Search

We present integrated in situ zircon U–Pb and Hf isotope data, along with whole‐rock and mineral chemistry data for the Salari granite of western Arunachal Himalaya to constrain its emplacement age, origin, and geodynamic evolution. The investigated Salari granites are high Fe2O3, CaO, and Nb, and low SiO2 and Rb/Sr ratio with fractionated rare earth element patterns ((Ce/Yb)N = 9.90–20.24) and minor negative Eu anomaly (Eu/Eu* = 0.69–0.94). They are metaluminous (molar A/CNK = 0.93–1.07) and have relatively similar FeOt/MgO ratio in biotite (1.58–1.60) to Mg‐biotite, indicating their affinity with I‐type granites. The enrichment of large‐ion lithophile elements with highly depleted negative Nb anomalies is consistent with their origin in a subduction‐related environment. Our zircon U–Pb ages suggest that the magmatic emplacement of the Salari granite took place between 1,791 and 1,768 Ma. The zircon grains have mostly negative εHf(t) values up to −5.5 and yield crustal Hf model ages from 2.4 to 2.8 Ga, suggesting the occurrence of a major crustal growth event in the Neoarchean and re‐melting of the crust during the Palaeoproterozoic. Our new results, that is, zircon U–Pb age and Hf isotope data, in conjunction with the field observations and petro‐mineralogical and geochemical characteristics, suggest that the Salari granite of eastern Himalaya was produced by partial melting of older metabasaltic/metatonalitic rocks in a continental arc setting of the supercontinent Columbia during the Palaeoproterozoic. [ABSTRACT FROM AUTHOR]

An initial Paleoproterozoic active continental margin formed along the northern margin of the Yangtze Craton. The early stages of this active tectonism involved the subduction of ocean crustal material and the formation of ca. 2.05 Ga Nb–enriched mafic dikes in the Kongling Complex, ca. 2.08 Ga arc–related granitoids in the Houhe area and arc–related I–type granite magmatism within the Feidong Complex. The final stages of subduction and the closure of the ocean in this area led to the collision of the South and North Yangtze cratons at 2.0–1.9 Ga, forming I– or S–type syn–collisional granites in the Kongling Lengshui, Hong'an, Tongbai, Susong, and Feidong complexes as well as granulite facies metamorphism in the Dabie Orogen and the Kongling and Douling complexes. [Display omitted] • Paleoproterozoic basement of the Yangtze Craton crops out within the Feidong Complex. • Ca. 2.0 Ga granitic rocks of the Feidong Complex have I-type affinities. • I–type granites in the Feidong Complex generated by the partial melting of older lower crustal material. • A ca. 2.0 Ga subduction-collision event is recorded within the northeastern Yangtze Craton. • The Yangtze Craton was a component of the Columbia supercontinent. The early history of the Yangtze Craton is not well constrained as a result of the lack of outcropping Archean to Paleoproterozoic rocks. This study presents new elemental and Laser Ablation–(Multicollector)–Inductively Coupled Plasma–Mass Spectrometry (LA–(MC)–ICP–MS) zircon U–Pb geochronological and Hf isotopic data for Paleoproterozoic granites of the Feidong Complex, located within the northeastern Yangtze Craton. Zircon U–Pb dating yields 207Pb/206Pb ages of 2054 ± 22 and 1994 ± 26 Ma for granite and granitic gneiss units in this area, respectively, confirming the existence of middle Paleoproterozoic basement rocks within the Feidong Complex and the northeastern Yangtze Craton. Zircons from the granite and granitic gneiss units have ε Hf (t) values ranging from –13.02 to –6.91, corresponding to two–stage Hf model ages (T DM2) of 3.44–3.07 Ga. The granites have whole–rock ε Nd (t) values from –0.25 to + 0.14 whereas the granitic gneisses have ε Nd (t) values that range from –8.90 to –8.12. This suggests that the granitic magmatism in this area was resulted from reworking of ancient crustal components but that the granites and granitic gneisses are derived from different magma sources. This is consistent with the fact that the granites in this area have volcanic arc affinities whereas the granitic gneisses have syn -collisional granite affinities, although all are classified as I–type granites. Combining these data with previous research on Paleoproterozoic magmatic and metamorphic events recorded elsewhere in the Yangtze Craton suggests that a middle–late Paleoproterozoic geological transition from plate subduction to collision occurred at ca. 2.0 Ga in the northeastern Yangtze Craton. This tectonism caused the partial melting of ancient crustal material, generating both the granites and granitic gneisses in the study area. [ABSTRACT FROM AUTHOR]

• Granite gneisses from the Xinghuadukou Complex yielded zircon U-Pb ages of 1.84–1.87 Ga. • These granites have I-type, likely formed by partial melting of a thickened crust and subsequently experienced extensive fractional crystallization. • The Xing'an Block in the CAOB was a micro-continental block with Paleoproterozoic basement and originally part of the Columbia supercontinent. The Precambrian evolution of the Central Asian Orogenic Belt (CAOB) in NE China remains enigmatic. The Xinghuadukou Complex, located in the Xing'an Block of NE China, contains important records of the Precambrian geological evolution of the eastern CAOB. In this study, we present petrographic observations, zircon U–Pb ages, and major and trace element data of Precambrian granitic gneisses from the Xinghuadukou Complex. The granitic gneisses are characterized by high SiO 2 (69.62–80.66 wt%) and K 2 O (2.15–3.80 wt%), enrichments in Rb, Th, Ba, and Pb, depletions in Nb, Ta, Sr, Ti, and P, and negative Eu anomalies. These geochemical signatures suggest that the granitic gneisses were derived from high-K, calc-alkaline, I-type granites, which were formed in a volcanic arc setting from magmas involving partial melting of thickened crust and extensive fractional crystallization. A total of 133 zircons in six granitic gneiss samples yielded weighted mean 207Pb/206Pb ages of 1865 ± 10, 1847 ± 13, 1858 ± 12, 1852 ± 9, 1872 ± 9, and 1859 ± 13 Ma, respectively. All the zircons combined define a weighted-mean 207Pb/206Pb age of 1861 ± 4 Ma, indicating a Paleoproterozoic basement in the Xing'an Block. In combination with data from previous studies, we suggest that the Xing'an Block was a microcontinent, likely part of the Columbia supercontinent. [ABSTRACT FROM AUTHOR]