In situ trace elements and U–Pb chronology of cassiterite reveal a long-lived Taoxiba large Sn system in SE China

Complex Intrusive-volcanic systems, critical reservoirs for porphyry and subvolcanic hydrothermal Sn deposits, have been a subject of great controversy regarding whether intrusion or volcanic events could effectively contribute to significant Sn mineralization. We address this issue through detailed field work, ore mineralogy, mineral geochemistry, and cassiterite U–Pb geochronology of the Taoxiba Sn deposit. Three metallogenic stages and seven generations of cassiterite have been identified: cassiterite Cst-G occurs in greisen, cassiterite Cst-W1–4 occur in altered volcanic rocks, and cassiterite Cst-V1 & V2 occur exclusively in mica-quartz veins. Each cassiterite generation showing distinct trace-element compositions. The Nb, Ta, and Sc accumulated in the Cst-G generations are derived from the inherited concentrations of Nb and Ta from the initial magma and absorbed through the mechanisms of Sc 3+ + (Nb 5+ , Ta 5+ ) ↔ 2Sn 4+ and Fe 2+ /Mn 2+ + 2Nb 5+ /Ta 5+ ↔ 3Sn 4+ . However, the Cst-W1–W4 and Cst-V1 generations followed the Fe 3+ + Nb 5+ /Ta 5+ ↔ 2Sn 4+ mechanism. The high Pb, Th, and ∑REE concentrations in are possibly originated from fluid-rock interactions, fluid mixing, differential partitioning, or fluid boiling, among other processes. However, the abnormal Fe, Ti, Hf, Zr, Ga, Be, and Mn concentrations in Cst-W4 record complex mixing of externally derived fluids in a distal open low-temperature system. The Taoxiba magmatic–hydrothermal system experienced at least three evolutionary stages: a high-temperature, reduced greisen stage; a subsequent cooling and oxidation stage; and a later overprinting stage involving externally derived hydrothermal fluids. Cassiterite U–Pb ages indicate multiple mineralization events, including volcanic-related Sn mineralization at 144.5–140.9 Ma, greisen-stage Sn mineralization at 138.9–137.5 Ma, broader main-stage mineralization at 141.6–134.6 Ma, which could be associated with the transition stage from extrusion to extension due to slab rollback and revolving (150 to 135 Ma) and a tectonic regime of forward subduction (120 to 100 Ma).