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In order to investigate their precise geochronological framework, petrogenesis, and tectonic implications, whole‐rock major and trace elements, together with zircon U–Pb and Hf isotope data, are reported for the Mo‐bearing granitoids from the eastern Jilin‐Heilongjiang provinces in the eastern segment of the Central Asian Orogenic Belt. Zircon U–Pb dating by LA–ICP–MS yields crystallization ages for the Liushengdian monzogranite porphyry (252.2 ± 1.6 Ma), the Luming monzogranite porphyry (197.1 ± 1.6 Ma), and the Baoshan granodiorite (164.4 ± 1.9 Ma) and quartz diorite (165.2 ± 1.7 Ma), respectively. This zircon U–Pb data, combined with previous ages, indicate that the eastern Jilin‐Heilongjiang provinces is dominated by 2 stages of ore‐related granitic magmatism and associated Mo mineralization, that is, Late Permian (259–252 Ma) and Early‐Middle Jurassic (200–165 Ma). Geochemically, these Mo‐bearing granitoids have high SiO2 (60.78–74.67 wt.%) and K2O (2.85–6.23 wt.%), low MgO (0.17–2.85 wt.%) and CaO (0.66–4.38 wt.%) contents, with A/NCK and δEu values of 0.87–1.08 and 0.19–1.07, respectively; we infer that they belong to high‐K calc‐alkaline series and are metaluminous to peraluminous in nature. They are characterized by enrichment in large ion lithophile elements and light rare earth elements, and weak depletion in high field strength elements and heavy rare earth elements, consistent with the geochemical signatures of subduction‐related genesis. In addition, in situ Hf isotopic analyses of zircons from 4 dated samples reveal that they have εHf(t) values of −0.4 to +10.3, with 2‐stage model ages varying from 551 to 1,261 Ma, indicating that they probably originated from the partial melting of a dominantly Mesoproterozoic–Neoproterozoic crustal source. On the basis of the geochemical data and regional geological investigations, we propose that the formation of the Late Permian Mo‐bearing granite was related to the subduction of the Paleo‐Asian Ocean plate, whereas the generation of the Early‐Middle Jurassic Mo‐bearing granitoids was associated with the subduction of the Paleo‐Pacific Plate beneath the Eurasian continent. [ABSTRACT FROM AUTHOR]

The Wuma magmatic suite is a group of large granite plutons and small diorite stocks in the Erguna Block, northeast China. These intrusions were emplaced along the Mongol–Okhotsk Suture Zone during the late Permian–early Triassic (253–248 Ma). Significant chemical and isotopic diversity within the granites and diorites suggests variable formation conditions and the involvement of multiple magmatic sources. The granitic intrusions are dominantly characterized by moderate to large, uniform light rare earth element enrichments and variable heavy rare earth element depletions. Zircons from the Wuma granites have εHf(t) values of −6.0 to 0.5 and TDM2 ages of 1.6–1.2 Ga, suggesting that these granitic magmas were generated by partial melting of Mesoproterozoic continental crust. The diorites are compositionally similar to Andean plutonic rocks with moderate light rare earth element and heavy rare earth element fractionations and likely formed by partial melting of a sediment‐metasomatized mantle. The Wuma intrusions belong to the high‐K calc‐alkaline series and are characterized by a significant enrichment in large‐ion lithophile elements (e.g., Rb, Ba, K, and U) and depletion of high‐field strength elements (e.g., Nb, Ta, and Ti). These geochemical characteristics are typical of subduction‐related magmatism, which can be linked to the southward subduction of the Mongol–Okhotsk oceanic plate. Combined with data from published studies, our Hf isotopic analyses indicate 4 main periods of crustal growth beneath the Erguna Block: Mesoarchean (3.0–2.8 Ga), Neoarchean–Paleoproterozoic (2.6–1.8 Ga), Meso‐ to Neoproterozoic (1.6–0.7 Ga), and Phanerozoic (mainly Ordovician and Late Triassic–Early Cretaceous). [ABSTRACT FROM AUTHOR]

This paper presents major element, trace element, and new zircon Hf isotopic data for the Early Mesozoic intrusive rocks in the south Hunchun, Yanbian area, Northeast China. These data are used to constrain the petrogenesis of these intrusive rocks and their implications for the Phanerozoic continental growth of the Central Asian Orogenic Belt (CAOB). Combining geology, geochronology, and whole-rock geochemistry, we identify three distinct episodes of magmatism as Early-Middle Triassic (249-237 Ma), Late Triassic (224-206 Ma), and Early Jurassic (200-187 Ma). The Early-Middle Triassic (249-237 Ma) adakitic tonalite and granodiorite were produced by the partial melting of subducted oceanic slabs, and the melts were contaminated by mantle peridotite during their ascent, whereas the coeval non-adakitic diorite and monzogranite were most likely derived from partial melting of crustal material. The remarkably high zircon Hf isotopic signature (εHf(t) = + 9.4 - +18.9), the enrichment in large-ion lithophile element and light rare earth elements, and the depletion in high field strength element suggest that these 224 Ma gabbros were derived from the partial melting of depleted mantle modified by subduction-related fluids. The 212 Ma monzogranite was most likely derived from juvenile material mixed with old crustal material as evidenced by their high SiO2, low MgO, and low Cr concentrations and variable εHf(t) values (-4.6 to +10.0). Except for the 197 Ma tonalites with affinity to the high silica adakites, the overall geochemical evolution of Early Jurassic (200-187 Ma) rocks was consistent with fractional crystallization from quartz diorite, granodiorite, and monzogranite to syenogranite. Both the Early Jurassic syn-subduction lateral continental growth by accretion of arc complexes and the Late Triassic post-collisional vertical continental growth by accretion of mantle-derived material played an important role in the Phanerozoic continental growth of the CAOB. [ABSTRACT FROM AUTHOR]

This study presents new information on the petrogenesis and tectonic setting of a hornblende gabbro in the northern Great Xing'an Range of northeastern China using new whole‐rock geochemical, mineral geochemical, and in situ zircon U–Pb and Hf isotopic data obtained for samples taken from near the town of Tayuan. Zircon U–Pb dating indicates that the hornblende gabbro was emplaced during the late Carboniferous (~311 Ma). The hornblende gabbros are alkaline with high K2O + Na2O (4.25–6.42 wt.%), low SiO2 (41.69–50.22 wt.%), and variable MgO (4.49–7.16 wt.%) and TiO2 (1.23–2.77 wt.%) contents. The pressure and temperature conditions of gabbro crystallization were determined using amphibole–plagioclase and amphibole thermobarometry, which indicate that the Tayuan hornblende gabbro formed at pressures of 4.1–6.9 kbar and temperatures of 686–762 °C, respectively. The hornblende gabbros are enriched in light rare earth elements and large ion lithophile elements, are depleted in the heavy rare earth elements and high field strength elements, and have positive zircon εHf(t) values (+3.9 to +9.9), all of which are indicative of formation from magmas generated by the partial melting of a depleted region of the lithospheric mantle that was previously metasomatized by subducted slab‐derived fluids and/or melts just before the generation of the hornblende gabbro magmas. The field observational, geochronological, geochemical, mineral geochemical, and zircon Hf isotopic data presented here are indicative of a complex petrogenetic history that involved crystal fractionation and magma mixing. These hornblende gabbros were emplaced in an extensional setting associated with the collision of the Xing'an and Songnen massifs. [ABSTRACT FROM AUTHOR]

Geology in the Yanbian area, NE China, is a key to understanding the relationship between the Paleo-Pacific tectonic regime and the older Paleo-Asian oceanic regime, especially the transition between the regimes during the Mesozoic. A compilation of 131 U–Pb zircon ages, including 18 obtained in the present study, shows that the late Paleozoic to Mesozoic magmatism in the Yanbian area took place from 285 to 105 Ma (mainly 205–160 Ma) and that there was a peak of activity at ∼175 Ma and a hiatus from the Late Jurassic to Early Cretaceous (150–130 Ma). Provisionally, we subdivide the magmatic activity into four dominant stages: Middle Permian to Middle Triassic (280–240 Ma), Late Triassic (230–205 Ma), Early to Middle Jurassic (205–160 Ma) and Early Cretaceous (130–105 Ma). Middle Permian intrusive rocks, including pyroxenite, gabbro, diorite, granodiorite, tonalite and monzogranite, are interpreted to have been emplaced along an Andean-style continental margin in association with the subduction of the Paleo-Asian oceanic plate. The Late Permian–Middle Triassic intrusive rocks are mainly quartz monzonite, monzogranite and syenogranite, and are considered to have been the result of syn-orogenic/post-collisional activities. The Late Triassic magmatism involved not only the emplacement of mafic–ultramafic intrusive rocks, but also coeval I- and A-type granitoids, indicating an extensional environment after the final closure of the Paleo-Asian Ocean. Since the Jurassic, the tectonic setting has been dominated by subduction of the Paleo-Pacific oceanic plate. Previously published data for the Yanbian area and age data from surrounding regions show that the entire region from the Yanbian area to the Korean Peninsula and the Japanese Islands experienced peaks in igneous activities that ranged from 200 to 165 Ma during the Jurassic, and 120 to 110 Ma and 90 to 65 Ma during the Cretaceous. The Jurassic intrusive rocks were emplaced mainly in the west and Cretaceous intrusive rocks in the east. In other words, there is a southeastwards younging of Mesozoic intrusive rocks that appears to have been closely associated with the evolution of the Paleo-Pacific Ocean. Taking all this into account, we conclude that the transition from the Paleo-Asian oceanic regime to the circum-Pacific tectonic regime took place during the Late Triassic to Early Jurassic. [ABSTRACT FROM AUTHOR]

Late Triassic–Early Jurassic intrusions of the Erguna Block, Northeast China, are located along the southern margin of the Mongol–Okhotsk orogenic belt. They comprise granodiorite, monzogranite, syenogranite, and lesser gabbro–diorite, of adakitic and calc­alkaline affinity. The adakite-like and calc­alkaline granites share similar light rare earth elements (LREE) characteristics; however, their heavy rare earth elements (HREE) trends differ from one another. The relative abundances of HREE in the calc­alkaline granites are relatively consistent and are similar to those of intrusive rocks formed from dehydration melting of garnet-free amphibolitic source rocks at relatively low pressures. In contrast, the adakite-like granites show more prominent HREE fractionation trends, indicating that they crystallized at higher pressures, where garnet in the source rocks was stable. At least two isotopically distinct sources were involved in the petrogenesis of the granites, but the extent to which they contributed varies between plutons. Most intrusions have incorporated an isotopically primitive component, possibly juvenile mafic crust. The other sources include a small proportion of old continental crustal material and isotopically evolved wall rocks. The gabbro–diorites have high MgO contents (>7 wt.%), a high Mg#(>0.6), and show moderate LREE and HREE fractionation, indicating they formed from the melting of subducted metasomatized lithospheric mantle. All of the intrusions in the study area are characterized by a relative enrichment in large ion lithophile elements (LILE) and depletion in high field strength elements (HFSE), indicating they were emplaced in an Andean-type active continental margin setting related to southward subduction of the Mongol–Okhotsk oceanic plate. [ABSTRACT FROM PUBLISHER]