<p>Table S1: SIMS zircon U–Pb dating data for amphibolites in the Hidaka metamorphic belt, Hokkaido, northern Japan. Table S2: Microprobe analysis of plagioclase compositions for amphibolites in the Hidaka metamorphic belt, Hokkaido, northern Japan. Table S3: Microprobe analysis of amphibole compositions for amphibolites in the Hidaka metamorphic belt, Hokkaido, northern Japan. Table S4: Major (wt%) and trace element (ppm) data for amphibolites in the Hidaka metamorphic belt, Hokkaido, northern Japan. Table S5: Sr–Nd–Hf–Pb isotopic data of amphibolites in the Hidaka metamorphic belt, Hokkaido, northern Japan.</p>
In this study, we present new U–Pb zircon ages and whole‐rock major and trace element data for the late Carboniferous–Middle Jurassic intrusive rocks in the Helong area, NE China. These data constrain the timing of tectonic transition from the Paleo‐Asian oceanic regime to the circum‐Pacific regime. U–Pb zircon dating indicates that the late Carboniferous–Middle Jurassic magmatic events in the Helong area can be subdivided into late Carboniferous, middle Permian, Early–Middle Triassic, Late Triassic, Early Jurassic, and early Middle Jurassic. The late Carboniferous granodiorites and middle Permian monzogranites belong to the calc‐alkaline series and have an affinity to I‐type granitoids, suggesting that they formed in a typical Andean‐type continental arc setting due to the southward subduction of the Paleo‐Asian oceanic plate beneath the NCC. The Middle Triassic granodiorites and monzogranites in the Helong area exhibit an affinity to adakitic rocks with their parental magma derived by the partial melting of thickened lower continental crust. The Late Triassic I‐type monzogranites and coeval ultramafic–mafic rocks constitute a bimodal igneous rock association, together with coeval A‐type granites and rhyolites, signifying an extensional environment. Combined with the absence of 240‐ to 225‐Ma sedimentation, the study area experienced a change from Early–Middle Triassic compression to Late Triassic extension related to the final closure of the Paleo‐Asian Ocean. The Early–early Middle Jurassic gabbros, diorites, granodiorites, and monzogranites are calc‐alkaline in nature and enriched in LREE and LILE but depleted in HREE and HFSE. Combined with the spatial variations in K contents of Early Jurassic igneous rocks in NE China from the continental margin to intracontinental region, and the presence of an Early Jurassic accretionary complex, we suggest that Early–early Middle Jurassic magmatism in the Helong area formed in an active continental margin setting related to the subduction of the Paleo‐Pacific Plate beneath Eurasia. We conclude that the tectonic transition from the Paleo‐Asian oceanic regime to the circum‐Pacific regime occurred in the Late Triassic–Early Jurassic.
Abstract: Laser ablation‐inductively coupled plasma mass spectrometry (LA‐ICP‐MS) zircon U‐Pb dating and geochemical data for the Permian gabbros and diorites in the Hunchun area are presented to constrain the regional tectonic evolution in the study area. Zircons from gabbro and diorite are euhedral‐subhedral in shape and display fine‐scale oscillatory zoning as well as high Th/U ratios (0.26–1.22), implying their magmatic origin. The dating results indicate that the gabbro and diorite formed in the Early Permian (282±2 Ma) and in the Late Permian (255±3 Ma), respectively. In addition, the captured zircons with the weighted mean age of 279±4 Ma are also found in the diorite, consistent with the formation age of the gabbro within uncertainty. The gabbros belong chemically to low‐K tholeiitic series, and are characterized by low rare earth element (REE) abundances, flat REE pattern, weak positive Eu anomalies (δEu), and depletion in high field strength elements (HFSEs, Nb, Ta, and Ti), similar to the high‐aluminum basalts from island arc setting. Initial Hf isotopic ratios of zircons from the gabbro range from +7.63 to +14.6, suggesting that its primary magma could be mainly derived from partial melting of a depleted lithospheric mantle. The diorites belong to middle K calc‐alkaline series. Compared with the gabbros, the diorites have higher REE abundance, weak negative Eu anomalies, and more depletion in HFSEs (Nb, Ta, and Ti), similar chemically to the volcanic rocks from an active continental margin setting. Initial Hf isotopic ratios and Hf two‐stage model ages of zircons from the diorite range from +11.22 to +14.17 and from 424 to 692 Ma, respectively, suggesting that its primary magma could be mainly derived from partial melting of the Early Paleozoic and/or Neoproterozoic accretted lower crust. Taken together, it is suggested that geochemical variations from the Early Permian gabbros to the Late Permian diorites reveal that the subduction of the Paleo‐Asian oceanic plate beneath the Khanka Massif and collision between the arc and continent (Khanka Massif) happened in the late stage of the Late Paleozoic.
This study reports zircon U–Pb geochronological, geochemical, and zircon Hf–O isotopic data for metavolcanic rocks from the Shitoukoumen and Yongji areas in central Jilin Province, northeast China, to reveal their petrogenesis and tectonic setting. The metavolcanic rocks collected from the Shitoukoumen and Yongji areas are composed of metabasaltic trachyandesite, metatrachyandesite, and metarhyolitic tuff. Zircon U–Pb dating results indicate that the metavolcanic rocks were erupted during 359–355 Ma. Metavolcanic rocks in the Shitoukoumen area can be divided into two groups according to their geochemical characteristics. Group‐I rocks (metabasaltic trachyandesite and metatrachyandesite) show geochemical features similar to those of ocean island basalt (OIB), with slightly lower zircon δ 18 O values (4.06 ± 0.42‰ to 5.16 ± 0.28‰) than those of mantle‐derived zircons, and depleted ε Hf (t) values (7.84–15.4). Group‐II rocks (metabasaltic andesite) show similar geochemical characteristics to those of normal mid‐ocean ridge basalt (N‐MORB). Group‐I rocks may have been derived from partial melting of enriched mantle involving high‐temperature altered oceanic crust, whereas Group‐II rocks originated mainly from partial melting of depleted mantle. Metarhyolitic tuffs from the Yongji area have high SiO 2 and K 2 O contents, as well as high Ga/Al ratios, and show similar geochemical characteristics to those of A‐type rhyolites. The results of the study, together with published data, indicate that the eastern segment of the northern margin of the North China Craton was a passive continental margin setting during the early Carboniferous, and that the Paleo‐Asian Ocean remained open along the Changchun–Yanji suture belt until the early Carboniferous.
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