Modeling Slab Temperature: A Reevaluation of the Thermal Parameter

摘要

We reevaluate the effects of slab age, speed, and dip on slab temperature with numerical models. The thermal parameter F = t v sin., where t is age, v is speed, and. is angle, is traditionally used as an indicator of slab temperature. However, we find that an empirically derived quantity, in which slab temperature T. log ( t - av - b), is more accurate at depths < 120 km, with the constants a and b depending on position within the slab. Shallower than the decoupling depth ( 70- 80 km), a 1 and b 0, that is, temperature is dependent on slab age alone. This has important implications for the early devolatilization of slabs in the hottest ( youngest) cases and for shallow slab seismicity. At subarc depths ( 100 km), within the slab mantle, a 1 and b 0 again. However, for the slab crust, now a 0.5 and b 1, that is, speed has the dominant effect. This is important when considering the generation of arc magmatism, and in particular, slab melting and the generation of slab- derived melange diapirs. Moving deeper into the Earth, the original thermal parameter performs well as a temperature indicator, initially in the core of the slab ( the region of interest for deep water cycling). Finally, varying the decoupling depth between 40 and 100 km has a dominant effect on slab temperatures down to 140- km depth, but only within the slab crust. Slab mantle temperature remains primarily dependent on age.