As the world’s largest accretionary orogen, the Central Asian Orogenic Belt (CAOB) underwent continuous juvenile crustal growth in the Phanerozoic. The northern margin of the North China Craton (NCC) and its adjacent area form the eastern segment of the CAOB, which is a key area for learning about the geological evolution of the Paleo-Asian Ocean (PAO). In the Permian, the west of the northern margin of the NCC was a post-collision extensional environment, while the east was in a subduction stage. As a connecting area, the Permian evolution of the PAO in the middle of the northern margin of the NCC has not been systematically studied. In order to fill the gap and understand the continuous temporal and spatial evolutionary process of the PAO, this paper focuses on the Permian granitic rocks in the Chifeng area. Zircon U-Pb dating and the geochemical analysis of whole-rock major and trace elements were conducted to build a granite chronological framework, and to discuss the genesis and tectonic background of the granitic rocks, along with tectono-magmatic evolutionary history in the Chifeng area. The respective LA-ICP-MS zircon U-Pb dating results from eight samples are 269 ± 1, 268 ± 3, 260 ± 4, 260 ± 1, 260 ± 1, 255 ± 2, 254 ± 2 and 256 ± 1 Ma, respectively. These results, combined with previous data, revealed that the Permian granitic rocks had undergone three events of magmatism: (1) monzogranitic-syenitic phase (294–284 Ma; Cisuralian); (2) monzogranitic phase (269–260 Ma; Guadalupian) and (3) late monzogranitic-syenitic phase (256–254 Ma; Lopingian). From the Early Permian (294–284 Ma) to the Middle Permian (269–260 Ma), granites with fine-medium-grained locally porphyritic texture and massive structure showed a high-potassium calc-alkaline series formed in a compressional setting, indicating a continuous collision between the Xing’an-Mongolian Orogenic Belt (XMOB) and the NCC. During the Late Permian-Early Triassic (256–248 Ma), granites with massive structure and medium-grained texture in the Chifeng area were magmatism dominated by A- and I-type granites of high-potassium calc-alkaline series, combined with the coeval basic rocks, which constituted a typical “bimodal” rock assemblage. This suggests that the Chifeng area was located in an extensional setting where the subducting slab broke off during the collision between the XMOB and NCC. These granitic plutons from the Permian are believed to have been generated by the subduction-collision of the Paleo-Asian oceanic crust beneath the NCC, according to emplacement time and occurrence location. Our findings provide strong evidence for Permian continuous temporal and spatial tectonic evolution and the characterization of the eventual closure of the PAO in Chifeng area at the northern margin of the NCC.

Petrological, geochronological, and geochemical analyses of mafic rocks in northern Liaoning were conducted to constrain the formation age of the Proterozoic strata, and to further study the source characteristics, genesis, and tectonic setting. The mafic rocks in northern Liaoning primarily consist of basalt, diabase, gabbro, and amphibolite. Results of zircon U-Pb chronology reveal four stages of mafic magma activities in northern Liaoning: the first stage of basalt (2209 ± 12 Ma), the second stage of diabase (2154 ± 15 Ma), the third stage of gabbro (2063 ± 7 Ma), and the fourth stage of magmatic protolith of amphibolite (2018 ± 13 Ma). Combined with the unconformity overlying Neoproterozoic granite, the formation age of the Proterozoic strata in northern Liaoning was found to be Paleoproterozoic rather than Middle Neoproterozoic by the geochronology of these mafic rocks. A chronological framework of mafic magmatic activities in the eastern segment of the North China Craton (NCC) is proposed. The mafic rocks in northern Liaoning exhibit compositional ranges of 46.39–50.33 wt% for SiO₂, 2.95–5.08 wt% for total alkalis (K₂O + Na₂O), 6.17–7.50 wt% for MgO, and 43.32–52.02 for the Mg number. TiO₂ contents lie between 1.61 and 2.39 wt%, and those of MnO between 0.17 and 0.21 wt%. The first basalt and the fourth amphibolite show low total rare earth element contents. Normalized against primitive mantle, they are enriched in large ion lithophile elements (Rb, Ba, K), depleted in high field strength elements (Th, U, Nb, Ta, Zr, Ti), and exhibit negative anomalies in Sr and P, as well as slight positive anomalies in Zr and Hf. The second diabase and the third gabbro have similar average total rare earth element contents. The diabase shows slight negative Eu anomalies (Eu/Eu* = 0.72–0.88), enrichment in large ion lithophile elements (Ba), depletion in Rb, and slight positive anomalies in high field strength elements (Th, U, Nb, Ta, Zr, Hf, Ti), with negative anomalies in K, Sr, and P. The gabbro is enriched in large ion lithophile elements (Rb, Ba, K), depleted in high field strength elements (Th, U, Nb, Ta, Zr, Hf), and exhibits positive anomalies in Eu (Eu/Eu* = 1.31–1.37). The contents of Cr, Co, and Ni of these four stages of mafic rocks are higher than those of N-MORB. The characteristics of trace element ratios indicate that the mafic rocks belong to the calc-alkaline series and originate from the transitional mantle. During the process of magma ascent and emplacement, it is contaminated by continental crustal materials. There are residual hornblende and spinel in the magma source of the first basalt. The other three magma sources contain residual garnet and spinel. The third gabbro was formed in an island arc environment, and the other three stages of mafic rocks originated from the Dupal OIB and were formed in an oceanic island environment. The discovery of mafic rocks in northern Liaoning suggests that the Longgang Block underwent oceanic subduction and extinction in both the north and south in the Paleoproterozoic, indicating the possibility of being in two different tectonic domains.

This paper presents a detailed study including LA-ICP-MS zircon U-Pb dating, geochemical, zircon Hf isotope, and whole rock Sr-Nd isotope analysis of magmatic rocks from the Yitong County, Jilin Province, NE China. These data are used to better constrain the Middle Silurian–Middle Devonian tectonic evolution in the eastern segment of the northern margin of the North China Craton (NCC). Zircon U-Pb dating results show that the Ximangzhang tonalite formed in the Late Silurian (425 ± 6 Ma); the basalt, andesite, and metamorphic olivine-bearing basalt in the Fangniugou volcanic rocks formed in the Middle Silurian (428 ± 6.6 Ma) and Middle Devonian (388.4 ± 3.9 Ma, and 384.1 ± 4.9 Ma). The Late Silurian tonalites are characterized by high SiO₂ and Na₂O and low K₂O, MgO, FeOT, and TiO₂, with an A/CNK ratio of 0.91–1.00, characteristic of calc-alkaline I-type granite. They are enriched in Rb, Ba, Th, U, and K, and depleted in Nb, Sr, P, and Ti, with positive ε_Nd(t) (+0.35) and ε_Hf(t) (+0.44 to +6.31) values, suggesting that they mainly originated from the partial melting of Meso–Neoproterozoic accretionary lower crustal material (basalt). The Middle Silurian basalts are characterized by low SiO₂, P₂O₅, TiO₂, and Na₂O and high Al₂O₃, FeOT, and K₂O, enriched in Rb, Ba, Th, U, and K and depleted in Nb, Ta, Sr, P, and Ti, indicative of shoshonitic basalt. The Late Silurian tonalites have positive ε_Nd(t) (+4.91 to +6.18) values and primarily originated from depleted mantle magmas metasomatized by subduction fluids, supplemented by a small amount of subducted sediments and crustal materials. The Middle Devonian volcanic rocks exhibit low SiO₂, TiO₂, and Na₂O and high K₂O, and MgO, enriched in Rb, K, and LREEs and depleted in Nb, Ta, Sr, and HREEs, characteristic of shoshonitic volcanic rocks. Their ε_Nd(t) (+2.11 to +3.77) and ε_Hf(t) (+5.90 to +11.73) values are positive. These characteristics indicate that the Middle Devonian volcanic rocks primarily originated from depleted mantle magmas metasomatized by subduction fluids, with the addition of crustal materials or subducted sediments during their formation. Based on regional geological data, it is believed that the study area underwent the following evolutionary stages during the Silurian–Devonian period: (1) active continental margin stage of southward subduction of the Paleo–Asian Ocean (PAO) (443–419 Ma); (2) arc-continent collision stage (419–405 Ma); (3) post-collision extension stage (404–375 Ma); (4) active continental margin stage, with the PAO plate subducting southward once again (375–360 Ma).

The subduction polarity of the Mongol–Okhotsk Ocean (MOO) during the Mesozoic remains contentious, with competing models advocating for southward, northward, or bidirectional subduction. The Xifengshan area in the northern Great Xing’an Range, located south of the Mongol–Okhotsk suture, preserves Early–Middle Jurassic calc-alkaline intrusions, which provides important constraints on this debate. We present zircon U–Pb ages, whole-rock geochemistry, and Lu–Hf isotopes for diorite, granodiorite, and monzogranite from this area. Zircon U–Pb dating yields ages of 178–173 Ma, defining a short-lived magmatic pulse. The suite is calc-alkaline, enriched in LILE and depleted in Nb–Ta–Ti, typical of arc magmas. The diorite represents the most mantle-proximal preserved end-member of the system and records substantial mantle input from a slab-modified mantle wedge. Geochemical trends (increasing Rb/Th, decreasing Sr with differentiation) reflect plagioclase-dominated fractional crystallization with minor AFC. Local adakitic-like signatures are better interpreted as differentiation-related effects than as direct evidence for slab melting. Zircon εHf(t) values (+1.62 to +11.55) and T_DM1 ages (363–772 Ma) are greater than the crystallization ages, indicating substantial juvenile input together with the variable involvement of previously accreted crustal components. We suggest that mantle wedge-derived magmas modified by slab-related components triggered the partial melting of the arc crust, whereas subsequent intracrustal differentiation produced the observed intrusive sequence. The continental arc system provides robust evidence for the southeastward subduction of the MOO during the Early–Middle Jurassic, resolving the long-standing polarity controversy.