Contents
Volume 18, ¹ 5, 1999
ContentsVolume 18, ¹ 5, 1999 |
|
Tectonics and Geodynamics
L.I.Krasny. On the interaction of the Central Asia and Pacific mobile belt 3
N.A.Bogdanov, N.l.Filatova. Structure and formation geodynamics of active continental margins 9
L.M.Parfenov, L.I.Popeko, Î. Tomurtogoo. The problems of tectonics of the Mongol-Okhotsk orogene 24
M.V.Alexutin, G.Ye.Bondarenko, P.S.Minyuk. The results of structural and paleomagnetic investigations of Jurassic and Cretaceous complexes on the Mesozoides of Northeastern Russia 44
Geomorphology and Seismology
G.F. Ufimtsev, A.A.Shchetnikov. Socle uplift of the Mongol-Siberian rejuvenated orogene 57
S. V.Gorkusha, F.S.Onukhov, F.G.Korchagin. Seismicity and neotectonics of the Russian Far East South 61
Stratigraphy
B.I.Pavlyutkin, T.I.Petrenko, E.I.Tsarko. Tertiary Sanduganskaya suite of Primorye: problems of age and correlations 69
Magmatism
V.P.Simanenko, V.V. Golozoubov, I.V.Kemkin. Basalts of the Erdagou suite in Taukha terrane of the Southern Sikhote-Alin and its geodynamic setting. 82
P.I. Fedorov, A.V.Koloskov. Cenozoic volcanism of southeastern Koryak Highland (Northeast Russia): Petrogenesis of rocks and their formation 90
Metallogeny
S.S.Zimin, V.G.Moiseenko, R.A.Oktyabrsky, B.M.Tishkin, V.V.Malakhov, V.P.Molchanov. On the role of boron in the formation of tourmaline-quartz type gold deposits in Priamurie 106
Â. G. Saxin. Deep-seated structure and peculiarities of mapping of the Bekchi-Ula gold major zone (the Amur lower reaches region) 115
Brief Communications
A.V.Litvinov, V.G.Patoka, B.A.Markovskiy, Yu.F.Frolov, A.A.Kolyada, A.I.Pozdyeev. Map of mineral resources of the Kamchatka district, scale 1:500 000 122
On the interaction of the Central Asia and Pacific mobile belt
On the basis of the Russian-Chinese Geological Map of Priamurie (L.I.Krasny and Pan Yunbiao eds., 1996) and the summary of the present concepts, problems of the interaction of the Central Asia and Pacific mobile belts are analyzed. Brief generalized tectono-magmatic, paleogeographical and geodynamic features of each belt are presented. Their interaction is manifested in the superposition of the diverse geological and geophysical processes of the Pacific belt on the more ancient Central Asia which is evidence for deep-seated mantle-crustal geodynamics.
Structure and formation geodynamics of active continental margins
Structure of active continental margins is characterized by the development of the volcanic and terrane plicated nappe orogenic belts which provide the margin extension both in area and crust thickness. Accretion wedges developing in the frontal part of the volcanic belt differ from terrane plicated belts in structure and genesis. In contrast to the latter, accretionary wedges are composed of mainly turbidites with olistostrome horizons which are typical of an internal slope of the deep-seated trough and in a lesser degree of abyssal ooze of the subsiding oceanic plate.
During the evolution of the active continental margins the alternation of subduction and accretionary-collisional processes takes place in time at the convergent transitions of the oceanic and continental plates. Terrane orogenic belts begin to form when subduction (and volcanism) terminated. Thus every orogenic belt serves as an indicator of reorganization of geodynamic regimes at the convergent plate transitions of the continental margins.
The problems of tectonics of the Mongol-Okhotsk orogene
The Mongol-Okhotsk orogenic belt occupies the axial position among the Paleozoic orogenic belts of Central Asia and at the same time is closely related to the Mesozoic orogenic belts of the western Pacific framing. The elucidation of its nature is of key importance when determining the relationships between the plates of the contiguous regions of the paleo-Pacific and paleo-Asian oceans and interpreting the history of formation of different-age orogenic belts of Asia.
The previous models of formation of the Mongol-Okhotsk belt do not explain its characteristic features, such as 1) linear, ribbon-like form; 2) discontinuous character; 3) “blind” termination in Central Mongolia; 4) absence of associated, fully developed passive continental margins and fold-thrust belts originating on their place; 5) absence of foredeeps and typical collisional granites; 6) broad distribution of large (hundreds of kilometers) latitudinal sinistral strike-slip motions, determining deformational style; 7) distribution of faunas of different paleobiogeographic belonging.
The characteristic features of the Mongol-Okhotsk belt may be conditioned by an oblique approaching of the Amur superterrane (microcontinent) to the Siberian continent. In the Early and Middle Paleozoic, the superterrane was contiguous to the Altai-Sayan area, and this is responsible for the similarity between their Cambrian, Silurian, Devonian and Early Carboniferous faunas. In the Late Paleozoic and Early Mesozoic, the Amur superterrane (microcontinent) was moving along the southern margin of the Siberian continent from southwest to northeast (in the modern coordinates), successively joining the continent.
The results of structural and paleomagnetic investigations of Jurassic an Cretaceous complexes on the Mesosoides of Northeastern Russia
This paper deals with the results of integrated structural (structural-geometrical analysis of planar elements and kinematic analysis of faults and joint tectonic crack system) and new paleomagnetic data for Jurassic rocks of the Elekchan graben (the Omulyov block), northern part of the Sugoi folded zone, Korkodon zone of the Omolon massif and the Late Cretaceous formation of the Ola segment of the Okhotsk-Chukchi volcanic belt (the Ola Bay of Magadan region). According to the new materials of structural investigations, the Elekchan graben had a multistaged structural history in the result of some pulse strike- slip deformations. The western margin of the Omolon and northern part of the Sugoi zone are characterized by post-Early Jurassic strike -slip deformations which are accompanied by the antyclockwise rotation of the tectonic domains. The post-Turonian strike- slip deformations are recognised on the Ola segment of the Okhotsk-Chukchi volcanic belt. These deformations are accompanied by clockwise rotations of the tectonic blocks. According to paleomagnetic data, the amplitude of the post-Late Jurassic lateral movements did not exceed that obtained by a paleomagnetic method. A wide age range of the Verkhoyan phase of tectonic deformations was manifest from the mid- Jurassic deformations on the western Omolon margin to the Kimmerigian-Volgian deformations on the eastern part of the Omulyov block. The paleolatitude characteristics of a pre-folded component of the observed tectonic elements are similar to those of Siberia (the Omulyov, Omolon and Sugoi zones) and to North America (the Ola segment of the Okhotsk-Chukchi volcanic belt).
Socle uplift of the Mongol-Siberian rejuvenated orogene
The principal peculiarity of the deep-seated structure of the Mongol-Siberian belt of rejuvenated mountains is a large asthenolith occurring under the belt lithosphere. The asthenolith causes a general dome-shaped uplifting of the mountain belt socle. The amplitudes of these uplifts conditioned by extension and common unconsolidation of the earth’s crust and the upper mantle with asthenolith formation have been calculated.
Seismicity and neotectonics of the Russian Far East South
The paper considers the main peculiarities of neotectonic structure in relation to distribution of epicentral field in the Russian Far East South. For this purpose the authors have analysed the distribution of earthquake epicentres M³l 8 and M³3 3,the average Bouguer Dg field with 50 km step amplitudes of the vertical neotectonic movements, densities of the surface(H £5 km), crustal(H £30 km) and also regional faults obtained by deciphering the aero- and satellite images. Based on the cluster analysis the unconventional division of neotectonic blocks of the first order into the blocks of higher orders which differ by seismic activity, is presented. It has been shown that the zones of increased and high seismicity are not in all cases related to activation of deep- seated faults. Locations of certain seismogenic zones correlate weakly with the neotectonic peculiarities displayed in modern relief, and apparently are related to the deep processes occurring in the lower crust.
Tertiary Sanduganskaya suite of Primorye: problems of age and correlations
The problems of toponymy of the Tertiary Sanduganskaya suite and typification of its section are discussed. Taking into account the new data on volcanic plateaux of Primorye, including the stratotype area of the Sanduganskaya suite, we think that it is illegal to compare it with the Ust’-Davydovskaya suite (Lower-Middle Miocene from the official papers). The results of palynological and diatomic analyses of interbasaltic layers as well as mineralogical and petrochemical study of volcanic components of the Sanduganskaya suite in the type section indicate its age similar to that of the Shufanskaja suite , except for the uppermost horizons which are Quaternary in age. It is considered that the Sandugan basalts were formed in the second half of the Late Miocene - Pliocene. However, the presence of Q - basalts in the Sanduganskaja suite is possible.
Basalts of the Erdagou suite in Taukha terrane of the Southern Sikhote-Alin and its geodynamic setting.
Data on petrography, petrochemistry and geochemistry of basalts from the Erdagou volcanic-cherty suite in the Taukha terrane of the Southern Sikhote-Alin are given. The mid- Jurassic (Callovian) age of the basalts is based on the radiolarians dating from associated cherts. The geochemical features both of N-type mid-oceanic ridge basalts and tholeites of island arc are characteristic for the examined rocks. It is assumed that these volcanic rocks were formed under back-arc spreading conditions, but not under open-ocean ones.
Cenozoic Volcanism of Southeastern Koryak Highland (Northeast Russia): Petrogenesis of rocks and their formation
Three complexes related to extension zones on the continental margin are recognized within Cenozoic volcanic formations in southeastern Koryak Highland: Danian-Paleocene, Miocene and early Quaternary. Danian-Paleocene and Miocene complexes are composed of the rocks of tholeite series, whereas the Early Quaternary complex contains rocks of alkaline olivine-basalt and basanite series. Specific petrogenetic features and rare element distribution are considered which allow a conclusion on the volcanite generation from heterogenic magma-producing sources under different geodynamic environs.
S.S. Zimin, V.G. Moiseenko, R.A.Oktyabrsky, B.M. Tishkin, V.V. Malakhov, V.P. Molchanov
On the role of boron in the formation of tourmaline-quartz type gold deposits in Priamurie
The paper considers peculiar features of tourmaline-quartz type gold distribution in the earth’s crust as well as its occurrence and main mineralogical and geochemical features. It is suggested that metal borides and boron hydrides of deep-seated mantle levels with mineral formation reduction regime played a great role in their genesis. The former served as major resources of ore matter while B10H14 boron hydrides reacting in the granite melting with water at high temperature (800-700°C) caused hydrogen generation in accordance with the reaction B10H14+15H2O=5B2O3+22H2. In high earth’s crust hydrogen interacts with oxygen at low temperature (200-100°C) resulting in water generation which is followed by an abrupt gas pressure reduction above the magmatic intrusions. Repeated changes in pressure related to the tectonic displacement influence on the gas supply resulted in the disturbance of rock stability in the base gas channel and finally in the formation of a clastic pipe above the granite or kimberlite boron- and hydrogen- bearing magma.
Deep-seated structure and peculiarities of mapping of the Bekchi-Ula gold major zone (the Amur lower reaches region)
Problems of localization of metallogenic targets of ore major zone and ore area are discussed with the special reference to the Bekchi-Ula gold major zone including a well known Mnogovershinnoe gold and silver deposit based on the geological and geophysical data. The latest data on the specific features of the ore major zone deep-seated structure and the degree of their manifestation while studying them by various methods are given. Empirical materials from the best studied type metallogenic targets are suggested to be accumulated to improve the techniques of their delineation at early stages of investigation.