A 4565 Myr old andesite from an extinct chondritic protoplanet
  The age of iron meteorites implies that accretion of protoplanets began
during the first millions of years of the solar system. Due to the heat
generated by 26Al decay, many early protoplanets were fully differentiated with
an igneous crust produced during the cooling of a magma ocean and the
segregation at depth of a metallic core. The formation and nature of the
primordial crust generated during the early stages of melting is poorly
understood, due in part to the scarcity of available samples. The newly
discovered meteorite Erg Chech 002 (EC 002) originates from one such primitive
igneous crust and has an andesite bulk composition. It derives from the partial
melting of a noncarbonaceous chondritic reservoir, with no depletion in alkalis
relative to the Sun photosphere and at a high degree of melting of around 25
percents. Moreover, EC 002 is, to date, the oldest known piece of an igneous
crust with a 26Al-26Mg crystallization age of 4,565.0 million years (My).
Partial melting took place at 1,220 C up to several hundred kyr before,
implying an accretion of the EC 002 parent body ca. 4,566 My ago. Protoplanets
covered by andesitic crusts were probably frequent. However, no asteroid shares
the spectral features of EC 002, indicating that almost all of these bodies
have disappeared, either because they went on to form the building blocks of
larger bodies or planets or were simply destroyed.
