Deposition temperature of some PDC deposits from the 1982 eruption of El Chichón volcano (Chiapas, Mexico) inferred from rock-magnetic data

Thermal remanent magnetization (TRM) analyses were carried out on lithic fragments from two different typologies of pyroclastic density current (PDC) deposits of the 1982 eruption of El Chichón volcano, in order to estimate their equilibrium temperature (Tdep) after deposition. The estimated Tdep range is 360–400 °C, which overlaps the direct measurements of temperature carried out four days after the eruption on the PDC deposits. This overlap demonstrates the reliability of the TRM method to estimate the Tdep of pyroclastic deposits and to approximate their depositional temperature. These results also constraint the time needed for reaching thermal equilibrium within four days for the studied PDC deposits, in agreement with predictions of theoretical models.Sedimentological analysis demonstrates that different thickness of aggrading granular dominated pulses does not affect significantly the estimated Tdep for the two studied PDCs. The component analysis highlights how the entrapment of a significant amount of pre-heated lithic fragments from the dome and the conduit walls reduced the cooling of the pyroclastic mixture.