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The Mesozoic South China is characterized by extensive magmatism, transition from Jurassic intraplate magmatism to Cretaceous active continental margin magmatism. However, the time and deep geodynamic processes accounting for the Mesozoic magmatism remains controversial. In this study, we presented new SIMS zircon U Pb ages, in-situ Sr isotope of plagioclase, whole-rock geochemical and Sr–Nd–Pb isotopic data on three suites of mafic dikes in eastern Guangdong, namely Anliu (AL) and Sanjiaowo (SJW) and Jishuimen (JSM) mafic dikes. The AL (154.3 ± 3.4 Ma) and SJW (141.3 ± 4.0 Ma and 143.2 ± 2.3 Ma) dikes show arc-like geochemistry and "crust-like" isotopic signatures, likely derived from partial melting of a subduction metasomatized lithospheric mantle. Meanwhile, the JSM dikes (141.7 ± 3.2 Ma) exhibit OIB-type geochemical and isotopic features, and were likely derived from partial melting of an enriched asthenospheric mantle. The development of late Jurassic AL lamprophyre may represent the oldest Paleo-Pacific subduction-related arc-type mafic rocks so far recorded in South China. Development of dikes (SJW vs JSM) with different geochemical signatures (Arc vs OIB) at the same time within a limited space indicates that asthenosphere-related process overprint and co-operate with subduction-related magmatism and imply the initiation of Paleo-Pacific subduction roll-back was potentially at least ca.141 Ma. • Late Jurassic–early Cretaceous mafic dikes were identified in Eastern Guangdong. • The ~154 Ma AL mafic dikes show typical arc-like features. • It was derived from the lithospheric mantle metasomatized by subducted slab fluids. • The simultaneous (~141) SJW and JSM dikes show arc-like and OIB-like features. • They imply the initiation of Paleo-Pacific subduction roll-back was before 141 Ma. [ABSTRACT FROM AUTHOR]

The Bailongshan pegmatite deposit is a newly discovered super-large Li–Rb–(Be–Ta–Nb) rare-metal deposit in the West Kunlun orogenic belt, northwest China. Fifty-two rare-metal orebodies (50–1230 m long by 1.5–157 m wide) have been discovered by detailed field surveying, making up a metallogenic field that is larger than 8250 × 400 m. The deposit is estimated to have ore reserves of more than 5.06 million tonnes (t) Li 2 O, 160,020 t BeO, 316,200 t Rb 2 O, 40,060 t Nb 2 O 5 , and 10,750 t Ta 2 O 5. Pegmatite dikes are zoned around a granodiorite batholith, ranging from barren through orebodies rich in Be, Nb, Ta, Rb, and Li with increasing distance from the batholith, similar to the classical model of a zoned Li–Ce–Ta (LCT)-type pegmatite. LA–ICP–MS analyses of coltan and zircon yield 206Pb/238U ages of 208.1 Ma and 212.3 Ma, respectively, representing the emplacement ages of the pegmatites and granodiorite. These data indicate a temporal link between the emplacement of the granodiorite batholith and rare-metal mineralization in the pegmatites, and that the Bailongshan rare-metal pegmatites are temporospatially related to the granodiorite batholith. The Bailongshan pegmatites and other rare-metal pegmatite deposits in the West Kunlun orogenic belt likely make up a >600-km-long Li metallogenic belt, and further exploration for rare-metal pegmatites should be focused on the area adjacent to Late Triassic granitoid plutons in the belt. This belt likely extends to the East Kunlun and West Sichuan rare-metal belts, forming the >2000-km-long, Late Triassic West Kunlun–Songpan–Garzê rare-metal metallogenic belt. • The Bailongshan deposit is a newly discovered superlarge Li-Rb-(Be-Nb-Ta) pegmatite deposit. • The Bailongshan Li-rich pegmatites (ca. 208 Ma) is closely related to the granodiorite batholith. • Further exploration of Li-rich pegmatite should be around the Late Triassic granitoids. • We highlight a huge "West Kunlun–Songpan-Ganzê rare-metal pegmatite metallogenic belt" occurs. [ABSTRACT FROM AUTHOR]