A.N. Derkachev, N.A. Nikolayeva, A.V. Mozherovsky, T.N. Grigoryeva, Ye.D. Ivanova, S.P. Pletnev, N.N. Barinov, V.M. Chubarov
The mineralogical-geophemical indications of existence of anoxide sedimentary environments in the local basins within the Sea of Okhotsk in the Late Pleistocene-Holocene

Mineralogical-geochemical specialization of deposits in the local basins of the Derugin depression is shown. These deposits formed in the environment of periodic change of conditions from oxide to anoxide with the signs of the hydrosulphuric contamination of the near-bottom waters. The deposits of this type can be represented as a modern model of ancient ore-bearing black-shale formations. In comparison with typical ore-bearing black-shale series which are characterized by high concentrations of organic matter, the investigated deposits within the Derugin depression are depleted in organophile chemical elements (Mo, Ni, Cu, Zn, V, U); however, they have high contents of Mn.

G.Z. Gilmanova, V.Ya. Podgorny
The gravity model of the lithosphere of Taiwan Island (based on the profile Taiwan Strait – Taiwan Island – West Philippine Basin)

Two-dimensional gravitational modeling has been done, and the density section of the lithosphere of Taiwan Island and its framing has been constructed. In terms of density parameters, the lithosphere is divided into continental and oceanic. The continental lithosphere is lighter than the oceanic lithosphere and is characterized by weak density differentiation throughout the entire series. The oceanic lithosphere is distinguished by the great density contrast range of both crust and mantle. In the contact area of the continental and the oceanic block of the lithosphere a superimposed and complexly built density structure of Taiwan Island is recognized – the Taiwan density structure. This structure is distinguished by contrast density boundaries and is marked by increased and high density of the heterogeneities making it up. The formation of the Taiwan density structure is related to geodynamic processes in the collision area of the Eurasian and Philippine plates which take place in the zone of Taiwan Island.

T.K. Zlobin, D.A. Safonov, L.M. Zlobina
Earthquake foci, and crustal and upper mantle deep structure along the South Sakhalin - Okhotsk Sea - Kamchatka profile

Earlier there was a general notion that the Kuril-Kamchatka seismic focal zone was a single plate of about 90 km wide and up to 700 km deep inclined at an angle of 40–45°. Such a notion reflects first of all physical differences (elastic wave velocities, density, temperature, etc.) between the seismic focal zone as a whole and the surrounding mantle, rather than the internal structure of the seismic focal zone. Detailed investigations show that the seismic focal zone determined as a combination of earthquake foci is heterogeneous. The earthquake hypocenters are differently concentrated and grouped inside this zone. Seismogenic and aseismic layers and also subvertical zones can be distinguished in it. The subvertical zones are reflected in the structure and faults of the Earth’s crust and upper mantle.

B.A. Kazansky
Bathymetry of the seas of the West Pacific transition zone based on the ЕТОРО 2'digital data

The new results of the statistical analysis of depths distribution in the seas of the West-Pacific transition zone based on the ЕТОРО 2' digital data are produced in the form of normalized cumulative bathygraphic and differential bathymetric curves with an interval of 100 m depth for the entire zone, for separate seas and for 5-degree latitudinal strips. An extreme variety of types of distribution of depths in the seas is noted given the good correlation of distributions on the latitudinal strips. New values of the average depths of the seas have been calculated which generally appeared somewhat higher than the previous ones.

 M.Ye. Melnikov, S.P. Pletnev, I.A. Basov, T.A. Punina, T.Ye. Sedysheva, V.D. Khudik, Yu.D. Zakharov
New geological and paleontological data on the Alba Guyot (Magellan Seamounts, Pacific Ocean)

Expeditionary investigations carried out by the "Yuzhmorgeologiya" in 2000-2001 in the Pacific Ocean on board R/V "Gelendzhik" resulted in new materials which made it possible to reveal the features of the morphological structure of the Alba Guyot and to ascertain the matter and paleontological character of the structural-formation complexes of rocks from the Early Cretaceous through the Pleistocene. The analysis of macro- and microfauna in sedimentary rocks allowed us to distinguish the “transgressive” phases in the development of the guyot: Cenomanian-Turonian, Late Campanian-Maastrichtian, Late Paleocene-Middle Eocene, and Late Cenozoic. Findings of Paleogene malacofauna and corals in association with planktonic foraminifers allow a conclusion about relatively shallow-water conditions in the Alba Guyot area in the Early Paleocene.

 V.P. Simanenko, S.V. Rasskazov, T.A. Yasnygina, A. I. Malinovsky, A.A. Chashchin
Early Cretaceous volcanics and Early Cenozoic extrusions in the area of the Cape of Mary (Shmidt Peninsula, North Sakhalin): geochemical studies

Igneous rocks outcropped at the northwestern extremity of the Schmidt Peninsula (North Sakhalin) are considered in the paper. The volcanics of the Mariysky sequence are Early Cretaceous in age and the vent extrusions of the Cape of Mary formed in Early Cenozoic time. By petrological-geochemical characteristics, the rocks under consideration can be classified into four groups. The first three of four recognized groups are volcanic rocks of the Mariysky sequence. The lower unit of this sequence is made up of calc-alkaline volcanics that are replaced with rocks having geochemical evidence for a transition from calc-alkaline to tholeiitic magma. The top levels of the section consist of incompatible-element-depleted tholeiite. Volcanic rocks of the Mariysky sequence suggest their origin in the subduction setting and are considered as a fragment of the Moneron-Samarga island-arc system. Based on the data of trace element modeling, the formation of these rocks was at first related to a garnet-bearing mantle source and then a garnet-free less deep-seated mantle source containing amphibole, pyroxene and probably spinel. The vent extrusions of the Сape of Mary combine geochemical features of subduction-related and intraplate magmatites and may be formed in a transform continental-margin setting.

N.S. Ostapenko, O.N. Neroda
Fluid pressure and hydrorupture of rocks in hydrothermal mineralization (as exemplified by gold deposits)

Based on the conducted detailed integrated research on the Tokur gold deposit (Upper Amur region, Russia) and the analysis of the published data on the levels of fluid pressures during the formation of other different geothermal deposits at different depths, the morphology of orebodies and the features of their location, a conclusion was made about the active role of fluids in the formation of ore-locating structures according to the mechanism of decompaction and hydrorupture of the fluid-containing medium. The conditions of appearance and possible consequences of hydrorupture of rocks in ore formation are considered. The evidence of participation of this mechanism in the formation of orebodies at the Pokrovskoe, Berezovskoe, Nezhdaninskoe (Russia) and Bendigo (Australia) gold deposits is given.

V. O. Khudolozhkin
The problem of quantitative evaluation of fluid composition under metamorphism (verification of physical-chemical modeling of water – mineral – rock reactions)

The paper offers results of comparison of physical-chemical quantitative calculation of the reaction fluid’s composition (based on the “Winsel” software package) with experimental data for the systems water– electrolyte (NaCl, HCl, NaOH, KOH) – mineral (quartz, corundum, microcline, plagioclase) – rock (granite, pelite) at T 400°-800°C and P 1-10 kbar. P-T and fluid composition constraints have been established which ensure agreement of calculations of rock and mineral dissolution and experimental data.