Non-KREEP origin for Chang'e-5 basalts in the Procellarum KREEP Terrane

Area of Science:

• Lunar geology
• Planetary science
• Geochemistry

Background:

• Lunar mare basalts are crucial for understanding the Moon's thermal and chemical evolution.
• Young basalts are concentrated in the Procellarum KREEP Terrane (PKT), previously thought to originate from KREEP-rich mantle sources.
• The origin of these young basalts has been debated due to a lack of direct study.

Purpose of the Study:

• To petrologically and geochemically analyze young basalt clasts from the PKT returned by the Chang'e-5 mission.
• To test the hypothesis that young basalts in the PKT formed from KREEP-rich sources.
• To investigate the thermal evolution of the lunar interior.

Main Methods:

• Petrological and geochemical analysis of lunar basalt clasts.
• Bulk rock composition analysis (titanium, iron, rare-earth elements, thorium).
• Strontium-neodymium isotope analysis.

Main Results:

• The studied basalts are two billion years old, the youngest lunar samples analyzed.
• Bulk compositions show moderate titanium, high iron, and KREEP-like rare-earth element and thorium concentrations.
• Strontium-neodymium isotopes indicate derivation from a non-KREEP mantle source, requiring low-degree partial melting and fractional crystallization.

Conclusions:

• The KREEP association is not necessarily a prerequisite for young mare volcanism.
• The Moon's youngest melts can be generated by a sustained interior cooling history without requiring heat-producing elements in the source.
• This study revises our understanding of lunar thermal evolution and mantle processes.