Geophysical constraints on the lunar Procellarum KREEP Terrane
Article first published online: 17 APR 2013
©2012. American Geophysical Union. All Rights Reserved.
Journal of Geophysical Research: Planets
Volume 118, Issue 4, pages 768–778, April 2013
How to Cite
2013), Geophysical constraints on the lunar Procellarum KREEP Terrane, J. Geophys. Res. Planets, 118, 768–777, doi:10.1029/2012JE004114.(
- Issue published online: 17 MAY 2013
- Article first published online: 17 APR 2013
- Manuscript Accepted: 30 NOV 2012
- Manuscript Revised: 28 NOV 2012
- Manuscript Received: 26 APR 2012
- heat flow;
 The Moon's Procellarum KREEP Terrane (PKT) is distinguished by unique geochemistry and extended volcanic history. Previous thermal-conduction models using enhanced radionuclide abundances in subcrustal potassium, rare earth elements, and phosphorus (KREEP) predicted the existence of a contemporary upper-mantle melt zone as well as heat flow consistent with Apollo measurements. Here I show that such models also predict large gravity or topography anomalies that are not observed. If the topography is suppressed by a rigid lithosphere, it is possible to eliminate the gravity anomaly and still match heat flow by completely fractionating the excess radionuclides into a thin crust. This implies that upper-mantle heat sources for mare volcanism were spatially discontinuous or transient and that radionuclides defining the PKT are not necessarily directly related to mare volcanic sources. However, the mantle temperature of a crustally fractionated PKT is insufficient to match the observed electrical conductivity: globally enhanced mantle heating or a thick megaregolith may be required. Alternatively, upper-mantle enrichment in iron, hydrogen, or aluminum can provide the requisite conductivity. Iron is the most plausible: the derived lower limit to the upper-mantle magnesium number 75–80% is consistent with seismic modeling. Regardless of the specific mechanism for electrical-conductivity enhancement, the overall excellent match to simple thermal-conduction models indicates that the lunar upper mantle is not convecting at present.