S.V. Rasskazov, V.S. Prikhodko, Ye.V. Saranina, M.N. Maslovskaya, T.A. Yasnygina, V.G. Semenova, A.V. Travin. Space-and-time variations of mantle and crustal components in the Late Cenozoic volcanic rocks from the Middle Amur basin, Southeastern Russia. 3

L.F. Mishin, Zhao Chunjing, A.I. Soldatov. Mesozoic-Cenozoic volcano-plutonic belts and systems in the continental part of Eastern Asia, and their zoning. 28

D.V. Kovalenko, Ye.Ye.Chernov. Paleomagnetism and tectonic evolution of Kamchatka and Southern Koryakia. 48

I.A. Tararin, V.M. Chubarov, T.M. Filosofova. Petrology and origin of gabbroic rocks of ophiolite assemblage from the Hunter Fracture Zone (Pacific Ocean). 74

M.I. Tuchkova, K.A. Krylov, V.N. Grigoryev, P.V. Markevich. Features of the Early Cretaceous terrigenous sedimentation in the Penzhina pre-arc basin. 93

T.K. Zlobin, A.O. Bobkov. Earthquake epicenters and seismic energy distribution in the Sakhalin lithosphere before and after the Neftegorsk Earthquake of May 27 (28), 1995. 107

E.L. Shkolnik, V.I. Gvozdev, S.V. Malinko, T.A. Punina, A.D. Slukin, A.V. Ignatyev. The origin of borosilicate mineralization of Dalnegorsk deposit, Primorye Territory. 122

S.V. Rasskazov, V.S. Prikhodko, Ye.V. Saranina, M.N. Maslovskaya, T.A. Yasnygina, V.G. Semenova, A.V. Travin
Space-and-time variations of mantle and crustal components in the Late Cenozoic volcanic rocks from the Middle Amur basin, Southeastern Russia

Space-and-time variations of major and trace elements (ICP-MS method) as well as strontium isotopes have been studied in Cenozoic volcanic rocks from the Middle Amur basin. Volcanic rocks of mantle origin (basanites, leucitites) and those contaminated with crustal components (hawaiites, transitional basalts, and andesitic basalts) have been distinguished on the diagram 1/86Sr versus (87Sr/86Sr)0 and those of indicative elemental ratios (K/Nb, K/Y, Ba/La, Nb/La, Ba/K, Сe/Pb, Nb/U). The Late Cenozoic volcanism was initiated by a contrast association of transitional basalts and basanites at ca. 15 Ma in the northwestern termination of the Middle Amur basin. At 11 Ma, a single andesitic basalt lava flow erupted in the southeastern part of the basin. The eruption of leucite basanite lavas in the central part of the basin was contemporaneous with the beginning of volcanic eruptions along the whole extent of the southeastern margin of the basin. Andesitic basalts and low-K basanites erupted in the time interval of 9.5-8.0 Ma and were followed by transitional basalts at 7.4 Ma. The final volcanic phase of basanite eruptions took place at 4.8-4.1 Ma. The pre-Cenozoic volcano-sedimentary strata in the Middle Amur basin belong to the Early Cretaceous accretionary wedge of the Khabarovsk, Amur, and Kiselevka-Manoma terranes. A thin crust is a characteristic of the accretionary wedge. At 15-4 Ma, the mantle magmatism shifted from its northwestern boundary to the southeastern boundary, and against its background, melting took place first in the collision-derived thickened crust of the Badzhal terrane and afterwards in the collision-derived thickened crust of the Anyuy microcontinent.

L.F. Mishin, Zhao Chunjing, A.I. Soldatov
Mesozoic-Cenozoic volcano-plutonic belts and systems in the continental part of Eastern Asia, and their zoning

In the eastern margin of the Asian continent, in the area of the Mesozoic-Cenozoic sub-aerial volcanism, three different-age zones (systems) are recognized. Their structural position and rock composition correspond to the continent-margin volcanic belts. From the west eastward, the following systems are distinguished: the Uda-Bolshehingansk (J3-K1), Okhotsk-Sungari (K1-2), and Sikhote-Alin (K2-Pg). Transverse zoning indicates that the structures are autonomous. In relation to the Pacific margin, an internal and an external zone are distinguished which differ strongly in redox conditions, Sr initial isotope ratios, REE distribution, and other features.
In accordance with the distribution of magmatic rocks, three different-age metallogenic systems are distinguished. In each of them two conjugated zones are formed (basing on the major element): internal gold-bearing and external tin-bearing. The age discreteness of mineralization is more sharply expressed than the analogous discreteness of magmatism itself, and this is a strong additional argument in support of reasonableness of recognizing three different-age spatially separated systems.

D.V. Kovalenko, Ye.Ye. Chernov
Paleomagnetism and tectonic evolution of Kamchatka and Southern Koryakia

Five island-arc segments were reconstructed for Kamchatka and Southern Koryakia. In the Late Cretaceous, the island-arc segments were located between 30° to 55° N and bounded the basins not more than 1,000 km wide. The collision of the segments with the continent occurred in different periods during the Late Cretaceous and Cenozoic.

I.A. Tararin, V.M. Chubarov, T.M. Filosofova
Petrology and origin of gabbroic rocks of the ophiolite assemblage from the Hunter Fracture Zone (Pacific Ocean

Dredge collections from the Hunter Fracture Zone include massive and cumulate textured gabbroic and ultramafic rocks and volcanic rocks ranging from basaltic to rhyolitic in composition. The ultramafic rocks are largely serpentinized harzburgite and lherzolite; their relict mineralogy is typical of peridotite considered to be the refractory residue of partial melting of the mantle. Cumulate textured ultramafic rocks probably are related to the cumulate gabbro and granodiorite rather than to the residual mantle material. The gabbroic rocks are dominantly cumulate textured Pl-Opx-Cpx±Ol gabbronorite and Pl-Cpx±Ol gabbros; the mineral features of these rocks are the resuld of their crystallization at moderate pressure (in a moderate level magma chamber). The massive Pl-Cpx±Ol gabbros are less common. Green and brown-green Ca-amphibole has partially or totally replaced the clinopyroxene in many samples. There is an overlap in mineral chemistry between the cumulate rocks and the Opx-Cpx-Pl volcanic rocks and boninites. We interpret this as the indication that the cumulate rocks were cogenetic with Opx-Cpx-Pl volcanic rocks and that they both constitute the remnants of an island arc volcanic-plutonic series. The petrologic evidence indicates that ophiolite gabbroic rocks were derived from an island-arc rather than from a mid-ocean ridge.

M.I. Tuchkova, K.A. Krylov, V.N. Grigoryev, P.V.

MarkevichFeatures of the Early Cretaceous terrigenous sedimentation in the Penzhina pre-arc basin

The composition of mineral and heavy fraction assemblages of Penzhina Bay clastic rocks is characterized on the basis of 64 analyses. It is established that the mineral compositions of sandstones from the Early Cretaceous terrigenous deposits of the Yelistratov and Mametchinskiy Peninsulas are similar. We define two Early Cretaceous sandstone assemblages: 1) Berriassian-Valanginian sandstones formed by scour of granite metamorphic rock complexes of the western mature continental margin, 2) Hauterivian sandstones formed by scour of island arc volcanic rocks. Hauterivian sandstone assemblages include three different types characterizing changes of island arc volcanism.

T.K. Zlobin, A.O. Bobkov
Earthquake epicenters and seismic energy distribution in the Sakhalin lithosphere before and after the Neftegorsk Earthquake of May 27 (28), 1995

An analysis was made of the relative earthquake epicenter location in the Sakhalin region and also directly in the lithospheric block, where the source of the Neftegorsk earthquake of May 27 (28), 1995 was located. The dynamics of variations of the earthquake seismic energy released in Sakhalin every year during the period of 1991-1997 was considered. Some regularities were established. They manifest themselves prior to the catastrophic Neftegorsk earthquake in the decrease of distance between the neighboring earthquake sources, in the peculiarities of the earthquake epicenter migration longitudinally and latitudinally in the Neftegorsk block, and in the concentration of energy only in this northern block and its almost complete absence in the remaining territory of Sakhalin though commonly energy is concentrated in three areas.

E.L. Shkolnik, V.I. Gvozdev, S.V. Malinko, T.A. Punina, A.D. Slukin, A.V. Ignatyev
The origin of borosilicate mineralization of Dalnegorsk deposit, Primorye Territory

The skarns of the Dalnegorsk borosilicate deposit and stromatolite build-ups discovered in the district have been studied in detail. The features of the skarn structure allowed the conclusion that they inherited the structural pattern of the stromatolite limestones. The character of isotope fractionation suggests a mixed nature of the boron source.