the deposit delineation, resource estimation and evaluation, and will also provide the quantitative parameter index for our country's active participation into the establishment of regulations on exploiting Co-enriched crust resources by the International Sea-bed Authority of United Nations.