Carbonate Massifs of Talas Sections in Tectonic Setting of the Middle Tien Shan
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onate Massifs of Talas Sections in Tectonic Setting of the Middle Tien Shan A. V. Mikolaichuka, b, *, N. O. Seitkazievb, c, and D. V. Gordeevc aInstitute
of Geology, National Academy of Sciences, Bishkek, 720481 Kyrgyzstan Kyrgyz Geological Expedition, Ivanovka, Chu region, 725008 Kyrgyzstan c Kyrgyz State University of Geology and Mining, Bishkek, 720001 Kyrgyzstan *e-mail: [email protected]
bNorthern
Received October 21, 2019; revised February 24, 2020; accepted March 24, 2020
Abstract—In the Dzhetym Range, there are well-known Precambrian massifs of marbled limestones and quartzites, which have no analogues throughout the Middle Tien Shan. The authors establish that the quartzite-carbonate stratum occupies the highest structural position in the series of nappes of the region. The U–Pb dating of detrital zircon and zircon from intrusions reliably proves the Riphean age of the quartzite-carbonate stratum, which grounds to compare it with the autochthonous complex of the Karatau–Talas terrane. The autochthonous and parautochthonous units of the Dzhetym Range are composed of Riphean–Vendian sediments of the Middle Tien Shan. The geochemical characteristics and the refined age of the Bolshoi Naryn volcanic-plutonic complex, obtained in the course of this study, indicate that in the Late Riphean this area was a segment of the periocean continental rift, manifested in the time interval of 750–700 Ma ago throughout the entire Tarim–Tien Shan–Kazakhstan region. Keywords: Late Proterozoic sediments, nappes, U–Pb dating, Tien Shan DOI: 10.1134/S0016852120040081
INTRODUCTION At the foot of the Dzhetymbel Range and along the northern slopes of the Dzhetym Range there is a terrigenous-carbonate stratum, the structural position of which remained unclear for several decades. The stratum was identified in 1957 by Korolev [21, 40], who called it the Bordinskaya sequence after the tributary of the Archaly River. The Riphean age of the stratum and its relation to the Caledonides of the Northern Tien Shan were inferred from the lithological similarity with the Taragai and Suek formations of the Burkhan zone [21]. However, proceeding from the fact that the Bordinskaya sequence is only observed in tectonic relations with adjacent complexes, in his later study [23], Korolev allowed for the possibility that its stratigraphic position might be at the base of the volcanic rocks of Bolshoi Naryn, which implied also that Bordinskaya strata belonged to the Precambrian complexes of the Middle Tien Shan. Subsequent studies have not resolved this dilemma. Moreover, they led to the complete uncertainty in understanding both the stratigraphic and structural position of this stratum. First, arguments were made mostly in favor of the uppermost position of the Bordinskaya sequence occurring in the section of the Bolshoi Naryn series [15], while the later studies suggested that it could occur between the upper and lower volcanic rocks of the Middle Tien Shan [37].
This study aims to solve the geological contradictions and ambiguities in t
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