Effects of Iron Spin Transition on the Structure and Stability of Large Primordial Reservoirs in Earth's Lower Mantle

Abstract

AbstractExperimental and theoretical studies have shown that the iron spin transition alters the properties of lower mantle minerals. This may have important implications for mantle dynamics. In particular, the vigor of convection is enhanced, which in turn may impact the stability of large primordial reservoirs at the base of the lower mantle. Here we performed numerical experiments of thermochemical convection in 2‐D annulus geometry including the change of density induced by iron spin transition. Our results show that this density change only slightly affects mantle dynamics by increasing the convection vigor. This, in turn, slightly increases the entrainment of primordial dense materials by plumes and leads to smaller reservoirs with sharper edges. However, this effect is small compared to those of the intrinsic density contrast between the dense primordial and regular mantle materials, which is the dominant parameter controlling the long‐term stability of the large primordial reservoirs.