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The Beishan Orogenic Belt is located in the central southernmost part of the Central Asian Orogenic Belt (CAOB), which plays a key role in understanding the formation and evolution of the CAOB. Granitoids are the documents of crustal and tectonic evolution in orogenic belts. However, little is known regarding the petrogenesis and geodynamic setting of the widely distributed Paleozoic granitoids in the Northern Beishan Orogenic Belt (NBOB). The present study reveals significant differences concerning the petrogenesis and tectonic setting of early and late Paleozoic granitoids from the NBOB. The early Paleozoic granitoids from the 446–430 Ma Hongliuxia granite complex of the Mazongshan unit and the 466–428 Ma Shibanjing complex of the Hanshan unit show classic I-type granite affinities as revealed by the relative enrichment of LILEs and LREEs, pronounced depletions of Nb, Ta and Ti and the abundant presence of hornblende. Furthermore, they are characterized by strongly variable zircon ε Hf(t) values between − 16.7 and + 12.8 and evolved plagioclase Sr isotopic compositions of 0.7145–0.7253, indicating the involvement of both juvenile and ancient continental crust in the magma source. Thus, we propose that the early Paleozoic granitoids in the NBOB were generated in a subduction-related continental arc setting. In contrast, the late Paleozoic 330–281 Ma granitoids from the Shuangjingzi complex of the Hanshan unit exhibit positive zircon ε Hf(t) values between + 5.8 and + 13.2 and relatively depleted plagioclase Sr isotopic compositions of 0.7037–0.7072, indicating that they were mainly formed by remelting of juvenile crust. Thus, an intra-plate extensional setting is proposed to have occurred during formation of the late Paleozoic granitoids. Therefore, between the early and late Paleozoic, the magma sources of the NBOB granitoids converted from the reworking of both juvenile and ancient crusts during a subduction-induced compressional setting to the remelting of juvenile crust during an intra-plate extensional setting, respectively. The corresponding crustal growth in the southern CAOB is dominated by early Paleozoic lateral accretion of arc complexes and late Paleozoic vertical addition of juvenile material from the mantle. [ABSTRACT FROM AUTHOR]

• Granitoids of Singhbhum Craton. • Two generation of TTGs at 3.42 and 3.32 Ga formed by melting of juvenile mafic crust. • Later K-rich, silicic granites at 3.28 and 3.25 Ga formed by melting of tonalites. • Recurring crustal melting in a gradually thickening oceanic plateau. • Final cratonisation of the Singhbhum Craton at 3.25 Ga. A significant part of many Archean cratons formed during Paleoarchean. Yet, the mechanism and tectonic setting of formation of Paleoarchean continental crust remain highly debated. In this contribution, we present field, petrographic, geochemical, zircon U-Pb age and Hf isotope data on Paleoarchean granitoids from west-central part of the Singhbhum Craton (Champua-Hat Gamharia corridor), India. The whole process starting from nucleation of a juvenile continent to its evolution and final stabilization is documented. The core of the craton nucleated with formation of 3.45–3.40 Ga TTGs showing juvenile character (zircon ɛHf t = +0.6 to +7.1). These rocks show slightly depleted HREE and Y, negligible Eu-anomaly (Eu/Eu* = 0.90 to 1.00) and moderate Sr/Y (25–64), consistent with derivation from a low-K mafic crust at a pressure near the lower end of the garnet stability field, causing subordinate garnet retention in the residue and negligible role of plagioclase. A second generation of TTG formation took place at 3.32 Ga in the area by deeper melting of a juvenile mafic crust (zircon ɛHf t = +1.3 to +5.7) as suggested by strongly depleted HREE and Y, and high Sr/Y (52–155) implying significant amount of garnet retention in the residue. Subsequently, the area witnessed intracrustal melting at 3.28 and 3.25 Ga which tapped moderately old to juvenile (zircon ɛHf t = −1.9 to +4.5), mostly TTG sources at variable depths generating potassic, LILE-enriched, high-silica granites. Intrusion of these potassic granites marks the final cratonization of the Singhbhum Craton. The sequence of events is interpreted in terms of repeated crustal melting and granitoid generation in a gradually thickening oceanic plateau with a progressive change in granitoid source from mafic to felsic in composition. A synthesis of rock assemblage, regional geological setting and structural pattern also supports intraplate nature of the magmatism in Singhbhum Craton, which might have been a significant mechanism of crustal growth worldwide during Paleoarchean. Further, a comparison of juvenile crustal growth and crustal reworking events of the Singhbhum and other Indian cratons show that these cratons record distinct evolutionary histories and were probably nucleated at different sites. [ABSTRACT FROM AUTHOR]

Although Mesozoic granites are widely distributed in the Gan-Hang Belt in Southeast China, their petrogenesis and geodynamic settings are still matters of dispute. Here, the major and trace elements, Sr-Nd isotopic compositions, zircon U‐Pb dating and Hf isotopes of three late Mesozoic granite plutons from Machebu, Shenzhongwu and Daixi in northern Zhejiang Province were analyzed to investigate their petrogenesis. These granite plutons are featured by an A2-type granite geochemical signature (e.g., high SiO 2 (71 to 78 wt.%), total alkalis (Na 2 O + K 2 O = 7.57 to 9.12 wt.%), rare earth elements (total REE = 174 to 519 ppm) and HFSE contents, with mostly high FeO T /(FeO T + MgO) (0.82 to 0.93) and Ga/Al ratios (2.49 to 5.07) and low Ce 4 + /Ce 3 + ratios in zircons (1 to 90)), suggesting they were formed in an extensional tectonic setting. Combining whole rock Zr contents, mineral assemblages and the An content of plagioclase, it was suggested that these granites could have formed at a high temperature (> 850 °C) with a low H 2 O content (~ 2.5 wt.%). Assuming the granite with the lowest SiO 2 and high CaO contents as the “primary granite melt”, the melting pressure was estimated to be 2.5 kbar based on model calculations using MELTs. Taking into account the effect of plagioclase fractional crystallization during the granite emplacement into shallow crustal levels, the initial melting pressure could be > 2.5 kbar at the stable field of plagioclase. This agrees well with the very low and variable Sr and Eu contents of these granite plutons. Zircon U–Pb dating yields a weighted mean 206 Pb/ 238 U age of 130.9 ± 1.0 Ma for the Machebu granite, 134.4 ± 2.1 Ma for the Shenzhongwu granite and 131.9 ± 1.2 Ma for the Daixi granite. The ε Hf (t) values of the zircons in these plutons gradually increase from southwest to northeast, i.e., from − 14.5 ~ − 3.5 for the Machebu granite to − 1.5 ~ − 0.2 for the Shenzhongwu granite and from 5.1 ~ 8.6 for the Daixi granite, suggesting the origin of different parent rocks. These granites have two-stage Nd model (T DM2 (Nd)) ages of 1099 Ma–838 Ma, and zircons from these granites and the Neoproterozoic basement in the Gan-Hang Belt plot on the same evolutionary trend in the ε Hf (t)-age diagram. It is interesting to note that the collection of literature data shows a positive correlation between SiO 2 and ε Nd (t) for the late Mesozoic A-granites in the Gan-Hang Belt, and the Neoproterozoic A-granites in the Gan-Hang Belt cluster in two groups of the high-SiO 2 -ε Nd (t) group and low-ε Nd (t) group. The positive correlation of SiO 2 -ε Nd (t) demonstrated by the late Mesozoic A-granites can be well explained by a high-degree of melting of mixtures between the two groups of Neoproterozoic A-granites. We thus suggest that the late Mesozoic A-type granites in the Gan-Hang Belt could have been derived from the rejuvenated Neoproterozoic rocks rather than directly from the Mesoproterozoic metamorphic basement as a result of subduction. [ABSTRACT FROM AUTHOR]

Palaeoarchaean granitoids are exposed over wide area in the Singhbhum craton whose origin and role in crustal evolution are not well constrained. This study presents whole-rock and mineral chemical data coupled with zircon U-Pb dating and Hf isotope results on such granitoids from the central part of the craton to understand their petrogenesis, tectonic setting and role in continental crustal evolution. The first phase of granitoid magmatism in this area is represented by a 3.47 Ga Na-rich, gneissic tonalite belonging to the Archaean TTG (tonalite-trondhjemite-granodiorite) suite. This rock is characterized by high-HREE (heavy rare earth elements), negative Eu anomaly, low Sr/Y ratio and positive zircon Hf isotope signature (εHf t = +2.1 to +4.8). It is interpreted to be formed by shallow melting of a juvenile mafic source. At 3.35 Ga a silicic, ferroan porphyritic biotite granite formed. It shows variable K/Na, low Y and high Sr/Y, moderately fractionated HREE and positive zircon εHf t (+1.8 to +4.0), and is explained as a product of high-temperature melting of a heterogeneous, juvenile source consisting of tonalites and mafic rocks at lower crustal depth. The final phase of granitoid magmatism is marked by a 3.30 Ga non-porphyritic ferroan, silica-rich biotite granite. Geochemical characteristics like moderately high K, moderately fractionated HREE, low Ca and Sr/Y, and zircon εHf t (+0.8 to +3.7) suggest that the granite was formed by high-pressure melting of a tonalite-dominated source with short crustal residence. All the three granitoid phases display low Mg, Ni and Cr contents and magnesium number (Mg#) precluding direct involvement of mantle in their origin. Rather, crustal reworking caused by episodic plume-related mafic-ultramafic magma underplating and intraplating in an oceanic plateau setting is suggested as the possible mechanism for formation of the granitoids. Successive crustal reworking events involved progressively greater amount of previously formed felsic crust generating more evolved, K-rich granitoids. It appears to be a globally important process which led to effective crustal differentiation and maturing of the cratons during Palaeoarchaean. [ABSTRACT FROM AUTHOR]

An integrated study of zircon U–Pb ages and Hf–O isotopic compositions, whole rock elemental and Sr–Nd isotope geochemistry was conducted on three lithologically diverse middle Jurassic plutons from the Eastern Hebei area of the North China Craton (NCC), in order to reveal both their petrogenesis and possible tectonic affinity. The three plutons have consistent magmatic zircon U–Pb ages from 167 ± 1 Ma to 173 ± 1 Ma. The Nianziyu pluton has typical characteristics of appinite with low SiO 2 (43.7–52.6%), high Ca, Mg, Fe and H 2 O contents. It possesses subduction-related trace element patterns, enriched Nd–Hf isotopic signatures as well as elevated zircon δ 18 O values (6.2–7.2‰), arguing for an enriched mantle source metasomatized by fluids related to subduction. The Shuihutong monzogranites have high silica (SiO 2 = 75.4–75.9%) and alkali contents, low Ca contents and striking negative Ba, Sr and Eu anomalies. Samples from the pluton have more evolved Nd–Hf isotopic values and are considered to be most likely derived from anatexis of ancient lower continental crust. Hybridization between mantle- and ancient lower crust-derived magmas is proposed for the mafic microgranular enclave-bearing Baijiadian granitoids, which are characterized by variable ε Nd (t) and ε Hf (t) values. Integrated with the regional geologic history, we suggest that the formation of the three middle Jurassic plutons were related to the subduction of the Paleo-Pacific ocean plate beneath the NCC. Their petrogenetic differences reflect complex magmatic processes in subduction settings involving melting of multiple sources, possible partly facilitated by fluid metasomatism and water-rich magma injection, accompanied with various degrees of magma mixing. The appearance of middle Jurassic appinitic rocks leads us to propose that the NCC destruction and lithosphere thinning were facilitated and controlled by the weakening of the lithospheric mantle after hydration because of the subduction of the paleo-Pacific ocean plate. The lower crust of the craton was also reactivated at the same time due to the subduction. [ABSTRACT FROM AUTHOR]

Highlights: [•] Granitoid magmatism changed in composition with evolution of Kadiri greenstone belt. [•] Initial sanukitoid magmatism was followed by transitional TTG, leucogranite and A-type granite. [•] A convergent setting characterized by repeated slab break-off and crustal reworking. [•] Finally post-subduction anorogenic granite magmatism. [•] Reworking of Mesoarchaean crust in eastern Dharwar craton identified. [Copyright &y& Elsevier]

Abstract: A combined study of zircon U–Pb and Lu–Hf isotopes and whole rock major and trace elements and Sr–Nd isotopes has been conducted for 10 tonalitic–trondhjemitic–granodioritic (TTG) and granitic gneisses from the Kongling terrain, the only known Archean microcontinent in the Yangtze craton, South China. The results reveal a significant magmatic event at ∼2.6–2.7Ga, in addition to the previously reported ∼2.9Ga and ∼3.2–3.3Ga magmatism. The ∼2.6–2.7Ga rocks show relatively high REE (530–1074ppm), apparently negative Eu anomaly (Eu/Eu*=0.22–0.35), low #Mg (19.51–22.63) and low LaN/YbN (10.3–24.2). Besides, they have high K-feldspar proportion and relatively evaluated (K2O+Na2O)/CaO, TFeO/MgO, Zr, Nb, Ce and Y contents. Their 10,000×Ga/Al ratios range between 3.00 and 3.54. All these features suggest that the protoliths of these gneisses are A-type granites. Most of the ∼2.6–2.7Ga zircon grains have ɛ Hf(t) values >0 (up to 7.93, close to the depleted mantle value). This clearly indicates a considerably higher proportion of new crustal components in the ∼2.6–2.7Ga granitoids compared to the ∼3.2–3.3Ga and ∼2.9Ga TTGs. Our results support the conclusion of worldwide studies of igneous and detrital zircons that age peaks at 2.65–2.76Ga represent increases in the volume of juvenile continental crust. The present study also confirms the existence of the two older magmatic events in the Kongling terrain. Both whole rock ɛ Nd(t) values (−3.74 to 1.59) and the zircon ɛ Hf(t) values (−11.18 to 3.55) for the ∼2.9Ga TTG and the Hf isotopes of ∼3.2–3.3Ga igneous zircons (−7.37 to 3.12) are chondritic or subchondritic, suggesting that they were mainly generated by reworking of older rocks with a small amount of new crustal additions. [Copyright &y& Elsevier]