Description of manganese deposits collected by RV Spencer F. Baird during the Trans-Pacific expedition in the Western Pacific in 1953

Fifty-five rock fragments and pebbles were dredged at 2,550-2,800 fathoms (4,650-5,100 metres) near Jimmu Seamount, 700 miles southeast of Kamchatka. Tuffaceous shale, andesitic and dacitic tuff, pyroxene-hornblende dacite-pumice, and augite-hypersthene andesite are the most abundant rock types. Minor constituents in the haul include augite-pigeonite basalt, augite-olivine basalt, olivine dolerite, quartz syenite porphyry, metabasalt, sandstone, and chert. Petrographic and chemical analyses indicate closer affinities with Kuril Islands and Kamchatka volcanic rocks than with Cenozoic Japanese or Pacific Basin types. Probably these rocks were dropped by Pleistocene icebergs carried south and east by ocean currents.

在勘察加半岛东南700英里处的神武海山（Jimmu Seamount）附近、水深2550-2800英寻（fathoms，4650-5100米）区域，采集到55块岩石碎片和卵石。凝灰质页岩（tuffaceous shale）、安山质（andesitic）及英安质凝灰岩（dacitic tuff）、辉石-角闪石英安岩-浮石（pyroxene-hornblende dacite-pumice），以及辉石-紫苏辉石安山岩（augite-hypersthene andesite）是最主要的岩石类型。采集样本中的次要成分包括辉石-易变辉石玄武岩（augite-pigeonite basalt）、辉石-橄榄石玄武岩（augite-olivine basalt）、橄榄石辉绿岩（olivine dolerite）、石英正长斑岩（quartz syenite porphyry）、变质玄武岩（metabasalt）、砂岩及燧石（chert）。岩相学的（petrographic）与化学分析表明，这些岩石与千岛群岛及勘察加半岛火山岩的亲缘关系，比其与新生代（Cenozoic）日本或太平洋盆地岩石类型的关系更为密切。这些岩石很可能是由洋流携带向南及向东移动的更新世（Pleistocene）冰山所遗留。