Abstract:Volcanoes are the only straightforward expression for the activity of magma on Earths surface. Ancient volcanoes could expose multi- stage eruptive products, magma plumbing systems and even the magma reservoirs. Therefore, they could preserve important information on interior structure of magma reservoir and magmatic evolution. Zircons can record crystallization differentiation, crystal- melt separation, and replenishment processes of magma system. In this work, we conducted zircon U- Pb, Lu- Hf isotopic and trace element concentration studies on the late Jurassic Liaotianshan caldera in southwest Fujian Province, which is one of the earliest and best preserved Late Mesozoic calderas in SE China, to reveal its eruptive history, magma source and evolution process. The Liaotianshan volcano started to erupt intermittently at ca. 161.5±0.7 Ma as the first stage with limited scales of eruptive products, then during 159.9±0.9~156.9±0.8 Ma erupted as the second stage forming the main part of the caldera. At the final stage, magma extruded along the magma conduit forming porphyritic rhyolite domes at ca. 153.2±0.7 Ma, marking the end of the eruption. Zircon Lu- Hf isotopic compositions show that, the Liaotianshan volcanic rocks were derived mainly from partial remelting of the Paleoproterozoic crustal basement, with decreasing and then increasing degree of depleted mantle- derived involvement. Different batches of magma raised separately from source region after magma mixing in deep reservoir, and then retained briefly in shallow reservoir with similar crystallization process. The change of magma origin together with volcanic lithofacies indicate that the Liaotianshan caldera formed under a slightly compressional and then depressional geological environment, plausibly corresponding to the paleo- Pacific subduction with varying subduction angle during Late Jurassic.