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The metamorphosed Early Paleoproterozoic granitoids in the Quanji massif, Northwestern China provide constraints for relationship between the Tarim Craton and North China Craton. Among granitoids batholiths, rocks of the Mohe quartz-diorite show typically adakitic geochemical characteristics, with medium KO/NaO ratios (0.56-1.17) and high Sr (519-619 ppm) low Y (9.37-20.40 ppm) and Yb (0.97-1.77 ppm) concentrations. The rocks have ɛ( t) values between +2.4 and +4.4 and depleted mantle Nd model ages of 2.43-2.59 Ga. The magmatic zircons have positive ɛ( t) values ranging from +0.40 to +7.60 and depleted mantle Hf model ages of 2.43-2.70 Ga, with major peaks at ∼2.54 and ∼2.65 Ga. The geochemical and Nd-Hf isotopic characteristics indicate that the Mohe quartz-dioritic rocks might be formed by partial melting of high-pressure metamorphosed juvenile crustal rocks in post-orogenic extensional regime in the Early Paleoproterozoic. It suggests that important crustal growth occurred in the Quanji massif and the Tarim Craton at ∼2.4 and 2.5-2.7 Ga. The Quanji massif and Tarim Craton might share a similar crustal evolution history with the North China Craton in the Neoarchean. [ABSTRACT FROM AUTHOR]

Abstract: A series of early Carboniferous volcanic rocks, i.e., basalt, andesite, and dacite, occur in the West Junggar. Zircon U–Pb isotopic data indicate that these rocks coevally erupted at 331–344Ma. These volcanic rocks have comparable trace element patterns, characterized by the enrichment of large ion lithophile elements (LILE) and the depletion of high field strength elements (HFSE). Isotopically, they display consistently depleted Sr–Nd isotopic compositions (initial 87Sr/86Sr ratios=0.7034–0.7054, ε Nd(t)=4.2–7.7). These rocks are interpreted to be derived from a slightly metasomatized depleted mantle in a normal subduction environment. In the context of a previously proposed ridge subduction model, this study constrains that ridge subduction, if it indeed occurred, commenced between 331 and 310Ma in the central West Junggar. [Copyright &y& Elsevier]

Abstract: Late Paleozoic High-Mg dioritic dikes widely occur in western Junggar, NW China. Ar–Ar dating on rock chips of the dikes has yielded a plateau age of 321±3 Ma, indicating an early Carboniferous age for the dikes. The dikes are enriched in SiO2 (52–57 wt.%), and characterized by high MgO (5.13–7.41 wt.%), Cr (134–204 ppm), Ni (59–141 ppm), Sr (468–724 ppm) and Ba (316–676 ppm) contents, with geochemical features analogous to those of sanukite of Setouchi volcanic belt, Japan. These dikes contain hornblende and biotite and generally have high Ba/La (27–124) and La/Nb (2.9–4.3) ratios and positive Eu anomalies, consistent with an origin from hydrous partial melting of a mantle source metasomatised by slab-derived component. The occurrence of sanukitic dikes, together with the coeval slab-related adakite in the area, implies that the western Junggar had been affected by hot, subduction-related regime, which gave rise to not only massive magmatism in the late Carboniferous, but also intensive Cu–Au mineralization in the area. [Copyright &y& Elsevier]

Abstract: Voluminous granitic intrusions are distributed in the West Junggar, NW China, and they can be classified as the dioritic rocks, charnockite and alkali-feldspar granite groups. The dioritic rocks (SiO2 =50.4–63.8wt.%) are calc-alkaline and Mg enriched (average MgO=4.54wt.%, Mg# =0.39–0.64), with high Sr/Y ratios (average=21.2), weak negative Eu (average Eu⁎/Eu=0.80) and pronounced negative Nb–Ta anomalies. Their Sr–Nd and zircon Hf isotopic compositions ((87Sr/86Sr)i =0.7035–0.7042, ε Nd(t)=4.5–7.9, ε Hf(t)=14.1–14.5) show a depleted mantle-like signature. These features are compatible with adakites derived from partial melting of subducted oceanic crust that interacted with mantle materials. The charnockites (SiO2 =60.0–65.3wt.%) show transitional geochemical characteristics from calc-alkaline to alkaline, with weak negative Eu (average Eu⁎/Eu=0.75) but pronounced negative Nb–Ta anomalies. Sr–Nd and zircon Hf isotopic compositions ((87Sr/86Sr)i =0.7037–0.7039, ε Nd(t)=5.2–8.0, ε Hf(t)=13.9–14.7) also indicate a depleted source, suggesting melts from a hot, juvenile lower crust. Alkali-feldspar granites (SiO2 =70.0–78.4wt.%) are alkali and Fe-enriched, and have distinct negative Eu and Nb–Ta anomalies (average Eu⁎/Eu=0.26), low Sr/Y ratios (average=2.11), and depleted Sr–Nd and zircon Hf isotopic compositions ((87Sr/86Sr)i =0.7024–0.7045, ε Nd(t)=5.1–8.9, ε Hf(t)=13.7–14.2). These characteristics are also comparable with those of rocks derived from juvenile lower crust. Despite of the differences in petrology, geochemistry and possibly different origins, zircon ages indicate that these three groups of rocks were coevally emplaced at ~305Ma. A ridge subduction model can account for the geochemical characteristics of these granitoids and coeval mafic rocks. As the “slab window” opened, upwelling asthenosphere provided enhanced heat flux and triggered voluminous magmatisms: partial melting of the subducting slab formed the dioritic rocks; partial melting of the hot juvenile lower crust produced charnockite and alkali-feldspar granite, and partial melting in the mantle wedge generated mafic rocks in the region. These results suggest that subduction was ongoing in the Late Carboniferous and, thus support that the accretion and collision in the Central Asian Orogenic Belt took place in North Xinjiang after 305Ma, and possibly in the Permian. [Copyright &y& Elsevier]

Highlights: [•] The granitic gneisses from Wuyi-Yunkai yield zircon U–Pb age of 913–982Ma. [•] The early Neoproterozoic S-type granitic magmatism is identified in Cathaysia. [•] They originated from the metapelitic and metaigneous source with little input of juvenile materials. [•] They are petrogenetically related to the closure of the Wuyi-Yunkai arc-back-arc system. [•] The arc-basin system is finally closed at ∼920Ma and the SCB is placed to the Rodinia margin. [ABSTRACT FROM AUTHOR]