Formation of the Liaotianshan Volcano in Southeastern China: Implications for the Evolution and Recharge of Crustal Magma System

Large-volume volcanic activity may offer significant insights into the evolution of silicic magma systems. The Liaotianshan volcano represents one of the earliest and best-preserved examples in SE China, comprising two stages of silicic volcanic rocks followed by extrusive rhyolite porphyries within the conduit. In this study, we present petrological and geochemical analyses, along with zircon dating, of the Liaotianshan volcano. LA–ICP–MS zircon U–Pb dating results revealed that two-stage eruptions occurred between approximately 160 and 157 Ma, and the latest batch of magma was extruded from the conduit around 153 Ma. Volcanic rocks from both stages exhibit similar geochemical compositions, characterized by pronounced depletion in high-field-strength elements and enrichment in large-ion lithophile elements, with the majority of zircon εHf(t) values falling within a narrow range of –9.8 to –5.4. In contrast, the extrusive rhyolite porphyries display distinct geochemical characteristics, demonstrating enrichment in heavy rare earth elements relative to light rare earth elements [(La/Yb)N = 0.14–0.61], obvious negative Eu anomalies (Eu/Eu* = 0.01–0.03), and positive Ce anomalies, alongside markedly depleted zircon Hf isotopic compositions. We propose that the volcanic rocks from the two stages were formed by the reworking of the Paleoproterozoic crustal basement with occasional recharge of parental magma, while the extrusive rhyolite porphyries resulted from the mixing of crustal-derived magma and significantly depleted mantle-derived materials. The Liaotianshan volcano was formed in contradiction to the model of melt extraction and crystal accumulation within a magma chamber, instead reflecting the evolutionary history and replenishment dynamics of the crustal magma system.