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The Xinlin–Xiguitu suture zone, located in the Great Xing’an Range, NE China, in the eastern segment of the Central Asian Orogenic Belt (CAOB), represents the boundary between the Erguna and Xing’an micro-continental blocks. The exact location of the Xinlin-Xiguitu suture zone has been debated, especially, the location of the northern extension of the suture zone. In this study, based on a detailed field, geochemical, geochronological and Sr–Nd–Hf isotope study, we focus our work on the Cambrian igneous rocks in the Erguna-Xing’an block. The Xinglong granitoids, mainly include ∼520 Ma diorite, ∼470 Ma monzogranite and ∼480 Ma pyroxene diorite. The granitoids show medium to high-K calc-alkaline series characteristics with post-collision granite affinity. The circa 500 Ma granitoids have low ε Hf ( t ) values (−16.6 to +2.2) and ancient two-stage model ( T DM2 ) ages between 1317 Ma and 2528 Ma. These results indicate the primary magmas of the Xinglong granitoids were probably derived from the partial melting of a dominantly Paleo-Mesoproterozoic “old” crustal source with possible different degrees of addition of juvenile materials, and formed in a post-collision tectonic setting after the amalgamation of the Erguna and Xing’an blocks. Compared with the Xinglong granitoids, the Duobaoshan igneous rocks are consisted of the approximately coeval rhyolitic tuffs (491 ± 5 Ma) and ultramafic intrusions (497 ± 5 Ma) within the Duobaoshan Formation. They are generally enriched in large ion lithophile elements (LILEs) and depleted in high field strength elements (HFSEs; e.g., Nb, Ta, and Ti), consistent with the geochemistry of igneous rocks from island arcs or active continental margins. The ultramafic rocks have high positive ε Hf ( t ) values (+1.3 to +15) and ε Nd ( t ) (+1.86 to +2.28), and relatively young two-stage model ( T DM2 ) ages and low initial 87 Sr/ 86 Sr ratios (0.70628–0.70853), indicating the partial melting of a depleted mantle source from a subducted slab in the ocean basin between the Erguna-Xing’an and Songliao blocks. The rhyolitic tuffs contain a group of Phanerozoic zircons with ε Hf ( t ) values (−4.6 to +15.0), suggesting that the rhyolitic tuffs were derived from juvenile lower crustal material with some ancient crustal material. Coupled with our previous geochemical and isotopic studies on Early Paleozoic igneous rocks, we proposed that the collision of the Erguna and Xing’an blocks at least took place ca. 500 Ma ago, and that there exist in a westward subduction of an oceanic plate between the Eruguna-Xing’an and Songliao blocks, took place during the Early Ordovician. Up to now, there are more evidences and constraints that the northern extension location of the Xinlin-Xiguitu suture zone is located in the Jifeng–Xinglong areas. [ABSTRACT FROM AUTHOR]

Northeast China occupies the majority of the eastern Central Asian Orogenic Belt, which mainly consists of continental blocks and accretionary terranes. The Devonian was a tectonic quiet period in the NE China region due to a lack of tectono-magmatism, but the tectonic background of this period has been unclear, especially for the Hegenshan-Heihe Suture between Xing'an and Songliao accretionary terranes, which represents the Paleozoic Nenjiang Ocean (a branch ocean of the eastern Paleo-Asian Ocean). Here we report granitic rocks from the Woluohe area, Northern Great Xing'an Range, NE China, to constrain the tectonic process of the transition from the Devonian quiet period to the Early Carboniferous active tectonic period. Three granitic rock samples produce zircon U-Pb ages of 389 Ma, 368 Ma, and 351 Ma, belonging to the Middle and Late Devonian and Early Carboniferous, respectively. They have high Si, Al, K, and Na contents, but with low Mg, Fe, and Ti contents, together with positive Hf isotopic features and low molar Al2O3/(MgO+FeOT) ratios, we suggest that they were derived from partial melting of lower crustal igneous rocks. Meanwhile, the narrow major element variation at odd with the fractionation process and their negative Nb and Ta anomalies imply the obvious contribution of crustal. Comprehensive tectonic setting analysis shows all samples are in calc-alkali magmatic series with rightward fractionated REE and trace element patterns that are enriched in LREE and LILE and depleted in HREE and HFS, indicating a subduction-related magmatic arc setting. Considering the regional tectonic setting and the small scale of the Devonian plutons, we suggest a limited subduction tectonic setting during the quiet period of the northern Great Xing'an Range, which might indicate the beginning of an initial northwestward subduction of the Nenjiang Oceanic lithosphere beneath the Xing'an Accretionary Terrane in the Middle Devonian, accelerated subduction in the Late Devonian, and bidirectional subduction in the Early Carboniferous. [ABSTRACT FROM AUTHOR]

There is a controversy regarding the amalgamation of Xing'an and Songnen Blocks along the Hegenshan‐Heihe Suture (HHS) in the eastern Central Asian Orogenic Belt (CAOB). To solve this problem, we performed detailed study on the granites from the Zhangdaqi area, adjacent to the north of the HHS in the northern part of the Great Xing'an Range, NE China. Geochemically, the granites in the study area are metaluminous‐weak peraluminous and high‐K calc‐alkaline series. Trace elements of the granites show that LREEs are relatively enriched, while HREEs are relatively deficient and obvious REE fractionation. The granites are characterized by obvious negative Eu anomalies, meanwhile, they are relatively enriched in Rb, K, Th and depleted in Ba, Nb, Sr, P, Ti. All the geochemical features suggest that the granites in the Zhangdaqi area are aluminum A‐type granites. The zircon LA‐ICP‐MS U‐Pb ages of these granites are 294–298 Ma, indicating that they formed in the Early Permian. These granites also have positive εHf (t) values (8.4–14.2) and a relatively young two‐stage model age between 449 Ma and 977 Ma, implying that the magma was derived from the re‐melting of the Early Paleozoic‐Neoproterozoic juvenile crust. Combined with geochemical characteristics (Nb/Ta ratios of 9.0–22.2, and Zr/Hf ratios of 52.3–152.0), we believe that the magmatic source area is a mixture of partial melting of the lower crust and depleted mantle. A‐type granites and bimodal volcanic rocks along the Hegenshan‐Heihe Suture formed during the Late Carboniferous‐Early Permian, indicating that the HHS between Xing'an and Songnen Blocks closed in the late Early‐Carboniferous. Subsequently, the Zhangdaqi area was in a post‐orogenic extensional environment from Late Carboniferous to Early Permian and resulted in the formation of the A‐type granites. [ABSTRACT FROM AUTHOR]