Modelación de temperaturas bajo la Caldera de Los Humeros, Puebla, México, en términos de profundidad de la cámara magmática

Abstract

Results of thermal modelling of a magma chamber in Los Humeros Caldera, located in the eastern part of lhe Mexican Volcanic Belt, are presented. The temperature distributions obtained from a magma chamber at different depths (4, 5 and 6 km) are depth-sensitive for relatively recent magma chambers (-0.1 Ma). For older magma chambers (-0.6 Ma), the differences in predicted temperatures are much smaller because the magma bodies are practically solidified. The simulation using dry and saturated rocks shows rather low differences between predicted temperatures, probably due to lack of aclual data on thermal properties. By taking into account the thermal effects of fractional crystallization within the magma chamber, a better agreement between the calculated and the measured temperatures is obtained. At least one episode of reinjection of basaltic magma as well as convection effects in shallow layers (1-2 km depth) must be assumed. An injecled volume of -62 km3 magma, sufficient lo increase the temperature in the magma chamber by -500 C, has been postulaled. Convective processes were simulated by a conveclive layer at a depth of 700-2200 m, increasing the termal conductivites lo 10 and 20 times. The best results correspond lo the highly convective model (thermal conductivity of 20K for the convective layer). The 2000C computed isotherm agrees well with the measured lemperatures in lhe wells H-12, H-lO, H-9 and H-6 (magma chamber at 4 and 5 km). The temperatures calculated al the top of the magma chamber are 4000 lo 5000C.