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[Display omitted] • Bega Batholith shows isotope-chemical correlations consistent with magma mixing. • Compositional zoning in Bega is strongly controlled by arc tectonic geometry. • Two discrete mantle sources are involved in granite petrogenesis in Bega. • Estimated ∼ 50 % of the batholith is constituted by juvenile-mantle material. • Bega Batholith represents an episode of crustal growth at ca 400 Ma. Cordilleran granitic batholiths represent significant episodes of crustal growth and differentiation, and commonly display lateral isotopic and chemical variations. Establishing the tectono-magmatic processes responsible for generating this compositional asymmetry is important for understanding crustal evolutionary processes throughout the Phanerozoic. The Bega Batholith, an example of a 'Cordilleran style' granite batholith, is the largest I-type Siluro-Devonian granite complex in the Lachlan Fold Belt (LFB) of southeastern Australia and comprises seven granite supersuites that display systematic lateral isotopic and chemical asymmetry. From west to east towards the present-day continental margin, an increase in the content of Na 2 O, Sr, Al 2 O 3 , and P 2 O 5 , with concomitant decreases in CaO, Sc, Rb, and V are observed. In the same direction, whole-rock initial 87Sr/86Sr decreases from 0.7098 to 0.7039, ε Nd values increase from −8.3 to +4.4, and δ18O decreases from 10.2 ‰ to 7.9 ‰. Depleted-mantle model ages also decrease from ca. 1800 Ma in the west to 600 Ma in the east. Here, we address whether these chemical and isotopic variations were generated by interaction between two distinct components (mantle-derived magmas and supracrustal sources) or were alternatively produced by partial melting of infracrustal source rocks formed sequentially by much earlier episodes of crustal underplating. Combined whole-rock Nd-Sr-O isotopic and geochemical analyses indicate that several I-type supersuites exhibit chemical and isotopic correlations consistent with two-component magma mixing. This new evidence challenges the long-held view that I-type granites derive exclusively from the melting of infracrustal sources, and that granite terranes represent wholesale crustal reworking rather than new crustal growth. Our results show that the compositional zoning within the Bega Batholith is multifaceted. Firstly, the presence of two discrete mantle sources endows chemically and isotopically distinct eastern and western segments in the batholith. Secondly, within these compositionally distinct regions the lateral compositional changes across supersuites derives from mixing between mantle-derived and supracrustal sources. Finally, progressive extension within a developing back-arc environment regulates the ratio of crust-mantle contributions and compositional architecture of each I-type supersuite. [ABSTRACT FROM AUTHOR]

Intermediate-acidic granites occur extensively in the Chazangcuo copper-lead-zinc mining area (hereinafter referred to as the Chazangcuo mining area) in Tibet, China. Exploring their rock types, sources, and tectonic settings is essential for understanding the genesis of granites in the region. This study investigated the petrology of the Chazangcuo granites, as well as the geochemical characteristics of their major elements, trace elements, and rare earth elements (REEs). Results indicate that the Chazangcuo granites are high-K calc-alkaline metaluminous rocks. These granites are enriched in large-ion lithophile elements (LILEs; e.g., Rb and Ba), depleted in high-field-strength elements (HFSEs; e.g., Nb, Ta, Zr, and Hf), with a relative enrichment in light rare earth elements (LREEs), and relatively depleted in heavy rare earth elements (HREEs), exhibiting a V-shaped distribution pattern and weak negative Eu anomalies. The granites are classified as typical I-type granites, displaying characteristics of crust-derived magmas with contributions from mantle sources and exhibiting significant fractional crystallization. The Chazangcuo granites were derived from the partial melting of mafic rocks, with protoliths formed in a moderate temperature environment. Influenced by the subduction of the Neotethys Ocean, the Chazangcuo granites were formed in an arc caused by the collision between the Indian and Eurasian plates (also referred to as the Indo–Eurasian collision) during the Late Triassic. Under the effect of geological activities such as upwelling of the asthenosphere and fluid intrusion and differentiation, metal mineralization was prompted to be distributed in the granite fissures, forming the Cu-Pb-Zn polymetallic deposits of Chazangcou in Tibet, suggesting that the granites are closely associated with mineralization. [ABSTRACT FROM AUTHOR]

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The southward extension of the Bangong-Nujiang Suture and the late Mesozoic tectonic affinity of the Tengchong Block have been subject to debate, and the Early Cretaceous magmatism in the eastern Tengchong Block provides a crucial window to address these issues. This paper reports comprehensive petrographic, geochemical, geochronological, and isotopic data of Early Cretaceous granitic rocks from the eastern Tengchong Block. Results show that these granitic rocks consist of monzogranites and granodiorites, with zircon U-Pb ages of 120.4–113.9 Ma. These granitic rocks are characterized by enrichments in large ion lithophile elements (e.g. Rb, U, K) and light rare earth elements, but depleted in high field strength elements (e.g. Nb, Ta, P, Ti), and have negative apatite εNd(t) values (−10.4 to −6.7) and negative zircon εHf(t) values (−11.7 to −1.2). The molar [Al2O3/(CaO + K2O + Na2O)] (A/CNK) values and whole-rock zircon saturated temperatures of the studied monzogranites of 1.04–1.09 and 714–799°C, respectively, indicate that they have I-type granite affinity. The presence of biotite indicative of I-type granite and the observation that P2O5 decrease with increasing SiO2 further indicated that the monzogranites have affinities of I-type granites. The petrography, geochemical and isotopic signatures of the studied monzogranites indicate that they originated from partial melting of mafic lower crustal rocks. The Na-rich granodiorites have elevated Na2O/K2O ratios and Na2O contents of 1.19–2.04 and 3.12–3.47 wt.%, respectively. These granodiorites also have relatively high Mg# values and the transition metal element Cr of 53.3–54.5 and up to 100 ppm, respectively. According to these isotopic and geochemical features and the occurrence of magnesiohornblende, we propose that the Na-rich granodiorites were derived from partial melting of ancient basaltic lower crust, with certain inputs of mantle materials in the magma source. Considering these results as well as published data, we finally propose that the Tengchong Block was likely the southeastern extension of the Lhasa Block and that these Early Cretaceous granitic rocks were formed in the setting of the volcanic arc due to westward subduction of the Bangong-Nujiang Tethys oceanic lithosphere beneath the Tengchong Block. [ABSTRACT FROM AUTHOR]

[Display omitted] • We measured δ114/110Cd values of granite and sphalerite from a large skarn system. • Little to no Cd isotopic fractionation took place during the magmatic–hydrothermal processes. • S- and I-type granite-related deposits have distinguishable δ114/110Cd values. • Cd isotopes provide a potentially effective tool in skarn systems. Granite-associated deposits are one of the important ore types in the Earth's crust and can dominantly be subdivided into S-, I- and A-type granite-related deposits with different mineralization elements and isotopic signatures (e.g., sulphur and boron). The object of this study is to investigate whether Cd isotopic difference exists between I- and S-type granite-related deposits, and to provide new insights on geochemical behavior of Cd in such systems that have not been well constrained. The Dulong deposit in southwest China is a world-class skarn-type polymetallic Zn–Sn–In deposit that is thought to be genetically related to the emplacement of the highly fractionated S-type Laojunshan granite. The extremely negative δ114/110Cd values of sulfides (−0.82 ‰ to −0.42 ‰) within the Dulong deposit are all lower than those of sulfides from other Zn–Pb ore deposits globally. In comparison, representative sphalerites from I-type granite-related deposits yield heavier Cd isotopic compositions relative to the samples from the Dulong deposit. The Laojunshan granite samples are enriched in light Cd isotopes and have δ114/110Cd values that range from −0.73 ‰ to −0.40 ‰, overlapping with the δ114/110Cd values of sphalerite within the Dulong deposit and suggesting that the Cd in the deposit was derived from the Laojunshan granite. Similarly, I-type granite-related deposits elsewhere have Cd isotopic compositions that are similar to mafic–intermediate igneous rocks, suggesting little or no Cd isotopic fractionation took place during the magmatic–hydrothermal processes that formed these deposits. These results suggest that geochemical signatures of metal sources are the most likely control on Zn/Cd ratios and δ114/110Cd values of sulfides in these deposits, with different mineral deposit types having different Zn/Cd ratios and δ114/110Cd values. In summary, Cd isotopes provide a potentially effective tool for discriminating between different types of hydrothermal system and may also be useful in the investigation of granite petrogenesis. [ABSTRACT FROM AUTHOR]

Located in the central part of the Central Asian Orogenic Belt, East Junggar represents one of the most important sites of juvenile crustal growth during the Phanerozoic. However, the mechanism of juvenile crustal growth during the Permian remains controversial. The Daheishan granites in the eastern segment of East Junggar are dated at ~292 Ma (Early Permian) and 269 Ma–267 Ma (Middle Permian). The Early Permian granites are coarse-grained with very high SiO2 (76.64 wt%–80.02 wt%), Al2O3 (10.72 wt%–12.96 wt%), and K2O/Na2O (1.27‒2.14), and low TiO2 (0.12 wt%–0.18 wt%), CaO (0.27 wt%–0.90 wt%), Mg# (25–32), and Sr/Yb (16–25). The Middle Permian granites are medium‒fine-grained with relatively high SiO2 (71.84 wt%–76.26 wt%), Al2O3 (11.26 wt%–13.00 wt%), and K2O/Na2O (0.53–1.54), and low TiO2 (0.17 wt%–0.21 wt%), CaO (0.37 wt%–3.20 wt%), Mg# (33–43), and Sr/Yb (5–9). These Permian granites display slightly positive whole-rock εNd(t) (+0.77 to + 1.04) and highly positive zircon εHf(t) (+7.3 to + 8.7) values, and low Ga/Al (2.04–2.55 < 2.6), P2O5 (0.02%–0.05% <0.14%), and zircon saturation temperature (690°C–749°C, take the median for each sample). Moreover, they display characteristic tetrad rare earth element patterns and non-CHARAC (CHArge-and-RAdius-Controlled) trace element behaviour, suggesting that the Daheishan granites are I-type granites that underwent both fractional crystallization (K-feldspar and plagioclase, e.g.) and crustal contamination prior to their emplacement. In combination with data from volcanic rocks in the Santanghu Basin, we infer that the Early Permian granitic magmas were derived from delamination of a thickened lithospheric mantle base and partial melting of pre-Permian arc components, while the Middle Permian granites formed during the subsequent stretching and thinning of the lithosphere. [ABSTRACT FROM AUTHOR]

The Shenxianshui granites in the western Gejiu area were formed in the Late Cretaceous. Laser ablation inductively coupled plasma mass spectrometry indicates zircon U‐Pb ages ranging from 90.67 ± 0.7 to 85.97 ± 0.6 Ma. The intrusive rocks are peraluminous (A/CNK = 1.03 to 1.33) and calc‐alkaline, showing an affinity towards I‐type granite. Large ion lithophilic elements are enriched in K and Rb, while high field strength elements are depleted. Moreover, light rare earth elements are significantly enriched, showing a slight negative Eu anomaly (Eu/Eu* = 0.39 to 0.58). Shenxianshui granite has a relatively high initial Sr isotope ratio (87Sr/86Sr)i (0.7098–0.7105), negative εNd(t) values (−7.99 to −7.44) and negative εHf(t) values (−8.37 to −2.58). Combined with previous studies, these characteristics suggest that the Shenxianshui alkaline granites were formed in a post‐collision extensional environment. The alkaline granitic magma possibly originated from the partial melting of the lower crust during the Mesoproterozoic era and may have contained mantle source materials. Shenxianshui alkaline granite was formed from mixed magma with a high degree of crystal differentiation. The abundance of ore‐forming elements indicates that Shenxianshui granite has the potential to mineralize key metals and rare earth elements. [ABSTRACT FROM AUTHOR]

The Wunugetu deposit, a large-scale porphyry copper–molybdenum deposit, is located in the southern Erguna block. Its ore bodies are primarily found within monzogranites, granite porphyries, and biotite monzogranites. Additionally, the deposit contains late-stage intrusive dykes of rhyolitic porphyries. This study examined the deposit's monzogranites and rhyolitic porphyries using lithogeochemistry, zircon U-Pb dating, and Hf isotopic analysis. The main findings include: (1) Zircon U-Pb dating showed that the monzogranites formed around 209.0 ± 1.0 Ma, whereas the rhyolitic porphyries in the northern portion formed around 170.49 ± 0.81 Ma, suggesting magmatic activity in the deposit spanned from the Late Triassic to the Middle Jurassic. (2) The monzogranites exhibited high silicon content (73.16–80.47 wt.%) and relatively low aluminum content (10.98–14.37 wt.%). They are enriched in alkalis (content: 3.42–10.10 wt.%) and deficient in magnesium and sodium, with aluminum saturation indices (A/CNK) ranging from 1.1 to 2.9. In addition, the monzogranites are enriched in large-ion lithophile elements (LILEs) such as Rb, K, and Ba and deficient in high-field-strength elements (HFSEs) like Nb, P, and Ti. (3) The monzogranites have low Zr + Nb + Ce + Y contents of (151.3–298.6 ppm) × 10−6 and 10,000 × Ga/Al ratios varying between 1.20 and 2.33, suggesting that they are characteristic of I-type granites. (4) Positive zircon εHf(t) values ranging from +0.3 to +7.6 in both rhyolitic porphyry and monzogranite samples, increasing with younger emplacement ages, imply that the deposit's rocks originated from magmatic mixing between mantle-derived mafic magmas and remelts of the juvenile crust. Considering these results and the regional geological evolution, this study proposes that the Wunugetu deposit was formed in an active continental margin setting and was influenced by the Late Triassic–Middle Jurassic southeastward subduction of the Mongol-Okhotsk Ocean. [ABSTRACT FROM AUTHOR]

The Tak Batholith is located in the western part of Thailand’s eastern granitoid belt. To better understand the geochemical characteristics of granitoid and identify their occurrence, rock samples collected from the eastern part of the Tak Batholith were used for petrographical, mineralogical, and geochemical analyses. According to field investigation and lithology, petrography classifies these granitic rocks as medium-grained granodiorite and granodioritic dike. The granodiorites are composed chiefly of plagioclase, orthoclase, quartz, hornblende, and biotite, with tiny amounts of zircon, apatite, and opaque minerals. Meanwhile, the granitic dike shows a highly porphyritic texture, presenting mostly plagioclase phenocrysts, with a small amount of orthoclase and unidentified mafic phenocrysts sitting in a fine-grained groundmass comprising K-feldspar and quartz with a small amount of plagioclase and present granophyric intergrowth. Geochemical data of the amphiboles classified them as Ferro-edenite symbolizing the I-type granite. Whole-rock geochemistry indicates that these rock suites are I-type metaluminous granodiorite, and diorite fractionated from the high K calc-alkaline magma melted from the mafic crust of arc magmatism agreeable with the enrichment of large ion lithophile elements and depletion of highfield-strength elements, and rare earth element patterns.

The Nyainqentanglha Metallogenic Belt (NMB) is an economically important lead-zinc ore province located in the Central and Southern Lhasa subterrane, Tibet. The NMB consists mainly of skarn-type lead-zinc polymetallic deposits that form at the contact between Late Cretaceous-Eocene intrusive rocks and carbonatite/volcanic-sedimentary strata. These deposits are generally considered to be related to S-type granites formed by the Indo-Asian continental collision. However, the εHf(t) (ave. −1.6) of zircons from the mineralization-related granitoids indicates that it is crust-mantle mixing products. In addition, the volcanic rocks of the Dianzhong Formation, which have a close spatio-temporal relationship with the skarn-type deposits, typically show mantle-derived features. Therefore, the occurrence of AFC processes in mantle-derived material passing through the thick basement of the Lhasa Terrane may better explain the genesis of the mineralization-related granitoids. In this study, we present results on zircon U–Pb ages, major and trace elements of the granitoids associated with skarn-type mineralization from the Narusongduo district. LA-ICP-MS zircon U–Pb dating shows that the granite formed in the Paleocene (58.6 ± 0.5 Ma). Combined with published regional data, we propose the mineralization age of the skarn-type deposits in the NMB ranges from the Late Cretaceous to Eocene. Detailed petrology and geochemistry of mineralization-related granitoids are evaluated to constrain the magmatic evolution process. The granitoids have high contents of SiO2 (mean 72.8 %), K2O (mean 4.0 %), Rb (mean 186.9 ppm), DI (differentiation index) 84.7, A/CNK (mean 1.3), and low contents of MgO, TFe, suggesting that the granitoids have undergone strong differentiation. In addition, the continuous decrease of P2O5 with progressive differentiation and the lower average P2O5 abundance suggest that the mineralization-related granitoids belong to the I-type granite. The results suggest that the mineralization-related granitoids in the NMB originated from the mantle and is the fractionated I-type granite formed by the process of AFC (Assimilation and Fractional Crystallization). Considering that Pb and Zn often coexist in deposits, we suggest that magmatic differentiation may play an important role in the formation of the granite-related Pb and Zn mineralization.

The Middle to Late Jurassic is an important transitional period in the tectonic evolution of Northeast China, the study of magmatic rocks during this period is relatively limited due to its rare exposure. In this study, LA-ICP-MS zircon U-Pb geochronology and rock geochemistry were used for the first time to investigate the Middle to Late Jurassic intrusive rocks located in the southern part of the Xing'an Block, analyzing its petrogenesis and geological significance, and further constraining the closure timing of the Mongolia-Okhotsk Ocean in the southern Xing'an Block. The study shows that the intrusive rocks include two types of rock: granite porphyry and diorite porphyrite, with crystallization ages of (167.0±0.5) Ma and (160.0 ± 0.7) Ma, respectively, indicating that they are products of Middle to Late Jurassic magmatic activities. Two rocks belong to the high-K calc-alkaline I-type series, characterized by Na2O contents ranging from 4. 57% to 4.97% and 3.21% to 3.98%, and weak aluminum saturation with A/CNK ratios ranging from 1.00 to 1.07 and 0.93 to 1.10. They also have characteristics of enrichment in large ion lith-ophile elements (Rb, Th and K), depletion in high field-strength elements (Ta, Nb, P and Ti), moderate rare earth element contents (ΣREE) of (90.5~153.1) X 10-6 and (111.6~128.8) X 10-6, significant frac-tionation between light and heavy rare earth elements with LREE/HREE ratios of 6. 74~10.26 and 5.14~8.84, (La/Yb)N of 5.61~9.58 and 4.92~10.38, and middle negative Eu anomalies (δEu) ranging from 0.58 to 0.68 and 0.83 to 1.02. These results can be inferred that the petrogenesis of the intrusive rocks is likely related to the closure of the Mongolia-Okhotsk Ocean, and they formed in a tectonic background of crustal thickening collapse or detachment, during the transition from compression to extension tectonics. [ABSTRACT FROM AUTHOR]

The North Qinling Orogenic Belt (NQOB) is a composite orogenic belt in central China. It started evolving during the Meso–Neoproterozoic period and underwent multiple stages of plate subduction and collision before entering intra‐continental orogeny in the Late Triassic. The Meso–Cenozoic intra‐continental orogeny and tectonic evolution had different responses in various terranes of the belt, with the tectonic evolution of the middle part of the belt being particularly controversial. The granites distributed in the Dayu and Kuyu areas in the middle part of the NQOB can provide an important window for revealing the geodynamic mechanisms of the NQOB. The main lithology of Dayu and Kuyu granites is biotite monzogranite, and the zircon U‐Pb dating yielded intrusive ages of 151.3 ± 3.4 Ma and 147.7 ± 1.5 Ma, respectively. The dates suggest that the biotite monzogranite were formed at the end of the Late Jurassic. The whole‐rock geochemistry analysis shows that the granites in the study areas are characterized by slightly high SiO2 (64.50–68.88 wt%) and high Al2O3 (15.12–16.24 wt%) and Na2O (3.55–3.80 wt%) contents. They are also enriched in light rare earth elements, large ion lithophile elements (e.g., Ba, K, La, Pb and Sr), and depleted in high field strength elements (HFSEs) (e.g., Ta, Nb, P and Ti). Additionally, the granites have weakly negative–slightly positive Eu anomalies (δEu = 0.91–1.19). Zircon Lu‐Hf isotopic analysis showed εHf(t) = –6.1—‐3.8, and the two‐stage model age is T2DM(crust) = 1.5–1.6 Ga. The granites in the study areas are analyzed as weak peraluminous high‐K calc‐alkaline I‐type granites. They formed by partial melting of the thickened ancient lower crust, accompanied by the addition of minor mantle‐derived materials. During magma ascent, they experienced fractional crystallization, with residual garnet and amphibole for a certain proportion in the magma source region. Comprehensive the geotectonic data suggest that the end of the Late Jurassic granite magmatism in the Dayu and Kuyu areas represents a compression–extension transition regime. It may have been a response to multiple tectonic mechanisms, such as the late Mesozoic intra‐continental southward subduction of the North China Craton and the remote effect of the Paleo‐Pacific Plate subduction. [ABSTRACT FROM AUTHOR]

Late Paleozoic intermediate-acidic intrusions, which are widespread in central West Junggar (NW China), provide critical information for regional tectonic evolution. The Hongyuan intrusion, distributed in the southeast of central West Junggar, is selected as a representative for discussion in this study. Petrological observation shows that the Hongyuan intrusion is dominated by syenogranite and monzonitic granite, with a small amount of quartz syenite. Zircons separated from the monzonitic granite yield a weighted mean 206Pb/238U age of 287±2Ma (n = 19, MSWD = 1.3). The Hongyuan intrusion displays a pronounced I-type affinity. It belongs to high-K calc-alkaline suit and has high concentrations of Na2O + K2O (7.00–8.09 wt%). It is peraluminous in composition and the FeOT/MgO ratios are low (2.55–4.43). The large ion lithophile elements (LILE, such as Th, U and Cs) and light rare earth elements (LREE) are enriched with significant Eu anomalies (EuN/EuN* = 0.26–0.51), and the high field strength elements (HFSE, such as Ti and Nb) are depleted. Initial Hf isotopic ratio of zircons separated from the monzonitic granite show small range of variation ((176Hf/177Hf)i = 0.282951–0.283025), the εHf(t) values are relatively high (+12.8 to +15.3) and the Hf model ages are very young (TDM1 = 315–425 Ma). The comprehensive petrological and geochemical features indicate that the Hongyuan intrusion was formed by decompression melting of a juvenile lower crust, and has undergone a remarkable process of fractional crystallization. [ABSTRACT FROM AUTHOR]

The Jiaodong Peninsula is located on the junction of the North China Craton (NCC) and South China Block (SCB), where Mesozoic igneous rocks are widespread. However, the petrogenesis and tectonic settings for these Mesozoic igneous rocks are still controversial. In this study, we present detailed geochronological and geochemical analyses of quartz monzonite, monzogranite, syenogranite, and alkali feldspar granite in the Qingdao area, east of the Jiaodong Peninsula, to constrain their petrogenesis and tectonic setting. Zircon U–Pb dating shows that they mainly formed in the Early Cretaceous (120.5–113.1 Ma). Quartz monzonite exhibits adakitic geochemical features (e.g., low Y and high Sr/Y). Combined with its Sr–Nd–Hf isotopic features, we suggest that quartz monzonite may have been produced by the partial melting of phengite-bearing eclogites at the base of the thickened continental crust of the NCC. In contrast, monzogranite and syenogranite exhibit I-type granite affinities, whereas alkali feldspar granite exhibits features consistent with A-type granite. The strongly negative εHf(t) and εNd(t) values of the I-type rocks indicate that they were most likely produced through partial melting of granitic gneisses from the NCC, whereas A-type magmas may be formed through fractional crystallization from the non-adakitic granitic magma. Combined with previous studies, we suggest that these granitoids were formed in a lithospheric extensional setting via the rollback of the subducted Paleo-Pacific slab, which resulted in the reworking of the deep crust beneath the Sulu ultrahigh-pressure metamorphic belt. [ABSTRACT FROM AUTHOR]

Early Cretaceous granitic rocks are widely distributed in the Great Xing’an Range, northeast China. However, their precise age and tectonic evolution remain controversial. This study presents new zircon U–Pb, Lu–Hf, and whole-rock geochemical data for the granitic plutons in the Yili area, Xing’an Massif, northern Great Xing’an Range. The aim of this study was to decipher the tectono-thermal history and obtain further understanding of the geodynamic setting of the large-scale Late Mesozoic magmatism in the Great Xing’an Range. Zircon U–Pb age dating indicated that the plutons were emplaced during the Early Cretaceous, with ages of 132.2–130.1 Ma. The plutons showed similar geochemical features, characterized by high concentrations of SiO2 and Na2O + K2O and low concentrations of P2O5, CaO, MgO, and TFe2O3. The plutons were enriched in light rare earth elements and large ion lithophile elements and depleted in heavy earth elements and high-field-strength elements. Such features indicate that the plutons are highly fractionated with I-type granite affinity. These findings, combined with pluton ε Hf(t) values of + 5.25 to + 8.28 and two-stage model ages (t DM2) of 661–855 Ma, indicate that the primary magmas originated from partial melting of juvenile basaltic crustal material accreted during the Neoproterozoic. These results combined with regional geological evolution indicated that the generation of Early Cretaceous plutons in the northern Great Xing’an Range might be closely related to the post-collisional gravitational collapse and subsequent extension resulting from the closure of the Mongolia-Okhotsk Ocean. Their generation also superimposed the back-arc extension resulting from retraction of the Paleo-Pacific subduction plate.

Zircon geochemistry provides a sensitive monitor of its parental magma composition. However, due to the complexity of the uptake of trace elements during zircon growth, identifying source magmas remains challenging, particularly for detrital grains whose petrological context is lost. We use a machine learning-based approach to explore the classifiers for zircon provenance, based on 3794 published, high-quality zircon trace element analyses compiled from I-, S-, and A-type granites. Three supervised machine learning algorithms, namely, Support Vector Machine (SVM), Random Forest (RF), and Multilayer Perceptron (MLP) were used and trained with 11 features, including 7 trace elements (Ce, Eu, Ho, Nb, Ta, Th, and U) and 4 derived trace element ratios (Th/U, U/Yb, Ce/Ce*, and Eu/Eu*). Our results show that all three trained machine learning methods perform very well with accuracy varying from 0.86 to 0.89, and that input–output relationships captured by different ML methods are nearly consistent and can be explained by the known petrological processes. The application of our trained machine learning classifiers to detrital zircon studies will enhance the interpretability of zircon assemblages of different origins. It also helps develop interpretations, approaches, and tools that will benefit, for example, the study of continental crust evolution and mineral exploration. [ABSTRACT FROM AUTHOR]

The Chinese Altai is characterized by abundant granitoids, which not only are indicators of the interaction between crust and mantle but also provide critical constraints on the tectonic evolution of the orogen. This study presents zircon U‒Pb‒O isotopes, whole-rock major and trace element and Nd‒Hf‒Pb isotopes data for granite porphyries from the Keziergayin region in the Kelan Basin. The granite porphyries intrude in the Kangbutiebao Formation with zircon U‒Pb dating of 394 ± 3 Ma. They have the characteristics of subalkaline and metaluminous to weakly peraluminous and show geochemical affinity with I-type granite. The granite porphyry samples display negative εNd(t) (−1.9 to −1.4), positive εHf(t) (+4.3 to +11.4) values, with Nd–Hf decoupling; low Pb isotope compositions; δ18OV-SMOW (6.38‰–8.45‰) is less than 10‰, within the range of O isotopes of medium-basic igneous rocks. These geochemical signatures indicate that the granite porphyries originated from lower crust medium−basic igneous rocks extracted from the lithospheric mantle metasomatized by subducted melt. They are characterized by high SiO2 contents and Rb/Sr ratios; low CaO contents and K/Rb ratios, hinting that they were formed by highly evolved magmas, with fractionation crystallization of feldspar, apatite, garnet, allanite and/or monazite. The granite porphyries possess positive Rb, Th, U, Nd, Zr, Pb and light rare Earth elements (LREEs) anomalies with strong negative Ba, Nb, Ta, Sr, P, Ti and Eu anomalies, implying that their formation were related to an island arc. Combined with previous studies, it is suggested that the existence of the Early Devonian arc-basin system associated with subducting slab rollback in the Chinese Altai, which belongs to the Siberian active continental margin system.

The widely distributed granitic intrusions in the Nubian Shield can provide comprehensive data for understanding its crustal evolution. We present new bulk-rock geochemistry and isotopic (zircon U-Pb and Lu-Hf) data from the Haweit granodiorites in the Gabgaba Terrane (NE Sudan). The dated zircons presented a 206Pb/238U Concordia age of 718.5 ± 2.2 Ma, indicating that they crystallized during the Cryogenian. The granodiorites contain both biotite and amphibole as the main mafic constituents. The samples exhibit metaluminous (A/CNK = 0.84–0.94) and calc-alkaline signatures. Their mineralogical composition and remarkable low P2O5, Zr, Ce, and Nb concentrations confirm that they belong to I-type granites. They exhibit subduction-related magma geochemical characters such as enrichment in LILEs and LREEs and depletion in HFSEs and HREEs, with a low (La/Yb)N ratio (3.0–5.9) and apparent negative Nb anomaly. The positive Hf(t) values (+7.34 to +11.21) and young crustal model age (TDMC = 734–985 Ma) indicates a juvenile composition of the granodiorites. The data suggest that the Haweit granodiorites may have formed from partially melting a juvenile low-K mafic source. During subduction, the ascending asthenosphere melts might heat and partially melt the pre-existing lower crust mafic materials to generate the Haweit granodiorites in the middle segment of the Nubian Shield. [ABSTRACT FROM AUTHOR]

New geochronological and geochemical data were presented for the Early Carboniferous basaltic to andesitic volcanic rocks and Late Carboniferous granitic intrusions in the Aqishan–Yamansu Belt of Eastern Tianshan, NW China. Zircon U–Pb dating indicates that the andesite and granite were emplaced at 330 Ma and 321 Ma, respectively. The andesitic rocks of the Yamansu Formation (FM) display subalkaline to calc-alkaline characteristics with moderate SiO2, relatively high Mg# values, and low Cr, Co and Ni, indicating an origin from mantle-derived melts. Their relatively low εNd(t) values (–0.02 ~ +0.61) and old TDM ages (TDM = 1.39–1.40 Ga) suggest a mantle source with addition of old crustal materials. Their high Rb/Y and Ba/La, low Nb/Y and Th/Yb ratios elucidate that the magma sources were probably metasomatized by slab-derived fluids. Besides, the high Th and low Ce/Th and Ba/Th ratios of the andesites suggest a contribution from subducted sediment–derived melts. Integrated with the depletion in high field strength elements and enrichment in light rare earth elements (LREEs), we suggest that the Yamansu andesites were formed by partial melting of relatively enriched mantle wedge metasomatized by both subducted sediment-derived melts and fluids. The basalts of the Tugutublak Formation (TF) have high MgO, Mg# (56–58) and εNd(t) (+5.9 ~ +6.3) values with enriched in LREEs and depleted in Nb–Ta–Ti anomalies, implying an arc setting. Their high Ba/Th, Ba/La and low Th/Ta, Th/Yb ratios suggest that the slab-derived fluids were involved. The basaltic andesites of the TF have higher SiO2, lower Mg# (48–50), Cr, Ni and εNd(t) (+1.21) values than the basalts of this formation, indicating that they were evolved from the basaltic magma. Therefore, the Carboniferous volcanic rocks in this study indicate that the Aqishan–Yamansu Belt was in a subduction background. The granites intruding into the TF show typical characteristics of I-type granite. Their highly positive εHf(t) values (+14 ~ +17) suggest a significant contribution from juvenile basaltic lower crust. Moreover, changes in the Dy/Yb and Ho/Yb ratios of Late Paleozoic felsic igneous rocks in the Aqishan–Yamansu Belt imply that the crust underwent four periods of thickening and thinning, which were likely triggered by the variation of subduction angles. [ABSTRACT FROM AUTHOR]

The Qimantag in the East Kunlun Orogenic Belt has widespread Triassic magmatic rocks that have received scant attention, with an unresolved issue relating to its petrogenesis and geodynamics. In this paper, we used zircon U–Pb–Hf isotopes and whole-rock geochemistry to trace the petrogenesis and tectonic settings of the moyite and monzogranite from the Qimantag Alananshan, East Kunlun. The moyite and monzogranite are silicic (SiO2 ~ 69.9–76.41%), highly alkali (Na2O + K2O ~ 7.29 to 8.96 wt.%), with Mg# about 10.4–30.34, indicative of a high-K calc-alkaline rock series. The rare earth element patterns diagram is right-leaning, with a negative Eu anomaly (δEu = 0.31–0.68). They are enriched in Rb, K, and light rare earth elements but depleted in Nb, Ta, and Ti, with abundant amphibole, typical of I-type granites. U–Pb on zircon constrained the emplacement of the moyite at 223.9 ± 2.6 Ma and monzogranite at 226.9 ± 2.9 Ma. The εHf(t) values range from − 2.8 to + 0.1 except for one outlier value of − 7.0, corresponding two-stage model age of 1249–1437 Ma. Our combined geochemical and isotopic results indicate that the moyite and monzogranite were derived from partial melting of the lower thicken crust with the contribution from the older basement materials. These rocks formed in a post-collision setting that is transitional between compressive collision and extension orogeny. [ABSTRACT FROM AUTHOR]

We present integrated in situ zircon U–Pb and Hf isotope data, along with whole‐rock and mineral chemistry data for the Salari granite of western Arunachal Himalaya to constrain its emplacement age, origin, and geodynamic evolution. The investigated Salari granites are high Fe2O3, CaO, and Nb, and low SiO2 and Rb/Sr ratio with fractionated rare earth element patterns ((Ce/Yb)N = 9.90–20.24) and minor negative Eu anomaly (Eu/Eu* = 0.69–0.94). They are metaluminous (molar A/CNK = 0.93–1.07) and have relatively similar FeOt/MgO ratio in biotite (1.58–1.60) to Mg‐biotite, indicating their affinity with I‐type granites. The enrichment of large‐ion lithophile elements with highly depleted negative Nb anomalies is consistent with their origin in a subduction‐related environment. Our zircon U–Pb ages suggest that the magmatic emplacement of the Salari granite took place between 1,791 and 1,768 Ma. The zircon grains have mostly negative εHf(t) values up to −5.5 and yield crustal Hf model ages from 2.4 to 2.8 Ga, suggesting the occurrence of a major crustal growth event in the Neoarchean and re‐melting of the crust during the Palaeoproterozoic. Our new results, that is, zircon U–Pb age and Hf isotope data, in conjunction with the field observations and petro‐mineralogical and geochemical characteristics, suggest that the Salari granite of eastern Himalaya was produced by partial melting of older metabasaltic/metatonalitic rocks in a continental arc setting of the supercontinent Columbia during the Palaeoproterozoic. [ABSTRACT FROM AUTHOR]

The Baimashan granitic complex in central Hunan is a giant multiphase complex pluton within the South China Plate, which contains three phases (the Shuiche, Longtan‐Xiaoshajiang, and Longcangwan superunits). It is located in the Jiangnan Orogenic Belt and is of great significance for the study of the regional tectonic magmatic evolution. Herein, we utilized zircon U–Pb dating, major and trace element geochemistry, and zircon Hf isotope geochemistry for three of the Baimashan granitic complexes; data for the Longcangwan superunit were obtained from previous studies. The new zircon U–Pb ages of 418 ± 3.2 Ma and 223 ± 2.6 Ma for the Shuiche and Longtan‐Xiaoshajiang superunits, respectively, suggest the existence of Late Silurian and Late Triassic magmatism. Both superunits exhibited weak peraluminosity and high‐K calc‐alkaline and weak negative Eu anomalies, which are similar to those of I‐type granites. The Longcangwan superunit showed strong peraluminosity and high‐K calc‐alkaline and stronger negative Eu anomalies; Hf isotope and mineralogical evidence suggest that it is a fractionated I‐type granite. The zircon Hf(t) values and two‐stage depleted mantle Hf model ages revealed that the magma of the Baimashan granitic complex originates from the partial melting of metamorphic igneous rocks; the crust–mantle differentiation age in the source area was 1.5–1.7 Ga for Longtan‐Xiaoshajiang and Longcangwan and 1.7–1.9 Ga for Shuiche. The superunits formed in a post‐collisional extensional tectonic setting. In the case of the Shuiche supersuit this is related to the remote effect of the interaction of the South China Plate with the Australian‐Indian margin of Eastern Gondwana. The formation of the Longtan‐Xiaoshajiang and Longcangwan superunits is linked to the remote effect of the Indosinian and South China Plate collision and the superimposition of the subduction of the Palaeo‐Pacific Plate. The weakly fractionated I‐type granite that formed during the Caledonian in South China is closely related to scheelite mineralisation. [ABSTRACT FROM AUTHOR]

Felsic dykes from the Dalat zone (southern Vietnam) are commonly NE–SW oriented and penetrate early cretaceous volcanic-plutonic rocks. These felsic dykes consist of predominant porphyritic granite, minor granitic aplite and aplite. The primary rock-forming minerals are plagioclase, K-feldspar, quartz and subordinate biotite, and the main secondary mineral is epidote. Geochemically, these felsic dykes are characterized by I-type affinity and high SiO2 content (>71 Wt%), low to moderate Al2O3, and variable total alkali (Na2O+K2O). Trace and rare-earth elements show the enrichment of LILEs such as Rb, U, Th, and K and the depletion of HFSEs such as Nb and Ti and a strongly negative Eu anomaly, indicating fractional crystallization of K-feldspar, plagioclase and titanite. Zircons obtained from the felsic dykes are prismatic and exhibit oscillatory zoning with Th/U ratio > 0.1 typical for magmatic origin. In situ zircon LA-ICP-MS zircon U-Pb dating yielded a weighted mean 206Pb/238U age of 91 Ma, temporally coeval with Early Cretaceous magmatism, which has been widely reported to originate from Paleo-Pacific subduction. Their (87Sr/86Sr)i ratio (0.709917 to 0.715288), whole-rock εNd(t) values (−1.3 to +0.9), zircon εHf(t) values (+3.1 to +9.5), and whole-rock Nd and zircon Hf model ages (TDM2) (999–552 Ma) of the studied felsic dykes indicate that they might derive from partial melting of neoproterozoic crustal materials with a input of mantle-derived melt during magma formation and differentiation. The obtained geochemical and isotopic characteristics suggest that these felsic dykes are genetically related to I-type granite and might have formed during the late stage of the Late Mesozoic Paleo-Pacific subduction beneath Indochina or shortly prior to the subsequent extensional regime due to slab retreat. [ABSTRACT FROM AUTHOR]

[Display omitted] • Zircon U-Pb ages for the Siluro-Devonian Bega Batholith of the Lachlan Fold Belt. • Systematic east to west age progression from 420 to 385 Ma. • Bega Batholith may record an undocumented episode of crustal growth along the Gondwanan margin. Earth's continental crust is primarily composed of buoyant, felsic igneous (granitic) material that has been extracted from the mantle along convergent plate margins. Establishing the timescales of subduction-related granite batholith assembly is key to understanding the processes of magma generation, segregation, and transport that define the dynamics and rates of crustal growth. The 'Cordilleran' Bega Batholith is the largest I-type granite batholith in the Lachlan Fold Belt (LFB) of south-eastern Australia. The product of accretionary orogenesis along the Terra Australis Orogen, it has been extensively characterised by isotopic and geochemical studies yet lacks a robust geochronological framework. We present new ID-TIMS and SHRIMP U-Pb zircon ages for twenty-two plutonic rocks of the Bega Batholith. This geochronological survey indicates a prolonged duration for I-type magmatism, with crystallisation ages ranging from ca. 420 Ma in the west, to 385 Ma in the eastern Bega Batholith. These I-type granites collectively occupy ∼90,000 km3 and were emplaced over a period of ∼20–35 Ma, corresponding to a magma production rate of ∼8–15 km3/Ma km−1, considerably lower than that of S-type granites of the region and other subduction-related granite terranes globally. Fundamentally, the temporal overlap between the Bega I-type granites and S- and A-type granites also argues against a hiatus between each phase of granite magmatism in the LFB, suggesting a continuum between the granite types and derivation from common source components. This new geochronological data provides the first comprehensive compilation of U-Pb ages from across the Bega Batholith, establishing initial constraints on the development and evolution of I-type magmatism in south-eastern Australia. Our results demonstrate that I-type granite petrogenesis is linked with crustal growth processes, requiring the modification of global crustal growth curves during the Phanerozoic to account for new continental crust generated within I-type granite terranes of the Paleo-Pacific Gondwanan margin. [ABSTRACT FROM AUTHOR]

This paper presents petrographic, structural, and geochemical data on metamorphic and magmatic rocks of the Letta area (eastern Cameroon), in the Central Cameroon domain, that lead to discuss the petrogenesis of these rocks in the context of the Pan-African orogeny. The study area is made of amphibolite, orthogneiss, and dioritic gneiss, and they are related to a various facies of plutons including granodiorite, biotite-granite, and alkali-feldspar granite. Field observations, structure, and texture support that amphibolite is an orthoderived rock, issued from the metamorphism of gabbro. Field relationships, microstructures, and geochemical signatures suggest that orthogneissess correspond to syntectonic intrusions transposed in the shear foliation, and their genesis involve a metasomatized mantle and/or crustal contamination. By contrast, the protolith of dioritic gneiss involves juvenile Neoproterozoic and reworked Archaean/Palaeoproterozoic materials, with the possible contribution of a Mesoproterozoic source. The high-K (7.31 wt%), shoshonitic affinity, and the high LILE/HFSE ratios and negative Nb, Ta, and Ti anomalies of dioritic gneiss are interpreted as indicating an origin of the protolith of this rock through interaction between the Archaean TTG continental crust and magmas derived from a LILE-enriched mantle. Granodiorite, by their medium Mg# (average = 37.54), geochemical features [(high Th/La (0.10–0.37), K/Rb and Rb/Sr (0.12–0.78)], and the presence of mafic enclave, indicate derivation of this magmatic rocks through partial melting of metamorphozed mafic rock (amphibolite) issued from the melting of metasomatized spinel lherzolite with a contribution of crustal material. Biotite granite is characterized by (a) the presence of enclave with mafic and felsic composition, (b) high-temperature zircon saturation, (c) I-type signature, (d) and high Zr/Sm ratio (37.34–60.29) point to an origin through partial melting of amphibolite and dioritic gneiss with contribution of sediments. Alkali-feldspar granite has features (positive Eu anomalies, enclave of felsic rock, and REE patterns) indicating that the magma of this rock is issued from the partial melting of dioritic gneiss with contribution of mantle-derived magma and was contaminated by sediments. The presence of the granodiorite enclave in alkali-feldspar granite suggests influence from magma mixing in their generation. The geochemical signature of studied rocks indicates that they were formed in magmatic arc developed further to subduction of the hot Yaounde oceanic crust beneath the Adamawa-Yade domain. [ABSTRACT FROM AUTHOR]

The evolution process of the North China Craton has been discussed by many scholars; however, the frame for the timing of the Trans-North China Block has not been fully agreed upon. Related research has mostly focused on the northern and southern sections of the Trans-North China Block, and in-depth studies on intrusive rocks in the central region are lacking. In this study, we conduct a systematic study of the petrography, the whole-rock geochemistry, and the zircon U–Pb dating for the beschtauite intrusion, located in the Mengjiaping area of the Southern Taihang Mountains. Our results demonstrate that the dyke intrusion is mainly composed of beschtauite. Laser ablation inductively coupled plasma mass spectrometry zircon U–Pb dating shows that the beschtauite intrusion occurred at ∼1,880 ± 69 Ma. The beschtauite belongs to I-type granite, Arc tholeiite series, and Cale-alkaline series, with low total alkali, low potassium, and high aluminum. They are also enriched in large-ion lithophile elements, relatively depleted in high-field strength elements, and low total rare-earth elements. Based on the abovementioned data, it is suggested that the magmas for the beschtauite intrusion were metasomatized by oceanic slab subduction in the Late Paleoproterozoic. The formation time of the North China Craton basement should be set to after 1,880 Ma.

In order to elucidate the petrogenesis of the Hughes Bluff granitic pluton, the petrological and geochemical studies were conducted, and the results show that the Hughes Bluff granitic pluton is composed of monzogranite, intruded by fine-grained monzogranite dikes in the later period. They both are characterized by high abundance of silicon, alkali and potassium, enriched in Rb, Th, U and K and depleted in Nb, Ta, Nd and Ti relative to those of the primitive mantle, with the Rittmann Indexes less than 3 and the A/CNK values less than 1. They both also have a low total amount of rare earth elements and an abundance of light rare earth, showing weakly negative Eu anomaly and slightly positive Eu anomaly in the chondrite-normalized REE pattern for the monzogranite and granitic monzogranite dike respectively. All the data show that the rocks from the Hughes Bluff granitic pluton belong to the I-type granites, and the source region is probably the lower continental crust, but the contribution of mantle material cannot be ruled out. The magma in the source region underwent varying degrees of fractional crystallization of plagioclase, ilmenite, rutile and apatite, and was derived from a volcanic island arc environment related to subduction.

• I-type monzogranites in the East Kunlun Orogen Belt were emplaced at 251–221 Ma. • The studied monzogranites were generated by partial melting of ancient lower crust. • The Early Triassic monzogranites were formed in a localized extensional environment during a subduction-dominated stage. • The Late Triassic (ca. 232–221 Ma) monzogranites were formed in a post-collisional environment. The Triassic granitoids in the East Kunlun Orogenic Belt (EKOB) are crucial for understanding the tectonic evolution of the Paleo-Tethys Ocean. This study presents zircon U–Pb ages, Lu–Hf isotopes, whole-rock major and trace elements, and Sr–Nd isotope compositions from monzogranite plutons in the central segment of EKOB to constrain their petrogenesis and tectonic evolution. These monzogranites are dominant composed of mineral assemblages of K-feldspars, plagioclase, minor biotite and accessory minerals. U–Pb dating of zircons from the Xinle South (XLS), Nanshankou (NSK) and Changgou South (CGS) plutons yield ages of 251 Ma, 232 Ma and 221 Ma, respectively. The studied monzogranites have relatively high SiO 2 and Al 2 O 3 , but have low contents of TiO 2 , Fe 2 O 3 T, MgO relative to the coeval granodiorites. These monzogranites are classified as fractionated I-type granites, ranging from calc-alkaline to high-K calc-alkaline compositions. Their negative εNd(t) values (−4.2 to −6.3) and zircon εHf(t) values (−6.1 to −9.3) suggest that magma generation occurred through partial melting of ancient lower crust, followed by extensive fractional crystallization. Integrating our new data with regional geological evidence, we propose that the Early Triassic XLS monzogranite emplaced in a localized extensional environment linked to the northward subduction of the Paleo-Tethys oceanic plate. In contrast, during the post-collisional extensional phase of the Late Triassic, the formation of the NSK and CGS monzogranite plutons was directly influenced by asthenospheric upwelling, lower crust delamination, and subsequent continental rifting. [ABSTRACT FROM AUTHOR]

• A prominent episode of ca. 800 Ma magmatism in the southern Dabie Orogen identified. • The granitoids show I-type features. • An accretion-type orogeny in the northern Yangtze Block produced the ca. 800 Ma granitoids. • The 'edge model' of Rodinia reconstruction is favored. Large-scale Neoproterozoic granitoids occur widely in the Dabie Orogen of the northern Yangtze Block and provide significant clues to understanding the geological evolution of the Block within the Rodinia supercontinent. We present evidence for a prominent episode of granitoid intrusion at ca. 800 Ma in the southern Dabie Orogen (SDO), verified by new zircon LA-ICP-MS ages from four separate granitoid intrusions ranging from 807 Ma to 795 Ma in age. The granitoids are dominated by monzogranite and granodiorite with bulk-rock A/CNK and zircon δ 18O values of 0.90–1.10 and 5.03–6.45‰, respectively, corresponding to I-type affinity. This is also supported by negative correlations of SiO 2 vs. P 2 O 5 and Sr vs. P 2 O 5 , and positive correlations of SiO 2 vs. A/CNK, Rb vs. Y and Rb vs. Th. Low zircon ε Hf (t) values (−15.03 to −3.84) and relatively old two-stage Hf model ages (mainly between 1900 and 2200 Ma) for these granitoids are consistent with primary derivation of magma from partial melting of Paleoproterozoic metabasites. Relatively low Ga/Al ratios, Zr contents, and zircon saturation temperatures and consistently negative zircon ε Hf (t) and bulk-rock ε Nd (t) values are distinct from those of 780–720 Ma A-type granites in the Dabie Orogen that formed in a rift setting. We propose that the ca. 800 Ma granitoids in the SDO were products of variable degrees of partial melting of ancient mafic crust, promoted by heating of the upwelled asthenosphere due to oceanic slab breakoff in an accretion-type orogeny. Our observations suggest that the formation of the unified Yangtze Block was achieved by diachronous assembly of multiple micro-blocks during the Neoproterozoic, consistent with a peripheral location of the Yangtze Block in the Rodinia supercontinent. [ABSTRACT FROM AUTHOR]

• The ca.750 Ma I-type granitic melts formed in a back-arc setting from water-fluxed melting. • Thermodynamic modeling shows I-type melts can be formed at 725–875 °C, 9 kbar, 2.0–3.5 wt.% H 2 O. • Asthenosphere upwelling from slab rollback caused underplating of hydrous basaltic magmas. • Water content was crucial in generating granitic rocks of various compositions in a continental arc. Water is crucial in generating granitic systems; however, its role (i.e., dehydration, low to high water-fluxed melting) in granitic magmatism in continental arcs remains unsettled and poorly understood. Neoproterozoic arc-related igneous rocks are uncovered along the western margin of the Yangtze Block, presenting a complex compositional array ideal for deciphering the influence of water content within the continental arc and its geodynamic significance. The Jinping granites, in the Ailaoshan zone, are emplaced at 750 ± 4 Ma, as determined by zircon U-Pb dating. These medium to coarse-grained granites consist predominantly of plagioclase, quartz, K-feldspar, muscovite, and biotite. Characterized by high SiO 2 (71.2–73.5 wt%), alkalis (K 2 O+Na 2 O=7.54–9.56 wt%) and low Fe 2 O 3 T (1.01–1.66 wt%), MgO (0.53–0.85 wt%), and CaO (0.15–0.93 wt%) concentrations, they exhibit high-K calc-alkaline signatures. The negative correlation between P 2 O 5 and SiO 2 , alongside the positive correlation between Rb and Y, typifies the Jinping granites as I-type granites. Low La/Nb (1.96–3.43) and Nb/Ta (8.57–11.3) ratios, but high Th/La (0.28–0.46) and Zr/Sm (30.5–47.7) ratios, as well as whole rock ε Nd(t) (−0.4 to +1.3) and zircon ε Hf(t) values (+5.25 to +8.53) of the studied granites are similar to synchronous mafic rocks at the western margin of the Yangtze Block. These features suggest partial melting origin from the mafic lower crust. Thermodynamic modeling posits that the Neoproterozoic Ailaoshan I-type granitic rocks may have formed through water-fluxed melting (2.0–3.5 wt% H 2 O) under medium pressure conditions (9 kbar). It is postulated that slab rollback could have prompted water (as hydrous melt or fluids) release from hydrous minerals in the underlying cumulate mafic rocks, subsequently triggering water-fluxed melting in the lower crust. In contrast, high water-fluxed melting-generated adakitic granites with low K 2 O/Na 2 O ratios (<0.8) in the region, spatially and temporally associated with the Jinping granites, reflect higher water content in the deeper crust. This supports the notion that water was conveyed from depths to surface, facilitating the conversion of adakitic rocks into I-type granites as water content diminished. Thus, water content within the lower crust plays a pivotal role in the genesis of granitic rocks with varied compositions in a continental arc setting. [ABSTRACT FROM AUTHOR]

The Qin-Hang Metallogenic Belt (QHMB), an important metallogenic belt in South China, hosts Cu and W–Sn polymetallic deposits. The Tongshanling ore field in the QHMB is characterized by the coexistence of Cu- and W-bearing polymetallic deposits, which are related to granodiorite and granite porphyry. This study examined whole-rock geochemistry, geochronology, and Sr–Nd–Hf isotopes to determine the genetic relationship between diverse ore-related granitoids (i.e., granodiorite and granite porphyry) and Cu–W metallogeny in the Tongshanling ore field. Zircon LA-ICP-MS U–Pb dating shows that the granodiorite and granite porphyry in the Tongshanling ore field were emplaced at 163.7 ± 0.4 Ma to 154.7 ± 0.6 Ma and 161.1 ± 0.3 Ma, respectively. Geochemically, the granodiorites are classified as oxidized I-type, while the highly evolved granite porphyry is reduced A-type. The Lu–Hf isotopic composition of the granodiorites is characterized by εHf(t) values ranging from –10.49 to –4.99 (average = –7.17), with corresponding TDMC ages ranging from 1524 to 1877 Ma (average = 1682 Ma). In contrast, the granite porphyry has higher εHf(t) values (–3.60 to –1.58, average = –2.78) and younger TDMC (1310–1438 Ma, average = 1387 Ma). The εNd(t) values of granodiorite are −8.06 to −7.37 and the two-stage model ages (TDM2) are 1543–1598 Ma, while the granite porphyry has higher εNd(t) values (−3.0 to −3.4) and younger TDM2 ages (1195–1223 Ma). The results show that the granodiorite and granite porphyry were formed from partial melting of different Mesoproterozoic basement rocks under varying degrees of crust–mantle interaction. Granite porphyry underwent well-recorded fractional crystallization. Compared to the Cu-forming granodiorite, the W-forming granite porphyry has a higher differentiation index, higher crystallization temperatures of zircon (average = 708 °C versus 631 °C), and lower oxygen fugacity (median ΔFMQ = –2.21 versus –1.77). [ABSTRACT FROM AUTHOR]

Radiogenic heat production (RHP) has been investigated from wide types of rocks based on regional setting and metamorphism grade. In this study, we analyze the abundance of heatproducing elements (U, Th, K) and Radiogenic Heat Production (RHP) on I-type and S-type granite rocks in Bangka Island, one of the main provinces in Tin Belt Island. The average U, Th, and K concentrations for both S-type and I-types granite are 10.27 ppm, 79.6 ppm, 3.1%, and 87.79 ppm, 99.2 ppm, and 1.93 % respectively. The highest concentration of U (681.22 ppm) and Th (99.2 ppm) are found in Pangkal Pinang and K (3.79%) in West Bangka. We analyze that the RHP average for I-type granite is higher at 27.87 (N=17, range from 12.97 to 550.28) than S-type with 8.43 (N=11, range from 4.93 to 12.64). The Th/U ratio shows an exponential correlation with RHP and classifies S-type granite tectonic discriminant as continental collision and I-type granite as a continental arc. [ABSTRACT FROM AUTHOR]

Cretaceous magmatism is widely distributed on both sides of the Bangong–Nujiang suture zone (BNSZ). These rocks record the subduction to closure history of the Bangong–Nujiang Tethys Ocean (BNO) and the collisional history between the Lhasa (LS) and Qiangtang (QT) terranes. The Xiabie Co granite in Nyima County, which located on the southern margin of the QT terrane, Tibet. In this study, whole‐rock geochemistry; Rb‐Sr, Sm‐Nd, and Pb isotopes; and laser ablation inductively coupled mass spectrometry (LA‐ICP‐MS) zircon U‐Pb ages and Lu‐Hf isotopes of the Xiabie Co granite in the Nyima area have been studied to constrain its petrogenesis and tectonic setting. Our study can help explain the tectonic evolution of the BNSZ and crust‐mantle interaction. Zircon U‐Pb dating indicates that the granite was emplaced at ca. 120 Ma. The granite contains a small amount of hornblende and has high silicon (SiO2 = 73.97–78.03 wt%), potassium (K2O = 4.75–6.53 wt%), and total alkali (K2O + Na2O = 7.98–8.98 wt%) contents; low calcium content (CaO = 2.33–4.11 wt%); and variable A/CNK (1.00–1.18) and A/NK (1.09–1.22) values. The P2O5 content of the granite negatively correlated with the SiO2 content. Thus, the Xiabie Co granite is a weakly peraluminous I‐type granite belonging to the high‐K calc‐alkaline to Shoshone series. It is enriched in light rare earth elements (LREEs) and relatively depleted in heavy rare earth elements (HREEs), with LREE/HREE ratios of 8.03–16.40 and LaN/YbN ratios of 10.2–27.1. Samples show right‐leaning chondrite‐normalized rare earth element patterns with pronounced negative Eu anomalies (Eu/Eu∗ = 0.67–0.76). The primitive‐mantle‐normalized trace element spider diagrams of the samples are right‐leaning zigzag curves, showing relative enrichment in large‐ion lithophile elements (LILEs, e.g., Rb, Th, U, and K) and depletion in high‐field‐strength elements (HFSEs, e.g., Nb, P, Ti, and Yb) and displaying striking Sr and Ba negative anomalies. The granite εHf(t) values were positive (2.9–9.9), whereas the whole‐rock εNd(t) values were negative (–2.841 to –2.33). The calculated (87Sr/86Sr)t, (206Pb/204Pb)t, (207Pb/204Pb)t, and (208Pb/204Pb)t values are 0.7014–0.7057 (0.7044 on average), 18.422–18.851 (18.670 on average), 15.625–15.642 (15.633 on average), and 38.332–38.681 (39.571 on average), respectively. On the basis of the aforementioned data, we propose that the Xiabie Co granite was derived from a primitive magma that originated from partial melting of juvenile lower crust with the addition of mantle materials. In addition, strong fractional crystallization occurred during the rock‐forming process. Given the geodynamic setting, our new data, together with previously reported achievements, imply that the Xiabie Co granite was formed during the LS–QT collision. [ABSTRACT FROM AUTHOR]

The Marivan granitoid body of the northern Sanandaj–Sirjan Zone (N-SaSZ) of northwest Iran was emplaced into Cretaceous sediments, and is associated with minor amounts of iron skarn-type mineralization along the contact between the intrusion and surrounding country rocks. The granitoids within the intrusion include (hornblende-rich) diorite, granodiorite, and granite phases, and zircon U–Pb dating of four samples from this intrusion indicate they were emplaced during the late Eocene (Bartonian; 37.7 ± 1.0 Ma). These plutonic rocks can be classified into two main types, granitic and dioritic rocks, according to petrography and whole-rock major element geochemistry. Both the granitic and dioritic rocks are high-K, and some of the granitic rocks have an I-type affinity and peraluminous to metaluminous compositions. Both the granitic and dioritic rocks have εNd(t) values that cluster around zero (–3.3 to +3.0) and low 87Sr/86Sr(i) values (0.7040–0.7076), suggesting derivation from a mafic juvenile crustal or depleted mantle source, which was possibly mafic calc-alkaline rocks or amphibolites within the lower crust. The new zircon U–Pb ages and petrological and geochemical data presented in this study suggest that the Palaeocene–early Eocene collision of the Arabian and Iranian plates caused the ascent and emplacement of hot mafic magma through a slab window into the crust. This increased the geothermal gradient within the root zone of the developing magmatic system at the base of the continental crust, causing the partial melting of lower crust in this region. This generated mafic to intermediate magmas that were either directly emplaced into the upper crust or mixed with varying amounts of upper crustal material prior to emplacement, which formed the diorite to leucogranite range of compositions within the Marivan granitoid intrusion. [ABSTRACT FROM AUTHOR]

Despite numerous years and avenues of investigation, the timing, evolution, and mechanism of lithospheric thinning of the North China Craton (NCC) are still highly debated. Late Triassic igneous rocks especially mantle derived mafic rocks could provide critical information related to the post-collisional lithospheric thinning of the Liaodong Peninsula in the eastern NCC. Using newly acquired geochronological data points, we determined that the intrusive rocks have emplacement ages of 219–209 Ma, which are typical of Late Triassic magmatism. The studied Qinghekou gabbros have low SiO2 (49.43–51.86 wt.%), Na2O+K2O (3.59–7.20 wt.%), high MgO (3.70–8.54 wt.%) and transition metal element contents, with Mg# values ranging from 49.2 to 69.3. While these samples are enriched in large ion lithophile elements such as Rb, Ba, and K and light rare earth elements, they are depleted in high field strength elements such as Nb, Ta, Ti, and P and heavy rare earth elements. We conclude that these gabbros samples were formed in a subduction-related tectonic setting, where the primary magmas were derived from partial melting of the lithospheric mantle that experienced metasomatism via slab-related fluids. Our Tongyuanpu granite samples have I-type granite affinity, as indicated by their high SiO2 (73.60–75.30 wt.%) and low MgO (0.08–0.32 wt.%) contents, as well as the A/CNK values of 0.99–1.25 and the zircon saturated temperature values of 757–832°C, the parental magmas for these granites were generated by partial melting of the lower crust. Combined with the spatio-temporal distribution and rock-assemblages of the Late Triassic intrusive rocks, we conclude that these rocks were formed in an extensional environment characterized by lithospheric thinning caused by lithospheric delamination after the collision between the NCC and the Yangtze Craton. Furthermore, we infer that the initial lithospheric thinning of the eastern NCC occurred during the Late Triassic. [ABSTRACT FROM AUTHOR]

Major and trace element data are presented for Berguda granitoids within the Neoproterozoic basement rocks of southern Ethiopia, East African Orogeny. Geochemical and petrological constrains indicate the presence of two distinct types of granitoid rocks: (1) Wolena Bokosa granitoid (WBG) and (2) Hida Korma granitoid (HKG). WBG is granite in composition with high SiO2 content (73.38–79.38 wt.%) and wider Al2O3 values (10.68–14.81 wt.%). It has relatively high molecular values (ASI = 0.99–1.05) with low contents of CaO, MgO, Fe2O3, TiO2, and P2O5. WBG is shoshonitic to high-k calc-alkaline, Al-rich metaluminous, and more felsic I-type granitoid, whereas HKG is quartz-monzonite in composition (SiO2 = 65.31–68.26) with relatively low molecular values (ASI = 0.86–0.96) with high contents of CaO, MgO, Fe2O3, TiO2, and P2O5. HKG is also shoshonitic to high-k calc-alkaline, metaluminous, and more mafic I-type granitoid. The observed positive anomalies in Rb, Th, K, Pb, and Zr and negative anomalies of Sr, P, Ti, Nb, and Ta in both groups reflect the involvements of crustal materials in their petrogenesis. In terms of geodynamic setting, WBG is classified as volcanic arc (VAG) and syn-collisional (syn-COLG) granite and inferred as syn-orogenic, whereas the HKG is classified as within-plate granite (WPG) with post-orogenic emplacement. Furthermore, this study infers that the transition from syn-orogenic calcic-alkalic WBG to alkalic HKG magmatism is marking the cessation of subduction control magmatism of the East African Orogeny (EAO) at about 529 ± 11 Ma. The continuation of the magmatism after the cessation of subduction control magmatism is shown by emplacement of more alkalic post-orogenic HKG with volcanic arc chemical affinities possibly the effect of previous subduction process. [ABSTRACT FROM AUTHOR]

The Neoproterozoic granites along the western margin of the Yangtze Block are crucial for understanding the evolution of the Rodinia supercontinent and crust–mantle interaction. Based on a regional geological survey, this study analyses the zircon U–Pb geochronology, Lu–Hf isotope, whole‐rock Sr–Nd isotopes, and geochemistry of the Maoniushan granites along the western margin of the Yangtze Block and discusses the Neoproterozoic tectonic evolution history of the Mianning–Maoniushan belt. The results show that the Maoniushan granites belong to calc‐alkaline weak peraluminous monzogranite. The granites are enriched in large‐ion lithophile elements (i.e., Rb, Sr, Cs, and Ba) but relatively depleted in high‐field‐ strength elements (i.e., Nb, Ta, U, and Th). The zircon saturation temperature (TZr) ranges from 628 to 766°C, and the weighted average 206Pb/238U ages of zircon range from 771 ± 30 to 759 ± 26 Ma. The εHf(t) values range from −2.0 to +7.2, with TDM2 model ages ranging from 1,797 to 1,208 Ma. The whole‐rock Sr–Nd isotopic data show (87Sr/86Sr)i ratios of 0.7039–0.7093, and the εNd(t) values range from +1.25 to +1.76 with TDM2 model ages ranging from 1,303 to 1,344 Ma. These findings indicate the presence of deep Mesoproterozoic crustal materials in the source area. The Maoniushan monzogranites belong to I‐type granite, which is formed by the partial melting of the basic rocks and pelites in the ancient lower crust due to the metasomatism of fluids from the subducted oceanic crust. The Maoniushan monzogranites may be formed in the process of transformation from regional thickening to thinning under the oceanic crust subduction setting. [ABSTRACT FROM AUTHOR]

The Central Asian Orogenic Belt had been formed by amalgamation of voluminous subduction–accretionary complexes during the Late Neoproterozoic to the Mesozoic period. Mongolia is situated in the center of this belt. This study presents new zircon U–Pb geochronological, whole-rock major and trace element data for granitoids within central Mongolia and discusses the tectonic setting and evolution of these granitic magmas during their formation and emplacement. The zircon U–Pb ages indicate that the magmatism can be divided into three stages: the 564–532 Ma Baidrag granitoids, the 269–248 and 238–237 Ma Khangai granitoids. The 564–532 Ma Baidrag granitoids are adakitic, have an I-type affinity, and were emplaced into metamorphic rocks. In comparison, the 269–248 Ma granitoids have high-K, calc-alkaline, granodioritic compositions and are I-type granites, whereas the associated the 238–237 Ma granites have an A-type affinity. The 564–532 Ma Baidrag and 269–248 Ma Khangai granitoids also both have volcanic arc-type affinities, whereas the 238–237 Ma granites formed in a post-collisional tectonic setting. These geochronological and geochemical results suggest that arc magmatism occurred at the 564–532 Ma which might be the oldest magmatic activity in central Mongolia. Between the Baidrag and the Khangai, there might be paleo-ocean and the oceanic plate subducted beneath the Khangai and produced voluminous granite bodies during the 269–248 Ma. After the closure of the paleo-ocean, the post collisional granitoids were formed at the 238–237 Ma based on the result of later granitoids in the Khangai area.

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The Urumieh-Dokhtar Magmatic Arc (UDMA) appears as a nearly linear suite of magmatic rocks that extends from NW to SE Iran parallel with the orogenic suture of the Zagros Fold-Thrust belt. The Qazan granitoids formed along the central part of UDMA and span a wide range of felsic rocks, including granodiorite, quartz diorite, diorite, and monzogranite. Their common rock-forming minerals are mainly quartz, feldspar, amphibole, biotite and clinopyroxene. These granitoids contain abundant mafic microgranular enclaves (MME). Bulk-rock major and trace element compositions returned a relatively low SiO2 content (ca. 51–55 wt %) and high Mg# (ca. 40–50) for MME samples, potentially reflecting a mantle-derived origin. The granitoid host rocks are metaluminous (A/CNK = ca. 0.7–1) I-type rocks with arc-related calc-alkaline affinity. They yield higher SiO2 contents with a comparatively larger variation (ca. 57–66 wt %) and lower Mg# (ca. 35–48), consistent with derivation from partial melting of lower continental crust. Mixing of two contrasting mafic (sourced from an enriched subcontinental lithospheric mantle wedge) and felsic (derived from lower continental crust) melts in the Neo-Tethyan subduction-related oxidizing system has resulted in generation of Qazan granitoid melts. Thermometry of Qazan intrusive rocks indicates that the ascending melt was crystallized at 1200–1100°C in lithospheric mantle to lower continental crust. [ABSTRACT FROM AUTHOR]

Zarrin granitoid, with mostly metaluminous to slightly peraluminous, and I-type composition, outcropped in Yazd block, Central Iran. The U-Pb SHRIMP zircon age from Zarrin granitoid yields 557-567 Ma age consistent with the Late Neoproterozoic-Early Cambrian ‘Cadomian’ plutonism at northern margin of Gondwana supercontinent. The chondrite and primitive mantle normalized trace elements patterns show light rare earth elements (LREE) enrichment relative to heavy rare earth elements (HREE) and enrichment of large ion lithophile elements (LILE) relative to high field strength elements (HFSE), accompanied by negative anomalies in Nb, Ti, and Eu consistent with arc-related magmatism, associated with subduction of Proto-Tethys oceanic crust beneath the northern margin of Gondwana. Geochronological and geochemical data including inherited zircon age suggest the Zarrin granitoid originated from partial melting of relatively younger mafic crust and point to the existence of hidden PaleoproterozoicMesoproterozoic rocks in the lower continental crust of Iran. [ABSTRACT FROM AUTHOR]

The East Kunlun orogenic belt (EKOB) is located in the northeastern part of the Qinghai-Tibetan Plateau, China. Voluminous Silurian-Devonian granitoids were formed during the Proto-Tethys Ocean subduction and collision process. In this study, zircon U-Pb age dating, in-situ Hf isotope analyses, and whole rock major and trace element analyses have been carried out on granitoids from the central to eastern EKOB. The formation ages of granodiorite in the Bairiqili area, the granodiorite in the Wulonggou area are 410 ± 2 Ma and 396 ± 1 Ma, respectively, and the granodiorites show I-type features. The Wulonggou syenogranite with a formation age of 398 ± 2 Ma has a high differentiation index (D.I. = 89.59–92.43), and may belong to the high fractionated I-type granite. The Lalangmai tonalite with a formation age of 423 ± 2 Ma has high Sr (339–590 µg/g), εHf(t) (1.5–7.3), and low Y (3.45–6.33 µg/g), which are similar to modern adakites. The Lalangmai tonalite is the latest adakite record during the Proto-Tethys evolution in EKOB. Combined with previous studies, it is concluded that the granitoids from Cambrian to Devonian divided into four episodes. The first episode (515–436 Ma) mainly consists of I-type island arc granites and adakite, which are formed in a subduction environment. The second episode (436–427 Ma) is characterized by the S-type granites related to the collision. The third episode (427–420 Ma) is the transition period between the collision and the post-collision environment. In the fourth episodes (420–385 Ma), granitoids were formed in post-collision extensional environment, which is characterized by I-type and A-type granites. The upwelling of asthenosphere material is likely caused by the collapse of the orogenic belt. After 420 Ma, I-type and A-type granites formed at different depths but in the same environment. [ABSTRACT FROM AUTHOR]

The petrogenesis and tectonic affinity of late Mesoproterozoic to early Neoproterozoic magmatic records in the Yangtze Block is important to understand its tectonic evolution within the context of the Rodinia supercontinent's reconstruction. In this paper, our new SHRIMP zircon U-Pb dating results demonstrate that the Luonie granodiorites and Gonghe granites were emplaced at 1019.2 ± 5.3 Ma and 925.0 ± 4.9 Ma, respectively. The Luonie granodiorites show high HFSE and HREE contents and Ga/Al ratios, resembling A-type granites. They exhibit negative εHf(t) values (−1.6 to −3.9) with TDM2 ages of 1980–2125 Ma, suggesting that they were derived from partial melting of pre-existing continental crust. The Gonghe granites are calc-alkaline, slightly peraluminous and have low P2O5 contents, which are typical features of I-type granites. Zircons from Gonghe granites possess positive εHf(t) values (+10.8 to +13.1) with TDM2 ages of 969–1113 Ma, indicating juvenile mafic lower crust source. In conclusion, Luonie granodiorites were formed in an intra-plate rifting environment, whereas Gonghe arc-related intrusion was emplaced into an arc-setting. On the basis of these results, we propose that the rifting-related igneous rocks and subduction-related magmatism in the southwestern Yangtze Block record a tectonic transition from a continental-rifting basin in the passive plate margin to a collisional setting in an active continental margin in the early Neoproterozoic. [ABSTRACT FROM AUTHOR]

We report new results of a comprehensive study into Carboniferous – Early Permian granite magmatism of the northern Taimyr Peninsula, Russia (southern part of the Kara Terrane). U-Pb zircon ages (SHRIMP and LA–ICP–MS) represent the crystallization ages of these intrusions and range from ca. 344.5 to 288.4 Ma, defining the onset of granite magmatism during the Early Carboniferous (Visean; ca. 344 Ma) and its termination in the Early Permian (Artinskian; ca. 288 Ma). Ar-Ar dating of micas and amphiboles indicates that Late Palaeozoic tectonic activity in northern Taimyr ceased during the Middle Permian (Roadian; ca. 272 Ma). Rb/Sr and Sm/Nd isotopic data from the same intrusions, show initial (87Sr/86Sr)i ratios of between 0.70288 and 0.71027, with εNd(t) values range between −3.3 and +3.1. The combined geochemical and isotopic compositions of the granites describe an affinity to peraluminous I-type granites, probably formed in an Andean-type active continental margin setting. Our new geochemical, isotopic, and geochronological data indicate the existence of a long-lived (ca. 56 Myr) Andean-type active continental margin along the southern edge of the Kara Terrane during the Late Palaeozoic. Furthermore, our study reveals a causal relationship between Late Palaeozoic magmatism across northern Taimyr and closure of the Uralian Ocean. [ABSTRACT FROM AUTHOR]

The Pamir orogen originated through the amalgamation of various arc terranes. Despite undergoing numerous studies, the subduction polarity and time regarding the accretion processes remain inadequately constrained. To address these issues, we carried out a detailed study of zircon and apatite U-Pb ages, zircon Hf isotopes, and whole-rock geochemistry for the Permian to Cretaceous gabbro, volcanic rocks and granitoids from the Southern Pamir and the Rushan-Pshart suture. Three stages of magmatism are identified, including 279–266 Ma gabbro and andesite to dacite, 209–208 Ma granitoids, and 108–103 Ma gabbro and granitoids, respectively. The Permian gabbro and basaltic andesite to dacite in Pshart Range are enriched in light rare earth elements (LREE) and large ion lithophile elements (LILE), but are depleted in Ta, Nb, and Ti, suggesting formation from an enriched mantle source in a subduction zone. The Late Triassic I-type granitoids are typical arc calc-alkaline magmatic rocks with ε Hf (t) values varying from −8.7 to −3.5, which mainly sourced from the partial melting of mixed crustal sources predominately consisting mafic rocks with minor metasedimentary rocks. The Early Cretaceous Pshart granites are I-type granites with relatively low ε Hf (t) values ranging from −14.6 to −2.9, suggesting that they were crust-derived rocks. The Early Cretaceous Bazardara granites are identified as A 2 -type granites with the ε Hf (t) values ranging from −18.3 to +5.3, and were derived from mixing of mantle-derived and crust-derived magmas, or interaction between mantle melts and old crustal rocks. The early Cretaceous gabbro exhibits -MORB-like geochemical characteristics with flat REE pattern (La/Yb N = 4.96), moderate enrichment of LILEs and weak depletion of Nb, Ta and Ti (Nb/La PM = 0.94). Thus, the early Cretaceous A 2 -type granite, E-MORB-like gabbro and volcanic rocks were formed in an extensional setting. Our new data indicate that the southward subduction of the Rushan-Pshart oceanic slab started in the Early Permian and continued to the Late Triassic. Moreover, combining the previous data, we conclude that the Early Cretaceous granites and gabbro in the Southern Pamir formed in an extensional environment due to the southward rollback after northward near-flat subduction of the Neo-Tethyan oceanic lithosphere. [Display omitted] • Permian, Triassic, and Cretaceous arc rocks are identified in the South Pamir. • Southward subduction of the Rushan-Pshart Ocean began before the Permian. • The southward subduction formed the late Triassic I-type granites. • Slab roll-back of the Shyok Ocean caused within-plate magmatism in the South Pamir. [ABSTRACT FROM AUTHOR]

[Display omitted] • Ca. 800 Ma I-type granites were identified in the Feidong Complex. • The I-type granitic rocks were produced by partial melting of ancient lower crust. • Ca. 800 Ma I-type granites in the Feidong Complex suggests a post-collisional extensional setting. Neoproterozoic magmatic rocks are widely distributed along the periphery of the Yangtze Block, but their petrogenesis and tectonic setting remain controversial. This study involved an integrated geochemical and geochronological analysis of mid–Neoproterozoic granitic rocks from the Feidong Complex on the northeastern margin of the Yangtze Block. LA–ICP–MS zircon U–Pb dating of two granitic gneiss samples yielded weighted mean ages of 803 ± 7 Ma and 792 ± 11 Ma. Combined with published age data from other Neoproterozoic magmatic rocks, these new dates suggest that the Feidong Complex experienced a magmatic flare–up at ca. 800 Ma. Geochemically, the granitic gneisses exhibit the characteristics of highly fractionated I–type granites. All of the studied samples have negative ε Hf (t) values of –18.20 to –8.51 and corresponding two–stage Hf model ages (T DM2) of 2.82–2.23 Ga, indicating their derivation from remelting of ancient crust. Geochemical characteristics suggest that the granitic rocks formed in a syn–collisional or post–orogenic environment. Integrating published geochemical data from other magmatic rocks along the northern margin of the Yangtze Block, we suggest that a plausible petrogenetic model for mid–Neoproterozoic magmatic rocks within the Feidong Complex may be tectonic collapse and remelting of the early to mid–Neoproterozoic collisional orogenic belt. In this model, melting represents a tectonothermal response to lithospheric extension before the breakup of the Rodinia supercontinent. [ABSTRACT FROM AUTHOR]

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