Measurement of Major and Trace Elements by ICP-MS in Lunar Basalt Fragments (1–2 mg) from Chang’e-6 Mission

The Chang’e-6 (CE-6) mission returned the first-ever farside lunar samples. The bulk chemical compositions of these samples could resolve key questions about lunar evolution and the nearside-farside dichotomy. However, obtaining accurate results from small sample aliquots (1–2 mg) remains a significant challenge for existing analytical techniques. Here we established an improved method for determining 50 (10 major and 40 trace) elements using only 1–2 mg samples by combining bomb digestion and inductively coupled plasma mass spectrometry for extra-terrestrial samples. This method significantly improves upon previous approaches by (1) eliminating sample loss during the weighing step and (2) accelerating complete sample dissolution by 6-fold (8 h vs 48 h). This method achieved the first comprehensive elemental analysis of the CE-6 lunar sample, including 10 previously undetected elements (Cu, Li, Zn, Be, Pb, W, Mo, Cs, Cd, and Sn). Our analysis revealed a low-Ti/low-Al/low-K signature of the CE-6 basalt sample, akin to the CE-5 basalts. The basalt exhibits depleted Ni, in contrast with the Ni-rich CE-6 soil, suggesting exotic meteoritic contamination in the bulk soil. The rare earth element pattern of the CE-6 basalt resembles that of nearside mare basalts, with concentrations falling within their range. Beyond lunar samples, this measurement procedure adapted to small sample sizes offers significant potential for studying future extra-terrestrial samples, including those from asteroids and Mars.