Speaker: Peng Ni

Affiliation: UCLA, EPSS

Date: Thursday, June 4, 2026

Time: 12:00 PM

Abstract

Constraining the age of individual diamonds is challenging because diamond itself lacks radioactive parent–daughter nuclides in its lattice for direct dating. I show that recent advancements in mass spectrometry enable in situ Rb–Sr isotope analysis of diamonds containing high-density fluid micro-inclusions. Application of this technique to a suite of diamonds from Kankan, Guinea, demonstrates its high efficiency in Rb-Sr isotope analysis compared with previous bulk methods. The improved spatial resolution also enables potential isochron Rb-Sr dating of these diamonds. One zoned diamond, ON-KAN-381, is found to be 73 ± 81 Ma in age, overlapping kimberlite eruption ages in West Africa. Together, these results place a quantitative constraint on the formation of Kankan fibrous diamonds, indicating that they originated from mantle metasomatism events in the West African continental lithospheric mantle within tens of millions prior to the kimberlite eruption.