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The Kunduleng granite hosts one of several significant uranium anomalies within the southern Great Xing'an Range, NE China. Whole-rock geochemistry and mineral chemistry data, along with the zircon U-Pb-Hf isotope have been used to constrain the petrogenesis of this granitic intrusion and the origin of the uranium anomaly. Microscopically, quartz, alkali-feldspar, and plagioclase are the essential mineral constituents of the granite, with minor biotite, while monazite, apatite, xenotime, and zircon are accessory minerals. Geochemically, the silica- and alkali-rich granites show a highly fractionated character with "seagull-shaped" REE patterns and significant negative anomalies of Ba and Sr, along with low Zr/Hf and Nb/Ta ratios. The granite has positive zircon εHf(t) values ranging from +12.7 to +14.5 and crustal model ages (TDM2) of 259–376 Ma, indicating a Paleozoic juvenile crustal source. Uraninite and brannerite are the main radioactive minerals responsible for the uranium anomaly within the Kunduleng granite. Uraninite presents well-developed cubic crystals and occurs as tiny inclusions in quartz and K-feldspar with magmatic characteristics (e.g., elevated ThO2, Y2O3, and REE2O3 contents and low CaO, FeO, and SiO2 concentrations). The calculated U-Th-Pb chemical ages (135.4 Ma) are contemporaneous with the U-Pb zircon age (135.4–135.6 Ma) of the granite, indicating a magmatic genesis for uraninite. The granites are highly differentiated, and extreme magmatic fractionation might be the main mechanism for the initial uranium enrichment. Brannerite is relatively less abundant and typically forms crusts on ilmenite and rutile or it cements them, representing the local redistribution and accumulation of uranium. [ABSTRACT FROM AUTHOR]

Shihuiyao Rb–Nb–Ta-rich granites from the Late Jurassic period are newly discovered rare-metal-bearing granites found in the southern Great Xing'an Range, NE China. Further research of these granites may contribute to better understanding the petrogenesis of rare-metal granites and their associated mineralization mechanisms. The granites are high-silica (SiO2 = 73.66–77.08 wt%), alkali-rich (K2O + Na2O = 8.18–9.49 wt%) and weakly to mildly peraluminous with A/CNK values (molar ratios of Al2O3/(CaO + Na2O + K2O)) ranging from 1.06 to 1.16. High differentiation indexes (DI = 95–97) and low P2O5 contents demonstrate that Shihuiyao rocks are low-P and peraluminous rare-metal granites. Mineral chemistry and whole-rock geochemistry can be used to obtain the following lithological sequence: zinnwaldite granite, muscovite–zinnwaldite granite, amazonite-bearing granite and amazonite pegmatite. The effect of the rare-earth element tetrad; low K/Rb (18.98–32.82), Nb/Ta (2.41–4.64) and Zr/Hf (5.99–8.80) ratios; and the occurrence of snowball-textured quartz suggest that extreme magmatic fractionation might be the key factor that causes Rb–Nb–Ta enrichment. [ABSTRACT FROM AUTHOR]

The super-large Baerzhe Be–Nb–Zr–REE deposit in NE China is hosted in the Early Cretaceous peralkaline granites. In this work, the newly discovered granitic dikes developed around the Baerzhe deposit were studied for the first time, focusing on their genesis and genetic relationships with the Baerzhe peralkaline granites. Zircon U-Pb dating of these granitic rocks (including the granite porphyry, rhyolite and miarolitic granite) yielded Early Cretaceous ages of 125–121 Ma. Their mineral assemblages and geochemical features suggest that they share similar features with the peralkaline A-type granites. Their geochemical data and zircon Hf isotopic compositions (εHf(t) = +3.4 to +10.5) indicate that the peralkaline granitic rocks were formed by the partial melting of dehydrated charnockite with extensive plagioclase crystal fractionation, which resulted in a peralkaline affinity. There are two types of distinct zircons in the studied samples: the type I zircon with a bright rim and dark core, which may represent a cumulate mineral phase captured together with aggregates during eruption, and the type II zircon with a higher evolution degree crystallized in the residual melts. Combined with the simulation results using whole-rock trace elements, we proposed that the peralkaline granitic dikes represent more evolved interstitial melts than the Baerzhe granitic magma. In the Early Cretaceous extensional tectonic settings, mantle-derived magma upwelled, which induced the melting of the lower crust and prolonged the evolutionary process of the magma crystal mush. [ABSTRACT FROM AUTHOR]

The Ordovician plutons in the Erguna Block, NE China, can be classified into two groups: Early Ordovician diorites with zircon U-Pb ages ranging from 486 to 485 Ma and Middle Ordovician gabbros and granites with zircon U-Pb ages ranging from 466 to 463 Ma. The diorites are calc-alkaline in nature and are characterized by weak to moderate enrichments of large ion lithophile elements (LILE) and light rare earth elements (LREE) relative to high field strength elements (HFSE) and heavy rare earth elements (HREE). The gabbros and granites have high total alkali contents, and all samples are enriched in LREE and LILE and depleted in HFSE such as Nb, Ta, and Ti. Isotopically, Early Ordovician diorites display values that are less radiogenic [εHf(t) = + 9.9-+16.8] compared to those of Middle Ordovician gabbros [εHf(t) = − 3.0-+5.0]. Middle Ordovician granites have positive εHf(t) values of +1.4 to +4.3 and two-stage Hf model ages (TDM2) of 1167 to 1356 Ma. These data indicate that the diorites may have been generated by the partial melting of a recently metasomatized mantle source, whereas the gabbros and granites may have been formed by the partial melting of enriched lithospheric mantle and Mesoproterozoic crust, respectively. Our results, combined with other regional results, suggest that Early Ordovician magmatism was likely associated with the northward subduction of the Heihe-Xilinhot oceanic plate beneath the Erguna-Xing'an Block, whereas the Middle Ordovician gabbros and granites were most likely formed in an extensional setting controlled by the rollback of this subducted oceanic plate. [ABSTRACT FROM AUTHOR]

Early Ordovician A-type granites in the northeastern (NE) Songnen Block NE China were studied to better understand the geodynamic settings in this region. This research presents new zircon U-Pb ages and whole-rock geochemical data for the Early Ordovician granites in the NE Songnen Block. Zircon U-Pb dating indicates that the granite in the Cuibei, Hongxing, and Meixi areas in the NE Songnen Block formed in the Early Ordovician with ages of 471-479 Ma. The granites show geochemical characteristics of high SiO2 and K2O compositions and low FeOT, MgO, CaO, and P2O5 compositions. They belong to a high K calc-alkaline series and display a weak peraluminous feature with A/CNK values of 0.98-1.14. The rocks have a ∑REE composition of 249.98-423.94 ppm, and are enriched in LREE with (La/Yb)N values of 2.87-9.87, and display obvious Eu anomalies (δEu = 0.01-0.29). Trace elements of the studied granites are characterized by enrichment in Rb, Th, U, Pb, Hf, and Sm, and depletion of Ba, Nb, Ta, and Sr. They display geochemical features of high Zr + Y + Nb + Ce values (324-795 ppm) and Ga/Al ratios consistent with A-type granites. Based on particular geochemical features, such as high Rb/Nb (7.98-24.19) and Y/Nb (1.07-3.43), the studied A-type granites can be further classified as an A2-type subgroup. This research indicates that the Early Ordovician A-type granites were formed by the partial melting of ancient crust in an extensional setting. Lower Sr/Y and (Ho/Yb)N ratios indicate that plagioclase and amphibole are residual in the source, and garnet is absent, implying that the magma was generated at low levels of pressure. By contrast, the contemporaneous granites in the SE Xing’an Block suggest a subduction-related tectonic setting, and its adakitic property indicates a thickened continental crust. We suggest that the Paleo-Asian Ocean plate between the Xing’an and Songnen blocks subducted northward during the Early Ordovician. Meanwhile, the NE Songnen Block was exposed to a passive continental margin tectonic setting. [ABSTRACT FROM AUTHOR]

Presents information on a study which analyzed the alkali-feldspar and alkaline granites found around the Nenjiang, Northwest Lesser Xing'an Ranges in China. Characteristics of the studied granite samples; Zircon-sample preparation and analytical method; Isotopic analytical results of the samples; Ages of plutons and their tectonic significance.

• The South Orogen underwent early post-collision during 1.90–1.85 Ga, followed by late post-collision during 1.80–1.73 Ga. • The North Orogen experienced early post-collision at 1.80–1.73 Ga and then entered the late post-collision at 1.67–1.60 Ga. • Finally, the South Orogen and North Orogen simultaneously entered the initial breakup stage during 1.55–1.47 Ga. The Tarim Craton located in the northwest of China, where the Paleo-Mesoproterozoic extensional magmatism related to the Columbia supercontinent is widely developed. However, the process and time of the extension and initial breakup of the Tarim Craton are still controversial during Paleo-Mesoproterozoic era. In this contribution, we present a systematic petrographic, geochemical, and zircon U-Pb-Hf investigation on Aketashitage granite dykes, Wulan granitic gneisses and Astingbulake metadiabases from the Tarim Craton. Results from our study indicate that the ca. 1.88–1.86 Ga Aketashitage granite dykes belong to I-type granites, which were probably derived from low degree partial melting of thickened Archean crust during early post-collisional setting. The ca. 1.55 Ga Wulan granitic gneisses also show the characteristics of I-type granites, which mainly came from partial melting of mafic lower crust with minor mantle-derived magma input during the rift setting. The ca. 1.55 Ga protoliths of Astingbulake metadiabases show affinity to ocean island basalts and/or continental flood basalts and were produced by partial melting of enriched continental lithospheric mantle under continental rifting setting. In conjunction with previous studies, it can be concluded that the Tarim Craton experienced episodic extension to initial breakup: the South Orogen underwent early post-collisional extension during ca. 1.90–1.85 Ga, followed by late post-collisional extension during ca. 1.80–1.73 Ga; the North Orogen experienced early post-collisional extension at ca. 1.80–1.73 Ga and then entered the late post-collisional extension at ca. 1.67–1.60 Ga; finally, the South Orogen and North Orogen simultaneously entered the initial breakup stage during ca. 1.55–1.47 Ga. Based on a comparison of the global Mesoproterozoic (ca. 1.58–1.45 Ga) magmatic activities as a response to the initial break up of the Columbia supercontinent, we suggest that the Tarim Craton (including the Oulongbuluke Block) and North China Craton were close to India, Australia, Yangtze, Siberia, Congo, São Francisco and West African. [ABSTRACT FROM AUTHOR]