K-Ca dating and Ca isotope composition of the oldest Solar System lava, Erg Chech 002

Abstract

(Figure Presented) Erg Chech 002 (EC 002) is an andesitic meteorite, which is the oldest lava in the Solar System as determined by the 26Al-26Mg relative chronometer. Here, we present high precision Ca isotope data for the bulk rock and mineral separates of EC 002, and for the first time, obtain a 40K-40Ca isochron by using the Nu Sapphire, a collision cell equipped MC-ICP-MS instrument. The mineral separates yield a 40K-40Ca age of 4545 ± 78 Ma with an initial 40Ca/44Ca = 47.16065 ± 0.00049 (ε40CaSRM 915a = −0.33 ± 0.10). The age is identical with those obtained from other long lived isotopic systematics but more precise, and it is consistent with the short lived 26Al-26Mg age. The δ44/40Ca of EC 002 is 0.87 ± 0.05 ％ suggesting that EC 002 might represent a differentiated melt from an ordinary chondritic parent body. The extremely old age of EC 002, along with the similar ε40Ca values among most meteorites, suggests that the 40Ca was homogeneously distributed within early formed planetesimals and the ε40Ca value of EC 002 could represent the average of initial ε40Ca of the Solar System.