Orthopyroxene-dominated upper mantle melting built the early crust of the Moon

The paradigm of lunar crust formation has been widely applied to other terrestrial bodies, but the nature of early crust building on the Moon remains enigmatic. Here we report non-Apollo-like highland clasts from the Chang'e-5 mission and find high-alumina melts enclosed in a noritic anorthosite. Geochemistry and phase equilibria modeling suggest that the melt is compositionally parental to lunar magnesian-suite rocks, and was sourced from a plagioclase-bearing, orthopyroxene-dominated upper mantle ( ~ 4.5 kbar and 1225°C). It was formed as a direct consequence of upper mantle melting at the onset of gravitational instability. We propose a continuous early crust formation on the Moon, started from multiple anorthositic cumulate flotations, to upper mantle melting caused by small-scale, in-situ overturn, and eventually ended up by decompression melting of lower mantle cumulates following large-scale, global overturn. The first magma on the Moon formed by decompression melting of orthopyroxene-dominated mantle rocks facilitated by density-driven mantle overturn, according to petrographic modelling and observations of lunar highland samples from the Chang'e-5 mission