Theoretical Studies of Phase Transformations of Mantle Minerals

Résumé du livre

Finally, I explore the effects of mineralogy on the descent velocities of subducting slabs. Thermo-kinetic modeling of olivine polymorphs is used to predict mineralogy and I compare the resultant buoyant force to the opposing viscous drag. As slabs first enter the transition zone, negative buoyancy anomalies should accelerate them, whereas positive anomalies that form when the slabs' ends exit the transition zone should decelerate them. These effects may induce geologically abrupt changes in plate motions. Also, metastable olivine in slabs should create regions of positive buoyancy which should reduce the slabs' velocities. This effect would be strongest for the coldest slabs, slowing them the most. Decreased descent rates, however, should allow slabs to warm up, thermally eroding the metastable wedges. Such a negative feedback mechanism may regulate plate speeds.