EEPS Colloquium: Bidong Zhang

 

Laserprobe Rb-Sr geochronology of lunar samples: From method development to applications

Rb-Sr geochronology is one of the most widely used chronometers in Earth science and planetary science. A major analytical challenge in Rb-Sr dating is the isobaric interference of ⁸⁷Rb on ⁸⁷Sr. Recent advances in inductively coupled plasma mass spectrometry (ICP-MS) equipped with collision/reaction cell technology (CCT) enable effective separation of this interference. Here, we used a Thermo Fisher Scientific Neoma MC-ICP-MS/MS coupled with an ESL NWR 193 nm nanosecond excimer laser-ablation (LA) system to establish analytical procedures for accurate in situ Rb-Sr geochronology. Method development and validation were conducted using two terrestrial granites (Shap and Dartmoor) and two ungrouped achondrites (Northwest Africa 6704 and Erg Chech) with well-established Rb-Sr ages. We subsequently applied the method to three types of lunar samples - a KREEP-rich meteorite, an Apollo mare basalt, and an Apollo impact-melt breccia. The resulting ages, with precisions of 1.5–3%, are consistent with published TIMS data. These results, acquired from samples spanning a wide range of feldspar compositions, demonstrate the broad applicability of laserprobe Rb-Sr geochronology to feldspar-bearing planetary materials, especially future returned samples from the Moon through the Artemis program and, by extension, samples from Mars and its moons through future sample-return missions such as Martian Moons eXploration (MMX).

Host: Kun Wang

EEPS Colloquia are made possible by the William C. Ferguson Fund