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The ultramafic rocks of the Kan block, East Sayan, are confined mainly to the Idar greenstone belt. In terms of formational
affiliation, they are subdivided into two groups: magmatic (Kingash Complex) and residual (Idar Complex) ones. The magmatic
ultramafic rocks compose hypabyssal and subvolcanic bodies, which are represented by rocks of dunite-wehrlite-picrite association
with cumulate textures. Uninterrupted chemical variations of the magmatic ultramafic rocks indicate subsequent magmatic differentiation
of parental picritic melt in the intermediate deep-seated chambers and emplacement of its derivatives in the crystallization
site. Differentiation leads to proportional increase of all rare-earth and other incompatible elements. The residual ultramafics
occur as boudined dunite-harzburgite bodies showing metamorphic granoblastic textures. They have more homogenous chemical
composition close to those of ophiolite complexes, which represent strongly depleted mantle rocks brought to the upper lithospheric
levels via deep-seated thrusts. Residual ultramafics differ from magmatic rocks in notably lower contents of some trace and
rare earth elements. 相似文献
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Doklady Earth Sciences - 相似文献
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A. I. Kiselev V. V. Yarmolyuk K. N. Egorov R. A. Chernyshov A. V. Nikiforov 《Petrology》2006,14(6):588-608
Middle Paleozoic magmatism at the eastern Siberian platform was related to riftogenic processes, which were most clearly expressed in the Vilyui Rift and led to the formation of rift depressions filled with sedimentary-volcanogenic rocks and extended basaltic dike belts in rift shoulders. Two fields of diamondiferous kimberlites were found along with basaltic dikes in the Vilyui-Markha dike belt surrounding rift in the northwest. Active subalkali basaltic magmatism predated the emplacement of kimberlite bodies, which occasionally (Nyurba pipe) are cut by dikes of potassium alkali basalts. Based on geochemical and Sr-Nd isotopic characteristics, deep-seated sources were determined for the intrusive and volcanic basalts of the northwestern shoulder of the Vilyui rift. The REE distribution patterns of the studied rocks normalized to the primitive mantle are close to that of OIB, except for somewhat higher HREE. In the diagrams of indicator ratios of trace and rare-earth elements, the basalts are also plotted in the OIB field, being located between the end member of plume composition (FOZO) and enriched mantle sources. The rocks have positive εSr (+3.5 and +28.6) and εNd (+1.3 and +5.3). In a diagram εNd(T)-εSr(T), two fields with distinct content of radiogenic Sr are distinguished, which can be regarded as derived by mixing of the moderately depleted PREMA-type mantle and a source enriched in radiogenic Sr. Available isotope-geochemical data confirm that OIB type basalts of the region were generated by plume activity. The geodynamic setting of Middle Paleozoic magmatism and rifting in the eastern part of the Siberian platform is considered in light of plume-lithosphere interaction. The sequence of tectonomagmatic events during evolution of the Vilyui rift is consistent with the model of plume-lithosphere interaction or the model of active rifting. 相似文献
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The petrology and ore potential of the Talazhin massif located in northwestern East Sayan are studied. The internal structure of the intrusion, the petrographic composition of its rocks, and their metallogenic, petrostructural, and petrogeochemical features are considered. The probable temperature and chemical composition of the parental magma of the pluton were computed using the KOMAGMAT-3.52 program on the modeling of equilibrium crystallization. The obtained data indicate that the Talazhin massif is a rhythmically layered plagiodunite–troctolite– anorthosite–gabbro intrusion formed from low-Ti high-alumina olivine–basalt melt. It is promising for Cu–Ni–PGE mineralization. 相似文献
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A. A. Chernyshov D. V. Chugunin M. M. Mogilevsky I. L. Moiseenko A. A. Ilyasov V. V. Vovchenko S. A. Pulinets M. V. Klimenko I. E. Zakharenkova A. V. Kostrov M. E. Gushchin S. V. Korobkov 《Geomagnetism and Aeronomy》2016,56(1):72-79
Permanent variation in parameters affecting the key characteristics of the auroral ionosphere hinders the creation of a sufficiently accurate model for practical application within classical approaches describing quasi-stationary phenomena. The fractal approach for describing the properties of plasma in the auroral region has the following advantages: the results are versatile and the emergence of self-similar structures is nature-independent. Due to the self-similarity and fractality of ionospheric structures, it will suffice to have a few measurements within a characteristic scale; therefore, it is necessary to obtain a series of simultaneous measurements at intervals of tens of meters to tens of kilometers to describe the spatial and temporal distribution of inhomogeneities in the ionospheric plasma. Small and relatively low-cost satellites (the socalled cubesats) are supposed to be used to check whether the fractal approach can be applied to study the inhomogeneous structure of the ionosphere, including with artificial heating. The satellites should be located at different distances from each other to span the scales ranging from the inertial length of electrons to the inertial length of O+ ions. For each satellite, it is supposed to measure the variations in plasma density and electric and magnetic fields. 相似文献
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The paper discusses earlier poorly studied mineralized rocks of the Kingash ultramafic complex in the Kan Block of the Eastern Sayan, including the large Cu–Ni–PGE deposit of the same name. Despite many researchers' increased interest in the Kingash massif, a number of questions related to the petrology, formation mechanism, and localization of Cu–Ni–PGE ore remain controversial. Along with already known ore minerals, we have identified and described a number of new mineral species: argentite, Fe-enriched sperrylite, a bismuth variety of merenskyite, gersdorffite, cobaltite, and thorianite. The ore minerals are distinguished by a higher relative amount of Fe, and this makes the Kingash deposits close to other Paleoproterozoic Cu–Ni deposits, e.g., the Jinchuan in China, Pechenga in Russia, Ungava in Canada, Mt. Scholl in Australia, etc. 相似文献
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Geomagnetism and Aeronomy - The influence of geomagnetic activity on slips of navigation signals of the global positioning system (GPS), as well as an increase in the amplitude of jumps in the... 相似文献