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All sourcesNASA NTRSDOE OSTI
NASA NTRS1974

K and U systematics and average concentrations on the moon

The K-U, Th-U, and Th-Al systematics for lunar samples from the Apollo 11-17 missions and the Luna 16 and 20 missions are summarized. With few exceptions (granitic portion of 12013 and the Apollo 17 mare basalts) the Th/U ratio is 3.8 plus or minus 0.2. The K/U ratio for lunar samples is about 2600 and is distinctly different from the K/U ratio found in terrestrial samples and in the majority of meteorites. The K-U systematics are similar to the K-La, K-Sm, K-Ba, and K-Zr systematics, suggesting that the moon accreted approximately homogeneously. Based on a model the moon contains an average abundance of about 80 ppb U, about 200 ppm K, and about 7 times chondritic abundances for all the refractory elements such as Al, Ca, Ti, Zr, Ba, Sr, and REE. The Th-Al systematics of many lunar highland rocks are dominated by the presence of the rock-type KREEP.

Schonfeld, E.↗
DOE OSTI2020

Materials Data on K3Zr by Materials Project

K3Zr is alpha bismuth trifluoride structured and crystallizes in the cubic Fm-3m space group. The structure is three-dimensional. there are two inequivalent K sites. In the first K site, K is bonded to four equivalent K and four equivalent Zr atoms to form a mixture of distorted edge, corner, and face-sharing KK4Zr4 tetrahedra. All K–K bond lengths are 4.04 Å. All K–Zr bond lengths are 4.04 Å. In the second K site, K is bonded in a body-centered cubic geometry to eight equivalent K atoms. Zr is bonded in a body-centered cubic geometry to eight equivalent K atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on K3Zr by Materials Project

K3Zr is Uranium Silicide-like structured and crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. there are two inequivalent K sites. In the first K site, K is bonded to eight K and four equivalent Zr atoms to form distorted KK8Zr4 cuboctahedra that share corners with twelve equivalent KK8Zr4 cuboctahedra, edges with eight equivalent KK8Zr4 cuboctahedra, edges with eight equivalent ZrK12 cuboctahedra, faces with four equivalent ZrK12 cuboctahedra, and faces with ten equivalent KK8Zr4 cuboctahedra. There are four shorter (4.08 Å) and four longer (4.24 Å) K–K bond lengths. All K–Zr bond lengths are 4.24 Å. In the second K site, K is bonded in a distorted square co-planar geometry to eight equivalent K and four equivalent Zr atoms. All K–Zr bond lengths are 4.08 Å. Zr is bonded to twelve K atoms to form ZrK12 cuboctahedra that share corners with four equivalent ZrK12 cuboctahedra, edges with eight equivalent ZrK12 cuboctahedra, edges with sixteen equivalent KK8Zr4 cuboctahedra, faces with four equivalent ZrK12 cuboctahedra, and faces with eight equivalent KK8Zr4 cuboctahedra.

36 MATERIALS SCIENCE↗