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A mafic granulite with relatively simple mineralogy and texture from the Miyun Complex in the northern part of the North China Craton is used to discuss the effect of bulk composition uncertainty determined by different techniques [X-ray fluorescence (XRF), mapping, and point counting] on the calculated phase diagrams. LA-ICP-MS U–Pb dating of zircon from this mafic granulite yields magmatic ages of ~ 2.5–2.45 Ga and metamorphic overprinting ages of ~ 1.8 Ga, consistent with previous results. Based on phase equilibrium modelling, we show that the topological relations of the P–T pseudo-sections calculated from the XRF and point-counting compositions are similar except for the K-feldspar and Fe–Ti oxide stability fields and that the mineral stability fields in the P–T pseudo-section calculated from the mapping composition are distinctly different from the others. Furthermore, the observed and calculated mineral compositions (XAn in plagioclase) and mineral proportions (garnet and plagioclase) are matched in the P–T pseudo-section calculated from the point-counting composition, but these are mismatched in the P–T pseudo-section calculated from the mapping composition. For the P–T pseudo-section calculated from the XRF composition, mineral composition isopleths can further constrain the narrow P–T conditions but the observed and calculated mineral proportions do not match. Moreover, we obtain similar T conditions using geo-thermometers (Ti-in-amphibole, two-feldspar, and REE-in-Grt-Cpx geo-thermometers). In addition, we calculated the uncertainties (of the phase-in/out lines and the mineral-proportions and -compositions isopleths) on the thermodynamic modelling and discussed the main source of uncertainties in detail. [ABSTRACT FROM AUTHOR]

Poly-metamorphism has been observed in many Precambrian metamorphic terranes. The metamorphic overprinting in the poly-metamorphic rocks makes it difficult to determine the timing and P − T path of each metamorphic event. In this study, in situ U–Pb dating of zircon, xenotime, and monazite, with simultaneously determination of trace element compositions, is utilized to provide new constraints on the timing of discrete metamorphic events involving reactivation of the Jiao-Liao-Ji Belt, the eastern edge of the North China Craton. Detrital zircons from metasandstones in the Gaixian Formation record a mixed provenance that includes late Neoarchean (ca. 2532 Ma) and middle Paleoproterozoic (ca. 2181 Ma). Xenotimes from the Gaixian pelitic schists yield an upper intercept age of 1906 ± 25 Ma, and this age is interpreted as the timing of greenschist-facies regional metamorphism. However, monazites from the same pelitic schists yield a distinctly younger age of 242 Ma, with late Paleoproterozoic inherited ages of 1894 and 1809 Ma, which are broadly consistent with the xenotime ages. In addition, magmatic zircons from a granitic mylonite vein yield a similar age of 245 Ma, making it coeval with the monazite. The interpretation of these ages is also reinforced by the mineral assemblage of inclusions in the dated accessory mineral grains. These new geochronological data, combined with published data from the Jiao-Liao-Ji Belt and the related regions, suggest that the Gaixian Formation in the Yanghe area was likely some time deposited at 2181–1900 Ma, and experienced both late Paleoproterozoic and Triassic low-grade metamorphic events related to two distinct orogenic phases in the eastern North China Craton. [ABSTRACT FROM AUTHOR]

• A clockwise P – T–t path was reconstructed from the cordierite-bearing granulites of the South Liaohe Group. • U–Pb age data reveal 1945 Ma peak and 1851–1839 Ma retrogressive metamorphisms. • Discovery of the cordierite-bearing granulites further suggests that the Jiao-Liao-Ji belt have undergone 1950–1800 Ma orogenesis. To better understand the formation of high-temperature metamorphic rocks, we present a detailed petrological and geochronological study of recently discovered cordierite-bearing granulites of the South Liaohe Group in the Jiao-Liao-Ji Belt, North China Craton. Petrographic observations indicate that four distinct mineral assemblages are present in the granulites: pre-peak amphibolite facies (M 1), peak granulite facies (M 2), post-peak decompression (M 3), and late cooling retrogression (M 4). M 1 is preserved as fine-grained inclusions in the cores of garnet grains, represented by quartz + plagioclase + biotite + ilmenite. M 2 is interpreted to have comprised garnet + sillimanite + plagioclase + quartz + biotite + ilmenite + melt. M 3 was characterized by the formation of cordierite + sillimanite symplectites and cordierite + quartz coronas replacing garnet. M 4 is indicated by the formation of staurolite, accompanied by the crystallization of melt. A combination of multi-equilibria geothermobarometers and pseudosection modeling constrains the P–T conditions of the M 1 , M 2 , M 3 , and M 4 stages to P = 0.66–0.71 GPa and T = 620–650 °C, P = 0.96–1.10 GPa and T = 790–840 °C, P = 0.62–0.65 GPa and T = 725–785 °C, and P = 0.43–0.55 GPa and T = 595–625 °C, respectively. Zircon and monazite U–Pb dating yields three distinct and meaningful ages for the granulites: (1) 2200–2100 Ma for the granulite protoliths, (2) ca. 1945 Ma for the near-peak metamorphism, and (3) 1851–1839 Ma for the post-peak and late retrogressive metamorphism. Thus, a clockwise P–T–t path is determined for the cordierite-bearing granulites of the South Liaohe Group. Petrological and geochronological evidence from regional metamorphic rocks in the Jiao-Liao-Ji Belt suggests that the belt experienced a continuous orogenesis from 1950 to 1800 Ma. [ABSTRACT FROM AUTHOR]

To constrain the processes of mantle–crust interactions during magma generation and reconstruct the tectonic evolution of the Paleo-Asian Ocean, we present an integrated study involving detailed geological field work, petrological observations, zircon U–Pb–Hf isotope analyses, whole-rock geochemistry, and mineral chemistry for the Tayuan Complex in the northern Great Xing'an Range, NE China. The Tayuan Complex is composed mainly of monzogranites (host granitoids) and gabbros with minor amounts of quartz monzonites, and microgranular enclaves (MMEs) are unevenly distributed within the host granitoids. Our new zircon U-Pb dating results show that the host granitoids were emplaced during the late Carboniferous (318 ± 4 Ma and 319 ± 2 Ma). The MMEs yield similar zircon U-Pb ages of 320 ± 2 Ma and 322 ± 5 Ma, within error of the emplacement ages of the host granitoids. In this study, the petrological and geochemical features of the Tayuan Complex indicate disequilibrium conditions, and we favor a magma mixing model to explain the genesis of various rock types within the complex. Combined with the petrological and geochemical observations, we suggest that the host granitoids can be ascribed to felsic end-member and they originated from the partial melting of the Meso–Neoproterozoic medium- to high-K basaltic lower crust. According to the petrological and geochemical features, the gabbros in Tayuan complex are closely related to the mafic end-member, and we conclude that they were derived from the partial melting of depleted mantle that was metasomatized by subducted slab-derived fluids, and that clinopyroxene, hornblende and Fe-Ti oxides were fractionated during magma generation. The MMEs and coeval quartz monzonites in Tayuan complex represent the mixing of felsic and mafic end-member magmas. Our new data, combined with the spatial distribution and temporal evolution of the Carboniferous magmatism in the Great Xing'an Range, indicate the generation of the late Carboniferous Tayuan complex was related to the northwestward subduction of the Paleo-Asian oceanic plate. Unlabelled Image • The host granitoids and associated MMEs were formed almost simultaneously. • The magma mixing model is favored to explain the generation of Tayuan complex. • Tayuan complex was formed in an active continental margin setting. • The Xing'an-Erguna Massif was in a continuous subduction environment in the Carboniferous. [ABSTRACT FROM AUTHOR]