Fig. 1: Magnesium isotope systematics of the Moon.
From: Titanium-rich basaltic melts on the Moon modulated by reactive flow processes
a, Model of the evolution of δ26/24Mg (solid lines; right ordinate) and MgO content (dashed lines; left ordinate) in the residual melt and instantaneous cumulates during crystallization of the lunar magma ocean. The models show the mean with a 2 s uncertainty band for δ26/24Mg that incorporates the uncertainty on the olivine–melt Mg isotope fractionation factor and that on δ26/24Mg of the bulk Moon, which we take to be that of the bulk silicate Earth (BSE)30,34 (Methods). The horizontal grey bar is the BSE composition that is taken as the starting point of the model. The instantaneous cumulate phases comprise olivine (OL), orthopyroxene (OPX), clinopyroxene (CPX), ilmenite (ILM) and 7 wt% plagioclase (PL) when present (remaining plagioclase is assumed to float to form the lunar anorthosite crust). Crystallizing phase assemblages are shown at the top; IBC crystallize from the last 2.5% melt. The model is based on equilibrium crystallization (EC) up to 70% LMO solidification with fractional crystallization (FC) of the remaining melt. The composition of cumulates that are a likely source for low-Ti magmas is shown in a darker shade of blue at 65–85% LMO solidification. b, Magnesium isotope composition (δ26/24Mg) of lunar basalts, grouped into low-Ti basalts (<4.5 wt% TiO2), high-Ti basalts (8.5–13.5 wt% TiO2) and a basalt rich in a K, rare-earth elements and P (KREEP) component (2 wt% TiO2). Uncertainties are 2 s based on the pooled 2 s.d. of 13 reference material measurements (Supplementary Fig. 1). The shaded fields are kernel density diagrams of previous Mg isotope data for lunar basalts27,28,29.
