scholarly journals New data on U-Pb-age and geochemistry of zircon (SHRIMP-II, SIMS) from Ichetu occurrence (Middle Timan)

Author(s):  
A. B. Makeev ◽  
◽  
A. O. Krasotkina ◽  
S. G. Skublov ◽  
◽  
...  
Keyword(s):  
Author(s):  
S. G. Skublov ◽  
A. O. Krasotkina ◽  
A. B. Makeyev ◽  
O. L. Galankina ◽  
A. E. Melnik

Findings of the growth relationships between baddeleyite and zircon are rare, due to significant differences in the formation conditions of the minerals. A reaction replacement (partial to complete) of baddeleyite by zircon is possible during metamorphism accompanied by the interaction with high-Si fluids. The opposite situation, when zircon is replaced by baddeleyite, is extremely rare in the nature. Transformation of zircon from polymineral (compound) ore occurrence Ichetju (the Middle Timan) with the formation of microaggregates of baddeleyite, ratile and florencite has been found out. The size of the largest segregations of baddeleyite does not exceed 10 microns in diameter. Microaggregates are unevenly related to the rim of zircon with a thickness of 10 to 50 rfn, voids and cracks across the grain. Altered zircon rim (a mixture of newly formed minerals) is characterized by sharply increased composition of REE (especially LREE), Y, Nb, Ca, Ti. The composition of Th and U also increases. An overview of the experimental studies on the reaction between zircon and baddeleyite and single natural analogues allows to make a conclusion that the most likely mechanism of the transformation of zircon from ore occurrence Ichetju to baddeleyite (intergrowth with ratile and florencite) is due to the effect of interaction of primary zircon with high-temperature (higher than 500—600°C) alkaline fluids transporting HFSE (REE, Y, Nb, Ti). This is indirectly confirmed by the findings of zircon with anomalous high composition of Y and REE up to 100000 and 70000 ppm respectively.


2021 ◽  
pp. 3-12
Author(s):  
N. Y. Nikulova ◽  
◽  
O. V. Udoratina ◽  
I. V. Kozyreva

The lithological and geochemical features of the metasandstones of the Svetlinskaya and Vizingskaya formations of the Middle Late Riphean Chetlas series in the Middle Timan, which are a substrate of rare-metal-rare-earth mineralization in several ore occurrences of the Kosyus ore cluster, have been investigated. The interpretation of the results of traditional weight chemical and mass spectrometric inductively coupled plasma (ICP MS) analyses allowed us to identify differences in the material composition of metapesanics, mainly due to changes in the degree of sedimentation maturity of terrigenous material coming from the demolition areas. The composition of metasandstones in various ratios includes both weakly weathered products of destruction of volcanic rocks of intermediate/basic composition, and altered, including under conditions of the weathering crust, metaterrigenous formations. The accumulation of sediments took place in a shallow coastal-marine environment with changing hydrodynamics, which affected the rate of destruction of rocks in paleo-catchments.


LITOSFERA ◽  
2021 ◽  
Vol 21 (5) ◽  
pp. 625-643
Author(s):  
O. P. Tel’nova ◽  
I. Kh. Shumilov

Research subject. Terrigenous rocks of the Sargaevo stage of sedimentation in various structural-facies settings within the Tsilma area (Middle Timan). Material and methods. The composition, structural features of rocks, and the species diversity of spores of higher plants were studied in the most complete natural outcrops proposed as a stratotype of the Paladinskaya Formation – a new straton of the Sargaevo age in the Middle Timan. Over a large area of the region, the deposits contain very few remains of fossil fauna, often indifferent. As a result, palynostratigraphy was selected as the main biostratigraphic method. Results. In the Middle Timan, a new straton, the Paladinskaya Formation, is described, which characterizes the Sargaevo stage of sedimentation in various structural-facies settings within the Tsil’ma area. The new straton has clear lithological and detailed palynological characteristics; a description of the limitotypes was performed.At present, the Paladinskaya Formation is the most complete sequence of Early Frasnian sedimentation in the European North-East of Russia, where it was possible to record regional responses to the global Frasnes event and to determine the position of the controversial level of the boundary between the Middle and Upper Devonian. Conclusions. The name “Ust’e Yarega” Formation in the Middle Timan cannot be considered valid, since it is a homonym of the sediments of the same age in the South Timan. The section is represented mainly by continental, rather than marine, deposits. A new name for the identifed formation is proposed – “Paladinskaya” with a description of the stratum section and limitotype.The Paladinskaya Formation is characterized by subcomplexes of spores (А and Б) of the regional miospore zone Cristatisporites pseudodeliquescens, which made it possible to correlate the marine and continental deposits of the Early Frasnian on the territory of the entire Timan-Pechora region and establish its exact position in the stratigraphic scheme of the Devonian.


Author(s):  
A. B. Makeyev ◽  
◽  
A. O. Krasotkina ◽  
S. G. Skublov ◽  
◽  
...  
Keyword(s):  

2020 ◽  
Vol 62 (8) ◽  
pp. 773-786
Author(s):  
A. B. Makeyev ◽  
S. G. Skublov ◽  
A. O. Krasotkina ◽  
S. E. Borisovskiy ◽  
T. B. Thomsen ◽  
...  
Keyword(s):  
Icp Ms ◽  

2021 ◽  
Vol 29 (6) ◽  
pp. 607-626
Author(s):  
E. A. Brusnitsyna ◽  
V. B. Ershova ◽  
A. K. Khudoley ◽  
T. Andersen ◽  
A. V. Maslov
Keyword(s):  
Icp Ms ◽  

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