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\"Cr-Zr-Ca armalcolite\" is a mineral originally found in Apollo samples five decades ago. However, no structural information has been obtained for this mineral. In this study, we report a new occurrence of \"Cr-Zr-Ca armalcolite\" and its associated mineral assemblage in an Mg-suite lithic clast (Clast-20) from the brecciated lunar meteorite Northwest Africa 8182. In this lithic clast, plagioclase (An=88-91), pyroxene (Mg#[Mg/(Mg+Fe)]=0.87-0.91) and olivine (Mg#=0.86-0.87) are the major rock-forming minerals. Armalcolite and \"Cr-Zr-Ca armalcolite\" are observed with other minor phases including ilmenite, chromite, rutile, fluorapatite, merrillite, monazite, FeNi metal, and Fe-sulfide. Based on 38 oxygen atoms, the chemical formula of \"Cr-Zr-Ca armalcolite\" is (Ca0.99Na0.01)Σ1.00(Ti14.22 Fe2.06 Cr2.01 Mg1.20 Zr0.54Al0.49 Ca0.21 Y0.05 Mn0.04 Ce0.03 Si0.03 La0.01 Nd0.01 Dy0.01)Σ20.91O38. Electron backscatter diffraction (EBSD) results reveal that the \"Cr-Zr-Ca armalcolite\" has a loveringite R3 structure, differing from the armalcolite Bbmm structure. The estimated hexagonal cell parameters a and c of \"Cr-Zr-Ca armalcolite\" are 10.55 and 20.85 Å, respectively. These structural and compositional features indicate that \"Cr-Zr-Ca armalcolite\" is loveringite, not belonging to the armalcolite family. Comparison with \"Cr-Zr-Ca armalcolite\" and loveringite of other occurrences implies that loveringite might be an important carrier of rare earth elements in lunar Mg-suite rocks. The compositional features of plagioclase and mafic silicate minerals in Clast-20 differ from those in other Mg-suite lithic clasts from Apollo samples and lunar meteorites, indicating that Clast-20 represents a new example of diverse lunar Mg-suite lithic clasts.

Loveringite, a rare member of the crichtonite group with nominal formula (Ca,Ce)(Ti,Fe,Cr,Mg)21O38, was found in the Khamal layered mafic intrusion, the first known locality for this mineral in the Arabian Shield. The Khamal intrusion, a large post-collisional mafic complex, is lithologically zoned, bottom to top, from olivine gabbro through gabbronorite, hornblende gabbro, anorthosite, and diorite to quartz diorite. Loveringite is found near the base of the complex, as an intercumulus phase in olivine gabbro. Most loveringite grains are homogeneous, although a few grains are zoned from cores rich in TiO2, Al2O3, Cr2O3, and CaO towards rims rich in FeO*, ZrO2, V2O3, Y2O3, and rare earth elements (REE). Petrographic relations indicate that loveringite formed after crystallization of cumulus olivine, pyroxenes, and plagioclase. Anhedral and corroded crystals of loveringite are surrounded by reaction rims of Mn-bearing ilmenite and baddeleyite, suggesting that the residual liquid evolved into and subsequently out of the stability field of loveringite. The budget of incompatible elements (Zr, Hf, REE, U, and Th) hosted in loveringite is anomalous for a primitive mafic liquid. Saturation in loveringite is likely the result of early contamination of the primary melt by anatexis of country rock, followed by isolation of evolving liquid in intercumulus space that restricted communication with the overlying magma chamber. The zoned crystals likely reflect diffusive equilibration between residual loveringite grains and their reaction rims of ilmenite.

Alkali-bearing Ti oxides were identified in mantle xenoliths enclosed in kimberlite-like rocks from Limeira 1 alkaline intrusion from the Alto Paranaíba Igneous Province, southeastern Brazil. The metasomatic mineral assemblages include mathiasite-loveringite and priderite associated with clinopyroxene, phlogopite, ilmenite and rutile. Mathiasite-loveringite (55–60 wt.% TiO2; 5.2–6.7 wt.% ZrO2) occurs in peridotite xenoliths rimming chromite (∼50 wt.% Cr2O3) and subordinate ilmenite (12–13.4 wt.% MgO) in double reaction rim coronas. Priderite (Ba/(K+Ba)< 0.05) occurs in phlogopite-rich xenoliths as lamellae within Mg-ilmenite (8.4–9.8 wt.% MgO) or as intergrowths in rutile crystals that may be included in sagenitic phlogopite. Mathiasite-loveringite was formed by reaction of peridotite primary minerals with alkaline melts. The priderite was formed by reaction of peridotite minerals with ultrapotassic melts. Disequilibrium textures and chemical zoning of associated minerals suggest that the metasomatic reactions responsible for the formation of the alkali-bearing Ti oxides took place shortly prior the entrainment of the xenoliths in the host magma, and is not connected to old (Proterozoic) mantle enrichment events.