Early Paleozoic High- and Ultrahigh-Pressure Complexes in the Western Part of the Central Asian Orogenic Belt: Ages, Compositions, and Geodynamic Models of Formation

Skoblenko, Anfisa V.; Degtyarev, K. E.

doi:10.1134/s0869591121030048

Cited by 7 publications

(1 citation statement)

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“…Multiple lines of evidence for the occurrence of UHP metamorphism between 530 and 470 Ma have been reported for the Kokchetav, Issyk-Kul, Chu-Kendyktas and Zheltau terranes within the western segment of the CAOB (e.g. Shatsky et al 1999; Togonbaeva et al 2009; Ragozin et al 2009; Alexeiev et al 2011; Rojas-Agramonte et al 2013; Klemd et al 2014; Meyer et al 2014; Konopelko et al 2012; Konopelko & Klemd, 2016; review of Skoblenko & Degtyarev, 2021) (Figure 1(b)). Formation of the early Palaeozoic UHP rocks is believed to have been related to the subduction of different rock associations to depths of at least 60 km and possibly deeper to the stability field of coesite (Makbal complex, Issyk-Kul terrane; Zerendy Group; Kokchetav terrane) or even of diamond (Zerendy Group; Kokchetav terrane).…”

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confidence: 99%

High-pressure metamorphism of Precambrian continental crust in the southwestern part of the Central Asian Orogenic Belt (South Kazakhstan and North Tien Shan) and tectonic implications for the evolution of the Palaeo-Asian Ocean

Skoblenko (Pilitsyna),

Kanygina,

Dubenskiy

et al. 2023

Geol. Mag.

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In this study, we investigated the high-pressure (HP) metamorphism of the Precambrian continental crust exposed in the Zheltau terrane in South Kazakhstan (Koyandy complex) and the Chu-Kendyktas terrane in the North Tien Shan of Kyrgyzstan (Aktyuz, Kemin and Kokdzhon complexes) within the SW part of the Central Asian Orogenic Belt. HP quartz–feldspar lithologies of the Koyandy complex consist of migmatized kyanite-bearing garnet–mica paragneisses, garnet–kyanite paragneisses and their derivatives associated with eclogites. Paragneisses demonstrate prograde evolution involving mica dehydration melting and producing magnesium-rich garnet, kyanite and K-feldspar at the near-peak to retrograde stages at pressures of 15–18.5 kbar and temperatures of 800–870°C. The widespread growth of micas in these rocks reflects lower stages of retrogression at P = 10–12 kbar and T = 720–770°C. The age distributions of the cores of detrital zircon grains from the paragneisses indicate a predominance of Neoproterozoic and minor occurrence of Mesoproterozoic and Palaeoproterozoic sources of their protoliths. The ages of ∼487–485 Ma obtained from the zircon rims of the paragneisses reflect the timing of their HP metamorphic re-equilibration. These age clusters are consistent with the age estimates obtained from the rims of zircons in the eclogite-bearing garnet gneisses of the adjacent Aktyuz complex in the North Tien Shan. The P–T paths and zircon ages obtained from the high-grade quartz–feldspar gneisses of the Zheltau and Chu-Kendyktas terranes are thus interpreted to indicate involvement of the crustal material derived from the Precambrian basement (magmatic zircons aged ca. 844 Ma) and its Ediacaran–Cambrian sedimentary cover (detrital zircons with maxima at 1 Ga and 800–600 Ma) in the latest Cambrian subduction processes induced by the closure of the oceanic basins assigned to the Palaeo-Asian Ocean.

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