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The tectonic transition from oceanic subduction to continental collision is a fundamental process during orogenesis, yet the nature of such transition and associated deep geodynamic processes for the Tibetan Plateau are still controversial. The long‐lived magmatism of the Gangdese Belt of southern Tibet provides an excellent opportunity to study the tectonic transition from subduction of the Neo‐Tethys oceanic lithosphere to the continental collision between Indian and Asian plates. We present zircon U–Pb–Hf isotopes, whole‐rock geochemistry, and Sr–Nd isotopes for the intrusions from Maizhokunggar, southern Lhasa Terrane. The zircon U–Pb dating indicates that two episodes of magmatism occurred in the Maizhokunggar region, ca. 70 Ma diorites and ca. 60 Ma granitoids. The ca. 70 Ma diorites are medium‐K calc‐alkaline and characterized by pronounced high‐field‐strength element depletion and light rare earth element enrichment, similar to arc‐type rocks. They have homogeneous (87Sr/86Sr)i ratios (0.70378–0.70424) and εNd(t) values (+2.6 to +3.4), and εHf(t) (+5.9 to +13.0) with relatively young depleted mantle model ages (307–762 Ma), suggesting that they were generated from the juvenile mafic lower crust induced by the underplating of basaltic magmas from depleted mantle wedge. The ca. 60 Ma granitoids, Kajiacun (KJC) granodiorites, and Qulongxue (QLX) and Bangdacun (BDC) monzogranites are high‐K series and metaluminous to weakly peraluminous. The KJC granodiorites with high Sr/Y ratios (25–43) are adakitic and were likely derived from partial melting of a thickened lower crust. The BDC monzogranites have more evolved Sr–Nd–Hf isotopes and older Nd–Hf model ages than the QLX monzogranites. These geochemical variations were mainly controlled by the fractionation crystallization with assimilation of ancient crustal materials. We propose that at ca. 70 Ma, the subduction of the Neo‐Tethys oceanic slab triggered the partial melting of the juvenile lower crust and formed the diorites with arc affinity, and then the initial collision (>60 Ma) between the Indian and Asian plates caused locally thickened lower crust, resulting in adakitic granodiorites. Our study sheds light on the lithospheric scale magma evolution from the deep mantle to the shallow crust during the critical geodynamic transition to collision, and early uplift. [ABSTRACT FROM AUTHOR]

The Indochina Block is considered as a part of the Indian and Australian margins of Gondwana, and the Tam Ky‐Phuoc Son Suture Zone (TPSZ) lies in its central region as the boundary between the Truong Son Belt and Kon Tum Massif (KTM). However, the early Palaeozoic tectonic nature and timing of magmatism within the TPSZ are still controversial. To tackle the issue, we present herein the zircon U–Pb ages with their trace‐element compositions of five dioritic–granitic granitoids in the TPSZ. U–Pb age dating of magmatic zircons from them suggests emplacement ages of ca. 447–450 Ma. Whole‐rock geochemistry of the samples shows low TiO2 contents (0.36–1.18 wt%) and Mg# (42.04–53.07). They display enrichment in light rare earth elements ([La/Yb]N = 4.10–15.19), pronounced negative Nb, Ta and Ti anomalies relative to the chondrite‐normalized rare earth element patterns and primitive mantle‐normalized trace‐element distribution diagrams. The whole‐rock geochemical characteristics together with zircon trace‐element compositions from the same samples revealed their petrogenesis of a continental arc tectonic setting. Combining the results from this study together with available data from the TPSZ and its neighbouring units, we suggest accretionary orogenesis was responsible for generation of the Ordovician magmatic arc in the KTM, which will provide better understanding of the Early Palaeozoic evolution of the eastern Indochina Block. [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 Heilongjiang Complex records the evolution history of the Mudanjiang Ocean, which is of great significance to constrain the amalgamation process of the Jiamusi and Songnen‐Zhangguangcai Range massifs. We carried out petrological, chronological, geochemical, mineral chemical and electron backscatter diffraction (EBSD) fabric analyses on the Heilongjiang Complex in the Yilan area. The latest zircon U–Pb dating results show that the protolith ages of the amphibolite are 261.3 ± 3.0 Ma and 261.8 ± 3.3 Ma, while that of the granodioritic mylonite is 207.8 ± 2.2 Ma. The amphibolites and granodioritic mylonite are enriched in large‐ion lithophile elements (e.g., Rb, Ba, and Sr) and light rare earth elements, with depletion in high‐field‐ strength elements (e.g., Nb, Ta, Zr, and Hf), indicating that the formation of the protoliths of the amphibolites and granodioritic mylonite is related to the subduction of the Mudanjiang oceanic plate under the Songnen‐Zhangguangcai Range Massif. The amphibolites and granodioritic mylonite both experienced two periods of metamorphic and deformation events. The metamorphic degree of the early period of metamorphism is low amphibolite facies, which records a clockwise P–T path from early increased temperature and pressure to a late isothermal depressurization. The P–T path reveals that this period of metamorphism is associated with the collision between two massifs. The later period of metamorphism reaches low greenschist facies, accompanied by deformation, which may be related to the rapid exhumation of the Heilongjiang Complex. This study provides a new perspective for exploring the collision and collage process of the Jiamusi and Songnen‐Zhangguangcai Range massifs. [ABSTRACT FROM AUTHOR]

The East Kunlun Orogenic Belt (E‐KOB) of the northern Tibetan Plateau is an accretionary orogenic belt, which has experienced complicated tectonic evolutionary processes of the Proto‐ to Palaeo‐Tethys Ocean. The Muztagh‐Buqingshan‐Anemaqen ophiolitic mélange zone (MBAM) is an accretionary complex related to the northward subduction of the Tethyan Ocean. Numerous intrusions outcropped in MBAM have witnessed the long‐term subduction‐accretionary process and thus site the key to comprehending the tectonic evolution of the E‐KOB, as well as the Tethyan Ocean. In this study, petrological, geochronological, and geochemical studies of the Marzheng diorites in the MBAM were carried out to explore the Early Palaeozoic tectonic evolution of the E‐KOB. Zircon U–Pb dating analysis suggests that the diorites were formed in the Early Ordovician at ca. 470 Ma. Furthermore, the εHf(t) values (5.3–14.1), Mg# values (39.7–51.2), and Nb/Ta (12.8–14.8), Zr/Hf (33.8–44.8), and Lu/Yb (0.15–0.16) ratios are generally close to those of depleted mantle‐derived rocks and the diorites were originated from a depleted asthenosphere mantle source. In addition, these diorites are characterized by enriched light rare earth elements (LREEs) (La and Nd) and depleted high‐field‐strength elements (HFSEs) (Nb, Ta, P, and Ti), similar to the fingerprints of arc‐related gabbroic‐dioritic rocks. This is also consistent with their high H2Omelt (6.0–8.3%) and oxygen fugacity (logfO2 = −14.3 to −13.5) features, indicating that they were formed in a subduction‐related setting. Our new investigations suggest that the Proto‐Tethys Ocean in the East Kunlun was still actively subducting northward during the Early Ordovician. [ABSTRACT FROM AUTHOR]

Early Jurassic Kaoshan medium‐ and fine‐grained syenogranites emplaced along the Yitong–Shulan Fault Zone in the southern part the Zhangguangcai Range, central Jilin Province, intruded Middle Triassic granitoids and Carboniferous‐Devonian intrusive rocks. They have medium‐ and fine‐grained textures and contain K‐feldspar, quartz, plagioclase, and biotite. They are peraluminous (A/CNK = 1.13–1.20) and have high values of SiO2 (74.60–75.82 wt%), total alkalis (Na2O + K2O = 8.28–9.18 wt%), light rare earth elements (20.89–56.14 ppm), large‐ion lithophile elements, and FeO/MgO = 2.78–5.93. In contrast, they feature low values of CaO (0.40–0.49 wt%), TiO2 (0.05–0.14 wt%), P2O5 (0.02–0.04 wt%), Sr (24.20–62.59 ppm), heavy rare earth elements (5.14–11.80 ppm), high‐field‐strength elements, and δEu (0.41–0.76), and the calculated zircon saturation temperatures (Tzr) range from 804 to 870°C, all of which are similar to the geochemical signatures of anorogenic A1‐type granites. Zircon U–Pb geochronology analyses from the medium‐ and fine‐grained syenogranites yield concordia ages of 193.18 ± 0.95 Ma (MSWD = 6.7, n = 18) and 190.29 ± 0.92 Ma (MSWD = 8.7, n = 17), respectively, and belong to the Early Jurassic Sinemurian stage. In situ Hf isotope analyses of dated zircons yield εHf(t) values ranging from +17.0 to +9.7 and Hf model ages (TDMC) of 225–614 Ma. Their whole‐rock (87Sr/86Sr)i (0.704740–0.704133) and εNd(t) values (+2.8 to +0.2) are similar to those of many coeval A2‐type granites in this region, and they form an A‐type granite assemblage. Consequently, the Kaoshan medium‐ and fine‐grained syenogranites were probably derived from partial melting of juvenile lower crust and might be related to the subduction of the Palaeo‐Pacific Plate. [ABSTRACT FROM AUTHOR]

Although a large number of Triassic magmatism were found in the Qiangtang terrane, central Tibet, the tectonic evolution of the Shuanghu Palaeo‐Tethys Ocean remains controversial. In this study, we present the zircon U–Pb age and major‐ and trace‐element data for the Late Triassic pluton from the Cairi area in the eastern Qiangtang terrane. Zircon U–Pb dating indicates that the samples were emplaced at ca. 230 Ma. The magmatism from the Cairi area primarily consists of granites (SiO2 = 67.28–77.74), with the characteristics of medium‐K calc‐alkaline, metaluminous, and peraluminous. The Cairi granites are enriched light rare earth elements ([La/Yb]N = 5.01–10.56), with obvious Eu anomaly (Eu/Eu* = 0.32–0.47). The Cairi granites are characterized by low 1,000 × Ga/Al (2.10–2.64), FeO*/MgO (3.41–5.03), Ce (57.95–114.36 ppm), Y (27.30–45.19 ppm), and negative correlation between P2O5 and SiO2. These geochemical features reveal that the Cairi granites are calc‐alkaline, I‐type granites. The four samples show relatively restricted (87Sr/86Sr)i ratios (0.70598–0.70724), 143Nd/144Nd ratios (0.51192–0.51196), and εNd(t) of −8.19 to −7.54. Based on the variations of Rb–Sr–Ba and Th–La–Nb and the zircon saturation of temperatures (806–868°C), we suggest that the primary magmas of the Cairi granites were generated through various degrees of mixing between sediments and mantle‐derived components. Petrological and geochemical characteristics, as well as regional geological characteristics indicate that the Cairi granites formed in a continental volcanic arc setting. Our results, in combination with the coeval granites and elcogite, indicate that the generation of Late Triassic (ca. 230 Ma) Cairi granites is related to ocean ridge subduction and subsequent development of a slab window. [ABSTRACT FROM AUTHOR]

Petrogenesis of the Gaozhuang granitic aplites (GZGA) plays an important role in understanding the regional tectonic evolution and metallogenesis of the Gaozhuang gold deposit (GZGD) in the northern Qinling orogenic belt (NQOB). Here, we present new zircon U–Pb dating on two granitic aplite samples yielding a 25‐zircon grain weighted average age of 129 ± 1 Ma (MSWD = 0.6), suggesting that GZGA formed in the Early Cretaceous. Major element results show that GZGA are: (a) characterized by higher SiO2 and alkali and lower MgO and CaO, belonging to the high‐K calc–alkaline series; (b) enriched in large‐ion lithophile elements and depleted in high‐field‐strength elements, which show negative spider–diagram anomalies of Nb, Ta, P, and Ti; (c) enriched in light rare earth elements and depleted in heavy rare earth elements without obvious Eu negative anomalies and (La/Yb) N ratios ranging from 71.9–107. GZGA compositional variation is controlled mainly by source composition and degree of partial melting and suggests no obvious relationship with fractional crystallization. GZGA samples belongs to the adakite, showing higher Sr (346–528 ppm), lower in Y (4.71–5.67 ppm) and Yb (0.26–0.33 ppm), and Sr/Y ratios of 63.5–93.2, indicating that GZGA originated from partial melting of the thickened lower crust (source depth >50 km) with residual phases of garnet, rutile, and insignificant plagioclase. Results find that GZGA is a product of the Early Cretaceous regional lithosphere delamination, in which Gaozhuang area adakitic aplite magmas and ore‐bearing fluids were discharged nearly simultaneously, and the mixed magma–fluid systems crystallized, forming GZGA and GZGD, while rapidly ascending to the shallow crust along faults. Using GZGA, a prospecting indicator, we infer that the deep part of the GZGD should possess endogenetic Au metallogenic potential. [ABSTRACT FROM AUTHOR]

The Kunyushan granitic complex in the Jiaodong Peninsula, East China, is located in the northeast part of the Sulu UHP metamorphic belt. It is the transition belt of the North China Craton and Sulu UHP metamorphic belt. Field relationship and dating results revealed five intrusive phases of the Kunyushan granitic complex were modified into gneissic fine‐grained garnet‐bearing monzogranite (G1), gneissic medium‐ to fine‐grained monzogranite (G2), medium‐ to coarse‐grained monzogranite (G3), medium‐grained monzogranite (G4), and porphyritic coarse‐ to medium‐grained monzogranite (G5). All these phases have similar rock assemblages of peraluminous, calc‐alkaline, I‐type monzogranites. The monzogranites had primitive mantle‐normalized patterns enriched in light rare earth elements (LREE) and lithophile elements (Sr, Ba, and Rb), but depleted in heavy rare earth elements (HREE) and high‐field‐strength elements (Nb, P, and Ti). LA‐ICP‐MS zircon U–Pb dating shows that the crystallization age of the Kunyushan granitic complex extends at least from 157.7–142.0 Ma. The weighted average ages of G1‐G5 were 145.6 ± 1.9 Ma, 145.8 ± 0.5 Ma, 147.2 ± 0.7 Ma, 154.2 ± 0.6 Ma, and 155.0 ± 0.7 Ma, respectively. G5 to G1, from the middle to the edge shows a trend of gradually becoming younger. Zircon grains from different phases have similar 176Hf/177Hf values from 0.281917 to 0.282298, and εHf(t) values from −27.6 to −14.0, with a weighted average of −22.6 ± 0.5, typical of crustal‐derived origin. The corresponding two‐stage model ages TCDM are from 2,910 to 2,066 Ma, with a weighted average of 2,603 ± 31 Ma. Hf–Sr–Nd–Pb isotopes and inherited zircons suggest that the parental magma of the Kunyushan granitic complex was derived from melting of basement rocks of the North China Craton and the Yangtze Craton. The magmatism presumably took place under the background of subduction and back‐arc extension of the Palaeo‐Pacific plate. We infer that the Kunyushan granitic complex was produced by partial melting of the thickened lower crust, through delamination of the thickened lower crust during the Late Jurassic. This magmatic event may mark the beginning of the extensive Mesozoic thinning of the lithosphere in East China. [ABSTRACT FROM AUTHOR]

The bulk sand samples and detrital zircons collected from the Atasta and Alvarado beach areas in the southwestern Gulf of Mexico have been analysed for geochemistry and U–Pb ages to constrain their provenance. The index of chemical maturity and SiO2/Al2O3 ratio of the Atasta and Alvarado beach sands indicated low compositional maturity. The chondrite‐normalized REE patterns and Eu anomalies of the Atasta and Alvarado beach sands suggested that the sands were derived from felsic and intermediate igneous rock types, respectively. A wide range in Th and U contents of the Atasta (~1.0–884 ppm and ~39–883 ppm, respectively) and Alvarado (~13–2,641 ppm and ~21–2,457 ppm, respectively) zircons likely indicates that the detrital zircon populations consist of zircons derived from multiple sources. The total rare earth element (ΣREE) content in the Atasta and Alvarado zircons ranges from ~151 to 2,088 ppm and ~154 to 3,580 ppm, respectively. The chondrite‐normalized REE patterns of zircons from the two beach areas show slightly depleted light REE (LREE) and enriched heavy REE (HREE), as well as positive Ce and negative Eu anomalies. A few zircons of Alvarado beach lack a Ce positive anomaly but exhibit a distinct Eu anomaly. The differences in REE patterns among zircons between the two beach areas revealed the variations in the type of source terranes, which supplied zircons to the beach areas. The detrital zircon age distribution for the Atasta beach is homogeneous, showing a prominent Proterozoic peak (~596–2,461 Ma; number of samples n = 62) with few Cenozoic (~10.43–65.2 Ma; n = 4) and Palaeozoic (~380–468 Ma; n = 5) zircons. The zircon U–Pb ages of Alvarado beach revealed Cenozoic (~0.25–63.9 Ma; n = 65), Mesozoic (~67.9–181.2 Ma), Palaeozoic (~252–297 Ma), and Proterozoic (~589–1,501 Ma) age clusters with predominant Cenozoic zircons. The comparison of zircon REE chemistry and geochronological data of this study with published data suggests that the source terranes, which supplied zircons to the Atasta beach, were the Chiapas Massif and Oaxacan complexes, whereas the zircons in the Alvarado beach were derived from the nearby Mexican Volcanic Belt and Eastern Alkaline Province. The provenance variation between the two beach areas was also revealed by the dissimilarities in zircon age clusters. [ABSTRACT FROM AUTHOR]

A number of Late Mesozoic (ca. 130 Ma) A‐type granitic plutons have been identified in Southeast (SE) China. The Lingshan pluton, located in the Gan‐Hang Belt, is a typical one which is mainly composed of coarse‐grained biotite monzogranite in the pluton centre and medium‐ to coarse‐grained syenogranite on the margin. Zircons from three representative samples show U–Pb ages of 132.0 ± 1.3, 134.4 ± 2.1, and 133.0 ± 1.9 Ma, respectively, indicating that the Lingshan pluton were formed in the Early Cretaceous. The Lingshan granites display typical A‐type affinities, with high SiO2, K2O, Na2O + K2O, rare earth element (REE) and high field strength element (HFSE) contents, high Ga/Al and Fe# [FeOT/(FeOT + MgO)] ratios and Zr + Nb + Ce + Y contents, and apparent depletion of Ba, Sr, Ti, and Eu. The calculated zircon saturation temperatures (TZr) are high, ranging from 841 to 966 °C (mean of 886 °C). The εHf (t) values and TDM2 (Hf) of the Lingshan granites mainly vary from −3.0 to 0.2 and 1.18 to 1.38 Ga, respectively. Consistently, the εNd(t) values vary from −3.9 to −2.8 and TDM2 (Nd) range from 1.16 to 1.26 Ga. These isotopic data indicate that the Lingshan granites were likely to be generated by partial melting of Mesoproterozoic metamorphic basement rocks with the involvement of a certain amount of mantle‐derived materials. Subsequent fractional crystallization processes were also suggested during subsequent magma evolution. We propose that the ca. 130 Ma Lingshan granites together with other coetaneous A‐type granitic rocks from adjacent region indicate a back‐arc extensional setting in SE China during Early Cretaceous. The extension event might be caused by the rollback of paleo‐Pacific Plate which results in upwelling of the asthenosphere and subsequently induces a high degree partial melting of Mesoproterozoic basement sedimentary material, to generate the A‐type granitic plutons along the Gan‐Hang Belt. [ABSTRACT FROM AUTHOR]