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Detrital zircons from quartzite–schist sequences of the Aktau–Mointy Massif (Central Kazakhstan), which occur in various structural positions relative to the Early Neoproterozoic felsic volcanics, were studied. The obtained U–Pb zircon dating results suggest similarity of detrital zircon age populations with a lower limiting depositional age of 1220 Ma in all quartzite–schist sequences. The different positions of quartzite–schist sequences relative to the felsic volcanics are due to subsequent deformations. The ages of detrital zircons studied fall mostly within the intervals of 1149–2105 and 2354–3159 Ma with major peaks at 1218, 1338, 1468, 1581, 1628, 1743, 1851, and 2520 Ma and minor peaks at 2016, 2619, 2696, 2791, 2823, and 3114 Ma. The structural features of quartzite–schist sequences and the presence of heavy minerals that are unstable during long-term transport indicate the predominance of local source areas, which either form the buried part of the basement of the Aktau–Mointy Massif or have been eroded completely. Within the Aktau–Mointy Massif, it enables us to use the U–Pb ages and Lu–Hf isotope compositions of detrital zircons from quartzite–schist sequences to reconstruct the history of Precambrian continental crust formation. Results suggest that the production of juvenile continental crust prevailed only during Middle Mesoproterozoic, while formation during the Mesoarchean–Neoproterozoic time accompanied magmatic reworking of the older crustal complexes. [ABSTRACT FROM AUTHOR]

U–Pb geochronological studies of detrital zircons from quartzite–schist sequences of the Akbastau Formation of the Chu Block (northwestern part of the Chu–Kendyktas terrane, Southern Kazakhstan) have been provided. The concordant ages of detrital zircons are predominantly within the intervals of 1672–2115 Ma with peaks at 1697, 1780, 1857, and 2066 Ma. Individual zircon grains display ages of 2291–2332 Ma with peaks at 2303 and 2322 Ma. Neoarchean ages of 2608–2747 Ma with a peak at 2681 Ma characterize another significant zircon population. The lower limit of deposition for the Akbastau Formation of the Chu Block, corresponding to the youngest statistically significant zircon population, is estimated at 1.7 Ga. [ABSTRACT FROM AUTHOR]

• Granulites were formed during the Neoproterozoic stage of magmatism at 770–790 Ma. • Orthogneisses associated with the granulites are of Neoproterozoic (790 Ma) age. • Amphibolites with Palaeoproterozoic detrital zircons are protoliths for granulites. • Mesoproterozoic rocks are the main source for protoliths of garnet-biotite schists. • Palaeoproterozoic continental crust is a source for the metamorphic complexes. Within the Chu-Kendyktas Precambrian terrane located in Southern Kazakhstan (in the western part of the Central Asian Orogenic Belt), medium- and high-grade metamorphic formations have been identified and attributed to the Aydaly and Shukyr Complexes. The Aydaly Complex is predominantly composed of orthogneisses with a Neoproterozoic protolith age of 790 Ma and subordinate high-temperature granulites comprising a succession of amphibolites, amphibole-rich granulites, mesocratic granulites, and melanocratic (clinopyroxene-rich) and leucocratic (melt-rich) granulites, which were evidently formed at moderate pressures of 6–9 kbar and high temperatures, increasing from 700 to 900 °C or more. The clinopyroxene-rich granulites of the Aydaly Complex contain detrital zircon grains of mainly Palaeoproterozoic (1790–2058 Ma) and, to a more limited extent, Neoarchean (~2500 Ma) ages, with preserved magmatic zoning and indicating a sedimentary origin of the protolith via mafic greywackes that were subsequently metamorphosed to amphibolites. The age estimates of the leucocratic melt-rich granulites, which form veins or layers within the clinopyroxene-rich melanosome, correspond to the range 770–790 Ma and define the Neoproterozoic stage of magmatism and granulite metamorphism. Hence, the deposition of the sedimentary protolith for the Aydaly Complex granulites and its subsequent emplacement at mid-crustal levels occurred from the middle Palaeoproterozoic (~1800 Ma) to the late Tonian (~770–790 Ma). In turn, the Shukyr Complex consists of garnet-biotite schists, which are characterised by a significantly lower grade of metamorphism compared to the Aydaly Complex, at around T ~600 °C. The garnet-biotite schists are thought to represent moderate-temperature hornfels, located at the contact between the protolith (shales) and the Early Palaeozoic Ulken massif granitoids. The deposition of the Shukyr Complex protolith occurred during the Ediacaran–Cambrian, as a result of the erosion of mainly Mesoproterozoic (1000 Ma), and to a lesser extent Palaeoproterozoic (2460 Ma), rocks. The Sm-Nd whole-rock isotopic compositions suggest that the formation of the protoliths of the Aydaly and Shukyr Complexes was related to the reworking of Palaeoproterozoic continental crust. [ABSTRACT FROM AUTHOR]