A Middle to Late Ordovician age of formation has been obtained for the granitoids of the Kurdai–Shatyrkol complex in Southern Kazakhstan (the Kendyktas Ridge) hosting the Shatyrkol and Zhaisan quartz-vein-type copper deposits. The U–Pb (SIMS) geochronological studies of the rocks from different phases of the Kurdai–Shatyrkol complex yielded age estimates of 464 to 457 Ma for quartz diorite and monzonite of the first phase, and 454 to 450 Ma for granodiorite and alkaline granite of the second and third phases. As suggested by the new data, the Kurdai–Shatyrkol complex is comparable to the ore-bearing Middle to Late Ordovician granitoids of Northern Kazakhstan and Northern Tien Shan, which allows referring them to a single large copper–gold type of metallogenic province.

The article presents the results of studying and substantiating the age of Late Precambrian volcanosedimentary and plutonic complexes of the northern part of the Ulutau terrane (Northern Ulutau) in western Central Kazakhstan. The obtained age estimates (SHRIMP II, ID-TIMS, LA-ICP-MS) indicate the formation of acidic effusives and granitoids in the second half of the Tonian of the Neoproterozoic 835‒747 Ma ago. Geochronological and isotope-geochemical data allow us to consider these formations as analogues of stratified and plutonic complexes of Southern Ulutau, which formed in various parts of the lateral series of structures of the Late Precambrian active continental margin.

The structure of serpentinite melange of the North Balkhash ophiolite zone (Central Kazakhstan; west Central Asian Orogenic Belt) is ascertained to be high-grade formations assigned to epidote-glaucophane eclogites and garnet blueschists, and their varieties. The rocks follow a clockwise 'subduction-type' evolution with the estimated near-peak metamorphic conditions of 1.6-1.9 GPa and 500-560 degrees C. 40Ar-39Ar phengite ages of -491 Ma and - 465 Ma obtained for the eclogites and garnet blueschists, respectively, are interpreted to reflect the nearpeak to shortly retrograde stages of rock evolution and to record the late Cambrian and Middle Ordovician episodes of high-pressure re-equilibration in the North Balkhash zone. Protoliths of the eclogites were N-MORBlike mafic rocks, which comprised structurally different (from the lower gabbroic to the upper dolerite/basalt) parts of pre-late Cambrian oceanic crust and were formed in the spreading centre setting at the expense of depleted mantle source. Protoliths of the garnet blueschists and associated rocks were represented by volcanogenic-sedimentary, predominantly mafic, complexes (tuffaceous sandstones, greywackes), an accumulation of which and subsequent involvement into subduction occurred at -478-465 Ma in the intra-oceanic (fore-arc) setting. Zircon core ages indicate formation of the source of the protoliths of the garnet blueschists occurred in the 509-478 Ma range. A comprehensive correlation of the metamorphic and igneous formations of the North Balkhash zone with those assigned to the adjacent complexes of the southern part of the West Junggar area (NW China) suggested their mutual Early Palaeozoic tectonic evolution within the Junggar-Balkhash Ocean.

The Late Ordovician and Silurian ages, previously considered as the Precambrian, were established for the first time for plutonic and volcanic complexes of the Karakamys block of Southwestern Kazakhstan. U–Pb (SIMS, and ID-TIMS) geochronological study of gneiss–granites and felsic volcanic rocks was carried out, and age estimates of 443 ± 5 Ma and 436 ± 2 Ma, consequently, were obtained. These data allow us to refer gneiss–granites to the very end of the Ordovician and the beginning of the Silurian, and felsic volcanic rocks and tuffs, to the Llandovery series of the Silurian. Special features of the composition of granitoids and felsic volcanic rocks indicate their formation in supra-subduction settings.

The article presents the results of studying of the Precambrian metasedimentary sequences of the Junggar terrane located in Southern Kazakhstan. In the structure of the Junggar terrane, we studied the rocks of the Sarychabyn Group and Kosagash Formation. Petrogeochemical data, combined with the results of U‒Pb and Lu‒Hf isotope-geochronological studies of detrital zircons, indicate that the Sarychabyn Group and Kosagash Formation are a single stratigraphic unit that accumulated during the Late Mesoproterozoic and Early Neoproterozoic (approximately 1026–920 Ma). The Mesoproterozoic and Paleoproterozoic complexes are believed to be the main sources of detrital zircon populations. These complexes include medium- and high grade metabasites and metapelites, as well as felsic igneous rocks that formed from different sources. The evolution of the Junggar terrane in the Late Precambrian is similar to the tectonomagmatic evolution of the Aktau–Mointy, Yili, Issyk-Kul, Chinese Central Tien Shan, and the Northern Kazakhstan terranes. At that time, the terranes were a single continental block that was located near the Sveconorwegian orogen in the western part of the Baltica paleocontinent during the formation of the Rodinia supercontinent.

The Kokchetav-North Tien Shan region in the west of the Central Asian Orogenic Belt (CAOB) comprises early Paleozoic island-arc volcanic-sedimentary and flysch strata, dismembered ophiolites, cherts, and basalts, composing Neoproterozoic terranes and Ediacaran-Cambrian cover. The Dzhalair-Naiman ophiolite zone located in the southwest of the Kokchetav-North Tienshan region, mainly hosts Cambrian plutonic and volcanogenic-sedimentary complexes of diverse tectonic affinities, and Lower Ordovician terrigenous strata. The oldest formations (Cambrian, Terreneuvian - Series 2) are referred to the Andassai-Dulankara supra-subduction ophiolites, comprised by the dunite-harzburgite and dunite-wehrlite-gabbro complexes along with differentiated volcanics, tonalites, and plagiogranites aged 519-521 Ma. Cambrian, Miaolingian-Furongian complexes here are represented by the Ashchisu oceanic intraplate basalts Formation with interlayers of cherts containing conodonts, as well as the East Dulankara island arc volcanic Formation. Cambrian, upper Furongian Sulusai tuffaceous-volcanic Formation is composed of tuffaceous siltstones, tuffaceous sandstones, and tuff conglomerates with rare flows of rhyolites aged ca. 490 Ma. The youngest (Lower Ordovician, Tremadocian) Dzhambul terrigenous Formation made up by predominant quartz-feldspar sandstones and siltstones, contains detrital zircons with ages ranging from 525 to 2500 Ma. The evolution of the Dzhalair-Naiman zone and adjacent complexes hence record three main stages: (i) Cambrian, Terreneuvian - early Furongian stage of the emergence and development of an intra-oceanic island arc and oceanic islands with OIB basalts; (ii) Cambrian, late Furongian stage of the accretion of the island arc and oceanic islands to the Chu-Kendyktas microcontinent, whose complexes underwent highpressure metamorphism, and switch of the subduction polarity with the formation of a new island arc with a heterogeneous basement; (iii) Early Ordovician stage of the cessation of magmatism, accumulation of thick terrigenous strata possibly in response to a change in the kinematics of the converging plates, and conversion of their boundary into a transform fault. (c) 2024 International Association for Gondwana Research. Published by Elsevier B.V. All rights are reserved, including those for text and data mining, AI training, and similar technologies.

The combined petrographic, petrological, geochemical and geochronological study of the Neoproterozoic gneisses of the Sarychabyn and Baskan complexes of the Junggar Alataw of South Kazakhstan elucidate the Precambrian tectonic evolution of the Aktau-Yili terrane. It is one of the largest Precambrian crustal blocks in the western Central Asian orogenic belt. The U-Pb single-grain zircon ages indicate that granite-gneisses formed from the same source and crystallised in the early Neoproterozoic ca. 930-920 Ma. The chemical composition of gneisses corresponds to A2-type granites. The whole-rock Nd isotopic characteristics (epsilon Nd(t) = -4.9 to -1.0 and TNd(DM-2st) = 1.9 to 1.7 Ga) indicate the involvement of Paleoproterozoic crustal rocks in magma generation. Early Neoproterozoic ca. 930-920 Ma A-type granitoids in the Aktau-Yili terrane of South and Central Kazakhstan might reflect within-plate magmatism adjacent to the collisional belt or a local extension setting in back-arc areas of the continental arc. image

The complex of volcanogenic rocks of the basalt–rhyolite composition of the Zhiide series has been studied in the southern part of the Ulutau Terrane in Central Kazakhstan. The age of rhyolites (1338 ± 5 Ma) was first estimated on the basis of the U–Pb (SIMS)-geochronological study of accessory zircons. This age corresponds to the first half of the Ectasian period of the Mesoproterozoic. The features of the composition of the mafic and felsic effusive rocks indicate their formation in the setting of continental rifting caused by activity of the mantle plume.

AbstractIn 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.

Metamorphic crustal formations of the Aktyuz block (SE part of the Chu-Kendyktas terrane; SW segment of the Central Asian Orogenic Belt) include garnet-bearing orthogneisses and gneissic granites of the Aktyuz Complex, garnet-bearing ortho- and paragneisses of the Kemin Complex and paragneisses with schists of the Kokdzhon Complex. The gneisses of the Aktyuz and Kemin Complexes associated with intensively altered eclogites, are referred to the retrogressed felsic granulites, which likely experienced high-pressure re-equilibration and dehydration melting under eclogite facies conditions. The eclogite-bearing garnet-mica gneisses of the Aktyuz Complex contain zircons with magmatic cores, overgrown by the rims with the low Th/U ratios of 0.005-0.05. The obtained age clusters of ca. 844 Ma and ca. 490 Ma likely characterize two stages of the rocks' evolution in the late Neoproterozoic (emplacement of the gneisses' protoliths) and in the latest Cambrian (high-pressure metamorphism of the gneisses' protoliths). The garnet-epidote gneissic granites of the Aktyuz Complex and garnet-bearing chloritized orthogneisses of the Kemin Complex yielded late Neoproterozoic (Tonian) protoliths' crystallization ages of 820-805 Ma, but these rocks do not show any evidence of the later re-equilibration and apparently avoided high-pressure metamorphism. Thus, the protoliths of the late Neoproterozoic orthogneisses represented by anorogenic granitoids, comprised Precambrian basement of the Aktyuz block in the Chu-Kendyktas terrane, and some part of the felsic rocks was involved into Early Palaeozoic subduction processes. Detrital zircons from the metasedimentary formations of the Kokdzhon and Kemin Complexes of the Aktyuz block display the main age peaks at 600, 800, 1000 Ma and weaker peaks at similar to 1.5 and 2.5 Ga. The protoliths of the rocks were terrigenous lithologies, which are believed to have been formed after eroded felsic complexes of mostly Ediacaran, late Neoproterozoic, Mesoproterozoic and Palaeoproterozoic-to-Neoarchean ages, and accumulated during the Cambrian. The rocks likely made up sedimentary cover of the Chu-Kendyktas terrane and constituted the sand-siltstone-shale series. The presence of varisized rims of 495-471 Ma in the detrital zircons of the metasedimentary formations of the Kokdzhon and Kemin Complexes is consistent with the near-peak-to-retrograde stages of the latest Cambrian-Middle Ordovician metamorphic evolution of the rocks. The age estimates obtained for the crustal complexes of the Aktyuz block correlate well with those of the similar complexes known from the adjacent Issyk-Kul (North Tien Shan) terrane (Makbal Complex) and Zheltau terrane (Southern Kazakhstan; Koyandy Complex) in the SW part of the Central Asian Orogenic Belt.

The article presents the results of studying and substantiating the age of the Ediacaran volcanogenic-sedimentary and Cambrian sedimentary strata isolated for the first time within the southern part of the Ulutau terrane (southern Ulutau) in the west of Central Kazakhstan. The age estimates (SHRIMP II) of 594 ± 3, 594 ± 5, and 600 ± 2 Ma obtained for effusive and tufogenic rocks, as well as their isotope-geochemical characteristics, are the first evidence of the manifestation of Ediacaran suprasubduction magmatism in the paleozoics of Kazakhstan and the northern Tien Shan. The obtained data indicate the participation of the Ulutau terrane at the end of the Precambrian in the structure of the volcanic-plutonic belt, fragments of which are also Neoproterozoic blocks within southwestern Kazakhstan (the Zheltavsky and Chuysko-Kendyktassky terranes) of the Southern Tien Shan and the Karakum‒Tajik terrane. The formation of the Ediacaran suprasubduction belt may be a continuation of the evolution of the Neoproterozoic active continental margin that arose in the Tonian period on the northwestern margin of the supercontinent Rodinia.

The isotopic U‒Th‒Pb age (SIMS (SHRIMP II) and La-ICP-MS) was obtained for accessory zircon from ash tuffs of the Basu and Zigan Formations of the Asha Vendian (Ediacaran) Group of the Southern Urals. The compositions of rare-metal enriched tuffs correspond to rhyolites, comendites, trachytes, and trachyandesites. The concordant value of the U–Pb age of zircon from the tuffs of the Basu Formation is 578 ± 7, 577 ± 7, and 568 ± 5 Ma (SHRIMP II). The age of the zircon from the other two points of the Basu Formation is 573 ± 4 and 574 ± 3 Ma (La-ICP-MS). The age of zircons from the tuffs of the Zigan Formation is 566 ± 5 Ma (SHRIMP II). Tuffs accumulated in the hinterland of the marginal continental volcanic belt.

Precambrian metamagmatic complexes of the Zhingeldy and Kendyktas blocks of the Zheltau and ChuKendyktas terranes of the SW part of the Central Asian Orogenic Belt (CAOB) consist of predominant Neoproterozoic orthogneisses with the estimated protolith ages of ca. 790-800 Ma, and subordinate epidote and garnet amphibolites, metabasalts and metadolerites of the lower metamorphic grades. The orthogneisses are characterized by negative epsilon Nd(t) values of-12 to-4 with Nd model ages of 2.3-1.7 Ga, indicating their protoliths could have formed by a reworking of the Palaeoproterozoic crustal materials. Precambrian metavolcanic rocks in the studied region are rhyolites with the estimated crystallization ages of ca. 800-830 Ma, and are associated with metabasalts. Metasedimentary complexes in the studied region consist of intensively retrogressed garnet-mica schists interlayered with marmorized limestones, metasilicic rocks, epidote and garnet amphibolites and strongly altered eclogites. The inferred protoliths of the garnet-mica schists are terrigenous rocks accumulated during the latest Ediacaran - middle Cambrian and formed from Mesoproterozoic (ca. 1.0 Ga) and to a lesser extent Palaeoproterozoic felsic source rocks (ca. 1.6-1.7 Ga and ca. 2.5 Ga). The garnet-mica schists of the Kendyktas block have negative epsilon Nd(t) of-13.4 and a model age tNd(DM) of 2.2 Ga, implying formation of their protolith from Palaeoproterozoic crustal source. The studied Zheltau and Chu-Kendyktas terranes from the SW part of the CAOB have much in common in terms of Precambrian and Early Palaeozoic evolution and chemical compositions of the key rock types. The presence of the Early Precambrian rocks (Zheltau terrane), an abundance of the Late Mesoproterozoic (1000-1100 Ma) detrital zircons in the Ediacaran-Cambrian metasedimentary complexes and a wide distribution of the Late Neoproterozoic magmatism, are distinctive features of the studied terranes. We refer such Precambrian terranes of the western CAOB to the Ulutau-Moyunkum group where tectono-magmatic evolution is consistent with that observed from the northern part of the Tarim craton. Our results also aid comprehensive correlation of metamorphic complexes of the Precambrian terranes from the SW CAOB. (C) 2021 International Association for Gondwana Research. Published by Elsevier B.V. All rights reserved.

The results of a study of Late Precambrian effusive and plutonic rocks of the Dyusembai and Aktass volcanic–plutonic associations of the western part of the Southern Ulutau are reported. A U‒Th‒Pb isotope–geochronological study of accessory zircons (SHRIMP II) showed that the formation of rhyolite–granite associations occurred in the second half of the Tonian in the Neoproterozoic ( 830 Ma, Dyusembai association, and 800–790 Ma, Aktass association). The formation of parental melts for effusive and plutonic rocks of both associations occurred via dehydration melting of metatonalite (metagreywacke) formations of the Early Precambrian continental crust in an intraplate environment. The Neoproterozoic evolution of the Southern Ulutau took place in an environment of an active continental margin. The formations of the eastern part of the Southern Ulutau were formed within the ensialic island arc, while the western part, in the area of riftogenic magmatism, upon extension in the rear area. The Tonian magmatism in the Southern Ulutau, as well as in the other terranes of the Ulutau‒Moyunkum Group, indicates their incorporation into the basement of a large volcanic–plutonic belt marking subduction of the oceanic lithosphere beneath the northwestern margin of the Rodinia supercontinent.

The metamorphosed iron ore volcanogenic–sedimentary strata of the Karsakpai series in the eastern Ulutau Precambrian terrane of Central Kazakhstan are studied. The crystallization age of 745 ± 3 Ma is first dated for the andesidacitic tuffs by the U–Th–Pb (SIMS) method, which indicates their formation at the end of the Tonian period of the Neoproterozoic Era.

Detailed structural analysis of the formations of the Maksyutov eclogite–glaucophane–schist complex in the Southern Urals has been carried out. U–Pb (LA-ICP-MS) isotopic dates of detrital zircons from quartzites of the Yumaguzino and Karamala groups (tectonostratigraphic units) making up the complex were obtained. The data show that both groups are similar in age but differ in the facies formations that comprise the proximal (Yumaguzino Group) and distal (Karamala Group) regions of the Paleozoic margin of the Baltica paleocontinent. The alternation of these groups in the Maksyutov Complex is explained by their tectonic juxtaposition during the formation of the scaly-thrust structure of this complex. Formations of the Maksyutov Complex subsided in the subduction zone beneath the Magnitogorsk island arc and were subjected to fold deformations during the subsequent exhumation. Four deformation stages have been established during the structural evolution of the complex. The first stage is associated with the development of the southwest-vergent folds and sheath folds F1 and corresponds to the eduction of the formations of the Maksyutov metamorphic complex from the subduction zone of the Magnitogorsk island arc in the southwestern direction (in modern coordinates) in the middle of the Famennian–Late Devonian. The second stage manifests itself in the development of the southeast-vergent folds F2, which are most common in the Maksyutov Complex. This stage is associated with an oblique sinistral collision of the Magnitogorsk island arc with the Baltica margin in the Late Devonian. At the third deformation stage, the west-vergent folds F3 were formed, caused by movements during the Late Paleozoic continental collision in the Main Ural Fault Zone. Postcollisional shear movements at the fourth deformation stage, marked by the development of folds F4 with steeply dipping hinges, completed the main stage of the structural evolution of the region.

Metasedimentary complexes represented by quartzite-schist Kiik Group quartzite-schists play a significant role in the Aktau-Mointy terrane structure, which is one of the largest Precambrian blocks in the western Central Asian Orogenic Belt (CAOB). U-Pb LA-ICP-MS dating of detrital zircons from quartzites in different Kiik Group areas and related magmatic age data establish that accumulation occurred in the late Mesoproterozoic to early Neoproterozoic (from 1150 to 920 Ma). Concordant age estimates of detrital zircons from Kiik Group quartzites predominately fell within intervals of 1149-2105 and 2272-2850 Ma with the prominent peaks at 1217, 1332, 1466, 1582, 1621, 1748, 1849, 2517 and 2689 Ma, and minor peaks at 1992, 2282, 2791 and 2823 Ma. Hf-inzircon and Nd whole rock data suggest that the primary stages of continental crustal growth in the Aktau-Mointy terrane were associated with the tectono-magmatic processes of the Neoarchean, Paleoproterozoic, and Mesoproterozoic. Juvenile continental crust production occurred during the Neoarchean and Paleoproterozoic, with older complex tectono-magmatic reworking, and juvenile crust production finally prevailed in the mid-Mesoproterozoic. Based on the age patterns and Hf isotopic compositions of detrital zircons from the Aktau-Mointy terrane and other terranes in the western CAOB, the crustal basement of the Aktau-Mointy terrane exhibits certain similarities with those of the Northern Kazakhstan and Issyk-Kul terranes. They all exhibit a close tectonic affinity with the Chinese Central Tian Shan terranes, Yili Block, North and China Craton, while differing from the Tarim Craton. In the Rodinia supercontinent structure, the Aktau-Mointy terrane was probably located near the Sveconorwegian Orogen in the western Baltica with other Kazakhstan and Northern Tian Shan Precambrian blocks.

Based on the results of U–Th–Pb (SIMS) dating, an Early Neoproterozoic (924 ± 4 Ma) age was obtained for granite–gneiss of the Sarychabyn Complex, which is one of the oldest complexes in the Junggar Alataw Range. This value constrains the minimum age of the metasedimentary rocks of the Sarychabyn Group hosting granite–gneiss as well. The most likely age of metasediments is Late Mesoproterozoic–Early Neoproterozoic, which is consistent with the age of lithologically similar complexes in the adjacent regions of Kazakhstan and China. The age of the gneiss of the Sarychabyn Complex coincides with the ages of anorogenic granitoids and felsic volcanic rocks from the Aktau-Mointy massif of Central Kazakhstan and the ages of granitoids in the Wenquan Complex in China. An episode of granitoid magmatism at ~920 Ma, widespread in the Aktau-Junggar microcontinent, is a characteristic feature that distinguishes it from other Precambrian crustal blocks of Kazakhstan and the Northern Tianshan.