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Late Paleozoic collision of the Tarimskiy and Kirghiz-Kazakh paleocontinents
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... The KSTS was formed in the late Paleozoic from the closure of the South Tien Shan Ocean as the Kazakhstan-Yili-Middle-Tien Shan Block and Tarim, Kazakhstan microcontinents collided and accreted (Biske 1995;Windley et al. 2007;Xiao et al. 2010). The KSTS consists mainly of fragments of Precambrian basement rocks along the northern margin of Tarim Craton and of Paleozoic deep and shallow marine sedimentary rocks, metamorphic rocks and subordinate ophiolites (Biske 1995). ...
... The KSTS was formed in the late Paleozoic from the closure of the South Tien Shan Ocean as the Kazakhstan-Yili-Middle-Tien Shan Block and Tarim, Kazakhstan microcontinents collided and accreted (Biske 1995;Windley et al. 2007;Xiao et al. 2010). The KSTS consists mainly of fragments of Precambrian basement rocks along the northern margin of Tarim Craton and of Paleozoic deep and shallow marine sedimentary rocks, metamorphic rocks and subordinate ophiolites (Biske 1995). In Kyrgyzstan, the KSTS is divided by the Talas-Farghana Fault into the western Alay and eastern Kokshaal segments (Biske and Seltmann 2010). ...
... The Palaeozoic orogenic belt of the Tianshan in Kyrgyzstan is traditionally subdivided into three tectonic zones, namely the North-, Middle-and South Tianshan. The Middle and South Tianshan represent a late Palaeozoic fold-and-thrust belt, formed due to convergence and collision of the Kazakhstan continent in the north with the Precambrian Tarim Craton and Afghan-Tadjik microcontinent in the south (Zonenshain et al., 1990;Dalimov et al., 1993;Biske, 1995;Maksumova et al., 2001). The South Tianshan (STS) extends for 2500 km from Uzbekistan to northwestern China and mainly consists of sedimentary assemblages and subordinate volcanic, metamorphic and ophiolitic rocks, which formed in the Turkestan ocean and on adjacent continental margins during the early Palaeozoic to early Permian. ...
... The South Tianshan (STS) extends for 2500 km from Uzbekistan to northwestern China and mainly consists of sedimentary assemblages and subordinate volcanic, metamorphic and ophiolitic rocks, which formed in the Turkestan ocean and on adjacent continental margins during the early Palaeozoic to early Permian. These rocks were stacked together by south-facing thrusts in an accretionary and collisional setting in the late Carboniferous and Permian (Burtman, 1975(Burtman, , 2006Biske, 1995;Hegner et al., 2010;Makarov et al., 2010;Han et al., 2011;Alexeiev et al., 2015). The Middle Tianshan (MTS) is dominated by passive margin carbonates and siliciclastic facies ranging in age from middle Devonian to Pennsylvanian and represents the deformed middle to late Palaeozoic southern margin of the Kazakhstan continent (Bakirov and Maksumova, 2001;Alexeiev et al., 2017b). ...
Geochronological, geochemical, and structural studies of magmatic and metamorphic complexes within the Kyrgyz North Tianshan (NTS) revealed an extensive area of early Palaeozoic magmatism with an age range of 540–475 Ma. During the first episode at 540–510 Ma, magmatism likely occurred in an intraplate setting within the NTS microcontinent and in an oceanic arc setting within the Kyrgyz-Terskey zone in the south. During the second episode at 500–475 Ma, the entire NTS represented an arc system. These two phases of magmatism were separated by an episode of accretionary tectonics of uncertain nature, which led to obduction of ophiolites from the Kyrgyz-Terskey zone onto the microcontinent. The occurrence of zircon xenocrysts and predominantly negative whole-rock ɛNd(t) values and ɛHf(t) values of magmatic zircons suggest a continental setting and melting of Precambrian continental sources with minor contributions of Palaeozoic juvenile melts in the generation of the
magmatic rocks. The late Cambrian to Early Ordovician 500–475 Ma arc evolved mainly on Mesoproterozoic continental crust in the north and partly on oceanic crust in the south. Arc magmatism was accompanied by spreading in a back-arc basin in the south, where supra-subduction ophiolitic gabbros yielded ages of 496 to 479 Ma.
The relative position of the arc and active back-arc basin implies that the subduction zone was located north of the arc, dipping to the south. Variably intense metamorphism and deformation in the NTS reflect an Early Ordovician orogenic event at 480–475 Ma, resulting from closure of the Djalair-Naiman ophiolite trough and collision
of the Djel'tau microcontinent with the northern margin of NTS. Сomparison of geological patterns and episodes of arc magmatism in Kyrgyz North Tianshan and Chinese Central Tianshan indicate, that these crustal units constituted a single early Palaeozoic arc and were separated from the Tarim Craton by an oceanic basin since the Neoproterozoic.
... The study of HP-LT metamorphism of accretionary orogens is often complicated by the collage of multiple (micro-) blocks and the subduction of numerous oceanic domains (e.g., Cawood et al., 2009;Xiao et al., 2014). The South Tien Shan (STS) range in Central Asia results from the docking of the Tarim craton with the Kazakh block or platform (Figure 1a) after the final closure of the Turkestan Ocean in the Late Carboniferous (e.g., Biske, 1995;Charvet et al., 2011). This is the final accretion event recorded in the western part of the Central Asian Orogenic Belt (CAOB; e.g., Kr€ oner et al., 2017;Windley, Alexeiev, Xiao, Kroner, & Badarch, 2007), before a new subduction initiated south of the Tarim craton with the closure of the Paleo-Tethys Ocean (e.g., Metcalfe, 2013). ...
... The Kyrgyz NTS and MTS were amalgamated in the early Palaeozoic (e.g., Alexeiev et al., 2011;Kr€ oner et al., 2013Kr€ oner et al., , 2017Mikolaichuk, Kurenkov, Degtyarev, & Rubstov, 1997). In the Late Carboniferous, the Tarim craton was accreted to the MTS following closure of the Turkestan Ocean (also referred as Paleo-Asian, STS, or Central Tien Shan, ocean), which resulted in the formation of the STS fold-and-thrust belt (Biske, 1995;Hegner et al., 2010). HP-LT metamorphism has been described along the STS suture zone in the Atbashi Range in Kyrgyzstan and in the Akeyazi area in western China (Figure 1a; e.g., Gao & Klemd, 2003;Hegner et al., 2010;Meyer, Klemd, John, Gao, & Menneken, 2016;Tagiri, Yano, Bakirov, Nakajima, & Uchiumi, 1995;van der Straaten, Schenk, John, & Gao, 2008;Wang et al., 2009). ...
The South Tien Shan (STS) belt results from the last collision event in the western Central Asian Orogenic Belt (CAOB). Understanding its formation is of prime importance in the general framework of the CAOB. The Atbashi Range preserves high‐pressure rocks along the South Tien Shan suture but still, its global metamorphic evolution remains poorly constrained. Several HP units have been identified: (i) a high‐pressure tectonic mélange including boudins of mafic eclogites in a sedimentary matrix, (ii) a large (> 100 km long) high‐pressure Metasedimentary Unit (HPMU) and (iii) a lower blueschist facies accretionary prism. Raman Spectroscopy on Carbonaceous Material combined with phengite and chlorite multi‐equilibria and isochemical phase diagram modelling indicates that the HPMU recorded homogeneous P‐T conditions of 23‐25 kbar and 560‐570°C along the whole unit. 40Ar/39Ar dating on phengite from the HPMU ranges between 328 and 319 Ma at regional scale. These ages are interpreted as (re‐) crystallization ages of phengite during Tmax conditions at a pressure range of 25 to 20 kbar. Thermobarometry on samples from the high‐pressure tectonic mélange provides similar metamorphic peak conditions. Thermobarometry on the blueschist to lower greenschist facies accretionary prism indicates that it underwent P‐T conditions of 5‐6 kbar and 290‐340°C, highlighting a 17‐20 kbar pressure gap between the HPMU‐tectonic mélange units and the accretionary prism. Comparison with available geochronological data suggests a very short time span between the prograde path (340 Ma), HP metamorphic peak (330 Ma), the Tmax (328‐319 Ma) and the final exhumation of the HPMU (303‐295 Ma). Extrusion of the HPMU, accommodated by a basal thrust and an upper detachment, was driven by buoyant forces from 70‐75 km up to 60 km depth, which directly followed continental subduction and detachment of the HPMU. At crustal depths, extrusion was controlled by collisional tectonics up to shallow levels. Lithological homogeneity of the HPMU and its continental‐derived character from the North Tien Shan suggest this unit corresponds to the hyper‐extended continental margin of the Kazakh continent, subducted southward below the north continental active margin of the Tarim craton. Integration of the available geological data allows us to propose a general geodynamic scenario for Tien Shan during the Carboniferous with a combination of (1) N‐dipping subduction below the Kazakh margin of Middle Tien Shan until 390‐340 Ma, and (2) S‐dipping subduction of remaining Turkestan marginal basins between 340 and 320 Ma. This article is protected by copyright. All rights reserved.
... It is represented by an assemblage of several metamorphic units and ophiolites (Alekseev et al., 2007;Biske, 1996a;Biske et al., 1985;Loury et al., 2015b). Recent studies on this suture evidenced a top-to-the-North thrust stack ( Fig. 1) with from bottom to top: (1) a low-grade unmetamorphosed ophiolite thrusted by (2) eclogite-facies micaschists and oceanic units (500-660°C and 20-25 kbar, Hegner et al., 2010;Loury et al., 2015a;Simonov et al., 2008;Tagiri et al., 1995), and (3) a greenschist to blueschist facies accretionary prism (Biske, 1996b;Burtman, 2008;Karpovitch et al., 1964;Loury et al., 2015a). ...
... However, there are two opposite interpretations regarding the age of that thrust. Some authors (Alekseev et al., 2007;Biske, 1996b;Burtman, 2008;Chen et al., 1999;Gao et al., 2009;Liu et al., 2014;Xiao et al., 2013) consider that the Tarim was underthrusted beneath the Tien Shan (NTS-MTS) during the Late Carboniferous and that the whole structure was back-thrusted towards the North afterwards. Other authors (Charvet et al., 2007;Choulet et al., 2011;Loury et al., 2015b;Wang et al., 2011) rather propose that the MTS was underthrusted beneath the Tarim during the Late Paleozoic and that the underthrusting of the Tarim beneath the Tien Shan highlighted by the seismic profile would be of Cenozoic age and not related to the Paleozoic deformation. ...
In the Tien Shan belt, Cenozoic to active deformation is guided by structures and rheological contrasts partly inherited from the Paleozoic Variscan orogeny and reactivated by the India-Asia collision. Cenozoic deformation net estimates are constrained by lithospheric scale geological cross-sections, which rely on reconstructions of the Paleozoic Central Asian Orogenic Belt (CAOB). However, several geodynamic scenarii have been proposed for its formation including a south or a north dipping subduction, which are still debated due to lack of constraints. Here, we designed numerical experiments to test different hypotheses about the initial geometry and the effective rheology of the paleo-sutures and especially the one located between the Tien Shan and the Tarim basin, where most Cenozoic deformation localizes. The different geometries of Paleozoic structures are used as input variables in the thermo-mechanical models, which are then run forward in time. After a finite amount of shortening, the structures that develop self-consistently out of the proposed heterogeneities are then compared to the current Cenozoic finite and active deformations. We find that a crustal south-dipping suture zone lying on a resistant lithospheric mantle best explains the localization of the deformation, the current geometry of the structures and the Moho depth variations. Using the model results, we propose a mechanically consistent depth-interpolated crustal cross-section of the Kyrgyz Tien Shan, which incorporates both geological and geophysical data.
... The South Tianshan is a late Paleozoic accretionary and collisional thrust-and-fold belt [23]. The belt consists mainly of middle to late Paleozoic shallowand deep-marine sedimentary rocks, fragments of ophiolites, and metamorphic rocks [24]. Late Paleozoic postcollisional plutons occur within the South Tianshan [19,[25][26][27]. ...
The Ortosuu and Uchkuduk regions of the Tianshan orogen contain a volumetrically small series of basaltic rocks erupted primarily during the late Mesozoic-Paleogene. Petrology, chemical composition, and P-T geotherm data from xenoliths within the basalts characterize the nature of the lithospheric mantle beneath this orogenic belt. Two groups of clinopyroxene can be identified from the studied xenoliths based on their Mg# and trace element patterns. Group 1, primitive clinopyroxenes, has lower Mg# (86–90) and LREE-depleted patterns than group 2, depleted clinopyroxenes, which are characterized by a relatively high Mg#, 91–92, and LREE-enriched patterns. The REE distribution in group 1 clinopyroxenes suggests that they were controlled by partial melting, whereas group 2 clinopyroxenes are far more complex involving partial melting degrees of 6–11%, and later metasomatism by carbonatite and/or silicate melts. Coupled P-T estimations from geothermobarometry indicate that the more fertile group 1 xenoliths were probably derived from the uppermost mantle, and the more depleted group 2 xenoliths were likely derived from a depth close to the crust mantle boundary.
... The relatively simple structure of Kyrgyz Tien Shan today is generally attributed to the large role of structural inheritance Macaulay et al., 2014). Yet, the structures' original orientation is largely debated (Biske, 1995;Charvet et al., 2011;Gao, Li, Xiao, Tang, & He, 1998;Windley, Alexeiev, Xiao, Kr€ oner, & Badarch, 2007). Jourdon, Le Pourhiet, et al. (2017) In pTatin2d, like in many thermo-mechanical codes, the sedimentation and erosion is approximated by Culling's (1965) law: Comp. ...
Evolving mountain belts dynamics is very sensitive to surface processes. They affect tectonics by enhancing crust exhumation and thermal weakening, and depositing soft yet cold sediments in surrounding basins. While 2D plane strain models approximate cylindrical tectonic structures well, simple 1D mass transfer cannot capture erosion‐sedimentation complexity. The Eastern Kyrgyz Tien Shan where structures, basins and exhumation rates are well constrained is used here to illustrate this issue. Thermo‐mechanical models demonstrate that 1D transport cannot adjust both basin geometry and AFT exhumation ages. When out‐of‐plane sediment transfer is considered, the amount of evacuated sediment delays or accelerates the formation of new faults, affecting the relative timing of exhumation. For our case study, lateral drainage must evacuate 80% of the sediments to match the geological constraints, which is consistent with other source to sink analyses. This indicates that lateral drainage should not be neglected in regional 2D models.
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... Ocean (Biske, 1995;Hegner et al., 2010;Jourdon et al., 2017a;Loury et al., 2016Loury et al., , 2015. The orientation of the subduction is still a matter of debate: structural evidences along the STS suture, underlined by high-pressure low-temperature units, suggest that the subduction of the Turkestan ...
The Permian history of the Central Asian Orogenic belt is marked by large-scale strike-slip faults that reactivate former Paleozoic structures, delineated by widespread alkaline magmatism. The genetic link between the syn-kinematic granitoids emplaced in the Tien Shan range and magmas emplaced within the Tarim Large Igneous Province, and the interaction between this plume and transcurrent tectonics, are still unsolved issues. We investigated the Pobeda massif, in the eastern Kyrgyz Tien Shan, located at the boundary between the Tien Shan range and the Tarim Craton, which exhibits a high-temperature unit. In this unit, Permian magmatism resulted in the emplacement of alkaline charnockites at mid-crustal levels. The primary mineralogical assemblage is nominally anhydrous and made of ortho- and clino-pyroxenes, fayalite, K-feldspar, plagioclase and quartz. These charnockites are associated with partially-molten paragneisses and marbles. Thermobarometry on these rocks indicates that the charnockites emplaced following the intrusion of a melt at a temperature > 1000 °C and pressure of around 6 kbar, corresponding to depth of ~20 km. The resulting thermal anomaly triggered the partial melting of paragneisses. Bulk geochemistry including Sr, Nd, Pb and Hf isotopes suggests that charnockites fit into the Tarim Large Igneous Province magmatic series, with minor crustal assimilation. U-Pb ages on zircons of charnockites and surrounding paragneisses indicate that charnockites intruded and triggered partial melting of the gneisses at c. 287, 275 and 265 Ma. ⁴⁰Ar/³⁹Ar dating on amphibole gives a similar age as the U-Pb age at 276.2 ± 2.0 Ma. ⁴⁰Ar/³⁹Ar dating on biotite from the Charnockite unit marbles gives ages at ca. 256–265 Ma, which shows that exhumation onset directly follows the HT history, and is tentatively correlated to top-to-the-North thrusting of the Charnockite unit in a transpressive context. Additional ⁴⁰Ar/³⁹Ar dating on syn-kinematic white micas from an adjacent transpressive shear-zone indicates continuation of the strike-slip tectonics at shallow crustal levels, after the exhumation of the Charnockite unit, at 248–257 Ma. These results demonstrate that Tien Shan Permian magmatism is linked to the Tarim mantle plume activity. Lithosphere-scale shear zones in the Tien Shan range, could have been responsible for lateral flow focusing of the Tarim mantle plume up to the boundary with the Tien Shan range and subsequent decompression melting resulting in the Permian magmatism observed in the Pobeda area.
... Ages for (U)HP, eclogite-bearing complexes in the Kokshaal STS (along the Turkestan suture) are generally interpreted to reflect early stages of collision. Sedimentologic collisional-timing constraints for the formation of the Turkestan suture include thick upper Carboniferous-lower Permian (Bashkirian-Asselian) foredeep turbidites and molasses [Biske, 1995[Biske, , 1996Biske and Seltmann, 2010], which span the collisional timeframe. It is uncertain and contentious whether or not the westward younging trend of the closure of the Turkestan ocean can be meaningfully extrapolated farther west into the Alai-Gissar-Kyzylkum South Tian Shan. ...
The amalgamation of the Central Asian Orogenic Belt in the southwestern Tian Shan in Tajikistan is represented by tectono-magmatic-metamorphic processes that accompanied late Paleozoic ocean closure and collision between the Karakum–Tarim and Kazakh–Kyrgyz terranes. Integrated U-Pb geochronology, thermobarometry, pseudosection modelling, and Hf geochemistry constrain the timing and petro-tectonic nature of these processes. The Gissar batholith and the Garm massif represent an eastward, along-strike increase in paleodepth from upper-batholith (~21–7 km) to arc-root (~36–19 km) levels of the Andean–syn-collisional Gissar arc, which developed from ~323–288 Ma in two stages: (i) Andean, I-type granitoid magmatism from ~323–306 Ma due to northward subduction of the Gissar back-arc ocean basin under the Gissar microcontinent, which was immediately followed by: (ii) syn-collisional, I–S-type granitoid magmatism in the Gissar batholith and the Garm massif from ~304–288 Ma due to northward subduction/underthrusting of Karakum marginal-continental crust under the Gissar microcontinent. A rapid isotopic pull-up from ~288–286 Ma signals the onset of juvenile, alkaline-syenitic, post-collisional magmatism by ~280 Ma, which was driven by delamination of the Gissar arclogite root and consequent convective asthenospheric upwelling. Whereas M–HT/LP prograde metamorphism in the Garm massif (650–750 °C / 6–7 kbar) from ~310–288 Ma was associated with subduction-magma inundation and crustal thickening, HT/LP heating and decompression to peak-metamorphic temperatures (~800–820 °C / 6–4 kbar) at ~288 ± 6 Ma was driven by the transmission of a post-collisional, mantle-derived heat wave through the Garm-massif crust.
Fluvial drainage patterns in orogenic belts reflect the interaction between tectonics, climate, and lithology. The central South Tian Shan displays a complex fluvial drainage pattern that shifts from longitudinal (flowing parallel to mountain ranges) in the west to transverse (flowing across ranges) in the east. Whether such drainage patterns reflect underlying patterns of tectonic deformation, lithology, climatic changes, or the influence of surface processes within a drainage basin is often unclear. We focus here on the anomalously large Saryjaz catchment of SE Kyrgyzstan, which marks the transition between longitudinal and transverse drainage. We analyse topographic and fluvial metrics including slope, river steepness (ksn) and the integral proxy χ along the river profile, and map the spatial distribution and characteristics of knickpoints to discern the possible controls on the observed drainage pattern. We discriminate between knickpoints of different origin: tectonic, lithologic, glacial, and those linked to transient waves of incision. We find a series of transient knickpoints in tributaries downstream of a sharp 180ᵒ bend in the main stem of the Saryjaz River, which also marks a striking increase in channel steepness. Both observations indicate accelerated incision along this lower reach of the catchment. Knickpoint elevations decrease downstream, whereas incision depth, χ values of knickpoints (measured from the tributary junctions) and ksn values and ratios are constant among tributaries. These results suggest that incision is driven “top-down” by a large-magnitude river-capture event rather than “bottom-up” by base-level fall. We estimate an erodibility parameter from 10Be derived catchment-average denudation rates and use this to estimate the celerity of knickpoints. We find that the knickpoints started retreating at a similar time, between ca. 1.5 and 4.4 Myr ago. Considering the river patterns and the timing constraints, we suggest that this capture event was likely driven by the overfill of Neogene intermontane basins, potentially affected by both tectonic and climate factors.
Palaeomagnetic constraints on the Phanerozoic evolution of Australia's North West Shelf Indicate successive dispersions of continental fragments. Such dispersions are characteristic for the evolution of the northeastem margin of Gondwana. Palaeomagnetic constraints are reviewed, therefore, within a wide spatial setting. A mainly graphic overview Is presented of relevant Phanerozoic palaeomagnetic data, with discussion of their implications on northeast Gondwana's dispersive and Laurasia's accretionary evolution. Regions covered are Australia and India as the main dispersive cratons of
northeast Gondwana, the Siberian Platform as the main accretionary craton, and continental fragments and terranes of established or presumed Gondwanan origin that are now accreted to the Siberian cratonic nucleus or to the North American craton, amongst others the Cathaysian continents, northeast Russian terranes east of the Verkhoyansk Mountains, and terranes In the North American Cordillera.
The Australian Phanerozoic APWP Is discussed In detail with emphasis on two widely different propositions for the Late Palaeozoic trajectory and their implications for Gondwana-Laurasia Interaction at the time of the Variscan Orogeny. Loops and cusps on the Australian and Indian APWPs are identified for further analysis of potential relationships with fundamental tectonic events.
Palaeolatitude plots are presented for continental blocks and terranes of probable Gondwanan origin that are now situated east of the Urals and south of the Central Asian Fold Belt, in the eastem and northem periphery of the Siberian craton, and within the North American Cordillera. The plots indicate, amongst others, four northward movement phases of potential global tectonic relevance, namely in the Early Devonian (Kazakhstan), in the latest Devonian-middle Carboniferous (northeast Gondwana), in the middle to Late Permian (northeast Gondwana), and in the Triassic (Cathaysian continents, northeast
Gondwana, Gondwanan fragments In Southeast AsIa and the North American Cordillera).
Palaeomagnetic reconstructions of the Palaeozoic configuration of northeast Gondwana have concentrated on relationships of the Cathaysian continents and Australia. Fitting of 'spline' approximations of Cambro-Ordoviclan to Late Devonian APWP trajectories for the North China block and Australia result in an unique lock of North China off northwestem Australia and westem Irian Jaya, in very good agreement with a recently proposed reconstruction based on biostratigraphic and lithostratigraphic evidence (Metcalfe and Nicoll,1994). Comparison of individual pole positions of mainly Devonian age for other Cathyaslan blocks - i.e. South China, Indochina and Tarim - with Australia show
reconstructions that are also in good agreement with the Metcalf and Nicoll model. Comparison of Early Devonian palaeomagnetic data for the Alexander terrane of the North American Cordillera and Australia allows relocation of the Alexander terrane off southeastem Australia, in good agreement with lithostratigraphic arguments for such a former relationship.
Finally, the identified loops and cusps on the Australian and Indian APWPs are tentatively correlated with and interpreted in terms of significant events in the Phanerozoic evolution of the North West Shelf and, to a lesser extent, eastem Australia.
Existing theories on the geologic structure of Khan Tengri, a massif that is extremely difficult to reach and has the largest glaciers (North and South Inyl'chek) and highest peaks in the Tien Shan, are based on data obtained in the middle of the 1930's. In recent reviews on the geology of the area, it was shown that carbonate rocks and shales of Late Silurian-Early Devonian age are exposed on the upper reaches of the Inyl'chek River. The Khan Tengri massif has a nappe structure the main component of its northern part being a large antiform that extends along sides of the North and the South Inyl'chek Glaciers. The core of this antiform exposes a sequence as thick as 1000 m, composed of rhythmically alternating, dark polymict sandstones with graded bedding and black calcareous siltstones and mudstones.
Stepwise thermal and A.F. demagnetizations have been carried out on 518 samples (47 sites) from the Sishichang section across the Akesu area, in the Tarim Basin. The results lead to a discussion on some problems concerning the tectonic history of the Tarim platform and adjacent blocks during the Late Paleozoic. From the Late Carboniferous until the Early Permian the Tarim platform collided with the Kazakhstan block, Siberian platform and Russian platform; no large displacements have occurred between these blocks since the Mesozoic. However, the Permian pole position of the Tarim platform obviously differs from that for the Sino-Korea platform. The difference in paleolatitude between the Tarim and Sino-Korea platforms in the Permian was about 10°. Their orientations were also different. The paleomagnetic result is in contrast to the geologically accepted idea that the two platforms in question occur as a whole in the Late Paleozoic.
Eclogite-bearing metamorphic formations as guides to junction zones of ancient continents
- A B Bakirov
- V V Kotov
Bakirov, A. B., and V. V. Kotov, Eclogite-bearing metamorphic formations as guides to junction zones of ancient
continents, in The Precambrian and Lower Paleozoic of
the Tien Shan Mountains, pp. 4 { 24, Ilim, Frunze, 1988.
On the origin of the Devonian contrasted volcanic series in the Atbashi-Kokshaal 34 biske: late paleozoic collision region
- Yu S Biske
- E V Tabuns
Biske, Yu. S., and E. V. Tabuns, On the origin of the Devonian contrasted volcanic series in the Atbashi-Kokshaal
34
biske: late paleozoic collision
region, South Tien Shan Mountains, Dokl. Acad. Sci.
USSR, 320(6), 1428 { 1432, 1991.
Hercynides of the Atbashi-Kokshaal R egion
- Yu S Biske
- S E Zubtsov
- G S Porshnyakov
Biske, Yu. S., S. E. Zubtsov, and G. S. Porshnyakov, Hercynides of the Atbashi-Kokshaal R egion, South Tien Shan
Mountains, 189 pp., Izd. Leningrad. un-ta, Leningrad,
1985.
Structural Evolution of Paleozoic Fold Systems
- V S Burtman
Burtman, V. S., Structural Evolution of Paleozoic Fold Systems, 162 pp., Nauka, Moscow, 1976.
Bel'govskiy, Major features of the Paleozoic structure of the eastern South Tien Shan Mountains
- L A Ektova
Ektova, L. A., and G. L. Bel'govskiy, Major features of the
Paleozoic structure of the eastern South Tien Shan Mountains, Geotectonics, Engl. Transl., no. 6, 62 { 71, 1980.