N. V. Tsukanov

Ferromanganese crusts on the bottom of the Bering Sea

Geologically, this discovery in a seismically active and ore rich region is of considerable importance. In connection with this, we have performed a compre hensive study of the mineralogy and geochemistry of representative samples collected by three copartici pants of the voyage from six stations of dredging in the area of the Massif of Volcanologists (1–3), the Alpha fault zone (4–6), and the underwater Shirshov Ridge (7–9) (Table 1).

New SHRIMP U-Pb Age Data on Zircons from Plagiogranites in the Ophiolites of the Kamchatsky Mys Peninsula, Eastern Kamchatka

Geological setting. Kamchatsky Mys peninsula has composite fold-and-thrust structure, constructed by Cretaceous and Paleocene-Eocene volcanic and terrigenous-tuffaceous rocks and tectonic slices of serpentinite mélange, gabbroids and ultrabasic rocks [Khotin, 1976; Zinkevich et al., 1985; Rasnitsyn et al., 1985; Fedorchuk, 1989; Shapiro, 1987; Accretional ... , 1993; Boyarinova et al., 2000, 2001; Saveliev, 2004]. Its southern part (Afrika block) according to [Zinkevich et al., 1985] is constructed by four allochtonous complexes. They are composed of: 1) Aptian-Albian and Albian-Cenomanian calcareouscherty-effusive assemblages (Afrika complex), 2) Campanian-Maastichtian cherty-tuffaceous and terrigenous deposits, 3) Paleocene-Lower Eocene chert-volcanic sequence (Kamensk complex), 4) serpentinite mélange and gabbroids. Serpentinite mélange contains unaltered ultrabasic rocks (Mountain Soldatskaya massif) and smaller bodies of gabbroids, Cretaceous and Paleogene tuffaceous and cherty rocks. Ophiolite fragments at Kamchatsky Mys peninsula are represented by gabbroids of Olenegorsk pluton and ultrabasic rocks of Soldatsky massif, by blocks of gabbroids with plagiogranites in serpentinite mélange, different basalts and calcareous-jasper-cherty deposits of Aptian-Cenomanian Afrika complex and tholeiite basalts, mudstones of Paleocene-Eocene Kamensk complex.