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• ∼1.4 Ga juvenile magmatism occurs in most microcontinents in the southern CAOB. • The microcontinents show distinct evolution compared to nearby cratons at ∼1.4 Ga. • Mesoproterozoic magmatism records geodynamic transition along the margin of Nuna. The southern Central Asian Orogenic Belt contains numerous microcontinents including the Kazakhstan-Yili block, Central Tianshan Arc and Junggar block in the west, the Erguna, Xing'an, Songliao and Jiamusi-Khanka blocks in the east, bridging by the Tuva-Mongolia block, Beishan Orogenic Belt and Alax block in the central region. New geochemical and geochronological data from the microcontinental blocks within the southern Beishan Orogenic Belt provide new insight into the Precambrian crustal evolution of this region. Five granitoids from the Jiujing region yielded igneous zircon 206Pb/238U ages of 1450–1401 Ma, and zircon xenocrysts from late Paleozoic plutons in the Jiujing, Qiaowan, and Shibandun regions have 206Pb/238U ages that also cluster at ∼1.4 Ga. Those data suggest that crust of this age is widespread beneath the southern Beishan Orogenic Belt. The ∼1.4 Ga zircons display depleted Hf isotopic signatures (ε Hf(t) = 2.0–11.1) and show relatively young two-stage Hf model ages (1.9–1.4 Ga), indicating rapid reworking of juvenile mantle-derived materials. Integrating these results with similar geochronological data from the Kyrgyz North Tianshan, Yili block, Central Tianshan Arc, northern Alxa block and Xilinhot block, we propose that the CAOB incorporates an extensive assemblage of Mesoproterozoic (1450–1360 Ma) magmatism that can be traced over ca. 3000-km long a west-east trending belt. These Mesoproterozoic granitoids display distinct geochemical signatures (e.g., Ga/Al*10,000 ranging from 1.46 to 3.88 and Zr + Nb + Ce + Y varying largely from 101 to 1066 ppm) and show a temporal progression from orogenic to anorogenic over a relatively short period. This suggests a tectonic setting that likely evolved from compressional to extensional environments during 1450–1360 Ma, perhaps resulting from slab roll back. We suggest that the 1450–1360 Ma magmatism along the southern CAOB corresponds with a transition from a compressional to extensional environment on the margin of the Nuna supercontinent. [ABSTRACT FROM AUTHOR]

The activity of melts and fluids may have played a key role in inducing the destruction of the eastern North China Craton in the early Cretaceous. Carbonate melts are important agents in mantle metasomatism and can significantly modify the physical and chemical properties of the subcontinental lithospheric mantle. Carbonate metasomatism can be identified by specific geochemical indices in clinopyroxene, such as high Ca/Al and low Ti/Eu ratios. This study presents the spatial and temporal variations of carbonate metasomatism in the lithospheric mantle beneath the eastern North China Craton. Three types of carbonate metasomatism are classified based on the geochemical compositions of clinopyroxene in mantle peridotites. Clinopyroxene formed by Type 1 carbonate metasomatism is characterized by very high Ca/Al ratios (15-70) and 87Sr/86Sr ratios (0.706-0.713). Clinopyroxene derived from Type 2 carbonate metasomatism shows relatively high Ca/Al ratios (5-18) and 87Sr/86Sr ratios (0.703-0.706). However, clinopyroxene resulting from Type 3 carbonate metasomatism has low Ca/Al ratios (5-9) and 87Sr/86Sr ratios (0.702-0.704). Deep (garnet-bearing) and shallow (spinel-bearing) lithospheric mantle beneath the Sulu orogen and surrounding areas in the eastern North China Craton were affected by intense Type 1 carbonate metasomatism before the late Triassic. The deep subduction of the South China Block with its accompanying carbonate sediments was the trigger for Type 1 carbonate metasomatism, which reduced strength of the lithospheric mantle and provided a prerequisite for the destruction of the eastern North China Craton in the early Cretaceous. After the destruction of the eastern North China Craton, the ancient relict lithospheric mantle, represented by spinel harzburgite xenoliths hosted in the late Cretaceous to Cenozoic basalts, only recorded Type 2 carbonate metasomatism. This implies that the lithospheric mantle experienced the intense Type 1 carbonate metasomatism was completely destroyed and not preserved during decratonization. Spinel lherzolite xenoliths hosted in the late Cretaceous to Cenozoic basalts represent the young, fertile lithospheric mantle formed after the cratonic destruction and only a few samples record Type 2 and 3 carbonate metasomatisms. We suggest that carbonate melts derived from the subduction-modified asthenospheric mantle with variable proportions of recycled crustal material was responsible for the Type 2 and 3 carbonate metasomatisms. The carbonate metasomatism of the lithospheric mantle beneath the Jiaodong Peninsula and surrounding areas is very pervasive and is spatially consistent with the remarkable thinning of lithospheric mantle and giant gold deposits in this region. Therefore, we conclude that carbonate metasomatism in the lithospheric mantle played a crucial part in the modification, destruction and gold deposits in the eastern North China Craton. [ABSTRACT FROM AUTHOR]

Highlights: [•] TTG in the interior of the Dunhuang blocks was formed at ∼2.7–2.6Ga. [•] Tarim experienced two-stage (∼2.7–2.6 and ∼2.5Ga) intrusion of Archean TTG. [•] Tarim was characterized by episodic generation of juvenile continental crust. [•] Paleoproterozoic and Paleozoic tectonothermal events were prevail in the Tarim craton. [•] Paleoarchean continental crust as old as ∼3.4Ga may have existed in the Dunhuang block [Copyright &y& Elsevier]

• 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]

Abstract Mechanisms of lithospheric transformation beneath the North China Craton (NCC) were widely discussed, but the northern NCC was less studied compare to the eastern part. In this research, In-situ major and trace element and Sr isotopic compositions of spinel peridotite and pyroxenite xenoliths carried by the Yangyuan Tertiary basalt were analyzed to constrain subduction style of the Paleo-Asian oceanic plate (PAOP) and its influence on the northern NCC. These xenoliths were classified into dunite, pyroxenite, and two groups of lherzolites according to their petrography and chemical features. The petrography and mineral chemistry suggest that the dunite, pyroxenite, and Group 1 lherzolites are residues of partial melting which experienced subsequent hydrous metasomatism. Correlations between 87Sr/86Sr with the Zr/La and Zr/Nb ratios in clinopyroxenes from these xenoliths suggest that the metasomatic agents should be fluids derived from the subducted PAOP. Mineral Rb Sr isochron of the pyroxenite show that the minimum age of the metasomatism event should be 295 ± 38 Ma. Major element compositions of minerals in the Group 2 lherzolites are more fertile compare to the dunite and Group 1 lherzolites. Clinopyroxenes in these xenoliths exhibit LREE-depleted REE patterns with relatively high HREE contents and 87Sr/86Sr ratios (0.70403–0.70482). Chemical zonations are preserved in several clinopyroxenes with incompatible elements depleted from core to rim, which should be the results of melt depletion after metasomatism. Patches of silica-rich glasses were present along the grain boundaries. These glasses have sediment-like Pb isotopic compositions and trace elements distribution patterns and thus are supposed to represent the melt from recycled sediments. Combined with geophysical and tectonic evidences, we propose that roll-back of the southward low-angle subducted PAOP in the late stage of subduction contributed to remelting of the PAOP subduction-modified mantle wedge beneath the northern NCC. Highlights • The Yangyuan basalt-borne xenoliths record subduction related metasomatism • Rb Sr isochron gives the minimum age of 295 ± 38 Ma for the metasomatism event. • Slab roll-back resulted in remelting of the subduction-modified mantle wedge. • Patches of silica-rich glass were derived from the subducted sediment diapirs. [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]

Three types of carbonates have been found in the Miocene basalt in the Dongbahao area (Inner Mongolia), including wide veins and veinlets of carbonate in basalt and carbonates in peridotite xenoliths. Except for the dolomitic zonation in the basalt, all of the carbonates are calcite. Despite their different appearances, they share almost identical geochemical characteristics of low LILE (low large ion lithophile element), HFSE (high field strength element), and REE (rare earth elements) contents (ΣREE = 0.51–137 ppm); negative Ce anomalies; and low Ce/Pb ratios (0.51–74.5). Moreover, they show high δ 18 O SMOW values (20.95–22.61‰) and 87 Sr/ 86 Sr ratios (0.7087 ± 0.0003 (1σ, n = 17)). These characteristics indicate a sedimentary precursor for these carbonates. However, the occurrence and petrographic characteristics imply an igneous origin for the carbonates rather than a hypergene process. Further, the trace element compositions of the silicate melt and carbonate melt in the calcite-dolomite-silicate zonations fall on the same variation lines in the plots of Y-Ho, La-Yb, Li-Pb and Ba-Cu. It is suggested that these melts could have evolved from one magma system or could have been equilibrated. Given the partition coefficients of REEs and alkali elements (Cs, Rb, and K) between the carbonate melt and silicate melt, it can be inferred that these melts could have been formed from a primary H 2 O-Si-bearing Mg-Ca-carbonate melt by an immiscibility process at 1–3 GPa. Considering the southward subduction of the Paleo-Asian ocean along the northern margin of the North China Craton (NCC), these carbonate melts could have been derived from the melting of subducted sedimentary carbonate rocks. Interestingly, these carbonates have quite depleted carbon isotopic compositions (δ 13 C PDB = −8.23‰ to −11.76‰) but moderate δ 18 O SMOW values, implying coupled H 2 O-CO 2 degassing during subduction and/or recycling to the Earth’s surface. Low-δ 13 C PBD carbonates appearing at the global scale may suggest an underestimated path of CO 2 emission back to the atmosphere. [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]

In-situ major and trace elements and Sr isotopic compositions of peridotite xenoliths of the Datong Quaternary alkaline basalt were analyzed to evaluate the influences of the southward subduction of the Paleo-Asian oceanic plate (PAOP) on the lithospheric mantle transformation of the North China Craton (NCC). These peridotite xenoliths including spinel harzburgites and lherzolites were classified into three groups. The type 1 peridotites have the lowest temperatures (961–1007 °C). Clinopyroxenes in these peridotites exhibit LREE-depleted REE patterns and have the lowest 87 Sr/ 86 Sr ratios of 0.70243–0.70411. The type 2 and 3 peridotites show higher temperatures (1017–1022 °C). Clinopyroxenes in the type 2 peridotite have V-shaped REE patterns and relatively higher 87 Sr/ 86 Sr ratios of 0.70418–0.70465. Clinopyroxenes in the type 3 peridotite have concave-downward REE patterns and unusually high 87 Sr/ 86 Sr ratios of 0.70769–0.70929. Carbonatitic veinlets are found in the type 1 peridotites. They show steep LREE-enriched REE patterns with enrichment in LILE and depletion in HFSE, and have the highest 87 Sr/ 86 Sr ratios of 0.71145–0.71285. The mineral chemistries and modal calculations suggest that the protolith of these peridotites experienced a variable degree of partial melting. The type 2 and 3 peridotites sampled from deeper depth experienced latter cryptic carbonatitic metasomatism. The carbonatitic veinlets have generally consistent trace element patterns and Sr isotopic ratios with the calculated melts equilibrated with clinopyroxenes in the type 3 peridotite, which may represent the percolated carbonatitic melt quickly solidified in the relatively cold and shallow mantle. The remarkable negative Eu anomalies (0.37–0.61) and highly radiogenic Sr isotopic compositions of the calculated metasomatic agents preclude indicate melt derived from carbonated peridotite or carbonated eclogite but point to a crustal sedimentary origin. Considering the tectonic setting and geophysical research, it is speculated that the carbonatitic melt was derived from the carbonated pelite carried by the southward subducted PAOP under the NCC. The PAOP subduction-related carbonatitic melt–peridotite reaction could have contributed to the transformation of the lithospheric mantle beneath the northern margin of the NCC. [ABSTRACT FROM AUTHOR]

High-Mg andesites (HMAs) and related basalts constitute a volumetrically minor, but genetically important occurrence along most convergent plate margins of various ages on Earth. The details of their petrogenesis can contain critical information for resolving essential geodynamic and crustal evolutionary issues. This zircon U–Pb dating and geochemical study documents the late Permian metamorphosed high-Mg basaltic to andesitic suite from Kaiyuan of northern Liaoning, North China. These rocks feature SiO 2 contents ranging from 48.7 to 63.2 wt.%, high Mg # values of 63–75, an enrichment in large-ion lithophile elements (LILE), and depletion in high field strength elements (HFSE). They possess whole-rock initial 87 Sr/ 86 Sr ratios of 0.70417–0.70457, ε Nd (t) values from − 0.4 to 5.0, and ε Hf (t) values from 5.1 to 11, as well as zircon ε Hf (t) values from − 9.4 to 0.4. These features indicate that their petrogenesis most likely involved precursory metasomatism of mantle peridotites by melts from subduction-related sediments, and subsequent partial melting. With a depleted mantle source and possible tectonic link to post-subduction slab break-off, the Kaiyuan suite could present a spatial reference not only for defining the demarcation line between the North China craton (NCC) and the Central Asian Orogenic belt (CAOB) in the region, but also for tracing the final location of the cryptic suturing zone of the Paleo-Asian Ocean. Synthesizing the suite with coeval igneous episodes as well as concomitant metamorphic events along the Solonker–Xra Moron–Changchun zone leads to the characterization of the eventual closure of the Paleo-Asian Ocean within a double-sided subduction system during late Permian–Early Triassic. [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]