Geochemistry of the submarine Vityaz Ridge at the pacific slope of the Kurile island arc |
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| Authors: | T A Emelyanova Yu A Kostitsyn E P Lelikov |
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| Institution: | 1.Il’ichev Pacific Institute of Oceanology, Far East Branch,Russian Academy of Sciences,Vladivostok,Russia;2.Vernadsky Institute of Geochemistry and Analytical Chemistry,Russian Academy of Sciences,Moscow,Russia |
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| Abstract: | This paper reports the results of geological studies at the submarine Vityaz Ridge carried out during cruises 37 and 41 on
the R/V “Akademik Lavrent’ev” in 2005 and 2006. The studied area is located at the near-island trench of the slope in the
central part of the Kurile island arc. Morphologically, it consists of two parts: inner volcanic arc represented by the Great
Kurile Range and outer arc corresponding to the submarine Vityaz Ridge. Diverse rocks that compose the basement and sedimentary
cover of the ridge were recovered by dredging. Based on K-Ar dating and geochemistry, the volcanics were divided into Paleocene,
Eocene, late Oligocene, and Pliocene-Pleistocene complexes. Each of the distinguished complexes reflects the tectonomagmatic
stage in the ridge evolution. The geochemical and isotope data on the volcanics indicate the contribution of ancient crustal
material in magma source and, correspondingly, the formation of this structure on the continental basement. Two-stage model
ages, TDM2, vary in a wide range from zero values in the mafic rocks to 0.77 Ga in felsic varieties, pointing to the presence of Precambrian
protolith in the source of the felsic rocks of the Vityaz Ridge. The Pliocene-Pleistocene volcanics are classed with the tholeiitic,
calc-alkaline, and subalkaline series, which differ in alkali contents and REE fractionation. The values of (La/Sm)N and (La/Yb)N ratios vary from 0.74 and 0,84 in the tholeiitic varieties to 1.19 and 1.44 in the calcalkaline and 2.32 and 3.73 in the
subalkaline rocks. All three varieties occur within the same volcanic edifices and were formed during differentiation of magmatic
melt that were channeled along fault zones from the mantle source slightly enriched in crustal component |
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