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Simanovich I. M. Golovin D. I. Bujakaite M. I. Vinogradov V. I. Sakharov B. A. Matsapulin V. U. Sokolova A. L. Pokrovskaya E. V. 《Lithology and Mineral Resources》2004,39(6):555-565
The influence of geodynamic factors on the postsedimentary lithogenesis of terrigenous sequences during the replacement of the passive continental-margin regime to the active regime is considered with the Toarcian–Aalenian complexes of southern Dagestan as an example. It has been established that clayey rocks were lithified under conditions of subsidence lithogenesis, whereas the orogenic catagenesis of sandy rocks was related to stress initiated by the initial (amagmatic) subduction phase. The Kübler index has been used to reveal the postsedimentary zonality that is consistent with the intensity of folding and cleavage. The metagenesis zone fits the cleavage zone. The Rb–Sr and K–Ar datings of clayey rocks from the metagenesis zone yielded 180–190 Ma that can be interpreted as the timing of the maximal manifestation of postsedimentary lithogenesis. 相似文献
2.
Postsedimentation alteration and structural assemblies of the Triassic sedimentary complexes of West Chukotka are discussed.
Zoning of the alteration is based on examination of newly formed structural and mineral assemblages, the chemical composition,
and the polytypes of clay minerals. Three zones of postsedimentation transformation of sandstones are distinguished: (1) the
zone of chlorite, illite, and mixed-layer disordered chlorite-smectite; (2) the zone of illite and chlorite; and (3) the zone
of phengite and ferroan chlorite. The grade of postsedimentation transformation and the composition of the newly formed micas
are correlated with the cleavage type. The development of two-three types of cleavage leads to the highest degree of rock
transformation. The assemblages of clay minerals and the crystal chemistry of the authigenic phengite show that the grade
of postsedimentation transformation of the Triassic rocks attains the stage of greenschistfacies metamorphism in the zone
of development of two cleavage types. Where the second cleavage is not documented or poorly developed, the rocks remain unmetamorphosed.
Evidence is given that postsedimentation transformation of terrigenous rocks in the foldbelt is controlled largely by deformation. 相似文献
3.
Secondary alterations of Cretaceous, Jurassic, and Triassic terrigenous complexes recovered by borehole SG-7 were studied
from the depth of 3620 m to 6920 m (roof of basalts). Down to the depth of ∼6770 m, the section shows a gradual intensification
of catagenetic alterations of sandy rocks: the formation of pressure dissolution textures and regeneration of clastic quartz.
Intensification of the transformation of clay minerals is not observed in this mineral. Variations in the contents of illite,
hydromicas, mixed-layer minerals, smectite, chlorite, and kaolinite at different depths of the recovered section are related
to changes in the provenance during the accumulation of sedimentary complexes. The Middle Triassic coarse-grained sandy rocks
(suprabasalt sequence) are more intensely transformed: they are marked by microstylolitic textures of pressure dissolution,
recrystallization blastesis of clastic quartz grains, and newly formed zoisite. The composition of clay minerals is also characterized
by variation: micas are represented by sericite with ΔD = 0; Fe-chlorite and kaolinite are noted. These features suggest the
absence of linear positive correlation of T and P with the subsidence depth of sedimentary complexes. Intense heating (up to 200–300°C) of the Middle Triassic suprabasalt
rocks is likely caused by trap activity (intense effusion of basalt lavas). Investigation of secondary minerals in basalts
recovered by borehole SG-7 revealed that the grade of their transformation matches the medium-temperature subfacies of the
greenschist facies. 相似文献
4.
I. M. Simanovich 《Lithology and Mineral Resources》2007,42(1):75-83
The simplest intergranular cleavage and foliation of clayey rocks are typical of postsedimentary lithogenesis of folded terrigenous complexes at passive continental margins if the rocks do not contain metamorphic minerals. Cleavage zones coincide with metagenesis (anchimetamorphism) zones. Cleavage is often superimposed on the rock fabric formed in the process of subsidence lithogenesis (e.g., in the Verkhoyansk terrigenous complex). In other cases, cleavage in terrigenous rocks is regarded as the final stage of the development of their microfabric formation related to folding (e.g., Jurassic sequence of southern Dagestan). 相似文献
5.
I. M. Simanovich O. V. Yapaskurt V. I. Gorbachev 《Moscow University Geology Bulletin》2010,65(3):153-160
Drill core material from the superdeep SG-6 and SG-7 wells (Koltogor-Urengoi Graben) has been examined. It has been established
that the temperature conditions of alteration of sediments were non-linear and discontinuous. The basalts underlying these
sediments are metamorphosed and metasomatically altered under the influence of high-temperature fluids associated with a superplume.
The tuffs under the basalts have a phreatic origin. It is assumed that the intrusion of basaltic sills into the coal-bearing
Permo-Carboniferous rock mass beneath the tuffs caused thermolysis of coals and the generation of hydrocarbon gases of a methane
composition. 相似文献
6.
I. M. Simanovich 《Lithology and Mineral Resources》2000,35(5):475-483
Based on the study of Upper Precambrian rocks penetrated by the Pavlovskii Posad parametric borehole in the 1770–4780 m interval,
the Riphean succession is underlain by quartzose sandstones. The aulacogen within the Moscow Syneclise was covered by sediments
accumulated during the intense chemical weathering of a peneplain. Above the 3550 m level, Upper Precambrian rocks comprise
arkoses with abundant garnet. The immature (in terms of lithology and mineralogy) arkosic sequence was probably accumulated
in grabenshaped structures (aulacogens). 相似文献
7.
Yu. G. Tsekhovsky M. G. Leonov A. V. Nikitin Zh. Badamgarav I. M. Simanovich T. F. Shcherbakova E. S. Przhiyaglovsky 《Lithology and Mineral Resources》2009,44(3):284-297
Specific rocks (tectonomixtites) developed in the framing of Mongolian granite massifs (Dzuramtai and some others) at the Mesozoic section bottom are studied. It is shown that the tectonomixtites are tectonic rocks rather than eluvial or sedimentary rocks, as was considered previously. They formed in the Cenozoic in the process of granite protrusion beneath a thick sedimentary cover owing to the crushing of granites and abrasion of granite fragments with the subsequent transformation of clastic rocks by groundwaters (suffosion). In this process, clastic rocks yielded fine products of the destruction of feldspars and quartz was concentrated. The rocks formed at relatively low temperatures (no more than 200–300°C) under stress strains. 相似文献
8.
I. M. Simanovich 《Lithology and Mineral Resources》2009,44(5):497-509
Geological and mineralogical specificity of the world’s largest Witwatersrand gold deposit was defined by geodynamic processes
in the Late Archean. The primary crust composed of felsic rocks (“gray gneisses”) was intruded 2.9–3.1 Ga ago by mafic melts
that gave rise to greenstone belts. This was followed by the appearance of long-lived granulite mobile zones that promoted
the formation of hydrosphere and atmosphere accompanied by an intense acidic leaching (weathering) of rocks in the greenstone
belts. Numerous conglomerate interbeds were formed in the Witwatersrand Basin section due to vigorous eolian processes and
floodwater washouts that produced a fan channel system mainly filled with quartz pebbles. At present, most researchers support
a modified paleoplacer model of the origin of gold mineralization in Witwatersrand, suggesting a hydrothermal-metamorphic
redistribution of the primary placer gold. According to various hydrothermal models, gold was introduced into sedimentary
rocks in a water medium from outer deep sources or during the filtration of postsedimentary hydrothermal fluids. The present
communication suggests that a significant portion of gold contained in reefs could be delivered to the sedimentation basin
by the auriferous hydrothermal quartz of pebble or sand dimension that was metamorphosed at approximately 350–400°C. Metamorphism
of gold was accompanied by its purification, transfer to matrix, and hydrothermal intrastratal redistribution. 相似文献
9.
Kostyleva V. V. Chamov N. P. Simanovich I. M. Anikeeva O. V. 《Lithology and Mineral Resources》2001,36(4):353-361
The Riphean Kresttsy and Pavlov Posad sedimentary basins, which occupy different positions in the East European Platform (EEP) are considered. Compositional features of terrigenous–mineral associations (TMA) of sedimentary complexes in these basins and their relation to the intrabasin and external sources of the detrital material are revealed. Two (preaulacogen and aulacogen) stages in the development of Riphean sedimentary basins in the central EEP are established. Relics of preaulacogen sequences are recorded only at the base of the sedimentary succession in the Pavlov Posad basin. These two basins formed at the aulacogen stage under an influence of strike-slip stresses. Aulacogen sequences of the Pavlov Posad basin formed in one stage, whereas sequences of the Kresttsy basin accumulated during two stages. 相似文献
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