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During the Late Paleocene, at least five ignimbrite units were emplaced from the Yakutinskaya caldera complex in Primorye, Russia. The erupted ignimbrites show two distinct chemical cycles, believed to represent the "high" silica and "low" silica parts of the compositionally zoned magma chamber. Two petrographically distinctive types of rhyolites are distinguishable in each chemical cycle, based on their phenocryst chemistry and silica content: (1) "low" silica rhyolites with mineral assemblages of quartz, sanidine, plagioclase, ferrohypersthene, ferroaugite (Ca 41 Mg 21 Fe 38 ), biotite, and hornblende, and (2) "high" silica rhyolites with a similar mineral assemblage to "low" silica, but containing more Fe rich clinopyroxene (Ca 44 Mg 2 Fe 54 ) and biotite, and a with lower phenocryst abundance. This difference is related to the variation in chemical composition and temperature of the magma in the zoned magma chamber for each eruption cycle. Rb Sr mineral rock isochron ages show that the ignimbrites erupted between 59.7 ± 1.6 and 54.8 ± 2.6 (2σ) Ma (Late Paleocene), and initial

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Mass cobalt-rich ferromanganese microcrusts and nodules similar in morphology and chemical composition to cobalt-rich ferromanganese deep-ocean crusts were found in Cenozoic volcanic rocks in southern Primorye. Research has shown that ore genesis of this type is genetically related to argillization and destruction of siliceous rocks by CO2-rich fluids, which is confirmed by experimental data on carbon erosion of iron-containing materials. Two types of this fluid ore genesis are recognized: (1) relatively high-temperature (vapor–condensate), related to late volcanic processes and fracture gas infiltration, and (2) low-temperature (vapor–liquid–condensate), controlled by degassing followed by carbon mobilization (gasification). Primarily colloidal ferromanganese segregations have high contents of Co, Ni, Pb, Cu, and Ce, typical of oceanic ore genesis. Regardless of the concentrations of these metals in the protoliths, their contents in microcrusts are similar (n–10n wt.%). This indicates the same ore genesis mechanism and similar sorption properties of the colloidal ferromanganese material formed. Barium- and cerium-rich ferromanganese microcrusts and nodules are abundant. Condensed drops of iron-containing platinum were found in apobasaltic nickel-rich ferromanganese segregations. There is a cerium paradox expressed as a minimum or a total lack of cerium among rare-earth phosphates associated with ferromanganese microcrusts. Fluid destruction and oxide metallization of ocean-floor basalts are assumed to be the main source of metals for oceanic ferromanganese crusts and nodules.