scholarly journals Rb-Sr age of the riphean glauconites of the Kamov group (Baikit anteklise, Siberian platform)

2019 ◽  
Vol 488 (1) ◽  
pp. 52-57
Author(s):  
T. S. Zaitseva ◽  
A. B. Kuznetsov ◽  
N. A. Ivanova ◽  
M. A. Maslennikov ◽  
V. V. Pustylnikova ◽  
...  
Keyword(s):  
Siberian Platform ◽  
Cation Distribution ◽  
Mossbauer Spectroscopy ◽  
Layered Silicates ◽  
86Sr Ratio ◽  
Partial Recrystallization ◽  
Epigenetic Alteration ◽  
Upper Limit ◽  
Geochemical Study ◽  
Model Rb

A mineralogical and geochemical study was conducted and the Rb-Sr age of globular layered silicates (GPS) of the glauconite-illite series of the Dolgokta Formation from a parametric Chunkinskaya-282 drillcore was determined. The assessment of suitability of the mineral for geochronological purposes took into account the data of Mössbauer spectroscopy and modeling of the cation distribution in the GPS octahedral net. Mineralogical and crystalochemical characteristics indicate an epigenetic alteration of glauconite structure; therefore, its Rb-Sr isochronous age (1300 ± 7 Ma) is “rejuvenated” and reflects the stage of partial recrystallization. The 87Sr/86Sr ratio in dolomites of the Dolgokta and Kuyumba formations varies from 0.70602 to 0.72230, which confirms the epigenetic recrystallization. The model Rb-Sr age of glauconite, calculated taking into account the enrichment of radiogenic 87Sr, is within 1340-1400 Ma. The age estimate determines the upper limit of distribution of the Mesoproterozoic fossil Tappania, found in the Yurubchen and Dolgokta formations of the Baikit anteclise.

Sr Isotope Chemostratigraphy and Pb–Pb Age of the Riphean Carbonate Deposits of the Kharaulakh Uplift (Northeastern Margin of the Siberian Platform)

2021 ◽  
Vol 62 (03) ◽  
pp. 377-387
Author(s):  
B.B. Kochnev ◽  
A.B. Kuznetsov ◽  
D.R. Sitkina ◽  
A.Yu. Kramchaninov
Keyword(s):  
Siberian Platform ◽  
Sedimentary Cover ◽  
Complex Structure ◽  
The Arctic ◽  
86Sr Ratio ◽  
Sr Isotope ◽  
Upper Riphean ◽  
Carbonate Deposits

Abstract —The least altered limestones of the Ukta and Eselekh formations in the Precambrian section of the Kharaulakh uplift have a minimum 87Sr/86Sr ratio of 0.70673–0.70715. The lowest 87Sr/86Sr ratio of the overlying Neleger and Sietachan formations is 0.70791–0.70817. Based on these data, along with the earlier obtained positive δ13С values (up to 8‰) for the Kharaulakh section, we have estimated the age of the Ukta and Eselekh formations at 800–670 Ma and the age of the Neleger and Sietachan formations at ~640–580 Ma. The Pb–Pb isochron age of the least altered limestones of the Eselekh Formation calculated from eight samples is 720 ± 30 Ma. This age permits us to define the lower part of the Kharaulakh section of the Ukta and Eselekh formations to be the late Tonian of the International Chronostratigraphic Chart or to the Upper Riphean of the General Stratigraphic Scale of Russia. The presence of reliably dated Upper Riphean sediments in the Kharaulakh uplift indicates a more complex structure of the Precambrian sedimentary cover on the Arctic margin of the Siberian Platform than assumed earlier.

Cation distribution in NixMg1−xFe2O4 studied by XPS and Mössbauer spectroscopy

2006 ◽  
Vol 137 (1-2) ◽  
pp. 6-10 ◽  
Author(s):  
V.K. Mittal ◽  
P. Chandramohan ◽  
Santanu Bera ◽  
M.P. Srinivasan ◽  
S. Velmurugan ◽  
...  
Keyword(s):  
Mössbauer Spectroscopy ◽  
Cation Distribution ◽  
Mossbauer Spectroscopy ◽  
Mößbauer Spectroscopy
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