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The Amdo microcontinent which separates the Qiangtang terrane to the north and the Lhasa terrane to the south is a key terrane for reconstructing the tectonic evolution of Central Tibet. We report the new finding of retrograde eclogites within the Amdo microcontinent in this study. The eclogites are characterized by peak metamorphic mineral assemblages of garnet, omphacite, rutile and quartz and underwent a four‐stage metamorphic evolution, including a peak eclogite facies stage (M1) at ~20–24 kbar and 580–620°C, followed by an HP granulite facies decompression stage (M2) at ~13–15 kbar and 750–780°C, a subsequent MP‐UHT granulite facies heating stage (M3) at 8–10 kbar and >840°C and a final amphibolite facies retrogression (M4) at 5.3–6.0 kbar and 560–580°C. The eclogites exhibit rare earth element distribution patterns and trace element abundances similar to those of N‐MORB and arc‐related volcanics, with depleted whole‐rock εNd(t) values of 3.4 to 4.2, and are inferred to have formed in a back‐arc basin tectonic setting. Zircon and rutile U–Pb dating yields a protolith age of 226 ± 5 Ma, a peak eclogite facies metamorphic age of 190 ± 1 Ma, an HP granulite facies metamorphic age of 179 ± 1 Ma and an amphibolite facies retrograde age of 172 ± 1 Ma. The clockwise P–T–t paths and the oceanic protolith signature of retrograde eclogites suggest that part of the back arc basin was subducted to depths of ~80 km. Tectonic erosion associated with the subduction of the Amdo microcontinent beneath the Tethys Ocean accounts for the deep subduction of the back‐arc basin and the absence of arc magmatic rocks in the northern Amdo microcontinent. [ABSTRACT FROM AUTHOR]

The Amdo microcontinent located within the Bangong–Nujiang Suture Zone (BNSZ) holds one of the important keys to understand the tectonic evolution of Central Tibet before the Qiangtang‐Lhasa terrane collision during the Mesozoic. Newly discovered eclogites were reported within the Amdo microcontinent in this study, and their metamorphic evolution is deciphered by petrographic observations, pseudosection modelling, geochemistry, and zircon U–Pb dating. The eclogites are characterized by peak metamorphic mineral assemblages of garnet, omphacite, rutile, and quartz, and underwent a four‐stage metamorphic evolution, including eclogite facies stage (M1) at ~20–24 kbar and 580–620°C, followed by HP granulite facies decompression stage (M2) at ~13–15 kbar and 750–780°C, subsequent MP–HT granulite facies heating stage (M3) at 8–10 kbar and >840°C, and final amphibolite facies retrogression (M4) at 5.3–6.0 kbar and 560–580°C. The eclogites exhibit rare earth element (REE) distribution patterns and trace element abundance similar to those of N‐MORB and arc‐related volcanics, which are inferred to have formed in a back‐arc Basin tectonic setting. Zircon U–Pb dating yields eclogite facies metamorphic age of 190 ± 1 Ma. The clockwise P–T–t paths and the oceanic protolith signature of retrograde eclogites suggest that part of the back‐arc Basin was subducted to the depths of ~80 km. The subsequent ultra‐high temperature metamorphic overprinting may be related to the upwelling of the asthenosphere. Tectonic erosion associated with the subduction of the Amdo microcontinent beneath the Tethys Ocean accounts for the deep subduction of the back‐arc Basin and the absence of arc magmatic rocks in the northern Amdo microcontinent. [ABSTRACT FROM AUTHOR]

The Bangor area is located in the middle part of the Bangong–Nujiang Suture Zone (BNSZ), where a large number of Middle Jurassic‐Early Cretaceous magmatic rocks are exposed, and is a key area for studying the tectonic evolution of the Bangong–Nujiang Tethys Ocean (BNO). However, the arc magmatic system triggered by the southward subduction of the BNO has not been systematically identified in the northern margin of the Lhasa Terrane, and the timing of initial subduction and closure is still controversial. In this study, four granite, two amphibolite, and one gabbro samples from the Bangor area yield two clusters intrusive ages of 162–168 Ma and 121–133 Ma. The Stages I and II granites show whole‐rock geochemistry similar to those of continent arc magmatism, characterized by enrichment in large ionic lithophile elements (LILEs; e.g., Th, Rb, K) and depletion in high field strength elements (HFSEs; e.g., Nb, Ta, P, Ti). The Stage I magmatic rocks consist of granodiorite, amphibolite, and gabbro and have similar zircon εHf(t) values of −10.1 to −3.5, which may be formed by partial melting of enriched mantle wedge related to the southward subduction of the BNO. The Stage II highly differentiated I‐type granites show positive zircon εHf(t) values of +1.5 to +9.9, which are considered the product of highly differentiated processes via the mixed magma derived from depleted mantle and lower crustal rocks. The Stage II I‐type granites show negative zircon εHf(t) values of −9.2 to −0.7, which are derived from a mixed magma source generated by partial melting of lower crust and enriched lithospheric mantle. On the basis of data from this study and previous research studies, a four‐stage tectonic evolutionary model of the Bangong–Nujiang Tethys Ocean is constructed: Stage 1 (190–145 Ma), the northward and southward subduction of BNO formed a series of arc magmatism; Stage 2 (145–135 Ma), a magmatism lull occurred on the north side due to the subduction effect of the ocean plateau, while the southward subduction still continued; Stage 3 (135–116 Ma), the roll‐back of subducted slab enhanced the magmatism in this stage; and Stage 4 (<116 Ma), the closure of BNO lead to the formation of syn‐collisional magmatism. [ABSTRACT FROM AUTHOR]

Earth's first continental crust is formed by Archaean and mainly consisted of tonalite–trondhjemite–granodiorite with a small amount of diorites (DTTGs), which has an essential role in probing early crust–mantle dynamic regime and in understanding the formation mechanism of continental crust. Here, we present zircon U‒Pb dating and Lu‒Hf isotopes, whole-rock geochemistry, and petrography on DTTGs rocks in the Dunhuang Block. Three episodes of DTTGs were emplaced circa 2.67 Ga, 2.60 Ga, and 2.50 Ga. The circa 2.67 Ga TTGs exhibit high SiO2 contents (68.14–71.70 wt%), low MgO contents (0.65–1.31 wt%), and high ratios of (La/Yb)N (146 on average), with their enriched Nd-Hf isotopes [ƐHf (t) = -5.48–3.19 and ƐNd (t) = -5.77–0.53], indicating origination from partial melting of amphibolites at thickened lower crust. In contrast, the circa 2.60 Ga transitional TTGs exhibit relatively high MgO contents (2.80–3.39 wt%), flat REE (Rare earth element) patterns with moderate ratios of (La/Yb)N (20.49 on average), and dispersed Nd-Hf isotopes [ƐHf (t) = -5.48–3.19 and ƐNd (t)= −3.99–3.08]. Accordingly, circa 2.60 Ga transitional TTGs melts were produced by partial melting of the shallower crust induced by mantle-derived magma upwelling. The circa 2.50 Ga diorites exhibit low SiO2 (55.72–59.11 wt%) but high MgO (3.51–4.52 wt%) contents with positive Nd-Hf isotopes [ƐHf (t) = -0.16–4.17 and ƐNd (t) = 2.00–4.45], suggesting that they originated from partial melting of mantle wedges metasomatized by fluid from subduction slabs. Combined with the detailed petrogenetic studies and crustal thickness variation, we conclude that the complex crust–mantle interaction may be an essential reason for the Neoarchaean diversity of DTTGs from the Dunhuang Block, which experienced prolonged arc accretion before Neoarchaean, followed by delamination between 2.67 and 2.60 Ga and subsequently transitioned to subduction. [ABSTRACT FROM AUTHOR]

The North Qaidam subduction-collision zone is a typical Alpine-type ultra-high pressure (UHP) metamorphic zone due to the Early Palaeozoic subduction of the Qaidam Block beneath the Oulongbuluke Block, with an integrated record of oceanic subduction, continental subduction, collision, and exhumation to post-collisional extensional collapse. In this study, systemic petrology, zircon U-Pb geochronology, Hf isotopic data and whole-rock geochemical analyses have been carried out for granitoids in the North Qaidam UHP metamorphic units to determine their petrogenesis and further reveal the tectonic evolution of the continental collision orogen. Zircon U-Pb dating yields weighted mean ages of 433 ± 2 Ma, 351 ± 8 Ma, 416 ± 4 Ma, 389 ± 3 Ma and 383 ± 1 Ma, with the εHf(t) values of the latter three ages ranging from −2.4 to 3.3, −5.9 to 1.1 and −3.3 to 2.4, respectively. Based on field relationship, petrological, geochronological, and geochemical results, these granitoids could be divided three groups. The early group granodiorites (~433 Ma) show a marked chemical resemblance to adakites: (1) high La/Yb and Sr/Y ratios, with low Y and HREE values; (2) high Al2O3 and low Mg#, Cr, and Ni values with obvious positive Eu anomalies. Petrological and geochemical characters indicate that the early group adaktic granodiorites may be derived from partial melting of metabasite in a thickened mafic lower crust. The middle group granites (~416 Ma) have an affinity to I-type granitoids, characterized by high Na2O contents (>4.18 wt.%) and low A/CNK values, which were probably generated by partial melting of felsic gneiss of subducted continental crust. The late group granites (389 ~ 351 Ma) are also I-type granitoids, which were originated from partial melting of Mesoproterozoic crust, with minor mantle material input. According to a comprehensive study of these granitoids, along with regional geological background and HP-UHP metamorphism, a four-stage evolutionary process of the North Qaidam UHP metamorphic belt from oceanic subduction, continental subduction, collision to extensional collapse is proposed. After the final closure of the Proto-Tethys Ocean, the subducted continental crust experienced HP-UHP eclogite-faces metamorphism (460 ~ 430 Ma), and thickening of the lower crust lead to generation of adakites and S-type granites. Following break-off of the subducting oceanic slab (425 ~ 400 Ma), the reduction in negative buoyancy caused the exhumation of deeply subducted continental crust accompanied by associated anataxis and syn-collisional I-type granitoids, representing the transition in tectonic regime from compression to extension. Due to the tectonic transition, mantle-derived intrusions and post-collisional granitoids were emplaced during 400 ~ 350 Ma. Simultaneously, the pronounced decreasing in La/Yb and Sr/Y ratios of magmatic rocks (age of 460 ~ 350 Ma) suggested that the crustal thickness decreased gradually from syn-collisional to post-collisional stage. [ABSTRACT FROM AUTHOR]

• The metamafic rocks can be classified into high-Fe and low-Fe groups, and the former is similar to N-MORB and the latter is similar to E-MORB. • The high-Fe and low-Fe groups may have been derived from different parts of a mantle plume. • The Tarim Craton, North China Craton, and North Australia Craton may potentially dominated by the same superplume. In the Mesoproterozoic, there was an epic transition on Earth, the final breakup of the Columbia supercontinent. Understanding the dynamic mechanism responsible for the final breakup of Columbia supercontinent is crucial for establishing Earth's evolution that includes geology, environment and life. However, there is little research on what drove the breakup of the Columbia supercontinent. Here we focus on this issue by integrating new zircon U-Pb ages, Lu-Hf isotopes, and whole-rock geochemical data for metamafic rocks from the Oulongbuluke Block in the southeast of Tarim Craton. These data show that the protoliths of these metamafic rocks were emplaced at ca. 1.37–1.35 Ga and were divided into high-Fe and low-Fe groups. The high-Fe and low-Fe groups show geochemical character similar to normal mid-ocean ridge basalt (N-MORB) and enriched mid-ocean ridge basalt (E-MORB), respectively. The high-Fe group was formed by high degree (7%-9%) partial melting of spinel-phase lherzolite mantle source, whereas the low-Fe group was derived from low degree (5%-6%) partial melting of spinel-phase lherzolite mantle source. We propose that the high-Fe and low-Fe groups may have been derived from magmas from different parts of a mantle plume. The formation of the 1.37–1.35 Ga metamafic rocks in the Oulongbuluke Block may be related to the separation of the Tarim Craton into North and South Tarim cratons, which resulted in the opening of the initial Middle Tarim Ocean Basin. By comparison with the plume-induced Yanliao Rift of North China Craton and McArthur Basin of North Australia Craton, we present that these three cratons may potentially dominated by a superplume, forming circular rift zone and radiating dykes. This superplume triggered the continuous extension to most parts of Columbia and led to the final breakup of the Columbia supercontinent. [ABSTRACT FROM AUTHOR]

Tonalitic–trondhjemitic–granodiorite (TTG)-like leucosomes, which are formed from anatectic melts, record crustal growth and evolution and thus provide constraints on the process of anatexis. However, potential Mg isotope disequilibrium during crustal anatexis makes interpreting the genesis of anatectic melts challenging, thereby potentially hindering the application of the Mg isotope system in investigations of crustal evolution and crustal anatexis. A key factor in Mg isotope fractionation during anatexis is the behaviour of garnet, which becomes preferentially enriched in light Mg isotopes compared with other Mg-hosting minerals during partial melting processes. In this study, a combination of petrography, whole-rock geochemistry, and mineral microanalysis reveals that garnets in leucosomes from the Dulan area of the North Qaidam orogen, were formed by dehydration melting of hornblende. Garnet-bearing leucosomes yield low δ26Mg values (−0.70‰ to −0.33‰) compared with garnet-free leucosomes (−0.19‰ to −0.16‰) and global arc rocks (−0.35‰ to 0.06‰). The different Mg isotopic compositions are attributed to the effect of peritectic garnets on the Mg isotope system in anatectic melts. Quantitative modelling further indicates that the lower Mg isotopic values of garnet-bearing leucosomes require the incorporation of ∼5% peritectic garnets into anatectic melts during magma ascent. Our results demonstrate the influence of peritectic garnets on the Mg stable isotope system and highlight that this influence on the Mg isotopic compositions of peritectic minerals during crustal anatexis must be considered in interpretations of crustal evolution using the Mg isotope system. • The Grt-bearing TTG-like leucosomes show low δ26Mg values than Grt-free ones. • The Grt-bearing leucosomes could be explained by incongruent melting and garnet entrainment. • Garnet entrainment is first-order factor of δ26Mg values of TTG-like melts. [ABSTRACT FROM AUTHOR]

• The South Orogen underwent early post-collision during 1.90–1.85 Ga, followed by late post-collision during 1.80–1.73 Ga. • The North Orogen experienced early post-collision at 1.80–1.73 Ga and then entered the late post-collision at 1.67–1.60 Ga. • Finally, the South Orogen and North Orogen simultaneously entered the initial breakup stage during 1.55–1.47 Ga. The Tarim Craton located in the northwest of China, where the Paleo-Mesoproterozoic extensional magmatism related to the Columbia supercontinent is widely developed. However, the process and time of the extension and initial breakup of the Tarim Craton are still controversial during Paleo-Mesoproterozoic era. In this contribution, we present a systematic petrographic, geochemical, and zircon U-Pb-Hf investigation on Aketashitage granite dykes, Wulan granitic gneisses and Astingbulake metadiabases from the Tarim Craton. Results from our study indicate that the ca. 1.88–1.86 Ga Aketashitage granite dykes belong to I-type granites, which were probably derived from low degree partial melting of thickened Archean crust during early post-collisional setting. The ca. 1.55 Ga Wulan granitic gneisses also show the characteristics of I-type granites, which mainly came from partial melting of mafic lower crust with minor mantle-derived magma input during the rift setting. The ca. 1.55 Ga protoliths of Astingbulake metadiabases show affinity to ocean island basalts and/or continental flood basalts and were produced by partial melting of enriched continental lithospheric mantle under continental rifting setting. In conjunction with previous studies, it can be concluded that the Tarim Craton experienced episodic extension to initial breakup: the South Orogen underwent early post-collisional extension during ca. 1.90–1.85 Ga, followed by late post-collisional extension during ca. 1.80–1.73 Ga; the North Orogen experienced early post-collisional extension at ca. 1.80–1.73 Ga and then entered the late post-collisional extension at ca. 1.67–1.60 Ga; finally, the South Orogen and North Orogen simultaneously entered the initial breakup stage during ca. 1.55–1.47 Ga. Based on a comparison of the global Mesoproterozoic (ca. 1.58–1.45 Ga) magmatic activities as a response to the initial break up of the Columbia supercontinent, we suggest that the Tarim Craton (including the Oulongbuluke Block) and North China Craton were close to India, Australia, Yangtze, Siberia, Congo, São Francisco and West African. [ABSTRACT FROM AUTHOR]

Compared with the statement of the mantle plume hypothesis for large-scale plus high-volume intraplate magmatism, a series of OIB-like mafic rocks which are low-volume and spatially closely related to subduction zones still remain mysterious and inapposite to be explained by using traditional mantle plume hypothesis. In the North Qaidam, most previous studies have focused on ultra-high pressure metamorphic rocks and have paid little attention to mafic magmatism as a mechanism of generating magma with a mantle signature. The Kendelong (KDL) metagabbro with consistently intrusive ages of 485–490 Ma within the Olongbuluke microblock that is overriding plate above the subduction zone is analogous to Oceanic Island Basalts (OIBs) in geochemistry and formed contemporaneously with oceanic subduction. Analyzed samples of the KDL metagabbro have sporadic (87Sr/86Sr) i ratios of 0.7008–0.7063 that have been influenced by paulopost alteration, relatively uniform positive ε Nd (t) values of +0.3 to +1.4, zircon ε Hf (t) values of +1.5 to +6.8, and coupled Nd–Hf isotopes that lie on the terrestrial array. After ruling out the possibility of contributions from subducted enriched components and mantle metasomatites, geochemical features and isotopic compositions indicate that the magmas were derived from a relatively primitive asthenosphere without prior large-volume melt extraction. Rare earth element modeling shows that a low degree of partial melting (<10%) of an asthenospheric mantle source in the garnet stability field should be responsible for the magmatic origin of the KDL OIB-like metagabbro. Considering the temporal and spatial correlations between the KDL metagabbro and other types of mafic rock in adjacent regions, we propose that decompression melting of upwelling asthenosphere triggered by rollback of subducted oceanic slab is a plausible regime to explain the petrogenesis of the early Paleozoic KDL OIB-like metagabbro and to trace a fortuitous tectonic transition event. Moreover, even if the OIB-like magmatism is spatially related to subduction zones, the participation of subduction materials could not be an exclusive prerequisite to sentence its genesis. [Display omitted] • OIB-like magmation is reported in the North Qaidam. • OIB-like magmation in the North Qaidam is related to plate tectonics. • Magmas were derived from decompression-induced melting of upwelling asthenosphere. • Slab only provided geodynamic regime for the Kendelong OIB-like metagabbro. [ABSTRACT FROM AUTHOR]

The Tibetan Plateau is located in the eastern part of the Tethys-Himalayan megatectonic domain and consists of a series of microplates that successively accreted to the southern edge of the Eurasian Continent. These microplates have undergone complex evolutionary processes during rifting, drift and collision. The gravity and magnetic anomalies show that the anomaly characteristics on the Tibetan Plateau is significantly different in the north-south direction, from the Qaidam Microplate to the Lhasa Microplate. In this paper, we apply an improved Logistic Filter method, combined with the upward continuation of gravity anomalies, to identify multi-scale tectonic boundaries in the Tibetan Plateau region. The results show that the edge detection results correspond well in space with fracture zones and suture/ophiolite zones. Also, there are clear discontinuities along both sides of the middle and western sections of the Bangong-Nujiang Suture Zone and the eastern section of the Jinshajiang-Ailaoshan Suture Zone. We refined the boundaries of five microplates, including the South and North Qiangtang and the South, Central and North Lhasa, in the southern Tibetan Plateau. Then, we analyzed the evolutionary processes of these microplates and the transformation of the types to which the microplates belonged during different historical periods by combining relevant evidences from other geological records and plate reconstruction. These microplates are strongly related to the evolutionary history of the Tethys Ocean. The closure of the Neo-Tethys Ocean triggered a large-scale orogeny between the Indo-Asian continents, and these microplates were eventually accreted in the orogenic belt. We analyze the formation patterns and boundary types of microplates in the evolutionary process and then divide into three stages, i.e., rifting-derived, accretion-derived, and subduction-derived stages. The transformation patterns of microplate types at different stages provide a new perspective for the study of the evolution of mega-orogenic belts. • Tectonic interpretation and microplate division of the Tibetan Plateau with gravity and magnetic data. • Multi-scale edge detection at different depths on the Tibetan Plateau by the improved Logistic Filter method. • A transformation pattern of microplate types during the evolution of Qiangtang and Lhasa microplates. [ABSTRACT FROM AUTHOR]

Magma mingling between mafic and felsic magmas is a plausible mechanism for the formation of mafic microgranular enclaves (MMEs) which are common worldwide. Through dissecting the MMEs with parentage of magma mingling, it can be ascertained how two types of magmas with contrasting physicochemical properties interplay and what implicit information magma mingling records in crust-mantle interaction. Here we present petrography, geochronology, major and trace elements, Sr-Nd-Hf isotopes, and mineral geochemistry for rock associations from the North Qaidam orogen, which provides new insights into the processes of magma mingling, petrogenesis of large-volume host plagiogranites and crust-mantle magmatic interaction. MORB (mid-ocean ridge basalt)-like and arc-like magmas can be distinguished from mantle-derived mafic samples with zircon U Pb ages ranging from 480 to 465 Ma. MORB-like magmas originated from a MORB-type asthenospheric mantle, whereas arc-like magmas were derived from an ultra-depleted asthenospheric mantle as a result of consecutive extraction of MORB-like magmas and late-stage metasomatism by subduction-related aqueous fluids. Given the content discrepancies for major oxides, gabbro-dioritic MMEs are formed by incipient mechanical mingling between gabbro-diorite magmas and felsic plagiogranite magmas. MMEs and host plagiogranites yield coincident crystallization ages of 478 Ma and overlapped whole-rock Sr Nd ((87Sr/86Sr) i = 0.7044–0.7052; ε Nd (t) = +4.6 ∼ +5.6) and zircon Hf isotopes (ε Hf (t) = +13 ∼ +16). The host plagiogranite magmas are most likely derived by partial melting of pre-existing analogues of gabbro-diorite intrusions under the condition of consecutive underplating of different batches of cognate magmas over short time scales, which in turn determine the consistent isotope compositions between MMEs and host plagiogranites. As for mineral geochemistry, the plagioclases with the highest An% value and the hornblendes implying the highest melt water content, appear within the MME-bearing plagiogranites next to the chilled margin of MMEs, illustrating that aqueous fluid and heat transfer play a pioneering but finite role in incipient magma mingling. The consecutive underplating of cognate mantle-derived magmas as an ultimate engine leads to the partial melting of newly emplaced basites to form massive plagiogranite magmas and geochemically stratified crust. With magma ascent into a shallow level of crust, magma mingling between underplated mafic magmas and resultant plagiogranite magmas is finally realized. • Enclaves originated from an ultra-depleted mantle metasomatized by subduction fluids. • Finite transfer of fluid and heat appeared from enclaves to hosts in magma mingling. • Consecutive underplating of cognate magmas resulted in overlapped isotopic signatures between enclaves and hosts. • Large-volume host plagiogranites derived from partial melting of antecedent basites. [ABSTRACT FROM AUTHOR]

[Display omitted] • Early Paleozoic syn-collisional I-type granitoids in the North Qaidam orogen reflect crustal reworking rather than growth. • Early Paleozoic granitoid magmas originated from Proterozoic and Paleozoic crustal sources in the North Qaidam orogen. • Inhomogenous thicknesses of overriding plate triggered by syn-collision induced hot mantle convection and granitoid incubation. Granitoids constitute the major theme in evaluating the growth and reworking of continental crust on Earth. Here we present U-Pb geochronology, geochemistry and Sr-Nd-Hf isotopes of the early Paleozoic granitoids emplaced during pre- and syn-collisional stages in the North Qaidam orogen to gain insights on the granitoid typology, genetic mechanism, as well as the implications for the evolution of continental crust. The pre- and syn-collisional granitoids in this region all belong to I-type granite and are derived from different continental crustal sources including late Mesoproterozoic to early Neoproterozoic metamorphic crystalline basement, and juvenile continental crust formed during early Paleozoic oceanic subduction. Granitic magmas derived from the two sources underwent a series of magmatic processes such as mixing or assimilation, which lead to the transitional geochemical and isotopic features, suggesting that besides source components, magmatic processes from melt extraction to granitoid emplacement also exerted an important influence on the formation of these granitoids and crustal maturation. Although S-type granitoids are commonly taken as the fingerprint for continental collision, our study emphasizes that the role of I-type granites formed in syn-collisional setting should not be underestimated. Besides subducted slab processes such as roll-back, retreat, or break-off, we propose a novel geodynamic model which envisages that the lateral inhomogeneity in lithospheric thickness triggered by continental collision within the overriding plate above subduction zone controlled the magmatism. Both growth and reworking of continental crust occur during oceanic subduction, whereas syn-collision setting is dominated by continental crust reworking as in the North Qaidam orogen. [ABSTRACT FROM AUTHOR]

• The Baibuziwan area has experienced three stages of metamorphism and anatexis at ~1.95 Ga, ~1.90 Ga, ~1.85 Ga, respectively. • It is confirmed for the first time that Baibuziwan migmatites were formed via Late-Paleoproterozoic fluid-fluxed melting. • The lithosphere after collisional orogeny of the Khondalite Belt may have experienced repeated asthenospheric upwelling. The metamorphism and anatexis of the Khondalite Belt may provide key information for the Late-Paleoproterozoic collisional orogeny of the North China Craton (NCC). Migmatites formed by anatexis are widely developed in the Daqingshan Complex, central Khondakite Belt. However, the timing and anatectic regime of these migmatites have not been constrained. In this paper, we present systematic petrographic, whole-rock geochemical, Sr-Nd isotopic, zircon U-Pb and Hf isotopic investigation of the Baibuziwan stromatic migmatite and different types of leucosome in the northwestern Daqingshan Complex. The results show that: (1) the metamorphic rocks in Baibuziwan underwent in-situ to in-source partial melting, and the anatectic melts migrated and gathered in different degrees; (2) the ∼2.37 Ga Bt-Hbl-Pl gneiss in the Daqingshan Complex is possible protolith of the Baibuziwan migmatites; (3) the Baibuziwan migmatites have experienced three stages of metamorphism and anatexis in the Late-Paleoproterozoic, i.e., ∼1.95 Ga, ∼1.90 Ga, ∼1.85 Ga; (4) the anatectic regime of the Baibuziwan migmatites is fluid-fluxed melting, which has been proposed for the first time in Daqingshan Complex. Combined with previous studies, we suggest that following the collisional orogeny, the thinned lithosphere of the Khondalite Belt may have experienced asthenospheric upwelling. The lower crust of the Daqingshan complex was heated and dehydrated repeatedly, and the generated fluid poured into the overlying crust, which eventually led to the episodic metamorphism and fluid-fluxed melting in the Baibuziwan area. [ABSTRACT FROM AUTHOR]