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This study focuses on using the chemical compositions of plagioclase to further investigate the petrogenesis of Chang'E-5 young mare basalts and constrain its parental melt composition. Together with previously published data, our results show that the plagioclase in mare basalts overall displays large variations in major and trace element concentrations. Inversion of the plagioclase data indicates that the melt compositions parental to Chang'E-5 basalts have high rare earth elements (REE) concentrations similar to the high-K KREEP rocks (potassium, rare earth elements, and phosphorus). Such a signature is unlikely to result from the assimilation of KREEP components, because the estimated melt Sr shows positive correlations with other trace elements (e.g., Ba, La), which are far from the KREEP end-member. Instead, the nearly parallel REE distributions and a high degree of trace element enrichment in plagioclase indicate an extensive fractional crystallization process. Furthermore, the estimated melt REE concentrations from plagioclase are slightly higher than those from clinopyroxene, consistent with its relatively later crystallization. Using the Ti partition coefficient between plagioclase and melt, we estimated the parental melt TiO2 content from the earliest crystallized plagioclase to be ~3.3 ± 0.4 wt%, thus providing robust evidence for a low-Ti and non-KREEP origin for the Chang'E-5 young basalts in the Procellarum KREEP terrane. [ABSTRACT FROM AUTHOR]

Focuses on a study that examined the similarities between the metamorphosed mafic rocks found in Hainan Island, China with depleted N-type mid-ocean ridge basalts. Protolith of the mafic rocks; Methodology of the study; Results and discussion; Conclusion.

The article discusses evidences for late paleozoic and mesozoic basaltic magmatism in Southwestern Cameroon. It mentions impacts for correlations between the Gulf of Guinea in Africa and Northeast Brazil. It mentions that basalt dikes are olivine-containing tholeiites, less enriched in trace and rare earth elements.

• Volcanic history of the Apollo basin where Chang'e-6 is going to land. • Crustal thickness controls the volcanic activities of the Apollo basin. • Scientific significances of the returned Chang'e-6 samples. A major lunar scientific question is the cause of the paucity of farside mare basalts. The South Pole-Aitken Basin (SPA) is the largest (2400×2050 km) and most ancient lunar impact basin. The Apollo peak-ring basin, the largest impact feature within the SPA, is located on its northeast edge in a transitional zone of crustal thickness and compositions. The Chang'e-6 (CE-6) mission, the first sample-return mission to the lunar farside, is targeted to land in the southern Apollo basin, sampling farside mare basalts with critical insights into early lunar evolution. In preparation for the CE-6 sample return, we conducted a comprehensive study of Apollo basin volcanism. We found that volcanic activity began in the Nectarian Period (∼4.05 Ga) (cryptomaria) and continued into the Eratosthenian Period (∼1.79 Ga). At least two Imbrian-aged episodes of eruptions occurred in the southern part of the Apollo basin where CE-6 is targeted to land. At ∼3.35 Ga, low-Ti (∼3.2 wt %) volcanism was active, and its products covered the entire low topographic region of the southern Apollo basin, between the inner and outer rings. Closely following its eruption at ∼3.07 Ga, high-Ti basalts (∼6.2 wt %) erupted close to the Chaffee S crater and flowed east with decreasing thickness until encountering proto-wrinkle ridges. In addition, volcanic activity in the region is significantly correlated with low crustal thickness, primarily thinned by the SPA and Apollo impact events. For regions of intermediate-thick crust (Oppenheimer crater), dikes stalled under the crater floor, spreading to form sills and a floor-fractured crater. For thin crust regions (Apollo basin interior), dikes erupted directly, forming extensive lava flows. In areas of thick highland crust, we see no evidence of extrusive activity or floor-fractured craters, suggesting that dikes there do not reach the surface and are intrusive. CE-6 samples returned from the unique geological setting will provide significant petrogenetic information to address further the paucity of farside mare basalts and the lunar nearside-farside dichotomy. To solve those scientific questions, the high-Ti mare region in south Apollo basin is recommended as the priority landing site. [ABSTRACT FROM AUTHOR]

Sulfides are important accessary minerals in lunar rocks and have great implications for lunar magma activity and subsequent evolution. Pentlandite, as one of important sulfides, has been found over 40 years. Its origin is however remain controversial. Here, we studied the texture, chemistry and crystallography of pentlandite and associated sulfides in Chang'e-5 (CE-5) lunar soils. Pentlandites occurred as lamella and veinlets in troilites, forming a troilite-pentlandite assemblage in basalt but troilite-pentlandite-taenite assemblage in breccia. Transmission electron microscopy (TEM) analyses provide the first robust evidence in lunar samples that pentlandites from both basalts and breccias were exsolved from troilite, rather than originate from the reaction between mobilized sulfur and metallic FeNi, or mobilized Ni with troilite. Considering that troilites in breccias have higher Ni content than basalts, we speculated the origin of pentlandite in breccia might involve a geological process with addition of exotic meteorites. These findings provide new clues for exploring the origin and geological evolution of sulfides on the Moon. • Pentlandites occurred as lamella and veinlets in the interior of troilites. • Troilite-pentlandite and pentlandite-taenite pairs have topotaxial relationships. • TEM demonstrated pentlandites were formed by exsolution in CE-5 basalt and breccia. • Pentlandites might indicate two geological processes in lunar soil. [ABSTRACT FROM AUTHOR]

Determining the types of lunar mare basalts (i.e., very low-Ti, low-Ti, and high-Ti) is important for constraining the chemical composition of the lunar mantle and the possible dynamic processes during their formation. To date, bulk-rock analysis and inversion of Ti abundances in olivine and plagioclase indicate the Chang'e-5 (CE5) basalts as the low-Ti type. In contrast, the chemical composition of pyroxenes, which is also used to distinguish basalt types, shows an affinity to the high-Ti type as inferred from the Fe#-Ti# relationship. To investigate this discrepancy, we reassessed the classification of CE5 basalts by combining previously available pyroxene composition and the newly obtained data for CE5 basalts and a lunar basalt meteorite (NWA 4898). Our results demonstrate a consistent decrease in Cr 2 O 3 content within pyroxenes from ∼0.8 wt% to nearly zero with magmatic differentiation, diverging from high-Ti basalts but resembling the Apollo low-Ti basalts. Approximately half of the CE5 pyroxenes with Mg# < 45 have lower Cr 2 O 3 content compared to both the Apollo low- and high-Ti basalts. In contrast, TiO 2 content in CE5 pyroxenes is higher than in most low-Ti basalts, but similar to high-Ti basalts, especially at Mg# between 60 and 40. However, such a high Ti signature is unlikely originated from a high-Ti source but more likely evolved from a low-Ti source wherein the Ti content in the melt significantly increased before eruption. This interpretation is supported by the increase-decrease of TiO 2 trend in pyroxene grains from lunar meteorites NWA 4898, NWA 4734, and LAP group. Thus, the relatively lower Cr 2 O 3 content in pyroxenes at Mg# < 45 and the relatively higher TiO 2 content in most pyroxenes ultimately resulted in high Ti# values, but the CE5 pyroxenes still record magmatic differentiation from a low-Ti melt. • Early crystallization before eruption probably increases Ti content in pyroxenes. • The relatively high Ti and low Cr content mainly account for the rise of Ti#. • The high Ti# of CE5 pyroxenes results from magmatic evolution of a low-Ti source. [ABSTRACT FROM AUTHOR]

Abstract: We report the petrography, mineralogy, trace element abundance geochemistry, and Pb–Pb geochronology of the lunar meteorite Northwest Africa (NWA) 4734 and make a comparison with the LaPaz Icefield (LAP) 02205/02224 low-Ti lunar basaltic meteorites. NWA 4734 is an unbrecciated low-Ti mare basalt composed mainly of subophitic-textured pyroxene (60vol%) and plagioclase (30%). Pyroxene, plagioclase, and olivine exhibit large compositional variations and intra-grain chemical zoning. Pyroxene and plagioclase in NWA 4734 have rare earth element (REE) concentrations and patterns similar to those of the LAPs. The crystallization age of NWA 4734, determined in situ in baddeleyite, is 3073±15Ma (2σ), nearly identical to that of the LAPs (3039±12Ma). NWA 4734 and the LAPs have similar textures, modal abundances, mineral chemistry, and crystallization ages, and are most likely source-crater paired on the Moon. One baddeleyite grain in LAP 02224 displays distinctively older and spatially variable ages, from 3349±62 to 3611±62Ma (2σ), similar to another baddeleyite grain (3109±29 to 3547±21Ma) reported by for the same meteorite. Raman spectra, cathodoluminescence, and stoichiometric studies of the baddeleyite suggest that the two older grains were not endogenic but were trapped by the parental magma. Equilibrium partition calculation shows that the parental melt from which the NWA 4734 plagioclase crystallized has much lower REE contents than its whole rock, indicating an open system during magma evolution. NWA 4734 could have originated from a parental melt with REE concentrations similar to that of the Apollo 12 olivine basalt. The magma likely assimilated a small amount (∼4wt%) of KREEP-rich material during its ascent through the lunar crust. [Copyright &y& Elsevier]