排序方式： 共有83条查询结果，搜索用时 109 毫秒
1.
2.
3.
A. A. Kalinin T. V. Kaulina L. M. Lyalina D. V. Elizarov P. A. Serov 《Geology of Ore Deposits》2016,58(7):594-599
On the basis of U–Pb, Rb–Sr and Sm–Nd isotopic data, it is shown that formation of uranium mineralization in the Paleoproterozoic Salla-Koulajarvinsky belt (Northern Karelia) was a long-lasting mult-stage process that developed over more than 1 Ga: from the Paleoproterozoic to the Paleozoic. The first stage, 1.75 Ga ago, corresponds to the Svekofennian metamorphic event—regional albitization. The process was dated by the Rb–Sr (isochronic age of albitites is 1754 ± 39 Ma) and U–Pb methods (the age of rutile is 1756 ± 8 Ma). At this stage, with a lower temperature limit of 400–450°C, conditions were favorable for the mobilization and migration of uranium, but not for its deposition in minerals. The second stage, 1.62 Ga ago, was a time of alteration of rocks at the regressive stage of the Svekofennian metamorphic event, when carbonate and chlorite rocks formed after albitites. The age of this stage was estimated as 1627 ± 42 Ma according to ThO2, UO2, and PbO contents in uraninite. Probably, the deposition of uraninite took place at this stage at temperature not higher than 300–350°C. The final, third stage, 385 Ma ago, corresponds to the Paleozoic tectonic activation and formation of Caledonian alkaline intrusions. Uranium minerals were probably redeposited at this stage; the U–Pb age of brannerite is 385 ± 2 Ma. 相似文献
4.
K. R. Kovalev O. N. Kuzmina B. A. Dyachkov A. G. Vladimirov Yu. A. Kalinin E. A. Naumov M. V. Kirillov I. Yu. Annikova 《Geology of Ore Deposits》2016,58(2):116-133
The Zhaima gold–sulfide deposit is located in the northwestern part of the West Kalba gold belt in eastern Kazakhstan. The mineralization is hosted in Lower Carboniferous volcanic and carbonate rocks formed under conditions of marginal-sea and island-arc volcanic activity. The paper considers the mineralogy and geochemistry of primary gold–sulfide ore and Au-bearing weathering crusts. Au-bearing arsenopyrite–pyrite mineralization formed during only one productive stage. Disseminated, stringer–disseminated, and massive rocks are enriched in Ti, Cr, V, Cu, and Ni, which correspond to the mafic profile of basement. The main ores minerals are represented by finely acicular arsenopyrite containing Au (up to few tens of ppm) and cubic and pentagonal dodecahedral pyrite with sporadic submicroscopic inclusions of native gold. The sulfur isotopic composition of sulfides is close to that of the meteoritic standard (δ34S =–0.2 to +0.2). The 40Ar/39Ar age of three sericite samples from ore veinlets corresponds to the Early Permian: 279 ± 3.3, 275.6 ± 2.9, and 272.2 ± 2.9 Ma. The mantle source of sulfur, ore geochemistry, and spatial compatibility of mineralization with basic dikes allow us to speak about the existence of deep fluid–magmatic systems apparently conjugate with the Tarim plume. 相似文献
5.
A Metamorphosed Au–Ag Deposit in the Precambrian of the Fennoscandian Shield: A New Conceptual Model
Doklady Earth Sciences - The Oleninskoe gold deposit is located in the northwestern part of the Kolmozero–Voron’ya greenstone belt (Kola Peninsula), in a sequence of amphibolite with... 相似文献
6.
A simple method to contour local inhomogeneities using seismic data is proposed. It formalizes an approximate inversion method which is based on the interpretation of local inhomogeneities as making the differences between an actual seismic data set and a previous reference model. It uses the optimal statistical criteria of parameter estimation and recognition and the ray representation of the waves spreading. Any combination of direct, reflected and/or other types of waves may be used as the database. Inhomogeneities, having a size two times above the wavelength of the seismic waves, can be resolved. Laboratory experiments, using ultrasonic waves and analysis of data from field experiments, confirmed the theoretical results. The method can be used to search for ore bodies, kimberlite cubes, oiltraps, etc. 相似文献
7.
8.
Carried out is the modeling of the process of temperature variations in a droplet and possible ice coating under synoptic conditions observed in the Perm krai on December 14, 2010 that are characterized with the freezing rain fall at the temperature inversion in the atmospheric boundary layer. The phase transition on the moving water-ice interface, the curvature of the phase transition boundary, and variations of heat exchange on the boundary between the ice coating and atmosphere are taken into account. Computed is the thickness of the ice crust formed on fine droplets under conditions that provide the initiation of freezing precipitation. The evolution of the rate of the front of water crystallization on the droplet surface is defined and explained. 相似文献
9.
On the basis of the complex of geological features, the eastern flank of the Salla-Pana-Kuolajarvi belt is a prospect structure for gold mineralization in the U-bearing albitites and related acid and mafic metasomatites. Visible tellurides and selenides, which are typical of gold deposits of the Fe-Co-Au-U group in the adjacent territory of Finland within the Salla-Pana-Kuolajarvi belt, were found in the Ozerny occurrence as a result of studies. Native gold is found in association with tellurides. Molybdenite from the occurrence has a high Re content up to 0.3%. 相似文献
10.
G. V. Nesterenko N. A. Roslyakov S. M. Zhmodik Yu. A. Kalinin N. S. Morozova M. V. Kirillov V. V. Kolpakov D. K. Belyanin S. R. Osintsev 《Lithology and Mineral Resources》2014,49(1):29-46
Study of gold potential of the Late Cenozoic alluvium in the Bauntov area is based on the Taloi basin and Sivo sector (China River basin). Primary placer-forming gold is mainly represented by endogenous varieties. In contrast to alluvium of streams in the Taloi basin, Middle-Upper Quaternary alluvium of the Sivo sector (China River basin) is enriched in fine and tiny gold (smaller than 0.25 mm). The paper presents data testifying to a low Au content in the silt fraction of slimes from boreholes drilled in the Cenozoic alluvium (alluvium-deluvium) from transverse valleys in the Taloi basin and, hence, to an significant manifestation of the chemogenic concentration of this metal therein. Issue of the existence of specific conditions favorable for the formation of hydrogenic gold in the northern high-latitude zones requires further studies. The results show that lithochemical gold aureoles have an important prospecting significance. They also suggest the practical significance of accumulations of fine and tiny gold in the syn-stratal alluvium and alluvium-deluvium of large ore placer areas. 相似文献