Rapid transition from primary to secondary crust building on the Moon explained by mantle overturn

Tabb C Prissel; Nan Zhang; Colin R M Jackson; Haoyuan Li

doi:10.1038/s41467-023-40751-7

Rapid transition from primary to secondary crust building on the Moon explained by mantle overturn

Nat Commun. 2023 Aug 17;14(1):5002. doi: 10.1038/s41467-023-40751-7.

Authors

Tabb C Prissel¹, Nan Zhang^{2

3}, Colin R M Jackson⁴, Haoyuan Li⁵

Affiliations

¹ NASA Johnson Space Center, Astromaterials Research and Exploration Science Division, 2101 NASA Parkway, MailCode XI3, Houston, TX, 77058, USA. tabb.c.prissel@nasa.gov.
² Key Laboratory of Orogenic Belts and Crustal Evolution, School of Earth and Space Sciences, Peking University, Beijing, 100871, China. nan_zhang@pku.edu.cn.
³ School of Earth and Planetary Sciences, Curtin University, GPO Box U1987, Bentley, WA, 6845, Australia. nan_zhang@pku.edu.cn.
⁴ Department of Earth and Environmental Sciences, Tulane University, 6823 St. Charles Avenue, New Orleans, LA, 70118-5698, USA.
⁵ Department of Earth and Planetary Sciences, University of California, Davis, One Shields Avenue, Davis, CA, 95616, USA.

Abstract

Geochronology indicates a rapid transition (tens of Myrs) from primary to secondary crust building on the Moon. The processes responsible for initiating secondary magmatism, however, remain in debate. Here we test the hypothesis that the earliest secondary crust (Mg-suite) formed as a direct consequence of density-driven mantle overturn, and advance 3D mantle convection models to quantify the resulting extent of lower mantle melting. Our modeling demonstrates that overturn of thin ilmenite-bearing cumulates ≤ 100 km triggers a rapid and short-lived episode of lower mantle melting which explains the key volume, geochronological, and spatial characteristics of early secondary crust building without contributions from other energy sources, namely KREEP (potassium, rare earth elements, phosphorus, radiogenic U, Th). Observations of globally distributed Mg-suite eliminate degree-1 overturn scenarios. We propose that gravitational instabilities in magma ocean cumulate piles are major driving forces for the onset of mantle convection and secondary crust building on differentiated bodies.