Os isotopic compositions of a cobalt-rich ferromanganese crust profile in Central Pacific

Cobalt-rich ferromanganese crusts occur throughout the global ocean on seamounts, ridges, and plateaus where currents have kept the rocks swept clean of sediments for millions of years. Crusts are important as a potential re-source for primarily cobalt, but also for titanium, nickel, REE, PGE, and other elements. Most Co-rich crusts pre-cipitate at water depths of about 1000-3000 m, and are easy to be exploited. Besides the high cobalt contents compared to abyssal Fe-Mn nodules, exploitati…

Os isotopic compositions of a cobalt-rich ferromanganese crust profile in Central Pacific

^187Os/^188Os ratios in all sub-layers of the Co-rich ferromanganese crust MP5D17 from Line Seamount in Central Pacific have been systematically determined. The ^187Os/^188Os values in this crust are highly variable, ranging from 0.4262 to 1.0155. From the bottom to the top, the osmium isotopic ratios of the crust display a regular variation trend, which correlates well with its changes in structure and texture in the vertical profile. In comparison with the evolution curve of Os isotopic composition in seawater over the past 80 Ma, a similar evolution tendency can be found with respect to the Os isotopic composition of the crust in this study. It is preliminarily concluded that the crust MP5D17 began to grow at about 72 Ma, and underwent three growth hiatuses, corresponding to the geological ages of 64, 53 and 37 Ma, respectively.