Pulsatile extractions of Lower Cretaceous silicic volcanic plumbing system beneath the Baiyunzhang and Lianhuashan Basins, eastern Guangdong: silicic magma evolution and related mineralization

Highly differentiated magmas are closely related to the formation of tin deposits. The Lianhuashan Basin and Baiyunzhang Basin, surrounded by multiple coeval tin deposits, developed various types of volcanic and subvolcanic rocks. The diagenetic connections between different types of rocks within the two basins will provide new insight on the silicic magma systems evolution and the impact of highly differentiated magmas on tin mineralization. Both basins have consistent zircon U-Pb ages (143 ∼ 138 Ma) and similar whole-rock Nd isotopes ( ε Nd ( t ) = -5.7 ∼ -3.4) and zircon Hf-O isotopes ranges ( ε Hf ( t ) = -9.0 ∼ -2.5; δ 18 O = 5.1 ∼ 7.9), suggesting both basins originate from the same deep-level magma reservoir, followed by different degrees of crystal differentiation and several episodes of crystal-melt separation in their respective shallow-level magma reservoirs. The multiple pulses of magma extraction eventually produced different volcanic rocks, granite porphyry and rhyolite porphyry, while the remaining crystal mush consolidated in situ to form quartz monzonite porphyry. Further studies show that the tectonic regime changed from a compressive to an extensional environment at ∼140 Ma. Consequently, mantle-derived magmas with low oxygen fugacity injected shallow magma reservoirs that able to evolve to a high degree of differentiation through multiple recharge, thus favoring the formation of the Sn deposit. Supplementary material: https://doi.org/10.6084/m9.figshare.c.7258282