Trace element and Sr isotopic composition of bottom and near-surface oceanic water in the southern region of the Emperor Ridge

Abstract

During the 86th voyage of the research vessel “Akademik M.A. Lavrentiev” (July–August 2019), near-bottom and near-surface water samples (at a depth of 10 m) were taken in the immediate vicinity and above the Koko, Jingu, Nintoku, and Suiko seamounts in the southern part of the Emperor seamount chain. Trace element concentrations (including REE) in these samples are higher than in the IAPSO Standard Atlantic Seawater. The distribution and mutual correlations of elements involved in biochemical processes indicate an active role of plankton in the accumulation of these elements, as well as an increase in its amount with increasing water temperature. 87Sr/86Sr ratios in water samples vary from 0.70891 to 0.70917. Moreover, near-bottom water, taken farther south of 44°N, is more radiogenic than near-surface. This difference can be explained by the dilution of the surface layer with meteoric water, because at the time of sample collection over the Koko, Jingu, and Nintoku seamounts it was raining daily, while no rainfall was observed over the Suiko seamount during the sample collection and the week before it. The rapid restoration of isotopic equilibrium indicates a high rate of vertical mixing of ocean water, which was indicated by the earlier studies of oceanic water chemical composition.