U–Pb Geochronology of zoisite samples found among blue sapphires from Aksum, Ethiopia

Abstract

Light blue zoisite fragments mixed in a parcel of blue sapphires reportedly from Aksum, Ethiopia were analyzed with LA-ICP-MS for U–Pb geochronological study and compared with the results on tanzanite samples collected in Merelani, Tanzania. Merelani samples provide an age of 555.2 ±5.7 | 8.1 Ma (n=37/45; MSWD=1.9). Aksum samples are isotopically indistinguishable from Merelani in terms of U–Pb isotope data. This result indicates the potential mixture with Tanzanian zoisites in the gemstone trade if zoisite deposits that is similar age as Merelani does not exist in northern Ethiopia.