Allan Patchen

Petrogenesis of lunar meteorite EET 96008

Abstract Lunar meteorite EET 96008 is a fragmental breccia that predominantly consists of basaltic mineral clasts (0.5–2 mm), along with minor lithic fragments and breccia clasts. The matrix consists mainly of smaller mineral fragments ( The molar Fe/Mn ratio in olivines and pyroxenes and the age of the meteorite are evidence for a lunar origin. The mineralogy of EET 96008 shows close affinity to a mare-basalt source, albeit with possible minor highland/non-mare components. The bulk-rock, major-, trace- and rare-earth-element (REE) contents are similar to that of very low-titanium (VLT) basalts, which have experienced extreme fractional crystallization to the point of silicate liquid immiscibility. Mineralogical and textural features of this sample suggest that at least some of the breccia components were derived from a slow-cooled magma. The mineralogy and petrology of EET 96008 is strikingly similar to the lunar meteorite EET 87521, and we support the conclusion that EET 96008 and EET 87521 should be paired. Isochron ages of 3530 ± 270 Ma for apatite and 3519 ± 100 Ma for whitlockite of this rock are consistent with derivation from a mare-basalt precursor. These ages are within error of the low-Ti basalts, dated from the Apollo 12 and 15 sites. The whole-rock, platinum-group-element (PGE) contents of EET 96008 overlap with pristine low-Ti mare basalts, suggesting the presence of only a minimal extraterrestrial component.

The most reduced rock from the moon, Apollo 14 basalt 14053: Its unique features and their origin

Abstract The Apollo 14 high-Al basalt, 14053, is the most reduced lunar rock examined to date. Both fayalite in the mesostasis and spinel minerals have been extensively reduced in the exterior of the rock, whereas the interior contains relatively limited reduction. It is shown that these products are the effects of solar-wind hydrogen that was implanted on the exterior of the .normal. 14053 basalt after it originally crystallized and was weathered to become part of the regolith. Subsequent reheating, probably in an impact-ejecta blanket, caused extreme subsolidus hydrogen reduction, particularly of the weathered exterior of this rock. The limited permeability of the rock prevented the entire rock from being subjected to the same degree of reduction. It is proposed that this extreme reduction, especially of the mesostasis, also affected the phosphate minerals, F-Cl apatite and merrillite, each of which vary greatly in REE contents. This effect on the phosphate minerals could relate to the upset Sm-Nd radiogenetic systematics, whereas the Rb-Sr system may have been largely immune to the subsolidus reduction.

Quantitative mineralogical characterization of lunar high‐Ti mare basalts and soils for oxygen production

Efficient lunar resource utilization requires accurate and quantitative evaluation of mineral and glass abundances, distribution, and extraction feasibility, especially for ilmenite. With this in mind, true modal analyses were performed on high-Ti mare basalts and soils with X ray/backscattered electron signal digital-imaging techniques, and these data indicate that (1) ilmenite concentrations are similar for basalts and immature-submature soils with similar TiO2 content; (2) ilmenite liberation of crushed mare basalts and immature-submature mare soils are comparable (i.e., both contain similar amounts of free ilmenite); and (3) because of impact melting and agglutination of primary minerals, mature mare soils contain less ilmenite (both free and attached). Modal analyses of magnetic separates of high-Ti mare basalts and soils show that (1) ilmenite was concentrated by a factor of ≥3.3 and (2) soil ilmenite was concentrated to factors of 1.7–2.3. The lower soil ilmenite separation efficiency is attributed to Fe°-bearing agglutinitic glass and amorphous rinds adhered to soil particles. Mass yields of magnetically generated feedstocks were generally less than 5 wt % in most cases. Calculation of oxygen yield (as released by hydrogen gas reduction of ilmenite) show that (1) beneficiated basalt will provide the most oxygen (8–10%), because of higher ilmenite concentration; (2) reduction of raw immature-submature mare soils and basalts will produce similar amounts of lunar liquid oxygen (LLOX) (2.1–3.1%); and (3) raw Fe-rich pyroclastic soil, 74220, will provide more oxygen (5.4%) than beneficiated high-Ti mare soils and half that of beneficiated high-Ti mare basalts. High-Ti mare soils are attractive resources for lunar liquid oxygen (LLOX) production because of their unconsolidated nature, high ilmenite abundance, and widespread occurrence. Energy-intensive excavation and comminution likely prohibits the basalt mining during early lunar occupation. Orange soils are important resources for LLOX and various volatile elements, but slower reaction kinetics and glass sintering pose potential difficulties for large-scale operations.

Solid-Solution CrCoCuFeNi High-Entropy Alloy Thin Films Synthesized by Sputter Deposition

The concept of high configurational entropy requires that the high-entropy alloys (HEAs) yield single-phase solid solutions. However, phase separations are quite common in bulk HEAs. A five-element alloy, CrCoCuFeNi, was deposited via radio frequency magnetron sputtering and confirmed to be a single-phase solid solution through the high-energy synchrotron X-ray diffraction, energy-dispersive spectroscopy, wavelength-dispersive spectroscopy, and transmission electron microscopy. The formation of the solid-solution phase is presumed to be due to the high cooling rate of the sputter-deposition process.

Ferrous freudenbergite in ilmenite megacrysts; a unique paragenesis from the Dalnaya kimberlite, Yakutia

Abstract A suite of picroilmenite megacrysts from the Dalnaya kimberlite, Siberia, was found to fall into one of two groups, the most abundant having 11-12 wt% MgO and 650-1500 ppm Nb, and the others having lower MgO (8.8-10.2 wt%) and higher Nb (1700-2700 ppm). Ferrous freudenbergite (Na2FeTi7O16) crystals were found included in many of the megacrysts from the first group. The freudenbergite-bearing ilmenite megacrysts are also pervaded by micrometer-size spots that have elevated Al2O3 (>2 wt%), SiO2 (>0.4 wt%), and Na2O (>0.15 wt%) contents. The low Cr2O3 vs. Nb content of the second group may reflect clinopyroxene crystallization. This may be a factor influencing the lack of freudenbergite in these megacrysts. All ferrous freudenbergite samples studied previously are manifested as metasomatic reaction mantles replacing rutile. The freudenbergite from the Dalnaya kimberlite described in this paper occurs as small (max. 150 μm × 40 μm), euhedral, prismatic inclusions in picroilmenite (11-12 wt% MgO) megacrysts, with no associated rutile. Minor-element (Cr, Al, and Mg) substitutions for Fe are more extensive than in previously studied freudenbergite, with up to 1.4 wt% Cr2O3, 1.9 wt% Al2O3, and 3.1 wt% MgO. Nb is relatively low, typically less than 0.3 wt% Nb2O5 with a maximum of 1.1 wt%. Reaction of some of the freudenbergite with an alkalic fluid has resulted in thin, discontinuous rims and embayments of perovskite and an unidentified hydrous calcium titanate, around most crystals. Rapid ascent from depth and shielding by ilmenite may have been contributing factors to the preservation of freudenbergite in these samples. The significance of the euhedral nature of freudenbergite and the lack of any genetic relationship with rutile suggest that it crystallized by a process other than simple metasomatic replacement of rutile. Indeed, the freudenbergite probably crystallized directly from a Na+ Ti-rich fluid infiltrating the ilmenite megacrysts. The several occurrences (Liberia, Bultfontein, and Dalnaya) of ferrous freudenbergite suggest that it may be more common in kimberlites than previously recognized.