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Many granitoids and their eruptive equivalents are substantially derived from the uppermost proportion of continental crust, and so their petrogenesis and source are significant in understanding the evolution and characteristics of continental crust. The Eocene felsic rocks in the Qiangtang block (central Tibet) commonly have enriched Nd isotope compositions and have been considered to be related to the recycling of ancient continental crustal material. In this paper we report new data on early Eocene felsic rocks with positive ε Nd (t) values in the northeastern Qiangtang block, which can be used to help understand Cenozoic evolution and characteristics of continental crust in the Qiangtang block. These rocks consist of rhyolites and occur in the Shanglaxiu and Xialaxiu areas in the north−eastern Qiangtang block. Zircon U−Pb dating yields ages of 47.8 ± 0.6 and 44.2 ± 0.7 Ma for the Shanglaxiu and Xialaxiu rhyolites, respectively, and so they represent the earliest record of Eocene magmatism in the Qiangtang block. The Shanglaxiu−Xialaxiu rhyolites have relatively low calculated zircon saturation temperatures (719–819 °C), along with high SiO 2 (74.8–83.3 wt%) and K 2 O (5.1–7.8 wt%) contents, and low MgO (0.2–0.3 wt%), Cr and Ni contents. They are enriched in light rare earth elements (LREEs), Rb, K, Th, Zr, and Hf, and are depleted in Nb, Ta, Ti, Sr, and P, with moderately negative Eu anomalies. The Shanglaxiu rhyolites have positive whole−rock ε Nd (t) (0.3–0.4) and zircon ε Hf (t) (1.8–10.4), and variable zircon δ18O (6.3–7.3‰). The Xialaxiu rhyolites have slightly different whole−rock ε Nd (t) (−1.5 to −1.6), but similar zircon ε Hf (t) (2.2–7.7) and δ18O (6.7–7.2‰). We propose that the Shanglaxiu−Xialaxiu rhyolites were most probably generated by partial melting of the pre−existing juvenile crust with the addition of minor sedimentary material. This partial melting was possibly triggered by the south−dipping continental subduction of the Songpan−Ganzi block. The pre−existing juvenile crust was probably formed during the subduction of Paleo−Tethyan oceanic slab in Paleozoic−Early Mesozoic. • The Shanglaxiu-Xialaxiu rhyolites were formed at 44–48 Ma. • These rhyolites were generated by partial melting of juvenile crust and sediments. • These rhyolites were formed during continental subduction. • The juvenile crust might be formed during Paleozoic-Early Mesozoic. [ABSTRACT FROM AUTHOR]

Due to the unclear tectonic setting of the Jurassic ophiolites within the Bangong-Nujiang suture, how and when intra-oceanic subduction initiated within the Bangong Meso-Tethys remain controversial. Based on the new petrological, geochemical, and geochronological data reported in this paper, ∼190–180 Ma MORB-like ophiolites and OIB-like mafic rocks were identified from the Shiquanhe ophiolitic complex in the western Bangong-Nujiang suture. The MORB-like gabbros exhibit strong light rare earth elements (LREEs) and heavy rare earth elements (HFSEs) depletion and were derived from partial melting of a highly refractory depleted mantle source with limited slab-derived fluids. The OIB-like mafic rocks are enriched in LREEs and HFSEs and were originated from the melting of upwelling asthenospheric mantle without subduction additions. The data for the MORB-like ophiolites reported in this paper and previously published data demonstrate the formation of Early Jurassic fore-arc ophiolites in response to the Early Jurassic intra-oceanic subduction initiation within the Bangong-Nujiang suture. The Early Jurassic OIB-like rocks formed in the extensional tectonic setting, together with regional geological evidence, suggest that the Early Jurassic initial subduction event within the Bangong Meso-Tethys resulted in broad upper plate extension. Our study not only reveals the intra-oceanic subduction initiation age of the Bangong Meso-Tethys but also implies that subduction initiation can cause strong extension in a wider region of the upper plate in the Tethys oceanic system, not just in the fore-arc region. • Discovery of MORB-like fore-arc ophiolite (190–185 Ma) in the Shiquanhe area. • Identifying of OIB-like gabbro-monzonite (185–180 Ma) in the Shiquanhe melange. • Confirming Early Jurassic intra-oceanic subduction initiation in Bangong Ocean. [ABSTRACT FROM AUTHOR]

The Gangdese arc underwent the most intense magmatic flare-up of southern Tibet in the early Eocene (peaked at ∼50 Ma), generating widespread plutonic and volcanic rocks both along and across the arc. However, the dynamic mechanism for the magmatic flare-up is mysterious. This paper systematically analyzed the petrology, mineralogy, geochronology, and geochemistry of the early Eocene volcanic and intrusive rocks in the Pangduo basin in the eastern Gangdese arc. These rocks yielded identical zircon U Pb ages of ∼50 Ma and similar isotopic compositions. The low-silica (< 60 wt%) rocks, including basalt andesite and trachyandesite, result from low degree (2–3%) partial melting of garnet-bearing lithospheric mantle. Based on textural observations and geochemical studies, coupled with Rhyolite-MELTS modeling and zircon trace elements Rayleigh fractionation models, the following research results were obtained. The high-silica rhyolite, ignimbrite, and granite porphyry are the product of limited melt extraction, while the quartz monzonite belongs to the associated residual silicic cumulates. The quartz monzonitic porphyry and trachydacite show a widespread dissolution structure and high formation temperature of ∼850 °C. Whole-rock geochemical mixing model results indicate that they are generated by mixing products of mafic magma, high-silica melts, and remelting melts of quartz monzonite. The volcanic and intrusive rocks in the Pangduo basin are considered as a volcanic-plutonic complex, resulting from the synergistic effect of melt extraction and cognate magma mixing. Both the complex magmatic processes and the early Eocene magmatic flare-up are attributed to mafic magma injection. • The Pangduo volcanic-plutonic complex with various rock types is well exposed in the Pangduo basin, southern Tibet. • The rhyolitic ignimbrite and the quartz monzonite are extracted melts and corresponding residual cumulates, respectively. • Melt extraction and magma mixing via mafic magma injection promote the large-scale magma formation. [ABSTRACT FROM AUTHOR]

When impinging on the lithosphere in spreading ridges or intra-plate settings, the asthenospheric mantle can significantly influence plate tectonics. However, the active role of the asthenospheric mantle on subducting slabs remains poorly understood. The main reason for this dispute is the lack of typical geochemical mafic rocks in the subduction zone. In this paper, we first report the Early Jurassic (187 Ma) Yurongguo Nb-enriched basalts in the western segment of the Bangong-Nujiang suture zone. These samples show typical Nb-enriched basaltic features with high Na 2 O, TiO 2 , Nb (>7 ppm), high Nb/Th (average = 11.05), Nb/La (average = 1.37) and Nb/U (average = 72.98) ratios. Unlike the adakite-related Nb-enriched basalts, the Yurongguo Nb-enriched basalts formed from the mixture of magmas derived from upwelling asthenosphere (20–30%) and depleted mantle (70–80%) in the spinel lherzolite region (<70 km). We conclude the Yurongguo Nb-enriched basalts were formed in the fore-arc basin setting with the influence of slab rollback, which occurred under the intra-oceanic subduction. Two southward intra-oceanic subductions may exist in the western part of the Bangong-Nujiang Tethyan Ocean in the Jurassic. The Early Jurassic (200–180 Ma) intra-oceanic subduction formed the fore-arc basin, probably accompanied by asthenospheric mantle activity at the same time, followed closely by flat subduction due to the oceanic plateau. After a period of geological stabilization, the Late Jurassic (170–150 Ma) was the period when the spreading of the little ocean basin ceased, and the second intra-oceanic subduction occurred. We proposed an oceanic plateau-subducted oceanic slab interaction and overriding intra-oceanic subduction model for the Meso-Tethyan subduction in the western Tibetan Plateau. • Yurongguo rocks were formed in 187 Ma, which are the typical Nb-enriched basalts. • OIB (20–30%) and MORB (70–80%) mixed to form the Yurongguo Nb-enriched basalts. • Yurongguo Nb-enriched basalts are the consequence of intra-oceanic subduction. • Oceanic plateau played an important role in the intra-oceanic subduction. [ABSTRACT FROM AUTHOR]

Magmatic flare-ups are well recognized as a fundamental feature of continental arc magmatism, but its driven mechanism still remains unresolved. Exploring this behavior is of significance in unraveling the deep dynamic processes related to plate subduction and crustal growth. In central Tibet, arc magmatism within the South Qiangtang terrane (SQT) caused by the northward subduction of the Bangong-Nujiang Ocean (BNO) is featured by a prominent high-flux event during Jurassic, but its details and corresponding geodynamic background are not determined. This paper reports geochronological and geochemical data of the granodiorites near the Rigen Co area in the middle part of SQT. These rocks were generated at ca. 150 Ma and display typical adakitic characters. Their low MgO (1.41–2.39 wt%), initial 87Sr/86Sr ratios (0.7055–0.7059) and slightly low ε Nd (t) values (−1.9 to −1.2), and high zircon ε Hf (t) (+1.9 to +8.4) and δ18O values (+6.6 to +9.2 ‰) suggest the adakitic granodiorites were derived from partial melting of subducted crust involving 10–20% inputs of overlying sediment. Our sample, together with previous reports delineates a distinct slab-window association (adakite and oceanic island basalt (OIB)-type diabase) along the southmost of SQT, which coincided with the magmatic flare-up at ca. 155 Ma as revealed by the age spectra of magmatic rocks and complementary detrital zircons. Furthermore, a trench-ward migration is recognized for the arc magmatism from ca. 170 Ma to 155 Ma, implying a slab-roll back process. Accordingly, this high-flux event with the slab-window formation is best explained by the trigger of ensuing slab break-off. These results, combined with other geological evidence, contribute new constraints on elucidating the Jurassic geodynamic evolution of the BNO subduction. • The Rigen Co granodiorites were generated by oceanic crust melting at ca. 150 Ma. • Jurassic arc magmatism in the South Qiangtang terrane shows a trench-ward migration. • The Late Jurassic magmatic flare-up was triggered by slab break-off. • A oceanic plateau-continent collision was proposed to explain these processes. [ABSTRACT FROM AUTHOR]

Genetic pattern of a continuous volcanic series of andesites, dacites, and rhyolites from the Ziruco area, northern Tibet was debated in this paper to evaluate the later evolution of A-type granites. We present new zircon U Pb ages, whole-rock geochemical, zircon Hf isotopic, and whole-rock Sr Nd isotopic data for these magmatic rocks. Our analysis shows that the zircon U Pb ages of the andesites, dacites, and rhyolites are ca. 105.4 Ma, ca.105.3 Ma, and ca.106.8 Ma, respectively. The andesites have high Nb contents (16.3–24.9 ppm) and Nb/U ratios (22.7–32.4), and chondrite normalized REE and primitive-mantle normalized trace element patterns similar to Nb-rich basalts. They were most likely derived from the mantle that had been metasomatized by melts derived from subducted slab and sediment, and then underwent fractional crystallization. The dacites and rhyolites have high Ga/Al ratios (3.05–3.70 and 2.93–3.43, respectively), REE (226–256 and 195–285 ppm, respectively), Nb (30.0–34.4 and 20.3–24.4 ppm, respectively) and Zr contents (443–513 and 147–163 ppm, respectively), and zircon saturation temperatures (856–886 °C and 823–837 °C, respectively), which are similar to A-type granites. The dacites were most likely formed by partial melting of underplated basaltic lower crust with ilmenite and zircon, followed by slight fractional crystallization. The rhyolites were most likely formed by fractional crystallization of the dacite magmas. The minerals of fractional crystallization probably include feldspar, apatite, zircon, and titanite. This continuous volcanic series in Ziruco area may be related to break-off of the Meso-Tethyan slab in northern Tibet during the late Early Cretaceous. Our studies indicate that fractional crystallization is important later evolutionary process for A-type granites from the crustal source area, and it mainly controls the geochemical characteristics of significant negative Ba, Sr, P, Ti, and Eu anomalies of A-type granites from the crustal source area. [Display omitted] • Albian A-type granites in northern Tibet were from underplated basaltic crust. • Break-off of the Meso-Tethyan slab occurred during the late Early Cretaceous. • Fractional crystallization is important for A-type granites from lower crust. [ABSTRACT FROM AUTHOR]

Exploring magmatic 'flare-up' events can be used to unravel dynamic Earth processes including plate subduction and crustal growth. However, the cause and mechanism of magmatic 'flare-up' remain unresolved. The abundant magmatic records that are preserved in the Lhasa Terrane on the southern Tibetan Plateau make it an important region to study the episodic nature of the secular magmatism. This paper presents geochronological, mineralogical, and geochemical data that describes the Dazhuka diorites in the central-western and Sangri granites in the eastern parts of the southern Lhasa Terrane. Zircon LA–ICP–MS U Pb data indicate that these rocks were generated around ~95–90 Ma. Both are enriched in large ion lithophile elements and depleted in high field strength elements, indicating geochemical affinity with subduction-related magmatic rocks. The Dazhuka diorites have low SiO 2 contents (54.49–56.72 wt%), with moderate Mg# (41.7–42.7) and rare earth element fractionation ((La/Yb) N = 6.9–8.6), and homogeneous whole-rock 87Sr/86Sr i (0.704204–0.704480), ε Nd (t) (+3.5 − +4.1), and zircon ε Hf (t) (+10.2 − +13.3). These features suggest that the Dazhuka diorites originated in the spinel-garnet transition zone within the lithospheric mantle of a mantle wedge environment. The Sangri granites have high SiO 2 (64.36–69.54 wt%), Al 2 O 3 (14.27–15.61 wt%), and (La/Yb) N (4.6–49.6) and Sr/Y (34.7–119.3) ratios, indicating geochemical affinity with adakites. Low MgO (1.3–2.22 wt%) and depleted Sr-Nd-Hf isotopes (whole-rock 87Sr/86Sr i = 0.704099–0.705453, ε Nd (t) = +2.9 − +3.5, zircon ε Hf (t) = +7.1 − +9.3) suggest that the granites were derived from oceanic crust. The types of magmatic rocks that are distributed over the central-western and the eastern parts of the southern Lhasa Terrane differ, with higher magmatic temperatures in the east as compared to the central-west. These results indicate that different areas in the southern Lhasa Terrane may have experienced different geodynamic processes, with oceanic ridge subduction in the eastern part of the southern Lhasa Terrane and normal oceanic plate subduction in the central-western part. These different types of subduction processes are likely to have caused the magmatic 'flare-up' and variation in the magmatism of southern Tibet. [Display omitted] • Both Dazhuka diorites and Sangri granites formed in early Late Cretaceous. • Dazhuka diorites were derived from the lithospheric mantle. • Sangri granites with adakitic affinity were sourced from the oceanic crust. • Multiply Neo-Tethys Ocean plate subduction processes result in magmatic 'flare-up'. [ABSTRACT FROM AUTHOR]

The history of crustal thickening is critical for comprehending the evolution process of the Tibetan plateau. The genetic relationship and spatiotemporal distribution of adakitic rocks with high Sr/Y, (La/Yb) N ratios may impose fundamental constraints on specific geodynamic and crustal thickening processes. The Songka intrusive suite consists of adakitic rocks with high-Mg adakite (monzonites), low-Mg adakitic rocks (quartz monzonites), and gabbroic-diorites. Their geochemical characteristics, petrogenesis, and geodynamic implication is discussed in this paper. Songka high-Mg adakites formed when subducting Neo-Tethyan oceanic slab melts were assimilated by mantle peridotite at elevated temperatures (average Ti-in-zircon temperatures of sample SK1319 are 830 °C). Low-Mg adakitic rocks exhibit markedly different geochemical characteristics than those formed in the juvenile thickened lower crust. The least-squares mass balance and trace element simulations indicate that Songka low-Mg adakitic samples were formed at a degree of 60–65% fractional crystallization of melts resembling Songka high-Mg adakites. Songka gabbroic diorites are formed in the metasomatic mantle wedge. The genetic relationship between these rocks indicates that the crust of the southern Tibet did not appear to thicken obviously during the early stage of late Cretaceous (100–90 Ma). The intensive emplacement of late Cretaceous high-Mg adakites (Mg# > 50) and mafic rocks (SiO 2 < 52%) in the southern Lhasa terrane around 95–90 Ma, together with the slow convergence velocity of the Indian-Asian continent, can be explained by the response of rapid crustal thickening and Neo-Tethyan slab rollback at 95–90 Ma. • High-Mg adakitic rocks were formed from partial melting of Neo-Tethyan slab. • Coeval low-Mg adakitic rocks were produced by fractional crystallization. • Rapid crustal growth and Neo-Tethyan slab rollback occurred at 95–90 Ma. [ABSTRACT FROM AUTHOR]

Mafic igneous rocks are volumetrically limited in collisional orogens but are significant for revealing specific geological processes. The mafic intrusive rocks in the eastern Lhasa batholiths along the Parlung fault (the easternmost branch of the Jiali fault zone), southern Tibet, are commonly regarded as the easternmost mafic components of an inferred Shiquanhe–Nam Tso–Jiali–Parlung suture zone, which is assumed to mark a back-arc oceanic basin related to the southward subduction of the Bangong-Nujiang Meso-Tethyan Ocean. However, the petrogenesis and tectonic setting of the mafic intrusive rocks have been poorly constrained. In this paper, we present petrological, geochemical and geochronological data for this mafic suite and evaluate the tectonic implications. The mafic intrusive rocks can be approximately divided into pyroxene-amphibole cumulate and medium-grained and pegmatitic hornblende gabbros that are characterized by the occurrence of very calcic plagioclase (An = 80–92) and abundant amphibole crystals, indicating an H 2 O-enriched magmatic signature. Their whole-rock compositions, which include negative Nb and Ta anomalies, also suggest a subduction-modified setting. Zircon Lu Hf isotope data show that their magmas were formed by magmatic mixing between melts derived from enriched subcontinental lithospheric mantle and liquids derived from upwelling asthenosphere. Zircon U Pb dating results reveal crystallization ages of ~114–110 Ma for this mafic suite, corresponding to the late stage of regional granitic magmatism (~135–110 Ma) that was related to the Lhasa-Qiangtang collision after the closure of the Bangong-Nujiang Meso-Tethyan Ocean. Given that coeval mafic and felsic rocks are distinctly controlled by the Parlung fault, we suggest that asthenospheric upwelling due to the break-off of the subducted Bangong-Nujiang oceanic slab not only induced partial melting of the enriched subcontinental lithospheric mantle but also resulted in regional rifting/extension and the initial development of the eastern Jiali (Parlung) fault. • Early Cretaceous mafic magmatism along the eastern Jiali fault is demonstrated. • The mafic suite marks the initial development of the eastern Jiali fault. • The active Jiali fault zone might exploit and connect the pre-existing faults. [ABSTRACT FROM AUTHOR]

The role of the Meso-Tethyan oceanic plateau in the growth of the Tibetan Plateau is debated. In this paper, we report coexistence of large-scale mid-ocean ridge basalt (MORB)-like and enormous ocean island basalt (OIB)-type mafic rocks from the Dongco ophiolitic rocks of the Bangong–Nujiang Suture Zone. The MORB-like rocks host tholeiitic geochemical characterizes, and have supra-subduction zone affinity such as enrichments in large ion lithophile elements (LILEs), depletions in high field strength elements, high ε Nd (t) values (+6.5 to +9.5) and low initial 87Sr/86Sr ratios (0.7033–0.7050). The OIB-type rocks have an alkaline affinity and are characterized by enrichments in LILEs and light rare earth elements, strongly negative Sr anomalies, variable ε Nd (t) values of −3.7 to +7.3, and low initial 87Sr/86Sr ratios ranging from 0.7034 to 0.7050. Metamorphic zircons from amphibolites in the sole of the ophiolitic rocks yielded U Pb ages of 104–100 Ma. Detrital zircons from the upper Cretaceous sandstone of the Abushan Formation (K 2 ab) yielded young U Pb ages of 100–86 Ma. Considering the regional geology, we suggest that the Dongco MORB-like rocks were derived from a depleted mantle source and formed from an intra-oceanic subduction-related setting, representing remnants of normal oceanic crust, whereas the OIB-type rocks were derived from an enriched mantle source representing remnants of a Meso-Tethyan oceanic plateau. Our preferred hypothesis is that the Meso-Tethyan oceanic plateau experienced a phase of accretion at 104–100 Ma, which probably increased local subduction erosion of the upper plate and providing provenance for the deposition of the K 2 ab sandstone. The maximum depositional ages of K 2 ab sandstone constraint the minimum ages for closure of the Bangong–Nujiang Tethys Ocean most likely at 100–86 Ma. • Identified a new 104 Ma metamorphic event in the western Bangong–Nujiang Suture • Closure of the Bangong–Nujiang Tethys Ocean most likely occurred during 100–86 Ma • Dongco ophiolitic rocks contain remnants of normal oceanic crust and oceanic plateau [ABSTRACT FROM AUTHOR]

The initial Hf isotope composition of zircon in high-grade metamorphic rocks is an important tracer for protolith origin as well as for the growth and evolution of continental crust. However, less attention has been paid to the behavior of Lu-Hf isotopes in peritectic reactions during partial melting of the continental crust. In this paper, we present a combined study of zircon U-Pb ages, Lu-Hf isotopes and trace elements as well as petrology and whole-rock geochemistry for migmatites close to the eastern Himalayan syntaxis in southeastern Tibet. The results show that peritectic zircons in the migmatites have significantly higher 176Hf/177Hf ratios than their protolith zircons. More interestingly, the 176Lu/177Hf ratios and the contents of high field strength elements (such as Nb, Ta, and Hf) and heavy rare earth elements are significantly elevated in the peritectic zircons compared to the protolith zircons. This suggests that garnets with high Lu/Hf ratios and other minerals (such as titanite, ilmenite, amphibole, and biotite) with moderate Lu/Hf ratios were decomposed during crustal anatexis, contributing to the Hf isotope composition of peritectic zircons. This is confirmed by petrographic observations that garnet and biotite occur as residues or remnants in mesosomes (biotite gneiss) and some leucosomes (felsic veins), but are absent in the melanosomes of the target migmatites. Therefore, the peritectic zircons were produced together with anatectic melts through peritectic reactions and acquired the elevated 176Lu/177Hf ratios compared to the inherited zircons from the protoliths if no peritectic garnet was coevally produced during the crustal anatexis. In this regard, the greatly elevated Hf isotope compositions of peritectic zircons in anatectic granites cannot faithfully reflect the Hf isotope composition of parental rocks. As such, great care must be taken when using Hf isotope ratios to trace the nature of parental rocks with respect to magmatic processes and crustal evolution. • Peritectic zircon have higher Lu/Hf and Hf isotopic ratios than protolith zircons. • Peritectic zircon also have higher HFSE contents than protolith zircons. • Minerals with high Lu/Hf ratios than zircon were decomposed during crustal anatexis. [ABSTRACT FROM AUTHOR]

Granitoids and related mafic microgranular enclaves (MMEs) in continental collision zones may provide crucial insights into the formation and evolution of continental crust. In this paper, we report an investigation into the mineralogy, zircon U–Pb geochronology, whole-rock major and trace elements, and Sr–Nd–Hf isotopic geochemistry of granodiorites and hosted MMEs, as well as monzogranites, from the Zhaxiding intrusive complex in the Gangdese batholith, southern Tibet. Zircon U–Pb dating suggests that these rocks were emplaced during the early Eocene (49 to 47 Ma). Field investigation and petrological observations indicate that the MMEs represent globules of a mafic magma that was injected into the host felsic magma. On the basis of depleted zircon Hf (ε Hf (t) values of +6.5 to +9.2) and whole-rock Sr–Nd (ε Nd (t) values of +1.6 to +2.6) isotopic compositions, along with their whole-rock compositions, the MMEs are interpreted as having resulted from mixing of mantle-derived magma with juvenile crust-derived melts. The granodiorites and monzogranites are metaluminous and have positive zircon ε Hf (t) (+6.3 to +8.9 for granodiorites and +1.7 to +10.2 for monzogranites) and whole-rock ε Nd (t) (+1.6 to +1.9 for granodiorites and +0.5 to +1.1 for monzogranites) values. The granodiorites further exhibit continental crust-like chemical compositions (e.g., enrichment in Rb, K, and Pb and depletion in Nb and Ta) and high Mg# values, suggesting that they originated from partial melting of juvenile crust with the involvement of mantle-derived melts. However, the monzogranites have lower P, Ti, and total rare earth element contents, similar Rb, Ba, and Sr contents, and uniform Eu anomalies compared with the granodiorites, and were likely generated by fractional crystallization of amphibole and Fe–Ti oxides from juvenile crust-derived magma. We propose that underplating of mantle-derived magma likely triggered coeval crustal magmatism and that mixing of the mantle- and crust-derived magmas and subsequent crystallization differentiation formed the intermediate to felsic Zhaxiding intrusive complex in the Gangdese batholith. The continental crust-like bulk compositions of the intermediate to felsic magmatic rocks represent a net addition of juvenile material to continental crust. Our study thus indicates that magma mixing and differentiation play a significant role in the formation of andesitic to dacitic continental crust in collision zones. • The granitoids in Gangdese batholith were emplaced between 49 and 47 Ma. • The host granite and associated MMEs are products of magma mixing. • Mantle and juvenile crust sources contribute to the Zhaxiding intrusive complex. • The syn -collisional magmatism makes a net contribution to continental crust growth. [ABSTRACT FROM AUTHOR]