In addition to the two new hydrothermal fields Krasnov (l6° 38' N) and Ashadze (13° N) discovered in 2003-2004, some later discoveries were made in the Northern Equatorial segment of the Mid-Atlantic Ridge (MAR). Two new major seafloor massive sulfide (SMS) deposits: Semyenov (13° 31' N) and Zenith-Victory (20° 08' N), as well as the now extended Puy des Folles hydrothermal field (20° 30.5' N), provide enough data to make conclusions about the general characteristics of SMS deposits in the northern equatorial MAR environment. Parameters of SMS deposits, such as their distribution, geological setting, morphology, composition and age, are discussed in this paper. A majority of studied SMS deposits (Ashadze, Logatchev, Semyenov) are associated with uplifted lower crust and mantle rocks (oceanic core complex, or OCC) at the MAR segments with asymmetric mode of accretion. OCC is tectonically uplifted along with detachment faults, which exhume deep-seated rocks onto the seafloor. Detachment faults, in turn, could be the conduits for the circulation of seawater and discharge of hydrothermal fluids. Gabbro-peridotite hosted deposits are characterized by high concentrations of copper, gold and cobalt. The relationship between the size of the deposits and their age is documented.

ice-wedge ice indicates winter conditions colder than during the MIS3 interstadial and warmer than during MIS2 stadial, and similar atmospheric winter moisture sources as during the MIS2 stadial. Buchchagy Ice Complex pollen spectra reveal tundra-steppe vegetation and harsher summer conditions than during the MIS3 interstadial and rather similar vegetation as during the MIS2 stadial. Short-term climatic variability during MIS5 is reflected in the record. Even though the regional chronostratigraphic relationship of the Buchchagy Ice Complex to the Last Interglacial remains unclear because numerical dating is widely lacking, the present study indicates permafrost (Ice Complex) formation during MIS5 sensu lato, and its preservation afterwards. Palaeoenvironmental insights into past climate and the periglacial landscape dynamics of arctic lowlands in eastern Siberia are deduced from the record.

Two new major hydrothermal fields have been discovered in the rift valley of the MAR at 13 N (Ashadze) and l6 38 0 N (Krasnov). The Ashadze field consists of a cluster of active hydrothermal sites associated with ultramafic rocks and located at the greatest depth in the ocean (4,200 m). By contrast, the Krasnov field consists of inactive sulfide mounds hosted in basalts. The Krasnov is the largest hydrothermal deposit on the MAR (17.4 Mt) so far discovered with iron sulfide as the principal mineral type. By contrast, Cu-Zn sulfides are the major minerals in the Ashadze deposits, which are also enriched in gold and several other metals.

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