Variation in growth rate of polymetallic crusts in the central and western Pacific Ocean and its constraining factors

The growth rate of polymetallic crust varies in different growing areas and layers, constrained by some marine factors. In this paper, the polymetallic crust growth rate and its variation with growth region, age and structures are studied, in addition to the relationship between growth discontinuity and growth rate change. It is found that from east to west of the study area, i.e. from the Line Seamounts to Magellan Seamounts, the growth rate of polymetallic crusts decreases as the crusts change from dense to loose to sub-dense in layers, from old to young in ages and from high to low in topography. The areas below OMZ, where it is strong in oxidability, abundant in terrigenous materials supply and high in dissolution rate of calcium carbonate, are the areas favorable to the growth of crusts. Hiatus of crusts corresponding to three types of growth rate changes are observed in the study area: a) before the growth rate turned from low to high, which mainly corresponds to the hiatus of 65～60 Ma, the hydrodynamic condition of the environment is not good enough to crust growth, so the crust stopped growing and the crust could only resume growing when conditions were improved. b) when the climate warmed up and the supply of continental-derived wind dust remain low, the growth rate of crust would drop from high, which mainly corresponds to the two hiatuses during 51～42 Ma and 40～35 Ma. The crusts stopped growing when the environment became severe, and could only resume growing when it was slightly getting better. c) the growth rate remained low, which corresponded to the hiatus of 28-18 Ma, while the dissolution rate of CaCO₃ in the ocean was low. The crusts grew intermittently if the growth environment remained poor.