pdf № 266, February

Actuality of the article is determined by necessity of elucidation of nature of ancient geological processes for determination of genesis of Pre-Cambrian deposits. Object of study was published data about ancient rocks of world and about Aldan shield. It was shown that in early Pre-Cambrian layered magma ocean existed on the Earth. The crystalline crust was resulted from crystallization of its acid layer. It covered all the Earth. Late tectonic deformations decreased its area. The magmas was resulted from ascent residual melts from magma ocean and from basic magma chambers in mantle plumes. Magmas were not formed as a result of partial melting. Due to rise of temperature during accretion, the temperature of lower mantle was less than upper mantle during early Pre-Cambrian. Therefore mantle plumes were not formed.

Keywords: magma ocean, crystalline crust, origin of magmas, mantle.

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The problem of Rudyanka structure is considered. Its decoding, apart from the palynological analysis, used mineral features of the Devonian sedimentary rocks. It is established that the quantity of grains of plagioclase with polysynthetic twinnings greatly varies depending on the age of deposits. In terminal Middle Devonian sandstones (Ustchirkka formation) they are either absent or found in single grains (up to 6 pieces per a microsection). In the Upper Devonian rocks the quantity of plagioclase clasts are estimated in dozens and hundreds per a microsection. At local scale, the quantity of plagioclase grains may be considered as a mineral indicator of a continental sediments age.

Keywords: Middle Timan, Devonian, continental sediments, plagioclase.

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DOI: DOI: 10.19110/2221-1381-2017-2-29-40

The paper represents the results of lithologic and spectroscopic investigations of the Upper Lower-Ordovician- Devonian deposits of the central part of Chernyshev Ridge. The studied deposits, simultaneously with regional progressive lithogenesis, suffered the secondary transformations connected with tectonic stress and activation of the epigenetic and metasomatic processes. We showed a certain correlation between manganese concentration ratio (Mg/CaDlt) in Mg- and Ca-positions of dolomite and predominance of irreversible deformations: recrystallization, dilatancy decompression or brittle fracture.

Keywords: carbonate tectonites, recrystallization, dilatancy, electron paramagnetic resonance, infrared spectroscopy, spectroscopic markers.

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 DOI: DOI: 10.19110/2221-1381-2017-2-41-44

The Pa-elements of the Early Carboniferous conodont Siphonodella quadruplicata (Branson et Mehl) were studied at the Skyscan 1272 micro-CT. The obtained results demonstrate three groups of tissues. The first one comprises interlamellar tissue possessing lowest radiodensity, the second group consists of lamellar tissue characterized by intermediate radiodensity, and the paralamellar and albid tissues demonstrate the highest radiodensity. The X-ray computed microtomography (micro-CT) allows reconstructing internal composition of the studyied Pa-elements and improving data about interlamellar tissue distribution. The results demonstrate perspectives of using the micro-CT in the histological study of conodont elements.

Keywords: Conodont, X-ray computed tomography, histology, hard tissues, Early Carboniferous.

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