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Cenozoic uplift in the Tianshan played an important role in driving Proto‐Paratethys Sea retreat and Asian aridification. However, most paleoclimate studies have focused on the Pamir‐Tianshan corridor, and frequently overlook the role of the entire Tianshan range in modifying the Central Asian climate during Cenozoic uplift. When and how Cenozoic deformation of Tianshan was initiated and propagated are intensively debated which makes its role in contributing to climate change in Central Asia more ambiguous. To address this issue, this study presents new detrital zircon U‐Pb and detrital apatite U‐Pb and fission track age data from Cenozoic sedimentary successions (54–0 Ma) in the northern margin of the Tarim Basin and integrates these data with published provenance data from adjacent regions. Our results show that deformation/uplift of the Baicheng‐Kuqa Depression and the South Tianshan occurred at ∼41–37 Ma and ∼24 Ma, when topographic growth of South Tianshan began to block the flow of sediment from the north. Continued uplift of the South Tianshan completely blocked fluvial transport from the Central Tianshan‐Yili Block by ∼10 Ma, as shown by the paucity of 380–310 Ma detrital zircons/apatites. Far‐field, north‐directed compressive stress resulting from the India‐Asia collision began to propagate toward the South Tianshan and its foreland during the Late Eocene, and continued to propagate into the South Tianshan and northward at the ∼24 Ma and 10 Ma. Finally, we suggest a two‐stage of aridification in the Tarim Basin which can be linked to two stages (∼24 and 10 Ma) of growth of the Tianshan. Plain Language Summary: The Tarim Basin and the Taklimakan Desert are located in Central Asia, between the Tibetan Plateau to the south and the Tianshan orogenic belt to the north. This region is a crucial area for exploring the primary drivers of Cenozoic desertification. We performed a systematic zircon and apatite provenance study (including detrital apatite and zircon U‐Pb dating, and detrital apatite fission track analysis) in Cenozoic strata from the northern margin of the Tarim Basin. Our results reveal pulsed deformation of the South Tianshan that initiated at ∼41–37 Ma with two subsequent pulses at ∼24 Ma and ∼10 Ma, the timing of which suggests a close link to the two‐step aridification (∼24 and 10 Ma) of the Tarim Basin. We suggest that the pulsed Cenozoic rise and growth of the South Tianshan played a crucial role in blocking westerly winds, restricting moisture from reaching the Tarim Basin, and driving Cenozoic aridification of the Tarim Basin. Key Points: Initiation of the Cenozoic uplift of the South Tianshan occurred in the Late EoceneFurther uplift of the South Tianshan completely blocked fluvial transport from the north by ∼10 MaPulsed growth of Tianshan play a dominant role in the two‐step aridification of the Tarim Basin [ABSTRACT FROM AUTHOR]

The Bengal Basin is a well‐known foreland basin that archives the tectonic evolution of the Himalayan and Indo‐Burman Ranges (IBR). The Dupi Tila Formation is the youngest among the stratigraphic successions of the Bengal Basin, which witnessed the last phase of the Himalayan uplift. However, there is still controversy regarding sediment provenances since the Himalayan and IBR are in the late Neogene exhumation stage. In this study, the petrographical and geochemical compositions of the Dupi Tila sandstones from the Lalmai Anticline of the Bengal Basin are examined to infer the source rocks, tectonic settings, palaeoclimate and weathering intensity in provenance areas. The detrital modes and geochemical discriminations, as well as Chondrite‐normalized rare earth elements patterns with enrichment in light rare earth elements and nearly flat heavy rare earth elements and negative Eu anomalies (average Eu/Eu* = 0.77) indicate dominantly felsic source rocks. The geochemical data also suggest that these source rocks in provenance areas were influenced by weak to moderate chemical weathering (chemical index of alteration: 65.64–75.62) and multiple recycling under warm and humid to semi‐humid climatic conditions. The detrital zircon ages show three dominant peaks at ca. 100, 500 and 1000 Ma with minor 1700 Ma. The amount of young zircon grains (<120 Ma) is noticeably higher (~18%) in this Lalmai outcrop compared to the Dupi Tila samples from the Sylhet Trough and Chittagong‐Tripura Fold Belt. Results from integrated zircon geochronology and geochemistry indicate that the detritus are likely derived from a recycled orogen provenance related mainly to active continental margin setting with subordinate influence from passive setting. Therefore, the regionally extensive Himalayan Orogen appears to be the primary sediment source, with additional mixing from the IBR and recycled sediments originating from the Gangdese batholith of the Trans‐Himalaya. [ABSTRACT FROM AUTHOR]

A dominantly NW-SE directed extensional tectonics in the Early Cretaceous significantly reworked the Late Permian-Triassic orogenic framework of the Dabie orogenic belt. The North Dabie complex (NDC) is the principal domain recording this tectonic event. However, the precise structure-kinematic architectures, particularly those observed in the ductile regime, along with the respective time scales for different extensional stages, have not been adequately established. This significantly impedes our comprehensive understanding of the extensional style and deformation history in the North Dabie complex. To better address these issues, we conducted a systematic structural study and LA-ICP-MS zircon U-Pb dating of the pre-, syn-, and post-kinematic intrusions and syn-kinematically metamorphosed high-grade gneisses/migmatites of the NDC. Our results demonstrate that the extensional deformation in the NDC may initiate at ca. 144 Ma, which is characterized by a pervasive NW-SE oriented coaxial plastic flow in the ductile regime of the middle-lower crust. A large-scale detachment processing zone subsequently started activating at ca. 140 Ma at the upper-middle level of the middle crust, and concentratedly accommodated the extensional strain by top-to-NW ductile shearing. Locally, there was uprising of sub-magmatic flow in the atatexite-diatexite from the deeper lower crust taking place in the manner of top-to-outward shearing as early as ca. 137 Ma. This composite process of extension manifests vertical strain partitioning across the ductile middle-lower crusts and progressive strain localization during the lithospheric thinning. The NW-SE orientation dominated extensional tectonics was strongly driven by the westward subduction of the Paleo-Pacific oceanic plate during the Late Mesozoic. [ABSTRACT FROM AUTHOR]

The Almogholagh Intrusive Complex (AIC) in the central part of the Sanandaj-Sirjan zone (C-SaSZ) includes gabbros to granites. Zircon U-Pb dating of mafic, intermediate, and felsic intrusions yield age of 146 to 141 Ma (Late Jurassic-Early Cretaceous). Bulk chemistry shows a wide range for SiO2 (46.8 to 73.3 wt.%), MgO (0.08 to 8.95 wt.%), and Fe2O3(T) (0.47 to 9.25 wt.%) and also alkali elements ranging from 3.59 to 10.12 wt.%. These rocks are characterized by a high content of large-ion lithophile elements (LILEs; e.g. Rb, U, Th, and K) and LREEs with weak Nb and Ta negative anomalies, showing many similarities to an extensional setting. The 176Hf/177Hf ratios vary from 0.282802 to 0.282985 with positive εHf(t) values from + 1.67 to +10.74 (avg: 7.85). Trace-element and isotope ratios modelling indicate that the AIC mafic-intermediate rocks were generated by partial melting of spinel lherzolite and then underwent considerable crustal contamination. The present work in combination with previous data confirm an extensional tectonic regime for the northern part of the C-SaSZ during the Late Jurassic to Early Cretaceous. Magmatic differentiation with crustal contamination played a fundamental role in the wide compositional range from mafic to felsic types that formed the AIC. [ABSTRACT FROM AUTHOR]

The Altaids is generally considered to be the largest Phanerozoic accretionary orogen on Earth, but it is unclear whether it was associated with extensive continental crustal growth and whether there is a link between the crustal growth and ore mineralization. This paper reviews whole-rock Nd and zircon Hf isotope data for felsic–intermediate–mafic igneous rocks in the Altaids and presents Nd + Hf isotopic contour maps for this region. The maps highlight the 3D lithospheric compositional architecture of the Altaids and make it possible to quantitatively evaluate the crustal growth and its relationship with ore deposits. The Altaids hosts ∼4 107 350 km2 and ∼184 830 750 km3 (assuming a crustal thickness of 40–50 km) juvenile crust (ϵ Nd(t) > 0), accounting for 58% by isotope-mapped area (∼7 010 375 km2) of almost all outcrops of the Altaids (∼8 745 000 km2) and formed during 1000–150 Ma (mainly 600–150 Ma). The juvenile crustal, slightly juvenile-reworked crustal and slightly reworked crustal provinces controlled the Cu–Au, the Pb–Zn–Ag and the Li–Be, Nb–Ta and W–Sn ore deposits. According to the crustal architecture and background of deep compositions, we propose that the ore deposits can be grouped into three types: juvenile crust-related, mixed-source (or slightly juvenile crust)-related and reworked crust-related. This highlights the close relationship between accretion, continental growth and mineralization, and will facilitate exploration for specific ore-deposit types in the Altaids. [ABSTRACT FROM AUTHOR]

Zircon U-Pb-Hf isotopes, integrated with bulk-rock major, trace element, and isotopic compositions of amphibolites from the Makran ophiolitic mélange complex (OMC), carry implications on the evolution of the Neo-Tethys Ocean. Field and petrographical-geochemical data confirm these amphibolites as products of the metamorphism of a mafic protolith. Zircons from the amphibolites have U-Pb ages of Late Early Permian (273 Ma) to Late Triassic (210 Ma), and their εHf(t) values vary from +6.32 to +15.4. The Makran amphibolites are geochemically similar to transitional- or enriched-MORBs. The 143Nd/144Nd(t) ratios for amphibolites range from 0.51260 to 0.512551, and 87Sr/86Sr(t) from 0.704433 to 0.706244. The Pb-isotope composition of these rocks is radiogenic, ranging from 15.61-15.64 for 207Pb/204Pb(t), 18.98-19.21 for 206Pb/204Pb(t) and 38.88-39.36 for 208Pb/204Pb(t). The isotopic and geochemical signatures of these rocks suggest that they were most likely formed during continental rifting and originated from a relatively enriched mantle source. This is also attested by their high zircon Ce/Ce* ratios. We interpret these amphibolites related to the Permian-Triassic plumes that triggered Gondwana rifting to open the Neo-Tethyan Ocean before metamorphosed, fragmented, and accreted into the Makran accretionary complex probably during Early to Late Cretaceous time. [ABSTRACT FROM AUTHOR]

As one of the widest terranes exposed in icy Antarctica, the Larsemann Hills in the Prydz Bay belt preserves diverse rock types with a complex metamorphic history and thus is critical to the tectono-metamorphic evolution of East Antarctica. Garnet-sillimanite-spinel-cordierite–bearing and garnet-orthopyroxene–bearing granulites are typical rocks in the region. Phase equilibrium modelling and mineral thermometry based on detailed petrological and mineralogical analyses indicate that the granulites underwent extreme metamorphism with peak conditions to ultrahigh temperatures (UHTs). The high-UHT metamorphism is characterised by extremely high dT/dP values (>1000°C/GPa) along a clockwise path with evident decompression at high temperatures and subsequent near isobaric cooling. Textural relationships, in situ NanoSIMS zircon U–Pb analysis, and LA-ICP-MS zircon and monazite dating and trace element analysis indicate protracted tectono-thermal evolution from the latest Neoproterozoic to early Palaeozoic (c. 570–500 Ma), with a prograde stage likely from c. 570 to c. 550 Ma, a peak stage from c. 550 to c. 540 Ma, and a retrograde stage from c. 540 to c. 500 Ma. During the retrograde stage, major decompression should have occurred before c. 530 Ma, as indicated by the age of zircon included in spinel, and then near isobaric cooling followed and persisted from c. 530 to c. 500 Ma. The geochronological data contribute to the establishment of the thermal–temporal framework of the late Neoproterozoic to early Palaeozoic Prydz tectonic event. The results also indicate that the assemblage of the investigated granulites basically resulted from the late Neoproterozoic to the early Palaeozoic tectono-thermal event, and the high-UHT conditions revealed by the granulites in the Larsemann Hills imply a much wider distribution of high heat flow and potential UHT metamorphism in the Prydz Bay region. Both the Larsemann Hills and the Rauer Group may have been in a similar and interrelated tectono-thermal setting from the late Neoproterozoic to the early Palaeozoic during the assembly of the Gondwana supercontinent. [ABSTRACT FROM AUTHOR]

The Early Cretaceous palaeogeography prior to the India‐Asia collision is still controversial. There are two end‐member models – an integrated passive margin versus an archipelago. Here, we report zircon U–Pb ages, Hf, and whole‐rock Nd isotopes of newly defined Cretaceous mica schists from the Main Central Thrust to constrain the Early Cretaceous palaeogeography of the Himalaya. The mica schists have Early Cretaceous zircons with εHf(t) values of −21.1 to −9.2. The mica schists are characterized by TDMC values of 1.8–2.5 Ga and whole‐rock εNd(0) value of −24.0. These features imply that these zircons generated from partial melting of lower crust as a result of an extension in some older continental crust, which were transported and deposted to form the protolith of the Cretaceous mica schists. Age pattern comparisons indicate that the age populations of the Cretaceous mica schists are significantly distinct from those of other Cretaceous strata in the Himalaya. It is obvious that the protolith of the Cretaceous mica schists were formed in an independent terrane (Arun) in the Neo‐Tethys with significant tectonic separations proventing any inputs from the Tibetan Himalaya, Greater Himalaya, or Indian Craton since 120 Ma. Combined with published U–Pb ages and other geological data, our data supports the archipelago palaeogeography with rifted terranes in the Neo‐Tethys Ocean, shedding light on the multiple amalgamation events along the India‐Asia collision zone. [ABSTRACT FROM AUTHOR]

The temporal–spatial framework of arc amalgamation is an important key for understanding the anatomy of orogenic collages, present and past. The Junggar‐Balkhash Ocean was a major branch of the southern Paleo‐Asian Ocean where several arcs were amalgamated. Among them, the Dananhu arc with its characteristic juvenile magmatism and lack of Precambrian basement is an efficient recorder of the evolutional history. From our U–Pb and Lu–Hf isotopic analyses of Devonian to Triassic sediments in the Dananhu arc and Permian sediments in the Yamansu‐Central Tianshan arc, we discovered two major changes in detrital zircon provenance of the Dananhu arc: (a) An increasing input of Precambrian ages from the Mongolia collage at 850, 1,850, and 2,500 Ma, together with Phanerozoic zircons ranging from 420 to 480 Ma with negative εHf(t) value since ca. 288 Ma; (b) the presence of the Yamansu‐Central Tianshan arclike Precambrian age cluster of 1,400–1,600 Ma around 243 Ma. In combination with regional tectonothermal events, these two changes correspond to the formation of the Harlik‐Dananhu composite arc in the latest Carboniferous–early Permian followed by its collision with the Yamansu‐Central Tianshan arc in the latest Permian–early Triassic, which marks the termination of the eastern Junggar‐Balkash Ocean. Analysis of the sedimentary successions within the intraoceanic arcs sheds light on the amalgamation history of the Central Asian Orogenic Belt. [ABSTRACT FROM AUTHOR]

The eastern Heilongjiang Province, NE China, is located in the eastern CAOB (Central Asian Orogenic Belt). Previous studies suggest that subduction of the Mudanjiang and Paleo‐Pacific oceans had been initiated in this area during the early Mesozoic. However, research on the Mesozoic volcanic rocks is insufficient, limiting our understanding of the relationship between magmatism and subduction process. To solve the problem, seven volcanic rocks in the Lesser Xing'an‐Zhangguangcai Range and the Jiamusi Block were collected for zircon U–Pb dating (SHRIMP) and whole‐rock geochemical analysis. Most samples from the Lesser Xing'an‐Zhangguangcai Range are Jurassic in age (189–178 Ma), including andesite, trachyandesite, trachydacite, and rhyolite. The andesitic to trachytic rocks were generated by magma mixing at an active continental margin, whereas the rhyolite is highly fractionated I‐type. All the samples from the Jiamusi Block and one basaltic andesite from the Lesser Xing'an Range are late Early Cretaceous in age (ca. 100 Ma) and were formed in a back‐arc extensional setting (roll‐back). Fractional crystallization was important in the generation of most Cretaceous rocks (basalt to trachydacite). However, magma mixing or crustal contamination was required to explain some andesites from the Jiamusi Block showing extremely low Cr, Ni, and Mg#. When integrated with the coeval blueschist‐facies metamorphism, the Early Jurassic volcanism indicates an active continental margin in the Lesser Xing'an‐Zhangguangcai Range due to the westward subduction of the Mudanjiang Ocean. After the closure of the Mudanjiang Ocean, two NE/NNE trending sinistral strike‐slip faults in NE China were triggered, accompanied by the slab roll‐back of the Paleo‐Pacific oceanic plate. The Jurassic continental arc and accretionary complexes in NE China were cut through by the two strike‐slip faults and bended to form small oroclines. At ca. 100 Ma, numerous accretionary complexes were accreted along the eastern margin of the CAOB, further forcing the retreat of trench and slab roll‐back. The late Early Cretaceous intra‐continental volcanism was generated in the Lesser Xing'an‐Zhangguangcai Range and Jiamusi Block during this roll‐back process. [ABSTRACT FROM AUTHOR]

There is a broad consensus that the final closure of the Paleo‐Asian Ocean lead to the formation of the southern segment of the Central Asian Orogenic Belt. However, the final closure of the Paleo‐Asian Ocean remains controversial. To address this issue, a systematical study of geochemical and zircon U–Pb on the Kawabulak ophiolite in the southern Eastern Tianshan was carried out. The Kawabulak ophiolite is an accretionary prism that consists of different lithological tectonic slices and marks the suture zone that welded the Central Tianshan composite arc and the northern passive margin of the Tarim Craton. Zircon U–Pb data show that gabbro blocks of the Kawabulak ophiolite formed at 360.9 ± 3.3 Ma in the northern part and 326.0 ± 3.3 Ma in the southern part, respectively. The geochemistry features of basalts and gabbros show OIB‐type, arc/subduction‐related affinities, indicating different tectonic setting origins. A granitic gneiss with an arc‐related geochemical feature yielded a zircon U–Pb age of 477.2 Ma, indicating the earliest subduction event. The youngest deformed arc‐related granitic intrusion (295 Ma) in the Kawabulak prism indicates that the final closure timing of the Paleo‐Asian Ocean in Eastern Tianshan is after the Early Permian. The results of our study shed light to the temporal and spatial evolution of the southern Central Asian Orogenic Belt. [ABSTRACT FROM AUTHOR]

The Carboniferous tectonic history of the northern West Junggar of NW China is of key importance for understanding the tectonics of the Altaids. This paper presents a systematic study of the emplacement of the E'min ophiolite, the ages of turbidites, and a stitching granite dike in order to constrain the late Carboniferous oceanic evolution of northern West Junggar. Our field investigation reveals that the Tarbagatay subduction–accretion complex formed by imbrication of turbidites and ophiolitic slices in the Western Tarbagatay Mountain, which is considered as the forearc of the Saur arc in northern West Junggar. Field relationships and zircon geochronology suggest that the emplacement of the E'min ophiolite was later than the minimum time of deposition of hanging wall turbidites, which have a zircon age of 324 Ma, and must be earlier than the crystallization time of a 311‐Ma stitching granite dike that intruded the younger turbidites. The turbidites become younger from north to south, with minimum deposition ages varying from 324 to 309 Ma. The 311‐Ma dike has an adakitic affinity suggesting that it may have formed by magma melted from a subduction slab wedge and from accreted material at ~310 Ma. Therefore, we propose an accretionary arc setting for the Saur arc, with southward migration of the trench and magma front. The 311‐Ma dike has a high Al enrichment and arc‐related geochemical signature suggesting that it was generated by melting of accreted trench sediments. This may indicate that subduction of the Saur arc may have lasted to at least the late Carboniferous. The development of such arc accretion suggests that the formation of the southern Altaids was fundamentally similar to that of accretionary orogens in the western Pacific. [ABSTRACT FROM AUTHOR]

The Central Asian Orogenic Belt (CAOB) resulted from accretion during the Paleozoic subduction of the Paleo‐Asian Ocean. The Xilinhot area in Inner Mongolia is located in the northern subduction zone of the central‐eastern CAOB and outcropped a large number of late Paleozoic mafic intrusions. The characteristics of magma source and tectonic setting of the mafic intrusions and their response to the closure process of the Paleo‐Asian Ocean are still controversial. This study presents LA‐ICPMS zircon U‐Pb ages and geochemical features of mafic intrusions in the Xilinhot area to constrain the northward subduction of the Paleo‐Asian Ocean. The mafic intrusions consist of gabbro, hornblende gabbro, and diabase. Their intrusion times can be divided into three stages of 326–321 Ma, 276 Ma and 254 Ma by zircon U‐Pb ages. The first two stages of the 326–276 Ma intrusions mostly originated from subduction‐modified continental lithospheric mantle sources that underwent a variable degree partial melting (5–30%), recording the subduction of oceanic crust. The third stage of the 254 Ma mafic rocks also show arc‐related features. The primary magma compositions calculated by PRIMELT2 modeling on three samples of ∼326 Ma and two samples of ∼254 Ma show that these mafic samples are characterized by a variable range in SiO2 (47.51–51.47 wt%), Al2O3 (11.46–15.55 wt%), ΣFeO (8.27–9.61 wt%), MgO (13.01–15.18 wt%) and CaO (9.13–11.67 wt%), consisting with the features between enriched mantle and lower continental crust. The source mantle melting of mafic intrusions occurred under temperatures of 1302–1351°C and pressures of 0.92–1.30 GPa. The magmatic processes occurred near the crust‐mantle boundary at about 33–45 km underground. Combined with previous studies, it is concluded that Carboniferous to early Permian (∼326–275 Ma) northward subduction of the Paleo‐Asian oceanic crust led to the formation of the mafic magmatism in the Baolidao arc zone. The whole region had entered the collision environment at ∼254 Ma, but with subduction‐related environments locally. The final collision between the North China craton and the South Mongolian microcontinent may have lasted until ca. 230 Ma. [ABSTRACT FROM AUTHOR]

The Solonker suture zone has long been considered to mark the location of the final disappearance of the Paleo‐Asian Ocean in the eastern Central Asian Orogenic Belt (CAOB). However, the time of final suturing is still controversial with two main different proposals of late Permian to early Triassic, and late Devonian. This study reports integrated whole‐rock geochemistry and LA‐ICP‐MS zircon U‐Pb ages of sedimentary rocks from the Silurian Xuniwusu Formation, the Devonian Xilingol Complex and the Permian Zhesi Formation in the Hegenshan‐Xilinhot‐Linxi area in central Inner Mongolia, China. The depositional environment, provenance and tectonic setting of the Silurian‐Devonian and the Permian sediments are compared to constrain the tectonic evolution of the Solonker suture zone and its neighboring zones. The protoliths of the silty slates from the Xuniwusu Formation in the Baolidao zone belong to wacke and were derived from felsic igneous rocks with steady‐state weathering, poor sorting and compositional immaturity. The protoliths of metasedimentary rocks from the Xilingol Complex were wackes and litharenites and were sourced from predominantly felsic igneous rocks with variable weathering conditions and moderate sorting. The Xuniwusu Formation and Xilingol Complex samples both have two groups of detrital zircon that peak at ca. 0.9–1.0 Ga and ca. 420–440 Ma, with maximum deposition ages of late Silurian and middle Devonian age, respectively. Considering the ca. 484–383 Ma volcanic arc in the Baolidao zone, the Xuxiniwu Formation represents an oceanic trench sediment and is covered by the sedimentary rocks in the Xilingol Complex that represents a continental slope sediment in front of the arc. The middle Permian Zhesi Formation metasandstones were derived from predominantly felsic igneous rocks and are texturally immature with very low degrees of rounding and sorting, indicating short transport and rapid burial. The Zhesi Formation in the Hegenshan zone has a main zircon age peak of 302 Ma and a subordinate peak of 423 Ma and was deposited in a back‐arc basin with an early marine transgression during extension and a late marine regression during contraction. The formation also crops out locally in the Baolidao zone with a main zircon age peak of 467 Ma and a minor peak of 359 Ma, and suggests it formed as a marine transgression sedimentary sequence in a restricted extensional basin and followed by a marine regressive event. Two obvious zircon age peaks of 444 Ma and 280 Ma in the Solonker zone and 435 Ma and 274 Ma in Ondor Sum are retrieved from the Zhesi Formation. This suggests as a result of the gradual closure of the Paleo‐Asian Ocean a narrow ocean sedimentary environment with marine regressive sedimentary sequences occupied the Solonker and Ondor Sum zones during the middle Permian. A restricted ocean is suggested by the Permian strata in the Bainaimiao zone. Early Paleozoic subduction until ca. 381 Ma and renewed subduction during ca. 310–254 Ma accompanied by the opening and closure of a back‐arc basin during ca. 298–269 Ma occurred in the northern accretionary zone. In contrast, the southern accretionary zone documented early Paleozoic subduction until ca. 400 Ma and a renewed subduction during ca. 298–246 Ma. The final closure of the Paleo‐Asian ocean therefore lasted at least until the early Triassic and ended with the formation of the Solonker suture zone. [ABSTRACT FROM AUTHOR]

Voluminous granitoids are widely distributed in the Langshan region, northeast of the Alxa block, and record the evolutionary processes of the southern Central Asian Orogenic Belt. The Dabashan pluton was emplaced into the Paleoproterozoic Diebusige complex. Early Carboniferous zircon LA‐ICP MS U‐Pb ages were from 327 Ma to 346 Ma. The Dabashan pluton can be classified as monzogranite and syenogranite, and exhibits high K2O contents and K2O/Na2O ratios, which reveal a high‐K calc‐alkaline nature. The samples display strongly fractionated REE patterns, and are enriched in large ion lithophile elements (LILE) relative to high field strength elements (HFSE). The Dabashan plutons display unusually high Ba (823–2817 ppm) and Sr (166–520 ppm) contents and K/Rb ratios (315–627), but low Rb/Ba ratios (0.02–0.14), and exhibit fertile zircon Hf isotopic compositions [εHf(t)=–14 to –20], which are comparable to those of typical high Ba–Sr granitoids. Based on the geochemical compositions of the samples, we suggest that subducted sediments and ancient crustal materials both played important roles in their generation. Basaltic melts were derived from partial melting of subcontinental lithophile mantle metasomatized by subducted sediment‐related melts with residual garnet in the source, which caused partial melting of ancient lower crust. Magmas derived from underplating ascended and emplaced in the middle–upper crust at different depths. The resultant magmas experienced some degree of fractional crystallization during their ascent. Given these geochemical characteristics, together with regional tectonic, magmatic, and structure analysis data, an active continental margin environment is proposed for the generation of these rocks. [ABSTRACT FROM AUTHOR]

The Datong area is located in the western part of the Western Kunlun Orogen (WKO), occupying a key area of the Tethyan domain. Our new SHRIMP U–Pb zircon ages from the Datong area provide new information about the Palaeozoic evolution of the Western Kunlun Orogen. A 473.0 ± 2.8 Ma granite with 493.6 ± 4.8 Ma inherited zircons from the Kusilafu extrusive rocks is interpretation as an A‐type granite formed in a fore‐arc tectonic setting. The 485.5 ± 1.9 Ma granitoid of the Datongdong pluton combined with the 452.7 ± 7 Ma granitoid of the Datong pluton indicate that the Datong pluton is an intra‐oceanic arc complex formed by the southern subduction of the Proto‐Tethyan ocean crust. Zircons from gabbros of the Datong mafic–ultramafic complex have a 499.2 ± 2.1 Ma U–Pb crystallization age. Combined with its complicated whole‐rock geochemistry, we propose that there may have existed a Datong seamount in the early Palaeozoic. The detrital zircon results of Silurian–Devonian sandstones reveal that the Late Silurian sandstones have the characteristic zircons both from the Tarim Block and Datong Arc, suggesting that the Datong arc collided with the Tarim Block in the Late Silurian. The tectonic history of the WKO was characterized by a southern subduction of Proto‐Tethys terminated in the Late Silurian. [ABSTRACT FROM AUTHOR]

The Bengal Basin is located in the foreland of the eastern Himalaya and records late Palaeocene to Pleistocene sedimentation. This makes the Bengal Basin an ideal place to study the evolution of the eastern Himalaya by provenance researches. Even though there have been several studies about its provenance, a consensus has not been reached about when the Himalayan and Gangdese‐derived detritus started to deposit in the eastern Himalayan foreland. Here, we study the provenance of Eocene to Pleistocene sedimentary successions of the Bengal Basin by detrital zircon U–Pb geochronology and Hf isotope analyses. Detrital zircon U–Pb age spectra show a predominant peak of ~470–580 Ma in all the samples. A peak at this time is prominent in sediments of the Tethyan Himalaya and Lesser Himalaya, which means the detritus eroded from Himalaya may have been deposited in the Bengal Basin after the late Palaeocene‐early Eocene, synchronous with detritus derived from the western and central Himalaya. Gangdese‐derived zircons were firstly recorded in the late Eocene Kopili Formation, and they were sporadic from the late Eocene to middle Miocene, which was probably due to the long distance between the Bengal Basin and the Lhasa Block, to the forebulge in the Lesser Himalayan Sequence, or to a wide tectonic separation at that time. The first influx of abundant Gangdese‐derived zircons occurred in the lower part of the Boka Bil Formation in the late Miocene (~10 Ma), which was probably caused either by the Brahmaputra River capturing the Yarlung Tsangpo River or by a much later terminal collision between India and Eurasia, or both. [ABSTRACT FROM AUTHOR]

The anatomy of an ancient accretionary complex has a significance for a better understanding of the tectonic processes of accretionary orogens and complex because of its complicated compositions and strong deformation. With a thorough structural and geochronological study of a fossil accretionary complex in the Atbashi Ridge, South Tianshan (Kyrgyzstan), we analyze the structure and architecture of ocean plate stratigraphy in the western Central Asian Orogenic Belt. The architecture of the Atbashi accretionary complex is subdivisible into four lithotectonic assemblages, some of which are mélanges with “block-in-matrix” structure: (1) North Ophiolitic Mélange; (2) High-pressure (HP)/Ultra-high-pressure (UHP) Metamorphic Assemblage; (3) Coherent & Mélange Assemblage; and (4) South Ophiolitic Mélange. Relationships between main units are tectonic contacts presented by faults. The major structures and lithostratigraphy of these units are thrust-fold nappes, thrusted duplexes, and imbricated ocean plate stratigraphy. All these rock units are complicatedly stacked in 3-D with the HP/UHP rocks being obliquely southwestward extruded. Detrital zircon ages of meta-sediments provide robust constraints on their provenance from the Ili-Central Tianshan Arc. The isotopic ages of the youngest components of the four units are Late Permian, Early-Middle Triassic, Early Carboniferous, and Early Triassic, respectively. We present a new tectonic model of the South Tianshan; a general northward subduction polarity led to final closure of the South Tianshan Ocean in the End-Permian to Late Triassic. These results help to resolve the long-standing controversy regarding the subduction polarity and the timing of the final closure of the South Tianshan Ocean. Finally, our work sheds lights on the use of ocean plate stratigraphy in the analysis of the tectonic evolution of accretionary orogens. [ABSTRACT FROM AUTHOR]

Miocene Surma Group from the Chittagong Tripura Fold Belt (CTFB), southeast Bengal Basin has been analyzed to evaluate their provenance, tectonic settings and paleoweathering conditions. The sandstones show moderate to high contents of SiO 2 (65–80%; 75% on average), and Al 2 O 3 (9.94% on average), with Fe 2 O 3 (total Fe as Fe 2 O 3 ) + MgO contents of 5.1%, TiO 2 (0.57% on average). Compared to the upper continental crust (UCC), the sandstones are depleted in CaO (1.49%) and enriched in Al 2 O 3 , Fe 2 O 3 and Na 2 O. The Neogene shales of the Surma Group are in fair concurrence when compared to the NASC (North American Shale Composite), UCC (the upper continental crust) with the exception of the low content of CaO but when compared with the PAAS (Post-Archaean Australian Shale), the Neogene shales are a little more depleted in Al 2 O 3 content. Sandstones and shales have Eu/Eu ∗ ∼0.61 and ∼0.65, (La/Lu) N ∼9.06 and ∼8.70, La/Sc- ∼3.90 and ∼2.86, Th/Sc ∼1.19 and ∼1.41, La/Co- ∼3.69 and ∼2.42, Th/Co ∼1.08 and ∼1.20 and Cr/Th ∼7.90 and ∼5.88 ratios as well as Chondrite-normalized REE patterns with flat HREE, LREE enrichment, and negative Eu anomalies indicate the derivation from predominantly felsic sources subjected to low to moderate chemical weathering [Chemical index of alteration (CIA) values of sandstones- 31.11–74.46, av. 60.08); shales- 43.96–73.07, av. 61.80]. Integrated geochemical and zircon U-Pb studies reveal that main sediment input might have been from the Himalaya with mixing influence from the east of the Indo-Burman Ranges in an active margin setting at the convergence of the Indian and Burmese plates. [ABSTRACT FROM AUTHOR]

The origin and tectonic affinity of the Alxa Block in NW China is currently debatable. This study reports new stratigraphically-constrained LA-ICP-MS zircon U-Pb data from Precambrian rocks exposed in the westernmost part of the Alxa Block, to constrain their ages and provenance. Ages obtained for a granitic gneiss from the Longshoushan Group are mainly discordant yielding an upper intercept near 1200 Ma and a lower intercept between ∼350 and ∼310 Ma, indicating the protolith for the granitic gneiss intruded during the Mesoproterozoic, and the gneissic fabric formed in late Paleozoic associated with the accretion of the Central Asian Orogenic Belt. Detrital zircons of a meta-sandstone from Pre-Sinian strata yielded predominant Mesoproterozoic ages with bimodal peaks at ∼1166 Ma and ∼1375 Ma. These ages are interpreted as tectonic events associated with the long-lived accretion and collision processes coeval with the amalgamation of the Rodinia supercontinent. The youngest concordant zircon age of 968 ± 70 Ma constrains its maximum depositional age to the Stenian-Tonian boundary. Two metasedimentary rocks from the Sinian strata share similar age patterns, yielding an earliest Paleoproterozoic peak at ∼2469–2460 Ma, and two Tonian peaks at ∼992–978 Ma and ∼826–807 Ma. The youngest detrital zircon ages constrain their maximum depositional age to be latest Neoproterozoic. The detrital age patterns, as well as zircon morphology, indicate that the protoliths for these metasedimentary rocks were probably deposited in collision-related foreland basins. Our new data combined with published data indicate that the Alxa Block is not a uniform early Precambrian craton like the North China Craton, but a Precambrian composite ribbon continent which originally detached from a main cratonic accretionary and collisional margin. The Alxa Block, like the South China Craton, underwent a multi-stage tectono-thermal evolution related to the assembly of Rodinia and Gondwana supercontinents during global plate margin reorganization. Current data support a close affinity of the Alxa Block to the SCC during the Precambrian. During the Paleozoic, the Alxa ribbon continent behaved as a backbone to the Paleo-Asian Ocean to the north, on which early Paleozoic-Permian magmatic arcs were built forming the southernmost segment of the Central Asian Orogenic Belt. [ABSTRACT FROM AUTHOR]

The exhumation and tectonic emplacement of eclogites and blueschists takes place in forearc accretionary complexes by either forearc- or backarc-directed extrusion, but few examples have been well analysed in detail. Here we present an example of oblique wedge extrusion of UHP/HP rocks in the Atbashi accretionary complex of the Kyrgyz South Tianshan. Our field mapping and structural analysis demonstrate that the Atbashi Eclogite–Blueschist Complex is situated in a complicated duplex formed by a northerly dextral transpression system and a southerly sinistral transtension system. The two major shear systems suggest that the Atbashi Complex was extruded obliquely southwestwards during eastward penetration of the southern tip of the Yili–Central Tianshan Arc of the Kazakhstan Orocline during the Late Triassic. Also, we report new zircon U–Pb metamorphic ages of four eclogites and one garnet-bearing quartz-schist from the Atbashi complex of 217–221 Ma and 223.9 Ma, respectively, suggesting that the main extrusion was later than previously proposed and that the final orogenesis was not completed until the Late Triassic. The HP/UHP rocks have an oblique plunge to the NE and extrusion took place southwestwards during escape tectonics along the South Tianshan accretionary wedge in the Late Triassic. Our work shows that the movement of HP/UHP rocks had a 3D style with an arc-parallel structure, and sheds light on earlier 2D models with either forearc- or backarc-directed extrusions, which indicates that more systematic structural and geochronological work is needed to characterize the accretionary tectonics of many orogens around the world. Our data on the timing of extrusion and emplacement of the Atbashi Eclogite–Blueschist Complex also help to resolve the long-standing controversy about the time of terminal orogeny of the Central Asian Orogenic Belt. [ABSTRACT FROM AUTHOR]

The Zagros Orogen developed as a result of Arabia-Eurasia collision. New in situ detrital zircon U-Pb and Hf isotopic analyses from a Cenozoic sedimentary sequence in SW Iran are used to unravel the amalgamation history of Neo-Tethys. Data indicate that: (1) Paleocene and Eocene strata (58 and 45 Ma, respectively) were sourced from obducted ophiolite and Triassic volcanics, (2) Lower Miocene (~18 Ma) strata indicate mixed provenance from obducted ophiolite and Iranian magmatic rocks, (3) Mid to Upper Miocene sediments (~14 to 11.2 Ma) were mainly sourced from Sanandaj-Sirjan zone granitoids to the north, and (4) Lower Pliocene (~5 Ma) sediments mainly show Arabian age characteristics, with a minor Eurasian affinity component. Two hypotheses are outlined to highlight the key events: Hypothesis A, previously published by several workers, suggests that the sequence studied lay on the Arabia passive margin and that initial collision occurred prior to 18 Ma; Hypothesis B, modified from the Makran model, which is here preferred, suggests that Paleogene to Upper Miocene sediments were sourced from the northern Neo-Tethyan accretionary complex or Eurasia, and carry no input from Arabia, whereas the Lower Pliocene sample shows a mixed provenance from both Arabia and Eurasia, suggesting that collision occurred between ~11.2 and 5 Ma. [ABSTRACT FROM AUTHOR]

High-grade metamorphic complexes or terranes in orogens play a vital role in reconstructing orogenic dynamics and tectonic history of Earth's past owing to their multi-tectono-thermal recording capacity. The Chijin Complex, located in the southernmost Altaids and composed of intensely deformed medium- to high-grade meta-volcanic rocks including (garnet-bearing) mica-quartz schists, felsic gneisses, and amphibolitic schists and gneisses, imposes crucial constraints on the fiercely disputed timing and tectonic architecture of the Paleo-Asian Ocean's (PAO) terminal evolution. This Complex has long been interpreted as the Precambrian basement of a microcontinent in tectonic reconstructions. Our detailed field investigations, geochemical research, and detrital age spectrum analyses of the Chijin Complex reveal structural-lithological-geochemical affinities to volcanic-magmatic extrusions originating from a continental arc regime. Anti-clockwise P-T paths and high T/P geothermal gradients (∼24–37 °C/km), reconstructed by thermodynamic modeling and geothermobarometry for the Complex, reveal magmatic underplating mechanism from prograde "hot" T/P metamorphism resulting from thermal intrusion and finite arc crustal thickening to in-situ retrograde isobaric cooling. Hornblende and biotite 40Ar/39Ar and zircon U Pb dating demonstrates that the continental arc system was still active as during the Late Permian to Middle Triassic (∼252–237 Ma) as a result of continuing southward subduction of the PAO, thereby constraining the final amalgamation of the Altaids to the Late Triassic. This study proposes a new perspective for redefining high-grade rocks at the southernmost Altaids as arc-metamorphic complexes rather than "reputed" ancient microcontinent, as well as a potential template example for discerning tectonic nature of semblable metamorphic complexes or terranes with distinct origins in global orogens. [Display omitted] • The Chijin Complex records anticlockwise P-T-t paths revealing arc metamorphism. • Active arc regime confines final closure of the Paleo-Asian Ocean to Late Triassic. • The Chijin Complex is re-defined as "young" arc root rather than "old" basement. [ABSTRACT FROM AUTHOR]

The sources of ancient zircons and the tectonic attributions and origins of metamorphic complexes in Phanerozoic accretionary orogens have long been difficult issues. Situated between the Tianshan and Inner Mongolia orogens, the Beishan orogenic collage (BOC) plays a pivotal role in understanding the accretionary processes of the southern Central Asian Orogenic Belt (CAOB), particularly the extensive metamorphic and high-strained complexes on the southern margin. Despite their importance in understanding the basic architecture of the southern CAOB, little consensus has been reached on their ages and origins. Our new structural, LA-ICP-MS zircon U-Pb and Hf isotopic data from the Baidunzi, Shibandun, Qiaowan and Wutongjing metamorphic complexes resolve current controversial relations. The metamorphic complexes have varied lithologies and structures. Detrital zircons from five para-metamorphic rocks yield predominantly Phanerozoic ages with single major peaks at ca. 276 Ma, 286 Ma, 427 Ma, 428 Ma and 461 Ma. Two orthogneisses have weighted mean ages of 294 ± 2 Ma and 304 ± 2 Ma with no Precambrian inherited zircons. Most Phanerozoic zircons show positive εHf (t) values indicating significant crustal growth in the Ordovician, Silurian and Permian. The imbricated fold-thrust deformation style combined with diagnostic zircon U-Pb-Hf isotopic data demonstrate that the metamorphic rocks developed in a subduction-accretion setting on an arc or active continental margin. This setting and conclusion are supported by the nearby occurrence of Ordovician-Silurian adakites, Nb-rich basalts, Carboniferous-Permian ophiolitic mélanges, and trench-type turbidites. Current data do not support the presence of a widespread Precambrian basement in the evolution of the BOC; the accretionary processes may have continued to the early Permian in this part of the CAOB. These relationships have meaningful implications for the interpretation of the tectonic attributions and origins of other metamorphic complexes in Central Asia and other ancient accretion-dominated orogens. [ABSTRACT FROM AUTHOR]

The Gongchang iron deposit, a typical Algoma-type banded iron formation (BIF) deposit located in the Eastern Block of the North China Craton (NCC), is hosted in Neoarchean metamorphic rocks, including amphibolite, biotite leptynite, garnet biotite schist, plagioclase-hornblende schist, garnet chlorite schist, muscovite quartz schist and actinolite magnetite quartzite. Geochemical data suggest that protoliths of the amphibolites and biotite leptynite should be basalt and dacite, respectively. SHRIMP U–Pb dating of zircons from the plagioclase-hornblende schist shows that the Gongchangling iron deposit was formed at 2554 ± 12 Ma. Major elements and REE data of the ores indicate that the Gongchangling BIF precipitated from seawater, and the ultimate iron and silica origins may have been related to nearby volcanic activity. The δ 18 O values of quartz from the BIFs range between 9.1 and 12.9‰, suggesting that exotic high δ 18 O fluids were involved during metamorphism. The pyrite have δ 34 S values of range between −3.5‰ and 14.7‰, suggesting that mineralization were originally from metamorphism. Comparison of the mineralization age of the Gongchangling BIF with those of other local BIFs in North China and other cratons throughout the world indicates that the Gongchangling BIF formed coevally with the global BIF mineralization at ∼2.5 Ga. Taken together, these data suggest that the Gongchangling iron deposit was formed in a volcanic submarine environment in which hydrothermal fluids associated with volcanic activity supplied both iron and silica for the banded iron formations. [ABSTRACT FROM AUTHOR]

The Lebaquan Complex in the central Beishan (NW China) plays a significant role in understanding the subduction–accretion–collision processes of the southern Central Asian Orogenic Belt. Four stages of deformation have been identified. The D 1 deformation is characterized by a pervasive foliation (S 1 ) defined by metamorphic layering and intrafolial isoclinally folded quartz veins (F 1 ). The D 2 deformation is marked by a crenulation cleavage (S 2 ) mainly developed in the schists, widespread tight to open folds and asymmetric folds (F 2 ) as well as pinch-and-swell structures (boudins). The D 3 deformation is characterized by high-strain ductile shears that modified the earlier structures. Small-scale asymmetric folds, σ-type porphyroclasts and S–C fabrics in the schists, metacherts and pegmatites indicate dextral shearing in an east–west direction. The D 4 deformation is represented by semi-ductile to brittle structures including open/gentle folds, kink folds and small-scale thrusts which overprinted earlier structures. The overall deformation pattern of this complex indicates a tectonic regime that changed from an earlier NS-directed compression to a later EW-directed transpression, and finally to an EW extension. Geochemical data show that the protoliths of the metasedimentary rocks were sourced from an active margin. New LA-ICP-MS zircon U–Pb dates indicate that the youngest age peak of detrital zircons from a garnet–mica–quartz schist is ~ 424 Ma, which constrains the depositional age of the rocks protoliths. A syn-deformation leucogranitic dyke, which underwent D 2 but not D 1 formed at ~ 423 Ma, and a post-deformation mafic dyke that intruded all the lithologies formed at ~ 280 Ma. These data indicate that D 1 occurred in the time interval of 424–423 Ma, that D 2 took place at or shortly after 423 Ma, and that D 3 and D 4 formed in the period of 423–280 Ma. Combined with other published data, we conclude that the Lebaquan Complex represents a subduction–accretionary complex formed in a forearc setting. [ABSTRACT FROM AUTHOR]

Abstract: This paper reports whole-rock Sr–Nd and zircon U–Pb and Hf isotopic compositions, as well as major and trace element data, for the granodiorites and their mafic microgranular enclaves (MMEs) in the Tuokesalei area, northwestern Chinese Altai. The granodiorites are characterized by peraluminous compositions (A/CNK=1.01–1.45), with relatively high SiO2 (64.4 to 70.9wt.%) and low MgO (0.75 to 1.97wt.%) contents. These rocks possess low total rare earth element (REE) contents (67–187ppm) with weakly negative Eu anomalies and mantle-like whole-rock Nd–Sr isotopic compositions (εNd(t)=+2.5 to +4.5; (87Sr/86Sr)i =0.7038 to 0.7048) and zircon εHf(t) values (+5.93 to +12.9). The MMEs contain abundant magmatic amphiboles and needle-like apatites, have low SiO2 (51.7 to 54.3wt.%) and high MgO (2.86 to 3.75wt.%) and REE contents (162–298ppm), and are characterized by moderately negative Eu anomalies (Eu/Eu*=0.40–0.60) and slightly depleted to enriched LREE ((La/Nd)N =0.74–1.41) and flat HREE ((Gd/Yb)N =1.16–1.39) patterns. The MMEs have whole-rock Nd–Sr isotopic compositions (εNd(t)=+2.6 to +2.7, (87Sr/86Sr)i =0.7034–0.7050) similar to those of the host granodiorites. Their similarities in crystallization age, mineral assemblage and isotopic composition document that the MMEs may represent an early crystallized phase, which was broken into pieces and brought to the shallow level during the host magma ascent and emplacement. Their precursor magmas were probably derived from an oceanic lithospheric mantle, which was characterized by pronounced Nd–Ta depletions. Mineral compositions of MMEs suggest that amphibole was a major early fractional mineral, which effectively differentiated the mantle-derived basaltic liquids to silica-rich melts. Zircon U–Pb dating yielded an age of 313±5Ma for the host granodiorites and 313±13Ma for their MMEs. The geochemical data of this study records an important episode of magmatism in an environment transitional from a subduction-related regime to a post-tectonic extension. Results of this study suggest that the accretionary orogenic process did not completely terminate until the Late Carboniferous to Permian in this region. [Copyright &y& Elsevier]

Abstract: The southern Central Asian Orogenic Belt (CAOB) is characterized by multiple and linear accretionary orogenic collages, including Paleozoic arcs, ophiolites, and accretionay wedges. A complex history of subduction–accretion processes makes it difficult to distinguish the origin of these various terranes and reconstruct the tectonic evolution of the southern CAOB. In order to provide constraints on the accretionary history, we analyzed major and trace element compositions of Paleozoic graywackes from the Huangcaopo Group (HG) and Kubusu Group (KG) in East Junggar. The HG graywackes have relatively low Chemical Index of Alteration (CIA) values (50 to 66), suggesting a source that underwent relatively weak chemical weathering. The identical average Index of Compositional Variability (ICV) values (~1.1) for both the KG and HG samples point to an immature source for the Paleozoic graywackes in East Junggar, which is consistent with an andesitic–felsic igneous source characterized by low La/Th ratios and relatively high Hf contents. These graywackes are geochemically similar to continental island arc sediments and therefore were probably deposited at an active continental margin. U–Pb dating of detrital zircons from the lower subgroup of the HG yielded a young age peak at ~440Ma, indicating a post-Early Silurian depositional age. However, the youngest populations of detrital zircons from the KG graywackes and the upper subgroup of the HG yielded 206Pb/238U ages of ~346Ma and ~355Ma, respectively, which suggest a post-Early Carboniferous depositional age. Because of similarities of rock assemblages, these two units should be incorporated into the Early Carboniferous Nanmingshui Formation. The detrital zircon age spectrum of the Early Paleozoic HG graywackes resembles that of the Habahe sediments in the Chinese Altai, which suggests that the ocean between East Junggar and the Chinese Altai was closed before the deposition of the sediments and that the Armantai ophiolite was emplaced prior to the Early Devonian. The differences in age spectra for detrital zircons from the post-Early Carboniferous graywackes in East Junggar and the Harlik arc indicate that the emplacement of the Kalamaili ophiolite postdates the Early Carboniferous. Therefore, a long-lasting northward subduction–accretion process is suggested for the formation of East Junggar and the reconstruction of the Early Paleozoic evolution of the southern CAOB. [Copyright &y& Elsevier]

Abstract: Some skarn-associated gold deposits display close spatial relations with shear zones in ancient orogens; however to date no skarn-associated iron mineralization has been genetically linked to a shear zone. To address this problem, we conducted a systematic study of the Mengku iron deposit in the Chinese Altai, Northwest China. All orebodies of the deposit are enclosed by skarn and stratabound by volcaniclastic rocks. LA–ICP-MS dating of zircon from a meta-rhyolitic volcaniclastic (MK19) yielded a weighted 206Pb/238U age of 404±5Ma. We interpret this date as the formation time of volcanic rocks in the Mengku area, which is consistent with the age of strata hosting nearby VMS deposits (400–413Ma). Zircon from the mineralized skarn (MK13) are considered to be hydrothermal in origin and yield a weighted 206Pb/238U age of 250±2Ma, which we interpret to represent the time of skarn formation based on the petrographic relationship between hydrothermal zircon and skarn garnet. This age is much younger than that determined from previous studies, younger than the regional igneous and metamorphism activities (early Permian), but synchronous with the movement of the nearby regional Erqis shear zone and Abagong Fault (late Permian to Triassic). The oxygen isotope values of the hydrothermal zircon are 2.3‰ to 3.0‰, consistent with the δ18O of garnet (1.2‰ to 3.2‰) in the skarn, but markedly different from those of zircon from igneous rocks in the mine area (MK1, 2, 3, 19; 6.3‰ to 8.0‰). The fluid source has a strong meteoric water signature as indicated by the oxygen isotope values of garnet and hydrothermal zircon, which are very different from those of the granite and volcanic rocks in the mine area. On the basis of field, chronological and geochemical evidence, we suggest that the Mengku is not a volcanogenic massive sulfide deposit, but is related to the Erqis strike–slip shear zone and Abagong Fault, which acted as fluid conduits. The upwelling of hot mantle in the Permian to Triassic supplied the heat, and thereby caused material to dehydrate and mixed with meteoric water that give rise to low-oxygen isotope fluids similar to the common genetic model for orogenic lode gold deposits. [Copyright &y& Elsevier]

Abstract: The timing and genesis of the major Ni–Cu–Co sulfide deposit in the Xiangshan intrusion have been studied based on newly obtained in-situ U–Pb, Hf and Re–Os isotopic analyses. The SIMS U–Pb zircon ages of the gabbro hosting the Ni–Cu–Co sulfide deposit indicate that the Xiangshan intrusion was emplaced at 279.6±1.1Ma (95% confidence level, MSWD=1.30, n =15). On the basis of combined geological and geochronological evidence, we suggest that the Xiangshan and other adjacent Ni–Cu deposits were formed in the same period. Sulphides have low common Os concentrations and high Re/Os ratios, similar to sulphide ores from the Duluth, Sally Malay and Voisey Bay complexes. The Re–Os isotopic data from the disseminated and massive ores from the Xiangshan intrusion do not form a single isochron, as they have different initial Os ratios. The Hf and Os isotopic data suggest that the Xiangshan intrusion and associated Ni–Cu–Co mineralization were derived from crustally contaminated mantle melts. The geochemical data show a tholeiitic affinity and a strong suprasubduction zone signature with negative Nb, Sr, and Ti anomalies similar to N-MORB and E-MORB. We suggest that the mafic–ultramafic rocks and associated Ni–Cu mineralization of the Eastern Tianshan orogen formed in an Alaska-type subduction zone-arc setting. Some diagnostic features of ridge–trench interaction are present in the Chinese East Tianshan orogen (e.g. granites, adakites, high-Mg andesites, near-trench magmatism, Alaskan-type mafic–ultramafic complexes, high-temperature metamorphic belts that prograde rapidly from low-grade belts, and orogenic gold deposits). The above distinctive rock groups are probably related to the same thermal event, ridge subduction, as in the Cenozoic orogen of Alaska. We suggest that ridge subduction is the most plausible mechanism to provide the necessary heat. Ridge subduction provides an important promising model for understanding many aspects of the evolution of the Chinese Eastern Tianshan orogen, and by inference, throughout much of Central Asia. [Copyright &y& Elsevier]

The eastern Tiklik belt is mainly composed of meta-sedimentary rocks of the Ailiankate and Sailajiazitage Groups that were previously interpreted as Palaeoproterozoic, Mesoproterozic and Neoproterozoic stratigraphic units, which are part of the Tarim Precambrian basement. Our new detrital (U-Pb) zircon ages yield a dominant single peak with a major range between ca. 700 Ma and 800 Ma for meta-sedimentary rocks from both the Ailiankate and Sailajiazitage Groups, which demonstrates that they were mainly derived from an independent Neoproterozoic terrane. There are several ages of 444–659 Ma, of which, the youngest has an age of 444 ± 6 Ma, indicating that the time of deposition of the meta-sedimentary rocks could have been in the Early Silurian. The porphyritic granite sample has a weighted mean crystallization age of 442 ± 2 Ma. The adakite-like geochemical characteristics of the porphytitic granite suggest derivation from the melting of the oceanic slab and formation in a subduction, arc-related tectonic setting. After integration with relevant published data, our work suggests that the Ailiankate and Sailajiazitage Groups belong to a tectonic mosaic that contains Middle Neoproterozoic extensional and Paleozoic accretionary and collisional complexes, rather than the Paleoproterozoic or Mesoproterozoic basement, as previously regarded. We propose a new tectonic model for the eastern Tiklik belt that started with a Middle Neoproterozoic extension and ended with Paleozoic continuous accretion and collision in a Paleo-Tethys archipelago, which contributed to the considerable continental growth of the southern Tarim Block. [ABSTRACT FROM AUTHOR]

Late Silurian‐early Devonian mafic–intermediate dykes occur in the Xiemisitai mountain of the northern West Junggar. However, their ages, petrogenesis and geodynamic process remain to be unraveled. We report firstly in situ zircon U–Pb and hornblende 40Ar‐39Ar ages, geochemical and in situ zircon Hf isotopic data for the Xiemisitai dykes. The Xiemisitai dykes give zircon U–Pb ages of 416.7±2.1 Ma and 405.1±2.5 Ma and hornblende40Ar‐39Ar age of 405.9±4.9 Ma, respectively. They are characterized by high ∊Hf(t)values (+11.9 to +15.5), suggesting a depleted mantle features. The Xiemisitai dykes show low Mg# (46–59) and low Cr (11.3–197 ppm) and Ni (19.9–102 ppm) abundances indicating that they have experienced significant fractional crystallization. These dykes contain hornblende and biotite and display negative Nb‐Ta‐Ti anomalies, enrichment of LREEs, LILEs and depletion of HREEs and HFSEs with high Ba/La ratios, similar with an origin from a depleted lithospheric mantle metasomatized by subducted slab‐derived fluids. In addition, the Xiemisitai dykes are plotted within melting trends with little to no garnet (Cpx:Grt=6:1) in their source. The La/Yb vs. Tb/Yb plot also indicates the presence of less than 1% residual garnet in the source region for the Xiemisitai dykes. Therefore, it can be inferred that the Xiemisitai dykes were generated at a correspondingly shallow depth, mostly within the spinel stability field. Finally, the Xiemisitai dykes were most probably generated by partial melting of metasomatized lithospheric mantle in relatively shallow level (<80 km). They could be possibly triggered by the asthenospheric upwelling as a result of the rollback of the subducted Irtysh‐Zaysan oceanic lithosphere. [ABSTRACT FROM AUTHOR]

The Tianshan and Altai mountain belts dominate the present‐day topography of central Asia and are major constituents of the Central Asian Orogenic Belt. These mountain belts have been extensively studied using low‐temperature thermochronology to understand their uplift and exhumation history. In comparison, few studies have focused on the spatial extent and timing of intracontinental deformation in the intervening ranges, such as the West Junggar Mountains. Apatite fission track (AFT) and apatite U‐Pb dating of igneous samples from the West Junggar Mountains reveals AFT central ages ranging from latest Carboniferous to Middle Jurassic and mean confined track lengths between 14.1 and 12.0 µm, which are negatively correlating to AFT central ages. Apatite U‐Pb dating produced mid‐Carboniferous‐early Permian ages within uncertainty of zircon U‐Pb crystallization ages, indicating cooling to below ∼450–550 °C immediately following emplacement. Thermal history modeling of our AFT data combined with published (U‐Th)/He data predicts rapid cooling to <60 °C during the early‐middle Permian (285–260 Ma), followed by slower cooling rates during the Mesozoic‐Cenozoic. The rapid cooling event coincides with (1) the timing of major basinward thrusting in the Junggar Basin adjacent to the study area and (2) exhumation in the Chinese Altai to the north. In contrast to previous studies, our results imply that the West Junggar Mountains do not record significant exhumation during the Mesozoic‐Cenozoic. This suggests that Mesozoic deformation of the Central Asian Orogenic Belt was less pervasive and widespread than previously assumed. Key Points: Apatite fission track data suggest rapid exhumation occurred during the early to middle PermianMesozoic tectonic activity at the Eurasian plate margin did not significantly affect the regionLow‐relief areas were cooled to below 60 °C by the Triassic, implying minimal subsequent exhumation [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Oligocene-Pliocene sediments in north Junggar mainly sourced from North Tianshan. • Accretion of Cimmerian blocks triggered two episodes of Mesozoic cooling in Tianshan. • Onset of the modern Tianshan orogeny commenced in Late Oligocene-Early Miocene time. • Ongoing India indentation caused rapid cooling between 11–3 Ma by stress propagation. Abstract It is generally accepted that the Tianshan was reactivated repeatedly throughout Meso-Cenozoic time. However, the extent of these episodes has not been fully understood. Using a previous magnetostratigraphic baseline, this study reports a detrital zircon U–Pb and apatite fission track dating study along the ~4 km thick Cenozoic Jingou River section at the southern margin of the Junggar Basin. Our results provide direct insight into the denudation history of the bordering Tianshan Mountains and suggest that they experienced two phases of rapid cooling in the Jurassic and Cretaceous. These cooling phases are attributed to tectonic events at distant plate margins such as the Late Triassic-Cretaceous accretion of peri-Gondwanan blocks (e.g. Qiangtang and Lhasa). The detrital zircon U–Pb ages range widely from ∼58 to 3055 Ma with a majority falling between ∼58 and 600 Ma. They can be statistically separated into two primary age peaks at 300–290 Ma and 450–410 Ma, as well as two secondary peaks at 170 Ma and 850 Ma. Detrital zircon U–Pb dating results suggest that the Central Tianshan may have still shed detritus into the Junggar Basin during the Early Palaeogene. In the Late Oligocene-Early Miocene, the modern North Tianshan started to form a topographic barrier that blocked all northward rivers flowing from the Central Tianshan to the Junggar Basin. Progressive northward indentation of India into Eurasia, caused a final intense phase of cooling and denudation of the Tianshan between ∼11 and 3 Ma, leading to deposition of the Xiyu Formation, a widely distributed thick conglomerate. [ABSTRACT FROM AUTHOR]

• The Langshan can be divisible into northeastern and southwestern Langshan based on different tectono-thermal evolution history. • Abundant magmatism and sedimentation related to the breakup of the Columbia supercontinent were identified in the northeastern Langshan. • A continental fragment with an affinity to the southwestern Langshan was juxtaposed to an early Paleozoic accretionary complex in the southern Central Asian Orogenic Belt. The Langshan connects the North China Craton (NCC) with the Alxa Block and occupies a key position to unraveling their Precambrian tectonic affinity. The tectonic origin and evolutionary history of the Precambrian basement of the Langshan is debated. To clarify these issues, we report zircon U-Pb ages and geochemical data for magmatic and metasedimentary rocks in the northern Langshan. The new results combined with previous data indicated that the northern Langshan experienced multistage magmatism at ∼2.53–2.49, ∼2.02, and ∼1.92–1.97 Ga, similar to those in the NCC. Late Paleoproterozoic (∼1.64–1.71 Ga) gneissic alkalic feldspar granite and monzogranite show A-type granite geochemical signatures. Detrital zircon U-Pb-Hf isotopic data indicated that the Baoyintu Group was deposited in the Mesoproterozoic and mainly sourced from the basement rocks and coeval rift-related granites in the northern Langshan and NCC. The A-type gneissic granites and Baoyintu Group were resulted from the breakup of the Columbia supercontinent. In addition, a K-feldspar granite with A-type granite geochemical characteristic was dated at 855 ± 5 Ma. A schist displays detrital zircon age peaks at ∼1577, ∼1443, ∼1348, and ∼1174 Ma with predominantly positive εHf(t) values, and the Alxa Block might provide significant detritus for it. A continental fragment was probably detached from the Alxa Block due to regional back-arc extension along the northern margin of the Rodinia supercontinent during the early Neoproterozoic, which was finally incorporated into an early Paleozoic accretionary complex in the southern Central Asian Orogenic Belt. The available data indicate that the Langshan can be subdivided into the northeastern Langshan and southwestern Langshan, with the former belonging to the NCC and the latter as a part of the Alxa Block. We advocate that the Alxa Block was an independent microcontinent with a different tectono-thermal evolution from the NCC at least during the Neoproterozoic. [ABSTRACT FROM AUTHOR]

The widely distributed Devonian granitoids comprise a significant part of the crust in the Chinese Altai, although their petrogenetic implications remain debated. The Habahe Intrusion, comprising biotite granite batholith, gabbroic diorite dikes, and biotite granite hosted-enclaves, is a key magmatic unit to understand the extensively developed magmatism in the Chinese Altai. To investigate their petrogenesis and tectono-magmatic significance, this study presents comprehensive petrological, geochronological, and geochemical studies on the Habahe Intrusion. The geochronological results indicate that the enclaves and the host biotite granite share similar ages (395.1 ± 3.7 Ma, MSWD = 4.5 and 395.1 ± 2.5 Ma, MSWD = 0.21, respectively), and slightly older than the gabbroic diorite dikes (378 ± 4 Ma), suggesting the Devonian magmatism. The biotite granite (SiO 2 = 73.9%–76.4%) is amphibole-bearing and shows I-type granite affinity. The enriched zircon Hf (εHf(t) = +2.5 to +5.4), near zero whole-rock Nd (εNd(t) = −1.0 to −0.3) and intermediate Sr isotopes (Isr = 0.7058–0.7072) suggest their generation from the partial melting of the lower crust. The enclaves display variable mineral proportions (amphibole dominated to quartz dominated), major (SiO 2 = 48.6%–62.4%, Mg# = 34.3–67.0), trace element compositions (ΣREE = 20.0–194.5 ppm) and Sr Nd isotopes (εNd(t) = −0.6 to +4.1, Isr = 0.7023–0.7055), indicating their hybrid nature. Together with the acicular apatite and quenched rims of the enclaves, they show a magma mixing event. Nevertheless, the biotite-rich rims of the enclaves and the homogenous compositional and isotopic characteristics of the host biotite granite suggest limited mixing/mingling. The gabbroic diorite dikes (SiO 2 = 48.8–52.4%), consisting of amphibole and plagioclase, display E -MORB-like trace and rare earth element patterns and have depleted Hf (εHf(t) = ∼ + 9), Nd (εNd(t) = +1.7 to +7.3) and low Sr (Isr = 0.7045–0.7089) isotopes, pointing to an asthenosphere mantle origin. Combining these, we propose a model suggesting that the biotite granite was generated by melting of the lower crust, trigged by upwelling of the asthenosphere mantle during subduction. The mafic magma, derived from the partial melted asthenosphere mantle, mixed weakly with the felsic magma from the partial melted lower crust, thereby supplied limited mantle materials for the generation of the biotite granite batholith. This study offers important insights into the extensive Devonian tectono-magmatic processes in the Chinese Altai. [Display omitted] • The gabbroic diorite dikes were derived from the partial melting of asthenosphere mantle in hydrous condition. • The biotite granite crystallized from a common magma derived from the partial melting of the lower crust. • Limited mixing/mingling occurred between mantle-derived mafic magma and crustal-derived felsic magma. • Habahe Intrusion traces the extensive magmatism during the subduction in the Chinese Altai. [ABSTRACT FROM AUTHOR]

Abstract: Gneissic rocks in the Chinese Altai Mountains have been interpreted as either Paleozoic metasedimentary rocks or Precambrian basement. This study reports geochemical and geochronological data for banded paragneisses and associated gneissic granitoids collected along a NE–SW traverse in the northwestern Chinese Altai. Petrological and geochemical data suggest that the protoliths of the banded gneisses were possibly immature sediments with significant volcanic input and that the gneissic granitoids were derived from I-type granites formed in a subduction environment. Three types of morphological features can be recognized in zircons from the banded gneisses and are interpreted to correlate with different sources. Zircons from five samples of banded paragneiss cluster predominantly between 466 and 528 Ma, some give Neoproterozoic ages, and a few yield discordant Paleoproterozoic to Archean ages. Zircon Hf isotopic compositions indicate that both juvenile/mantle and crust materials were involved in the generation of the source rocks from which these zircons were derived. In contrast, zircons occur ubiquitously as elongated euhedral prismatic crystals in the four samples of the gneissic granitoids, and define single populations for each sample with mean ages between 380 and 453 Ma. The general absence of Precambrian inheritance and positive zircon ɛHf values for these granitoids suggest insignificant crustal contribution to the generation of the precursor magmas. Our data can be interpreted in terms of a progressive accretionary history in early to middle Palaeozoic times, and the Chinese Altai may possibly represent a magmatic arc built on a continental margin dominated by Neoproterozoic rocks. [Copyright &y& Elsevier]

Numerous leucogranite dykes, and spatially associated high-grade metamorphic rocks, are well-preserved in the Chinese Altai orogenic belt. Integrated petrological, geochronological, and geochemical results of the leucogranite dykes are presented to decipher their petrogenesis and constrain the tectono-thermal setting of the Altai orogen. The leucogranite dykes have high SiO 2 (71.9–81.2 wt%) and Al 2 O 3 contents (11.1–15.7 wt%), and low CaO, MgO and TiO 2 contents, with a total alkali content (K 2 O + Na 2 O) of 4.55–9.88 wt%. All leucogranites show weakly to strongly peraluminous S-type granite affinities with A/CNK ratios of 1.0–2.2. Trace element concentrations indicate a characteristic high Rb content, low Ba and Sr contents, and Rb/Sr ratios of 0.43–35.8. They exhibit nearly flat REE patterns with strong negative Eu anomalies on chondrite-normalized REE patterns. Considering their low zircon saturation temperatures (682–758 °C) and low εNd(t) values (˗12.4 to ˗2.7), as well as the presence of Al-rich minerals (muscovite and garnet), we infer that the leucogranites were low-temperature granites and generated mainly by fluid-absent muscovite dehydration melting of metasediments. LA-ICPMS zircon and monazite U-Pb dating suggests crystallization ages of 279–267 Ma, which places these leucogranite dykes in temporal association with the ultrahigh- to high-grade metamorphic rocks and implies a prolonged heat budget in the region. Together with contemporary magmatic activities and metamorphism in the Chinese Altai orogen, the generation of the leucogranite dykes may have been attributed to long-lasting high heat flow in the early Permian, most likely related to the assembly of the Junggar plate and the Chinese Altai. • The leucogranites in the high-grade metamorphic belt formed at 279–267 Ma. • Fluid-absent muscovite dehydration melting of metasediments sourced leucogranites. • A prolonged high heat budget may have operated in Permian. [ABSTRACT FROM AUTHOR]

• Metasedimentary rocks in Huangyuan Group represent a sedimentary series with a long history of deposition. • The deposition started at ca. 1317 Ma in an oceanic island arc-related basin that developed through a transitional continental arc-related basin into an active continental marginal basin at ca. 927 Ma. • The 1795–1321 Ma detritus was sourced from juvenile arc crust at the margin of the Indian or the Western Australian craton. • The source rocks for 1317–913 Ma detritus were arc magmatic rocks formed by oceanic lithosphere subduction at the margin of Rodinia. We present a systematic study of micaschists and felsic gneisses from the Huangyuan Group of the Central Qilian block in NW China, with aims to unravel the connection with the Rodinia supercontinent. The micaschists have detrital zircon ages of 2895–928 Ma that peaking at 1.80–1.40 Ga. They show strongly increasing zircon εHf(t) values of −8.1 to +12.1 from 1.6 Ga to 1.4 Ga. Detrital zircon ages from the felsic gneisses are dominantly 960–913 Ma with εHf(t) values of −0.1 to −10.7. The micaschists have a wide range of whole-rock major element compositions, and the felsic gneisses have higher SiO 2 contents, combined with lower other major element contents than those of the micaschists. All samples have trace element compositions consistent with upper continental crustal origin. The protoliths of the micaschists are dominantly shales and minor wackes with maximum depositional ages from ca. 1317 to 928 Ma. The protoliths of the felsic gneisses are mostly wackes with a maximum depositional age of ca. 927 Ma. The source materials for these metasedimentary rocks originated from intermediate to felsic igneous rocks. The variable maximum depositional ages of the metasedimentary rocks in the Huangyuan Group indicate that their protoliths constituted a sedimentary series with a long history of deposition starting at ca. 1317 Ma in an oceanic island arc-related basin that developed through a transitional continental arc-related basin into an active continental marginal basin at ca. 927 Ma. It is inferred that the 1795–1321 Ma detritus was sourced from juvenile arc crust at the margin of the Indian or the Western Australian craton. The source rocks for 1317–913 Ma detritus were arc magmatic rocks formed during assembly of Rodinia. A sequence of initial intra-oceanic subduction (ca. 1317–967 Ma) and continuous oceanic crust-continent subduction with formation of a mature continental arc (ca. 967–896 Ma) at the margin of Rodinia during the formation of the Central Qilian block is suggested. [ABSTRACT FROM AUTHOR]

Abstract Geological evolution of the Eastern Tianshan in the Late Paleozoic is significant to understanding the multiple accretions and final formation of the southern Central Asian Orogenic Belt. Here, we report new whole-rock geochemical and Sr–Nd isotopic data, and in situ zircon U–Pb ages for three typical A-type granitic intrusions (syenogranite, K-feldspar granite and monzonitic granite) and one dioritic pluton in the central Eastern Tianshan, NW China, in order to constrain their petrogenesis, tectonic setting and geodynamic evolution. Zircon LA-ICP-MS U–Pb ages indicate that the syenogranites and K-feldspar granites were both formed during a short time interval in the Early Permian (284–286 Ma), whereas the diorites were crystallized at 293 ± 6 Ma. The monzonitic granites were generated at 307 ± 3 Ma, earlier than the other two granitic intrusions. The three kinds of granites (syenogranite, K-feldspar granite and monzonitic granite) have high HFSE, HREE and Y/Nb ratios (1.68–2.84), and remarkably low Sr and Ba contents, with the absence of aluminium-rich minerals and show metaluminous to weakly peraluminous natures, indicating geochemical characteristics of aluminous A 2 -type granites. These granites show negative ε Nd (t) (−3.32 to −4.40) values and Mesoproterozoic two stage Nd model ages (T DM 2 = 1.36 to 1.43 Ga), which suggest a relatively old crustal source for these rocks. The Sr–Nd isotopic compositions imply that the Mesoproterozoic metamorphic basement of the Central Tianshan Block can be considered as a potential magmatic source for these aluminous A 2 -type granites. In addition, they have geochemical characteristics similar to the experimental melt that was derived from partial melting of crustal metaigneous rocks at the depth of middle to lower crust levels. Therefore, the granites were most likely produced by partial melting of metaigneous rocks in a post-collisional extensional setting. The diorites have low SiO 2 and high MgO, with uniform (87Sr/86Sr) i values (~0.7055), negative ε Nd (t) values (−4.11 to −4.59) and Mesoproterozoic two stage Nd model ages (T DM 2 = 1.41 to 1.45 Ga). They have higher Ti/Zr (42.8–46.7) and Ti/Y (280–359) ratios than continental crust and show negative Nb-Ta-Ti anomalies, which can be explained by partial melting of a relatively fertile mantle modified by old crustal materials of the Central Tianshan Block. The formation of the dioritic pluton was induced by an upwelling asthenosphere in an extensional geodynamic setting. Based on the zircon saturation temperatures of these A-type granites and the distribution of Late Carboniferous to Early Permian mantle-derived intrusions, a slab breakoff model is suggested to interpret the formation of the studied A-type granites and diorites. We infer that the slab breakoff was initiated in the Late Carboniferous and ended in the Early Permian. Highlights • Early Permian A2-type granites were identified in the Central Tianshan Block. • The Early Permian diorites were produced by partial melting of a fertile mantle. • These rocks were formed in a post-collisional extensional geodynamic setting. • The extension setting was triggered by a Late Carboniferous-Early Permian slab breakoff. [ABSTRACT FROM AUTHOR]

The Yili-Central Tianshan Block, as a Late Paleozoic major continental silver of the Central Asian Orogenic Belt, holds a massive volume of Carboniferous volcanic rocks, occurring as subparallel magmatic belts. However, the petrogenesis and tectonic implications of these volcanic rocks remain enigmatic. This study compiled isotopic age data for mapping their temporal-spatial character, and conducted petrogenetic study of these magmatic belts, aiming to understand their tectonic implications. Our compiled dataset reveals four magmatic belts in the Yili-Central Tianshan Block, including the Keguqinshan-Tulasu belt and the Awulale belt in the north, and the Wusun Mountain belt and the Haerk-Nalati belt in the south. In addition, our new zircon U-Pb dating results define two significant Early Carboniferous eruptive events (ca. 355–350 Ma and 325 Ma) in the Wusun Mountain belt. Volcanic rocks of the early significant eruptive event (ca. 355–350 Ma) in the Wusun Mountain comprise basalt, trachy-andesite, andesite, dacite and rhyolite, which are similar to the typical rock assemblage of a continental arc. Their positive ε Nd (t) values (+0.3 to +1.5) and relatively high Th/Yb and Nb/Yb ratios suggest the derivation from a mantle source with additions of slab-derived components. The gabbroic dykes and rhyolites of the late volcanic event (ca. 325 Ma) form a bimodal rock association, and they show alkaline features, with relatively low Th/Yb and Th/Nb ratios, and higher positive ε Nd (t) values (ε Nd (t) = +3.3–+5.0). It is interpreted that the gabbroic dykes and rhyolites may have been derived from mantle and juvenile crustal sources, respectively. The isotopic and trace elemental variations with time elapse of the Wusun Mountain magmatic belt show an important clue for strengthening depletion of the magma sources. Considering the distinctive temporal-spatial character of the Carboniferous volcanic rocks, two separate subduction systems in the southern and northern margins of the Yili-Central Tianshan Block were suggested to be the causes for extensive emplacements of the igneous products, which may be in an association with synchronous subduction of the South Tianshan and the North Tianshan oceanic plates, respectively. In this tectonic context, the Carboniferous magmatic rocks of the Wusun Mountain may be a tectonic response to the change in magma sources due to back-arc propagation in the western Chinese Tianshan. [ABSTRACT FROM AUTHOR]

Granitoid magmatism is extensively developed in the Altai Superterrane, but the timing of magmatic events is not so well determined. In this study, twelve granitoid intrusions from Southwest Mongolia were dated by the zircon U–Pb method and analyzed for zircon Hf isotopic compositions. The new age data indicated three phases of magmatic emplacement: Middle Paleozoic (398–350 Ma), Late Paleozoic (317–289 Ma) and Triassic (ca. 244–211 Ma). The first-phase magmatism is mainly composed of hornblende-bearing I-type granitoids, formed during a long-lasting subduction process in the Early to Middle Paleozoic. The second-phase magmatism was manifested by a few small intrusions, primarily distributed along the Erqis fault zone, and probably formed in a transitional tectonic regime from subduction to post-tectonic setting in the Late Paleozoic. The third-phase magmatism was represented by post-tectonic granitoids emplaced in an intraplate extensional setting. Model ages that were calculated using the composition of new continental crust are predominantly Neoproterozoic to Early Paleozoic, indicating that the protoliths of granitoids were likely dominated by Paleozoic juvenile crust with minor Neoproterozoic materials. The Altai Superterrane was a huge Paleozoic tectonic collage produced by amalgamation of subduction–accretion complexes in the margin of the Siberian continent and the Tuva–Mongol microcontinent. [ABSTRACT FROM AUTHOR]

Abstract: Paleozoic intermediate-acidic volcanic rocks exposed in the northwestern Chinese Altai mainly consist of two different lithologic suites: rhyolite suite (RS) and dacite–rhyolite suite (DRS), which were both assigned to the late Ordovician Dongxileke Formation. Zircon U–Pb dating results demonstrate that the RS suite was formed in the late Ordovician (443±2 and 445±2Ma), while the DRS suite yielded much younger ages (411±4Ma) that are consistent with the early Devonian Kangbutiebao Formation of the Chinese Altai. Zircons from the two suites all have high ε Hf(t) values (mostly +2 to +9), indicating a source dominated by juvenile crustal materials. Rhyolites from the two suites are strongly peraluminous and have high SiO2 (70.53–76.94wt.%) and ε Nd(t) values between −1.7 and −0.6, similar to those of the Paleozoic granitoids (>300Ma) but higher than the Early Paleozoic Habahe sediments, suggesting an origin by partial melting of a juvenile crustal source dominated by meta-igneous rocks. Dacite samples from the DRS suite possess high SiO2 contents (64.71–67.77wt.%) and Mg# values (∼52). They have ε Nd(t) values similar to those of the Habahe sediments, which, in combination with their relative high Th/Yb (>3.5) and low Ba/La (<40) ratios, suggests the dacite was originated from sediment-derived melts modified by depleted mantle peridotite. The Mg-rich dacite formed in a critical period (around 410Ma), during which voluminous granitic intrusions and rhyolite were produced. Extensive partial melting of subducting sediments in the early Devonian is in agreement with a high geothermal gradient in the Chinese Altai. A hot subduction regime is proposed to interpret the early Devonian tectonic evolution of the Chinese Altai. [Copyright &y& Elsevier]

Abstract: Paleozoic granitoid magmatism played an important role in the tectonic evolution of the Chinese Altai, and zircon U–Pb and Hf isotopic compositions have been determined for samples from eleven granitic plutons/batholiths. The Jiadengyu gneissic granitic pluton yielded a zircon U–Pb age of 479Ma, and thus it does not represent Precambrian basement as suggested previously. Our results and published data demonstrate that voluminous granitoids were continuously emplaced over more than 30% area of the Chinese Altai during the period from 447Ma to 368Ma with a climax at ca. 400Ma. Ages for zircon overgrowth rims demonstrate additional thermal events at ca. 360 and 280Ma, respectively. Positive ε Hf(t) values (0 to +9) of normal magmatic zircons suggest that the granitoid magmas were derived from juvenile sources. Xenocrystic zircon cores are 543–421Ma old and also give positive ε Hf(t) values (+2.5 to +12), suggesting their origin as early crystallized minerals in the magma chambers or as inherited cores from newly-accreted meterials. The strong magmatism at ca. 400Ma significantly changed the Hf isotopic composition of the magma source by substantial input of juvenile material in a relatively short period. Geophysical, geological and geochemical data support that ridge subduction was a possible mechanism for the strong magmatism ca. 400Ma and the above mentioned change of Hf isotopic composition in the magma source. [Copyright &y& Elsevier]

Abstract: The basement characteristic of the Chinese Altai is not firmly constrained, which has strictly hindered our understanding of the early crustal growth in the region. The presence of Precambrian detrital zircons in metasedimentary rocks and xenocrystic zircons in granitoids may be regarded as evidence for the existence of unexposed old basement rocks, but can also be explained as detritus originally derived from a nearby cratonic fragment. This paper reports detrital zircon U–Pb and Hf isotopic data for both low- and high-grade metasedimentary rocks from the Chinese Altai. Zircons from these samples have similar age patterns and Hf isotopic compositions. They are characterized by an overwhelming dominance of Neoproterozoic-Early Paleozoic ages, with prominent peaks around 465–542Ma and ɛ Hf(t) values varying from −25 to +15. Besides, a few zircons cluster at 1.8–2.0Ga and sparse ones yield discordant ages around 2.3–2.6Ga, and both give negative ɛ Hf(t) values between 0 and −28. Combined with previous results in the region, our data suggest that low- and high-grade metasedimentary rocks most likely derived from similar provenances. These data, plus some xenocrystic zircon ages from the granitoid rocks, are quite comparable with the age patterns of the micro-continents and arc terranes in western Mongolia. The zircon population of 440–580Ma is dominant for gneissic granitoids within the Neoproterozoic–Early Paleozoic terranes in western Mongolian and the Chinese Altai. The Precambrian zircons (>540Ma) resemble those from old rocks preserved in the Tuva-Mongolian (TM) block and its adjacent arc terranes. Therefore, we suggest that old zircons in the Chinese Altai more likely represent the detritus recycled from western Mongolia. Moreover, information from the TM-derived Precambrian zircons, combined with previous palaeomagnetic constraints, favors northern India as the potential origin for the TM block, from which a small micro-continent drifted northwards and incorporated into the CAOB in a time interval from the Neoproterozoic to Early Paleozoic. Accordingly, the crustal growth of the CAOB in western Mongolia and the Chinese Altai could be outlined by a single accretionary system, and secular amalgamation of magmatic arcs around a Precambrian micro-continent can account for the accretionary history of the region in the Early Paleozoic time. [Copyright &y& Elsevier]

Abstract: Tarim craton is one of the major cratons in Central Asia. Basement rocks of the craton, such as TTG gneisses, are dominantly exposed in the northern (Kuluketage area) and the Eastern (Altyn Tagh Mountain). Recent years, only a few reliable Archean ages have been obtained for the basement rocks in the Altyn Tagh Mountain. Geochronological and geochemical studies have been conducted on the orthogneisses exposed in the Kuluketage area in order to unravel complex history of the Tarim craton. Zircon U–Pb dating of the rocks yielded three weighted mean 207Pb/206Pb ages of 2516±6, 2575±13 and 2460±3Ma, indicating that their protoliths were formed in the late Neoarchean to early Paleoproterozoic. The late Neoarchean orthogneisses exhibit low Sr/Y ratios (4–19) and Mg# values (35–44), with depleted Sr contents, negative Nb, Ta and Ti anomalies and strongly fractionated REE patterns ((La/Yb)N =13–62), displaying typical geochemical features of arc igneous rocks. In contrast, the early Paleoproterozoic orthogneisses are characterized by high-SiO2 contents, Sr/Y ratios (37–67) and Mg# values (46–67), with variably fractionated REE patterns ((La/Yb)N =9–89), slight Sr enrichment and positive Eu anomalies, resembling high-SiO2 adakites derived from subducted basaltic slab-melts. The late Neoarchean TTGs have low ɛ Hf(t) values (–5 to +1) and initial Hf compositions (0.280987–0.281160) with Mesoarchean two-stage model ages (T DM2 =2.9–3.3Ga), suggesting that the crustal materials of the basement rocks in this area were initially extracted from a depleted mantle in the late Paleo- to Mesoarchean and were reworked in the late Neoarchean. The history of crustal growth is different from that of the North China and Yangtze cratons and thus implies relatively younger cratonization than the North China and Yangtze cratons. Zircons in the early Paleoproterozoic orthogneisses have high ɛ Hf(t) values (+4 to +10) and young Neoarchean two-stage model ages (2.5–2.7Ga), revealing a juvenile crustal growth event in the late Neoarchean. Because there is no record of coeval juvenile crustal growth in the other two cratons, we suggest a separate crustal evolution for the northern Tarim craton which was stayed far from the other two cratons before the early Paleoproterozoic. [Copyright &y& Elsevier]

Abstract: Subduction–accretion complexes occur widely in the Central Asian Orogenic Belt (CAOB). Due to the scarcity of fossils, the depositional timing of the Habahe flysch sequence of the subduction–accretion complex in the Chinese Altai is poorly constrained, which gave rise to much controversy in understanding the time of the basement and the tectonic evolution of the Chinese Altai. U–Pb dating of detrital zircons from the Habahe sequence in the northwestern Chinese Altai reveals a young zircon population with a mean 206Pb/238U age around 438Ma which, together with a mean 206Pb/238U age of 411±5Ma for the overlying rhyolite of the Dongxileke Formation, brackets the time of deposition of the sequence between early Silurian and early Devonian. The age of the Dongxileke rhyolite also indicates that the overlying Baihaba Formation possibly began to be deposited in the early Devonian, though U–Pb dating of detrital zircons from this formation gave a maximum depositional age of ∼438Ma. The youngest detrital zircons and metamorphic grains of the Habahe sequence reveal different provenance to the sequence in the east. The youngest and metamorphic zircon grains, with early Paleozoic, Neoproterozoic and pre-Neoproterozoic populations, suggest a multi-source for the Habahe sequence. The predominantly early Paleozoic zircons, characterized by concentric zoning, high Th/U ratios and euhedral shapes, imply that the sediments of the sequence were mostly derived from a proximal magmatic source. Based on the age patterns of the Neoproterozoic and pre-Neoproterozoic populations, the Tuva–Mongol Massif, along with adjacent island arcs and metamorphic belts, may be an alternative source region for the Habahe sequence. In view of new geochemical and chronological data for granitoids and advancement in the study of regional metamorphism in the Chinese Altai, we suggest a tectonic model of subduction beneath a huge subduction–accretion complex for the evolution of the Chinese Altai in the early Paleozoic. [Copyright &y& Elsevier]

Northeast Asia located at the margin of the Paleo-Pacific/Pacific plate provides a detailed record of subduction-related orogenic activity. In order to shed light on Mesozoic-Cenozoic tectonic processes arising from the complex interaction and juxtaposition of multiple tectonic domains, we performed zircon U-Pb and apatite U-Pb, fission-track (FT) and (U-Th)/He analyses in the Zhangguangcai Range, a major mountain range in northeastern Asia. Our zircon and apatite U-Pb results indicate that most granites in the Zhangguangcai Range were emplaced at shallow crustal levels in the early Jurassic (~200–173 Ma) along with a minor amount of Triassic granites (~232 Ma). Volcanic rocks of the Maoershan and Ningyuancun formations were erupted at ~190–175 Ma and ~182–177 Ma, respectively. This Early Mesozoic magmatic activity is related to subduction of the Mudanjiang oceanic plate that separated the Jiamusi and Songliao blocks. Apatite FT analysis of granites and volcanic rocks reveals three groups of cooling ages clustering at ~193–171 Ma, ~158–129 Ma and ~118–102 Ma, while AHe analysis of granites yielded three groups of cooling ages at ~149–135 Ma, ~106–85 Ma and ~57–48 Ma. Based on these data and thermal history modelling, we propose that the central Zhangguangcai Range experienced episodic, multi-stage exhumation at shallow crustal levels since the Jurassic. Early-Middle Jurassic exhumation took place during the closure of the Mudanjiang Ocean, which resulted in unroofing of granites in the central Zhangguangcai Range and topographic growth of the Songliao block. Late Jurassic-Early Cretaceous exhumation occurred within an extensional tectonic setting, which has previously been documented across northeast Asia. Such exhumation could have been linked to lithosphere delamination and resulted in basin and range topography style, prior to the change in subduction parameters of the Paleo-Pacific plate and/or collision and strike-slip translation of the Okhotomorsk block in the Late Cretaceous. • Most of the granites in the Zhangguangcai Range were emplaced at shallow crustal levels in the early Jurassic. • The Zhangguangcai Range experienced pulsed Mesozoic exhumation. • Early to Middle Jurassic exhumation resulted in the unroofing of granites in the central Zhangguangcai Range. • Late Jurassic-Early Cretaceous exhumation likely resulted in a basin and range topography. [ABSTRACT FROM AUTHOR]