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Date submitted2022-09-26
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Date accepted2023-03-23
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Date published2023-12-25
A new diamond find and primary diamond potential of the Chetlas uplift (Middle Timan)
In the previously poorly studied southeastern part of the Chetlas uplift in the Middle Timan, a new occurrence of diamond satellite minerals and a diamond grain were found in the modern channel sediments of the Uvuy River basin. In order to assess the prospects of the area under consideration for identification of diamondiferous objects of practical interest, a characteristic of chromium-bearing pyropes and chromospinelides as the main kimberlite of diamond satellite minerals are given and the diamond grain itself is described. The material for the research was 16 schlich samples, each with a volume of 8 to 15 l. The minerals were studied using optical and scanning electron microscopy, Raman spectroscopy, laser luminescence and X-ray diffraction (Debye – Sherrer method). It is shown that among the pyropes, most of which correspond in composition to minerals of the lherzolite paragenesis, there are varieties belonging to the dunite-harzburgite paragenesis, including those belonging to diamond phase stability regions. Among the studied chromospinelides, chrompicotites and aluminochromites similar in composition to those found in rocks such as lherzolites and harzburgites, as well as in kimberlites, were identified. A diamond grain found in one of the samples has the form of a flattened intergrowth with distinct octahedron faces, complicated by co-growth surfaces with other mineral grains that have not been preserved to date. The discovery of the diamond and the established signs the formation of aureoles of the diamond satellites minerals in the channel sediments of the studied area open up the prospects for discovering their primary sources here.
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Date submitted2021-04-04
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Date accepted2022-04-26
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Date published2022-07-26
Vendian age of igneous rocks of the Chamberlain valley area (Northern part of the Wedel Jarlsberg Land, Svalbard Archipelago)
The geological structure, structural relations with the underlying complexes, mineral composition, age and origin of sedimentary-volcanogenic and intrusive formations of the Chamberlain valley area (northern part of the Wedel Jarlsberg Land, Svalbard Archipelago) are considered. As a result of the studies, two stages of the Late Precambrian endogenous activity in this area have been identified. For the first time the Vendian ages (593-559 Ma) of intrusive (dolerites) and effusive (basalts, andesites, tuffs) rocks were determined by U-Pb-method (SHRIMP-II) for Svalbard Archipelago. At the same time, the Grenville ages for large bodies of gabbro-diorites, metadolerites bodies (1152-967 Ma), and metagranites (936 Ma) were determined for the first time for this area, which correlates well with the ages of magmatic formations obtained earlier in the southern part of Wedel Jarlsberg Land. A detailed petrographic and petrochemical characterization of all the described objects were compiled and the paleotectonic conditions of their formation were reconstructed. Based on these data, the Chemberlendalen series, which is dated to the Late Vendian, and the Rechurchbreen series, which the authors attribute to the Middle Riphean and correlate with the lower part of the Nordbucht series are distinguished. The data obtained indicate a two-stage Precambrian magmatism in this area of the Svalbard archipelago and, most importantly, provide evidence for the first time ever of endogenous activity on Svalbard in the Vendian time. This fact makes it possible to reconsider in the future the history of the formation of folded basement of the Svalbard archipelago and the nature of the geodynamic conditions in which it was formed.
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Date submitted2018-07-05
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Date accepted2018-08-31
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Date published2018-12-21
The lake Il’men clint, Russia: a potential devonian geopark
- Authors:
- John E.A. Marshall
- David J. Siveter
The Devonian rocks exposed on the shores of Lake Il’men, some 150 km SSE of Saint Petersburg, are important historically in the context of the recognition of the Devonian System. Moreover, they provide unique potential for a range of geological studies today. The non-geological heritage of the area – its flora, fauna, past and current industrial use and cultural links – is also a very worthy one. Since 2001 the area has been recognised asa Specially Protected Natural Territory. A ‘Geopark’ is a unified area of local or wider extent that has been so designated based on its significant geological and associated natural and cultural heritage. There are many positive criteria for considering that the Lake Il’men area could acquire the appellation of a Geopark. Scientific investigations dedicated to understanding the geodynamical conditions operating at Lake Il’men would resolve how to best to help promote the future preservation of this unique natural area.
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Date submitted2009-08-05
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Date accepted2009-10-06
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Date published2010-02-01
The problems of stratigraphy on devon оf Polar Urals and Pay-Hoi
- Authors:
- A. L. Zherlygin
The legends of the Polar Urals and Pay-Hoi map series were estimated for proving the mapped subdivisions due to geological survey in the scale 1:200000 conducted in Kara-Silovskaya area (on western slope of the Arctic Urals and the range Pay-Hoi). In the result it was found out that Eletskaya Structure-Formation Zone in Devon was divided into a great number of stratigraphic units, reflecting the lateral substance changes of the same age level. According to it all units are conventionally valid and there are same equal ones among them. The biohermal massifs are not distinguished as independent units.
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Date submitted2008-10-21
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Date accepted2008-12-25
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Date published2009-12-11
Comparative analysis of spiriferida complexes of the frasnian stage in the south of Novaya Zemlya and one-aged complexes of East-European platform and other districts
- Authors:
- D. V. Bezgodova
The Article contains a brief characteristic of spiriferida (brachiopod) complexes spread in the Frasnian sediments in the South of Novaya Zemlya, and their comparison with one-aged complexes of several regions of East-European platform, such as Main Devonian field, Central districts, the Volga-Urals region, South Timan, south-western districts and also outlying districts of the Kuznetsk coal basin and North-West of Russia.
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Date submitted2008-10-04
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Date accepted2008-12-23
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Date published2009-12-11
Importance of taphonomic researches for solution of biotopes and ecological-facial ostracod communities of some Silurian and lower devonian ostracoda from the South Tien Shan
- Authors:
- E. D. Michailova
Importance of taphonomic researches of ostracod remains from the Middle Paleozoic deposits of the South Tien Shan for solution of ecological-facial and biostratigraphical problems is demonstrated. The allochthonous and subautochthonous ostracod burials of some Silurian and lower Devonian stratigraphic units from the South Tien Shan are described. Six stable pattern types of ecological-facial ostracod communities, connected with different paleoenvironments are presented. The development of communities is traced through lower Silurian and lower Devonian.
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Date submitted2008-10-11
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Date accepted2008-12-21
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Date published2009-12-11
Cyclicity of the devonian and carboniferous deposits of Novaya Zemlya
- Authors:
- R. A. Schekoldin
Two structural-formational zones are recognized in the Devonian and Carboniferous deposits of Novaya Zemlya: the Barents zone and the Kara zone. The first one is characterized by thick, predominantly carbonate deposits, containing a rich complex of benthic fossils, and corresponds to the shelf paleoenvironments. The second one is characterized by thin hemipelagic argillaceous, lime and siliceous deposits, containing scarce pelagic fossils. This zone is suggested to represent bathyal paleoenvironments (slope and basin floor). The main control on sedimentation in both zones provided relative sea-level rises and falls, which repeated with mean periodicity equal to an age (third-order cycles). Sea-level highstands correspord to periods of low sedimentation rates and stagnation in deep-water zone. Sea-level lowstands were favourable to intensification of sediment gravity flows and better aeration of bottom waters.
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Date submitted2008-10-11
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Date accepted2008-12-22
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Date published2009-12-11
On specific features of stratigraphy of the middle devonian deposits of the Leningrad region
- Authors:
- M. G. Tsinkoburova
The revision of stratigraphical schemes is one of the urgent problems at present time. This article gives data on history of formation of stratigraphical schemes of the Middle Devonian of North-West of the East-European platform. Modern stratigraphy of terrigenous layers of Middle Devonian is considered. The special attention is given to a problem of the boundary of the Middle and Upper Devonian. On the example of particular outcrops of the Leningrad region the importance of rhythmic stratigraphy in the splitting and correlation of deposits of the Middle and Upper Devonian is shown.
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Date submitted2008-10-24
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Date accepted2008-12-06
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Date published2009-12-11
Geological structure, characteristics of ores and genesis of ore occurrences in the Halvdanpiggen field (West Spitsbergen island)
- Authors:
- A. N. Sirotkin
- V. V. Khailov
- D. V. Nikitin
A new metallogenic zone was separated out in a central part of the archipelago Spitsbergen by the results of exploration work. It was shown an integral series of ore areas and fields in the limits of this zone, including the ore field Halvdanpiggen. This field integrates several non-uniformly scaled the ore occurrences, which present a great interest in regard to a material composition of the ore. They likewise produce an information for determination of genesis and outlooks of total metallogenic zone. The article contains data on geology, mineralogy and geochemistry of deposits; it is established their genesis, formation membership and time of origination.