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Acta Geochimica - The article presents the results of a comparative geochemical study of cherts and siliceous–clayey rocks composing the tectono-sedimentary complexes of various structural... 相似文献
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Doklady Earth Sciences - The results of mineralogical–geochemical study of the Albaza gold deposit (Khabarovsk Krai) are presented here. The ore mineral assemblage, in addition to already... 相似文献
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R. A. Kemkina 《Russian Journal of Pacific Geology》2007,1(2):130-143
The chemical study shows that fahlores from the Prasolovka deposit are complex compounds with significant variations in their composition and the proportions of their constituent elements. Based on their major-element composition, they are subdivided into 3 species and 11 inter-and intra-species varieties. The chemical composition of the fahlores in different mineral assemblages from different ore types indicates that As fahlores subsequently replaced by Sb, Te-Sb, and Te fahlores during ore precipitation. The revealed evolution of the ore solutions from the early to late stages testifies that different ores at the Prasolovka deposit were formed under different physicochemical conditions. 相似文献
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We have studied the geochemistry of Late Triassic cherts from tectonic sedimentary complexes of different structural levels of the Samarka terrane. The results show that the contents and distribution patterns of major rock-forming oxides, trace elements, and REE in the cherts of the upper and lower structural levels are somewhat different, which is due to different facies environments of chert accumulation. In particular, the contents of Al2O3, TiO2, and K2O gradually decrease and the contents of Fe2O3 and MnO increase downsection. The contents of Zr, Rb, Hf, Th, and Cr, which were supplied into the bottom sediments with a terrigenous suspension of heavy-mineral fragments, are twice to ten-fold lower than their average contents in the upper crust. In contrast, the contents of Pb, Cu, and Ni, which got into the sediments mostly with metalliferous hydrothermal solutions, are rather high and even exceed their average contents in the middle and upper crust. That is, the contents of the first-group trace elements gradually decrease and the contents of the second-group trace elements increase from upper to lower structural level. The calculated negative Ce anomaly gradually decreases from lower (0.75) to upper (0.88) structural level. The geochemical parameters altogether indicate that the cherts accumulated in the same pelagic depositional environment but in its different parts. The Katen complex composing the lower structural level is the most remote from the continental margin, and the Amba-Matay complex forming the upper structural level is the most proximal. Based on the geochemical and biostratigraphic data and on the time of accretion of paleo-oceanic fragments, we have established the location of each complex within the not yet subducted oceanic plate and estimated the extensionof this plate. Throughout the Jurassic, about 6000 km of the oceanic lithosphere was subducted beneath the eastern margin of the Paleo-Asian continent and partly accreted to it. 相似文献
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The data of geochemical study of Late Triassic cherts from tectonic–sedimentary complexes from different structural levels of the Samarka Terrane are reported. It is shown that the concentration and character of distribution of the major petrogenic oxides and minor and rare-earth elements in cherts of the upper and lower structural levels differ significantly, which results from differences in the facies environments of chert deposition. All the geochemical characteristics of cherts show that their deposition proceeded in the pelagic area of sedimentation, but in different parts. The Katen Complex composing the lower structural level is the most distant from the continental margin. The closest is the Amba-Matay Complex composing the upper structural level. Based on the geochemical and biostratigraphic data and the age of accretion of paleooceanic fragments, the length of the subducted oceanic plate (>6000 km) is calculated. 相似文献
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