P.Yu. Kovtunovich, V.A. Lebedev, I.V. Chernyshev, Ye.V. Arutyunyan
Chronology and evolution of magmatism in Urup Island (Kuril Archipelago) from K-Ar isotope datings and diatomic analysis

The isotope-geochronological study of Neogene-Quaternary igneous rocks from Urup Island (Greater Kuril Ridge) was carried out. It was established that magmatic activity in the island developed during the last 10 mln.y., and it was not interrupted by prolonged “tranquil” intervals. The K-Ar data obtained along with the results of diatomic analysis are in good agreement with the regional stratigraphic scheme of Paleogene and Neogene deposits and the intraregional correlation scheme of magmatic rocks in the Kuril Islands, which are developed for the State Geologic Map, scale 1:200 000 (Second edition).
In the present-day territory of Urup Island, the earliest Late Miocene – Early Pliocene (10.5-4.5 Ma) magmatic stage was associated with the formation of the Rybakovskiy andesite volcanic complex which is represented by an effusive series (Rybakovskaya Suite) and subvolcanic rocks. Actually at the same time (6.6-4.7Ma) but at a great depth the intrusive bodies of the Prasolovskiy plagiogranite-diorite plutonic complex were intruded. The Pliocene stage of magmatism in Urup Island is characterized by the formation of rocks of the Kamiyskiy dacitic volcanic complex (4.0-2.1Ma). This complex is locally represented only by subvolcanic acidic bodies, and its occurrence in the island is limited. During the Pliocene – Early Neopleistocene stage of magmatism (3.0-0.8Ma), the Fregatskiy andesibasalt volcanic complex was formed in Urup Island. This complex includes effusive series (Fregatskaya unit) and subvolcanic bodies. The Quaternary time in Urup Island is characterized by eruptive activity in subaerial conditions with the formation of effusive-pyroclastic intermediate-basic rocks of the Bogatyrskiy Middle Neopleistocene-Holocene complex (<0.5 Ma). The rocks of this complex formed stratovolcano cones. The pyroclastic rocks of the Rokovskiy dacitic volcanic complex were erupted simultaneously. The above-mentioned magmatic complexes of Urup Island are well correlated with the distinguished magmatic complexes within the bounds of the contiguous insular blocks of the Greater Kuril Arc and confirm the uniform geologic history of magmatic development of the region.

 V.S. Sitnikov, V.B. Spektor
Neotectonics of oil and gas territories in South-Western Yakutia

The neotectonics of the territory located in the basin of the Lena River left tributaries - Peledui and Nyuya is considered. Geomorphologic studies of the territory were carried out, and statistic analysis of the relief along watershed profiles was performed. The territory belongs to the Prilenskoe plateau; within its bounds there were distinguished three different age stages of relief (Paleogene, Neogene, and Neopleistocene) as well as related planation surfaces. The plateau is mainly the area of distribution of the Neogene planation surface. Deformations of the latter allowed evaluation of neotectonic movements. Two types of local neotectonic structures are distinguished: brachymorphic and linear. The neotectonic brachymorphic structures, often inverse, are clearly related to structures of basement and lower horizons of the sedimentary cover (coefficient of correlation =0.6-0.9). Some of these structures coincide in plan with structural traps of the known oil and gas fields. The linear structures, represented in relief directly, are related to nappe-folded deformations of the upper part of the sedimentary cover. They are poorly correlated with the structures of the lower part of the platform cover which enclose hydrocarbon deposits.

T.V. Merkulova, G.L. Kirillova
The structure and prospects for oil and gas content in the northern sector

A comparative analysis was made of Cenozoic grabens of the Tan-Lu system within the San-Jiang-Middle Amur Basin located at the boundary between Russia and China. A detailed study was made of the results of geologic-geophysical work and parameters controlling localization of oil and gas-bearing structures in the Tangyuan graben, where oil and gas deposits have been discovered. It is shown that transfer (transverse) fault and graben zones with uncompensated sedimentation are important for determining oil and gas potential, in which oil source rocks of lacustrine origin may be present. An analysis was made of geologic-geophysical evidence of the less studied grabens of the Lobei-Birofeldian link in the territory of Russia aimed at evaluation of their oil and gas potential.

I.A.Tararin, V.M.Chubarov
Sulfide copper-nickel mineralization in the metavolcanic rocks of the Andrianovskaya suite from the Sredinny Kamchatka massif

This paper presents detailed mineralogical data on the composition of amphibolite and epidote amphibolite of the Andrianovskaya suite of the Sredinny Kamchatka massif. It is shown that these rocks formed under metamorphism of picrite, picritic basalt and basalt of the island arc calc-alkaline series.
For the first time the mineralized zones with sulfide copper-nickel mineralization confined to metamorphosed picrite and picritic basalt have been studied. These mineralized zones are presumed to be potentially promising also for palladium mineralization which is typical of peridotite-gabbronotite intrusives – plutonic analogues of the volcanic rocks of the Andrianovskaya suite.

 V.B. Kaplun
The geoelectrical model of the lithosphere of the Komsomolsk and Badzhal ore districts from data of magnetotelluric sounding

A spatial geoelectrical model of the lithosphere of the Komsomolsk and Badzhal ore districts and of the surrounding areas has been constructed based on the method of magnetotelluric sounding. It is shown that the ore districts in the geoelectrical section are distinguished by reduced values of electric resistance in the upper mantle and by channels branching from them which penetrate into the lower strata of the Earth’s crust. Districts with anomalously low values of upper mantle resistance have been discriminated which can be promising for ore deposits prospecting.

Ye.G. Ivolga
Metallogenic specialization of the region of gravity and magnetic fields in the southern part of the Russian Far East

An original method has been offered for the use of joint zoning of gravitational and magnetic fields and metallogeny for regional prediction. 16 geophysical domains have been distinguished, which reflect different-level regional inhomogeneities of geological structures and ore magmatic systems of different types. A new quantitative base has been used (spectra diagrams and mineralization extensiveness) to analyze distribution of different-type endogenic mineralization in the distinguished areas. This made it possible to specify for each geophysical domain metallogenic specialization, which allows reckoning the geophysical domains as metallogenic units. Special attention is directed to the greater sensitivity of magmatic fields to the changes of metallogenic features of the regions as compared with gravitational fields, and in this connection, to the necessity of a more close study of magnetic inhomogeneities of the Earth’s crust.