125 Lunar Science and Exploration in the Artemis Era

Current and anticipated science return in the areas of geology, composition, and interior of the Moon from current lunar-focused studies and upcoming payloads expected to land on the Moon in the next decade.

Monday, 20 October 2025
1:30 PM - 5:30 PM
HBGCC, 214C

High-resolution Chronology of the Lunar Crust

Paper number: 125-1
Program: Technical Sessions
Time: 1:35 PM – 1:50 PM

Authors

Abstract

Lunar crustal rocks preserve a critical record of the Moon’s earliest evolution, including lunar magma ocean (LMO) differentiation and secondary crustal magmatism [1]. The lunar crust consists of three major crustal rock suites: The primordial ferroan anorthosite suite (FAS) alongside the secondary Mg-suite (MGS) and alkali-suite (AKS). According to the LMO model, the MGS and AKS should have postdated the FAS. However, published ages for these suites exhibit a wide range of overlapping ages [2], challenging this prediction and suggesting either gaps in our understanding of lunar differentiation or inaccuracies in existing age determinations. To address this, we present high-resolution ages for lunar crustal samples measured at LLNL, highlighting the importance of employing multiple radiometric systems for reliably dating lunar crustal rocks. While the U-Pb system provides the required level of precision, the Sm-Nd systems help confirm the ages obtained are accurate. New 238,235U-206,207Pb zircon ages obtained by ID-TIMS alongside 147,146Sm-143,142Nd isochron analyses of MGS sample 78236/8 and AKS sample 15405 QMD yield precise and concordant mean ages of 4334.1±3.5 Ma and 4337.19±0.49 Ma. These ages are ~25 Ma younger than the most precisely dated FAS sample, 60025 (4359.3±2.3 Ma [2]). Our results have key implications for the igneous evolution of the Moon. First, the ~25 Ma formation interval aligns with the geochemical characteristics of these suites, supporting the interpretation that the FAS predates the MGS/AKS. Second, this brief interval between primary and secondary crust formation indicates that crustal growth occurred within a narrow timeframe, necessitating an efficient secondary process, such as tidal heating [3] or cumulate overturn [e.g., 4], to initiate secondary magmatism soon after LMO differentiation. Third, the concordant ages and identical initial isotopic compositions of MGS and AKS samples suggest derivation from a common source. Collectively, these findings refine the timeline of lunar crustal evolution and resolve two distinct stages of crustal growth, primordial FAS magmatism followed by secondary MGS and AKS magmatism. This is consistent with both the geochemical stratigraphy of the lunar crust and the LMO model. [1] Shearer C.K. et al. (2006) RIMG 60, 365-318. [2] Borg L.E. Carlson R.W. (2022) AREPS 51: 25-52. [3] Nimmo F. et al. (2024) 636, 598-602. [4] Shearer C.K. et al. (2015) Am. Min. 100, 294-325.

Geological Society of America Abstracts with Programs. Vol. 57, No. 6

doi: 10.1130/abs/2025AM-412821

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