GENESIS AND ND ISOTOPE COMPOSITION OF FERROMANGANESE DEPOSITS OF THE SEA OF OKHOTSK AND THE KURIL ISLAND ARC
P.E. Mikhailik1, I.A. Vishnevskaya2,3,4, E.V. Mikhailik1, M.G. Blokhin1, M.V. Chervyakovskaya4, V.A. Rashidov5, Ren Xiangwen6
1Far Eastern Geological Institute, Far Eastern Branch of the Russian Academy of Sciences, Vladivostok, Russia
2Vernadsky Institute of Geochemistry and Analytical Chemistry, Russian Academy of Sciences, Moscow, Russia
3Novosibirsk State University, Novosibirsk, Russia
4Zavaritsky Institute of Geology and Geochemistry, Ural Branch of the Russian Academy of Sciences, Yekaterinburg, Russia
5Institute of Volcanology and Seismology, Far Eastern Branch of the Russian Academy of Sciences, Petropavlovsk-Kamchatsky, Russia
6First Institute of Oceanography, State Oceanic Administration, Qingdao, China
Keywords: Ferromanganese deposits, Nd isotope composition, genesis, Kuril island arc, Sea of Okhotsk
Abstract
The Nd isotope composition of ferromanganese deposits (FMD) from the central part of the Sea of Okhotsk and the Kuril island arc has been studied. The results showed that diagenetic samples from the Deryugin Basin have a heterogeneous Nd isotope composition. The positive εNd values here might be both due to the input of a terrigenous impurity and due to diffuse endogenous element supply. The FMD samples from the Sonne underwater ridge show a εNd value specific to seawater (-3.2). The εNd value of hydrogenetic FMD from Volcano 7.14 is -3.4, which corresponds to the εNd value of the Pacific water. The FMD samples from Volcano 5.5 are characterized by εNd = -2.0. The higher εNd value might be due to a moderate dilution of the hydrothermal fluid by seawater and might also indicate the presence of volcanic fragments in the FMD samples. The highest εNd value (+4.4) has been established for volcaniclastic sandstone saturated with Fe and Mn hydroxides. It points to a mixing of volcanomictic and hydrothermal materials.
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