Volume 19, 5, 2000
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Volume 19, 5, 2000 |
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Yu. I. Bakulin. 300th anniversary of the Decree on Mining and 150th anniversary of geological research in the Amur region 3
Metallogeny
V. I. Sukhov. Metallogenic zoning of the territory of the Russian Far East 7
L. V. Eirish. Gold-bearing systems of Amur region (Russia) 21
Magmatism
V.E. Strikha, N.N. Petruk, K.D. Vakhtomin, I.P. Volskaya, A.M. Korshunov, Yu.P. Shergina. Geology and genezis of the Khaikta intrusive complex of the Upper Priamurye 25
M.Ye. Melnikov, V.B. Podschuveit, I.A.Pulyaeva, Er.B. Nevretdinov. Middle Miocene volcanic
structures on the Dalmorgeologiya Guyot (Magellan Seamounts, Pacific Ocean) 38
Sedimentology
A.S. Astakhov, S.A.Gorbarenko, N.G.Vashchenkova, Yu.G.Volokhin. Manganese distribution and accumulation rates in bottom sediments of the Sea of Okhotsk 47
A.M. Korotkiy, N.G. Razjigaeva, T.A. Grebennikova, L.M. Mokhova. B. Bazarova, L.D. Superzhitskiy, K.A. Lutaenko. Late Pleistocene-Holocene sedimentation and paleolandscapes of the Kurilka River basin (Iturup Island, Kuriles) 61
Geophysics
M.N. Luneva, D.V. Droznin, V.E. Ovchinnikov. Shear wave splitting study on Kamchatka Peninsula from earthquakes of 1998 78
S.V.Voroshin, V.M. Sharafutdinov, Ye.E. Tyukova. Anomalies of petromagnetic parameters conditioned by sulfide mineralization established by mineralization forecasting in the Yana-Kolyma gold-bearing belt 91
V. G. Bykov. Model of seismic slip initiation in the inhomogeneous crustal fault 105
Morphotectonics
G.F. Ufimtsev. The third face of geotectonics 111
Reviews
N.A. Shilo, N.G. Patyk-Kara.The book "Postmagmatic minerals of kimberlites" 121
Metallogenic zoning of the territory of the Russian Far East
V. I. Sukhov
The following metallogenic provinces corresponding to the largest geotectonic elements of the studied territory have been recognized in the Russian Far East: Aldan-Stanovoi, East Transbaikal region (Upper Amur system), Amur, Verkhoyansk-Chukotka, Okhotsk-Chukotka, (Hokkaido) Sakhalin, and Kuril-Kamchatka-Koryak. The metallogenic structure of the provinces is determined by regional ore-bearing and ore-magmatic systems, metallogenic zones and ore districts.
The metallogenic specialties of the provinces are conditioned by megacyclic-cyclic formation and development of the earth’s crust in various geotectonic regimes - a regime of formation of the primary continental crust (AR1), riftogenic-geosynclinal (AR2, PR1, PR2-PZ, MZ, KZ), platform and pericratonal depressions (PR2-PZ1), collision-related (PZ, MZ), island-arc (MZ, KZ), active continental margins (PR1, MZ), and continental taphro- and riftogenesis (KZ). The distinctions between the provinces are determined by completeness of manifestation of megacycles – metallogenic zones. Incidentally, in different provinces geological complexes of geotectonic regimes of the same type are characterized by close metallogenic specifics.
Gold-bearing systems of Amur region (Russia)
L. V. Eirish
Areal geochemical survey of stray fluxes at a scale of 1: 200,000 carried out over a greater part of the Amur region was the basis for distinguishing structures of transport (percolation) of gold-bearing fluids and localization of ore matter, which made it possible to supplement with available data the concept of gold-bearing systems as ensembles of interaction of factors of generation, transport and localization of ore matter.
Geology and genezis of the Khaikta intrusive complex of the Upper Priamurye
V.E. Strikha, N.N. Petruk, K.D. Vakhtomin, I.P. Volskaya, A.M. Korshunov, Yu.P. Shergina
The results of investigation of the Khaikta pluton – petrotype of the Khaikta complex of the Upper Priamurye subalkaline granitoids are given. Rocks of two intrusive phases participate in the structure of the pluton: 1st phase– quartz monzodiorites and granosyenites; the 2nd phase – composite-facies structure formed by granosyenites, subalkaline granites, and to a lesser extent, by granodiorites and granites. By study of petrographic peculiarities of rocks and composition of rock-forming minerals the formation of the complex in hypabyssal conditions from moderate and low-aluminiferous low-water melts of increased alkalinity is established. The crystallization of rocks took place at high temperatures, high activity of potassium and oxygen. Petrochemical peculiaries of composition of rocks and biotites confirm the belonging of the Khaikta granitoids to the late-orogen formations of I-type, formed at the final stages of subduction in the conditions of active continental margin with mature continental crust. The study of Rb-Sr and K-Ar isotope systems in rock-forming minerals allows us to determine the absolute age of the complex as 132±3 Ma, which is close to the age of the Berezitovy gold deposit (130 Ma), determined earlier. Together with other features it allows us to consider the Khaikta complex and associated gold mineralization as derivatives of one single ore-magmatic system. The initial isotopic ratios (ISr=0,7075-0,7083) in rocks give evidence of considerable participation of the mature upper-crust matter in their genesis. The formation of the Kaikta complex probably took place at the rear of the Greater Khingan active margin.
Middle Miocene volcanic structures on the Dalmorgeologiya Guyot (Magellan Seamounts, Pacific Ocean)
M.Ye. Melnikov, V.B. Podschuveit, I.A.Pulyaeva, Er.B. Nevretdinov
Complex geological and geophysical studies on the Dalmorgeologiya guyot conducted in 1991-1992 allowed us to get a detailed understanding of manifestation of the superimposed Miocene volcanism. The use of a long-range side-scan sonar "OKEAN" together with a single-beam echosounder made it possible to describe in detail the morphological features of volcanic structures and surrounding areas. Superposition of photoprofiling helped in interpreting the acoustic images and has shown additional details in the construction of different surfaces. Sampling with rock dredges allowed us to describe the composition and age of rocks making up volcanic structures. The volcanic cones with rounded basements up to 3 km in diameter and height up to 650 m are formed by interbedded alkaline basaltoid flows, tuffs, orthotuffites with fine layers of coccolith-foraminiferal limestones. A complex of the coccolithophores revealed in the cement of tuffites and in limestones has allowed to date these formations as Middle Miocene. Effusive rocks themselves presented by porous slag-like basaltoid, by their petrographic descriptions and chemical composition were referred to basanite. The absolute age of one of the samples of these rocks is 15 Ma, which corresponds to biostratigraphical determination of the tuffites age. The main value of the received results is that for the first time in ocean conditions a complete picture of volcanic activity, superimposed on earlier volcano-tectonic structure has been obtained.
Manganese distribution and accumulation rates in bottom sediments of the Sea of Okhotsk
A.S. Astakhov, S.A.Gorbarenko, N.G.Vashchenkova, Yu.G.Volokhin
The Mn contents in redoxing sediments and accumulation rates were investigated. The Mn contents in sediment most of cores are background (0.03-0.07 %). The anomalous concentration (up to 2.5 %) and accumulation rates (up to 60 mg/cm2 1000 y.) are revealed near the known region of hydrothermal barite mineralization in Derugin Basin. The intensive accumulation rates of Mn (>10 mg/cm2 1000 y.) are revealed also in Holocene sediments to south-east from Derugin Basin. It can be assumed that the great Mn contents and accumulation rates occurred there due to transportation of Mn-rich water from Derugin Basin in the near-bottom layer under the lower border of the Sea of Okhotsk Intermediate Water. Intensive Mn accumulation is typical also of part of the South Okhotsk Basin near the Bussol Strait. The Mn accumulation rates of glacial sediments of the second isotopic-oxygen stage are less significant, which is presumed to be caused by paleooceanological reasons.
Late Pleistocene-Holocene sedimentation and paleolandscapes of the Kurilka River basin (Iturup Island, Kuriles)
A.M. Korotkiy, N.G. Razjigaeva, T.A. Grebennikova, L.M. Mokhova. B. Bazarova, L.D. Superzhitskiy, K.A. Lutaenko
Stages of development of natural environment of the Iturup Island have been reconstructed for the Late Pleistocene, and a detailed record of paleogeographical events is offered for the Middle-Late Holocene. In the warming period in the second half of the Late Pleistocene birch forests were widely spread on the island. A sudden cooling at the end of the Late Pleistocene resulted in the development of forest-tundra landscapes. In the Middle Holocene the central part of the island was covered by nemoral oak-broad-leaved forests with participation of such thermophilous elements as the Amur cork-tree, hornbeam, walnut, beech, ash-tree, and lilac, which shows evidence of substantial rise in summer and sum of active temperatures. Disappearance of these thermophilous elements from modern forests groups is linked to repeated cooling of climate in the late subboreal and in the subatlantic. Three transgressive phases of sedimentation have been distinguished comparable with the Atlantic, subboreal and subatlantic periods attended by a maximal sea level rise up to 3.5 m higher than in the contemporary Atlantic.
Shear wave splitting study on Kamchatka Peninsula from earthquakes of 1998
M.N. Luneva, D.V. Droznin, V.E. Ovchinnikov
A technique for analyzing and processing of shear wave splitting is proposed. Based on this technique parameters of direct compressional and shear waves from small energy crustal and mantle earthquakes were investigated for the period of 1998 near the city of Petropavlovsk-Kamchatskiy. The temporal variations in the leading shear wave polarization and travel time difference between leading and slower shear waves were examined. The location of anisotropic layer and its velocity anisotropy coefficient were estimated. A correlation is observed in variation behavior between the leading shear wave polarization and regional seismic regime.
Anomalies of petromagnetic parameters conditioned by sulfide mineralization established by mineralization forecasting in the Yana-Kolyma gold-bearing belt
S.V.Voroshin, V.M. Sharafutdinov, Ye.E. Tyukova
The authors of this article discuss an opportunity for the use of petromagnetic methods for searching and exploration of lode deposits in the Yana-Kolyma gold belt. Two groups of magnetic anomalies are examined allowing regional and local geologic predictions. The regional prediction is based on establishing Au quartz occurrence above the pyrite-to-pyrrhotite alteration in terrigenous rocks, the result of which is a sharp change in magnetic properties of rocks. The local prediction is based on a drastic growth of petromagnetic characters in wallrock aureoles. An exclusive interpretation of this phenomenon from the viewpoint of palaeotemperature factors affecting petromagnetic parameters contradicts mineralogical data; therefore, the authors use the principle of superposition of palaeotemperature and geochemical fields to explain the formation mechanism of wallrock magnetic anomalies. Cobalt sulphoarsenides may have anomalous magnetic properties and mark wallrock areas in Au quartz deposits and ore bodies in gold-rare metal deposits.
Model of seismic slip initiation in the inhomogeneous crustal fault
V. G. Bykov
A mathematical model of initiation of stick-slip along the crustal fault is presented. On the basis of generalized sine-Gordon equation, analysis is made of asperity and friction effects in the fault and also the amplitude and frequency of periodic load on fault dynamics. A relative role of different processes in the initiation of seismic slip is investigated.
The third face of geotectonics
G.F. Ufimtsev
Geotectonics is a complex science involving three directions, each having different investigation targets (geological bodies – tectonics, physical bodies – deep tectonics, earth’s surface relief – neotectonics) and forming a common subject – knowledge of the structure and development of the earth. The third face of tectonics is neotectonics dealing with the earth’s surface relief, correlative (with respect to it) deposits and also conformable (with respect to it) young structural forms; it is aimed at recognition of structural forms according to geomorphological properties, and definition of their genesis and development. This science formulates our knowledge of young tectonics of the near-surface parts of the lithosphere where conditions for structure formation are specific: small lithostatic load, free semispace and deformation of fields of tectonic stresses. The theoretical base of neotectonics is the principle of accordance of relief to the rate and character of young tectonic processes. The theory of neotectonics, methods of its investigations, experience of regional and global generalizations allow using it when assessing tectonics of its geosections (geoid surfaces, Conrad and Moho discontinuities, and core-mantle bounadries).