U-Pb ages in zircon of the Grão Mogol diamond-bearing conglomerate (Espinhaço Supergroup)

U-Pb ages in zircon of the Grão Mogol diamond-bearing conglomerate (Espinhaço Supergroup): implications for the diamond origin in the Espinhaço Range in Minas Gerais.
The Espinhaço Range in the Grão Mogol region, center-north of Minas Gerais state, is composed by fine grained quartzites with large cross stratifications (Resplandecente Formation), which are covered with erosional unconformity by monomictic conglomerates, and medium to coarse grained quartzites (Grão Mogol Formation), both units belonging to the Espinhaço Supergroup, of Proterozoic age. At the locality known as "Pedra Rica" (signify Rich Rock, an old diamond digging), rocks of these formations were sampled and separated detrital zircons to acquire U-Pb by Laser Ablation Inductively LA-ICPMS) ages. The analyzed grains are rounded to slightly rounded and show oscillatory zoning. The obtained results indicate a maximum depositional age of 1,595 ± 20 Ma for the Resplandecente Formation, and 1,052 ± 50 Ma for the Grão Mogol Formation. The comparison between the obtained data and the available ages for the Diamantina region and proximities, in the same diamond province, indicates a strong evidence for the existence of at least two primary mineralizing events in the basin, in the age range of 1.35 to 1.05 Ga.