Recently, our research paper titled “Abundance and Distribution of Radioelements in Lunar Terranes: Results of Chang’E-1 Gamma Ray Spectrometer Data” (Chen et al., 2016, Advances in Space Research, 57(3), 919-927, doi:10.1016/j.asr.2015.11.018) was published on the journal Advances in Space Research.

Link: http://www.sciencedirect.com/science/article/pii/S0273117715008157

Based on the preliminary interpretations of Chang’E-1 Gamma ray spectrometer data by other researchers utilizing energy window methods, this work improved the data processing method, extracted the Gamma ray intensities of radioactive elements on lunar surface with spectral fitting techniques and mapped the global absolute abundance of radioelements in terms of the ground truths from lunar samples and meteorites.

Lunar radioelements are enriched in KREEP (Potassium (K), rare earth elements (REE), Phosphorus (P)) materials, thus the radioelements distribution can also be regarded as KREEP distribution. The global concentration maps of KREEP indicate heterogeneous distribution among three major lunar crustal terranes in relation with their origin and distinct geologic history:

The majority of radioelements are restricted in PKT (Procellarum KREEP terrane), approving the scenario of KREEP residua cumulates. Imbrium impact event was expected to have excavated substantial KREEP-rich materials covering regions around the basin;

Radioactive enhancements are observed within SPA compared with FHT (Feldspathic Highlands Terrane) outsides, while the magnitude is much less than the peak values of PKT;

Asymmetrical distribution of radioactive abundances decreases along the northwest to southeast direction suggests that the event forming SPA might be an oblique impact;

Moreover, we found the consistency of distribution for radioelements and basalts, concluding that the subsequent volcanism might be associated with local concentrations of radioelements in western Oceanus Procellarum and northwestern South Pole Aitken Basin.

FHT is originated from initial differentiation of the Moon. Incompatible radioelements would gradually concentrate in the late-formed crust as the cooling of LMO. This scenario could lead to an inverse correlation between incompatible components and crustal thickness;

Besides protosomatic sources, KREEP-bearing ejecta from Imbrium impact could contaminate as far as the surface of FHT and even SPA. Anyway, further investigations are required to examine the weight of protosomatic or enthetic sources for the radioactivity of FHT.