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Textural and compositional variations of apatite from rift-related gabbros, syenogabbros, syenites, quartz-syenites, and nepheline syenites of the Mid-Proterozoic Gardar Province (South Greenland) are presented and compared to apatite compositions from other rock suites. The observed zoning textures of apatite are interpreted to represent (1) primary growth zonation (concentric and oscillatory) that formed during magmatic differentiation and (2) secondary irregular overgrowths, patchy zonation, and resorption textures, assigned to metasomatic overprinting due to interaction with fluids/melts and intra-crystalline diffusion. Compositional variation in the apatites is mainly due to coupled substitutions of Ca and P by variable amounts of Si, Na, and REE, which show increasing concentrations during magmatic differentiation. Furthermore, F concentrations in apatites increase from gabbroic through syenogabbroic to syenitic rocks, whereas Cl concentrations show the opposite trend.Compared to apatite compositions from gabbroic, dioritic, and granitic rocks in general, apatites from alkaline rock suites are characterized by exceptionally high contents of REE and Si and in some alkaline rocks they attain Sr contents comparable to those reported from carbonatites. Typical low Mn and S contents are probably a result of low oxygen fugacity during crystallization at relatively high temperatures.

Rare-earth deposits associated with intrusive carbonatite complexes are the world’s most important source of these elements (REE). One of the largest deposits of this type is Maoniuping in the Mianning-Dechang metallogenic belt of eastern Tibet (Sichuan, China). In the currently mined central part of the deposit (Dagudao section), REE mineralization is hosted by a structurally and mineralogically complex Late Oligocene (26.4 ± 1.2 Ma, 40Ar/39Ar age of fluorphlogopite associated with bastnäsite) hydrothermal vein system developed in a coeval syenite intrusion. Low-grade stockworks of multiple veinlets and breccias in the lower part of the orebody grade upwards into progressively thicker veins (up to 12 m in width) that are typically zoned and comprise ferromagnesian micas (biotite to fluorphlogopite), sodium clinopyroxenes (aegirine to aegirine-augite), sodium amphiboles (magnesio-arfvedsonite to fluororichterite), K-feldspar, fluorite, barite, calcite, and bastnäsite. The latter four minerals are most common in the uppermost 80 m of the Dagudao section and represent the climax of hydrothermal activity. Systematic variations in the fluid inclusion data indicate a continuous hydrothermal evolution from about 230–400 °C (fluid inclusions in feldspar, clinopyroxene, and amphibole) to 140–240 °C (fluid inclusions in bastnäsite, fluorite, calcite). Hydrothermal REE transport was probably controlled by F−, (SO4)2−, Cl−, and (CO3)2− as complexing ligands. We propose that at Dagudao, silicate magmas produced orthomagmatic fluids that explored and expanded a fissure system generated by strike-slip faulting. Initially, the fluids had appreciable capacity to transport REE and, consequently, no major mineralization developed. The earliest minerals to precipitate were alkali- and Fe-rich silicates containing low levels of F, which caused progressive enrichment of the fluid in Ca, Mg, F, Cl, REE, (SO4)2−, and (CO3)2−, leading to the crystallization of aegirine-augite, fluororichterite, fluorphlogopite, fluorite, barite, calcite, and bastnäsite gradually. Barite, fluorite, calcite, and bastnäsite are the most common minerals in typical ores, and bastnäsite generally postdates these gangue minerals. Thus, it is very probable that fluid cooling and formation of large amount of fluorite, barite, and calcite triggered bastnäsite precipitation in the waning stage of hydrothermal activity.

We report high-precision K isotopes, apatite U–Pb ages, whole-rock elements and Sr–Nd isotopes for the Saima nephelite syenite in the North China Craton. Trace-element and Sr–Nd–Hf–O isotope data indicate the presence of subducting sediments in the source region, while K isotopic compositions show a narrow range between –0.54 ‰ and –0.28 ‰, with an average of –0.41 ± 0.06 ‰, identical to the value of the asthenosphere. The nearly identical K isotopic compositions are low probability events compared with the K isotopic compositions of island arc lavas reported previously (–1.55 ‰ to +0.2 ‰). Although crustal contamination is consistent with the Sr–Nd–K isotopic data, alternatively we propose that the isotopic data also reconcile with the interaction between cratonic roots and the underlying convective asthenosphere, if this interaction is over prolonged periods of time. Numerical simulations successfully reproduced the observed data, if the metasomatism of the lithospheric mantle root, the source of the Saima alkaline rocks, occurred 500 Ma ago. Our study reveals that the isotopic compositions of fast-diffusion components in a lithospheric mantle metasomatized by ancient subducting melts can be effectively homogenized by convective asthenosphere through diffusion over a long time interval.

This paper describes a detailed petrographic and isotopic study of hypabyssal sheets of quartz-syenite that represent the ultimate differentiation product of the oceanite alkaline magmatic reservoir of the Piton des Neiges stratovolcano (Reunion Island). Clay minerals of the corrensite to chlorite series crystallized during the late-magmatic activity, with quartz, carbonates and accessory minerals from juvenile fluids filling the primary porosity of the quartz-syenite. It is proposed that a double chemical transfer occurred at the end of the crystallization process: degassing of the exsolved CO2-rich and SiO2-rich fluid from the magmatic chamber through the porous quartz-syenite and diffusion of Al, Fe and Mg from the intruded basalts affected by the juvenile fluids towards the primary porosity of the quartz-syenite, feeding the crystallization of late-magmatic clays in the residual primary pores after quartz and carbonate deposition. This process may be generalized to alkaline plutonism, as well as to the primitive crusts of terrestrial planets, and may be the first source of clays in early planets.

Calcioancylite-(La), ideally (La,Ca)2(CO3)2(OH,H2O)2, has been discovered from nepheline syenite of the Gejiu alkaline complex in the Honghe Hani and Yi Autonomous Prefecture, Yunnan Province, China. The mineral occurs as aggregates of subhedral grains, and the size of single crystals varies between 5-20 µm. Calcioancylite-(La) is colourless to pale pinkish grey and has transparent to translucent lustre. It is brittle with a Mohs hardness of 4. The calculated density is 4.324 g/cm3. The mineral is biaxial (-), with α =1.662, β = 1.730, γ = 1.771, 2Vmeas. = 70°(1) and 2Vcalc. = 73°. Electron microprobe analysis for holotype material yielded an empirical formula of (La0.58Ce0.55Pr0.14Nd0.10Ca0.39Sr0.20K0.04)Σ2.00(CO3 )2[(OH)1.25F0.06·0.69H2O]Σ2.00. Calcioancylite-(La) is orthorhombic, with space group Pmcn, a = 5.0253(3) Å, b = 8.5152(6) Å, c = 7.2717(6) Å, V = 311.17(4) Å3 and Z = 2. By using single-crystal X-ray diffraction, the crystal structure has been determined and refined to a final R1 = 0.0652 on the basis of 347 independent reflections (I > 2σ). The seven strongest powder X-ray diffraction lines [d in Å (I) (hkl)] are: 2.334 (100) (013), 2.970 (80) (121), 4.334 (75) (110), 3.678 (68) (111), 2.517 (55) (200), 2.647 (47) (031) and 2.077 (44) (221). Calcioancylite-(La) is the La-analogue of calcioancylite-(Ce) and is a new member of ancylite-group minerals. The mineral and its name have been approved by the Commission on New Minerals, Nomenclature and Classification of the International Mineralogical Association (IMA2021-090).

Zircon laser ablation inductively coupled plasma mass spectrometry U-Pb age and geochemical and Sr-Nd-Hf isotopic data are reported for the Bachu layered intrusive complex (BLIC) in the western Tarim Block and are used to assess the possible presence of a Permian large igneous province (LIP) in the region. The BLIC intrudes the Silurian-Devonian sedimentary rocks, and our U-Pb zircon dating gives a crystallization age of Ma. Rock types of the BLIC include pyroxenite, diorite, syenite, and quartz syenite, with a wide range of SiO2 contents (38.6%-68.7%) and variably high alkalinity (Na2O+K2O = 1.5%-12.0%, K2O/Na2O = 0.23-0.9). They are enriched in Rb, Ba, Th, Nb, Ta, Zr, Hf, and light rare earth elements. Isotopically, they are characterized by positive whole-rock εNd(t) values (0.25-2.8, mostly above 2.0) and zircon Hf(t) values (5.8-8.9) and low initial 87Sr/86Sr ratios (0.7035-0.7045). These features suggest that the BLIC was likely formed by crystal cumulation and fractionation (with negligible crustal contamination) of alkali basalts derived from an ocean island basalt-like mantle source (i.e., the asthenospheric mantle) in an extensional regime. We suggest that these mid-Permian igneous rocks, in combination with the voluminous coeval basalts and intrusive rocks covering an total area of ca. 250,000 km2 in the Tarim Block and surrounding regions, constitute an LIP (the \"Bachu LIP\") and that the BLIC could be the residue of a feeder for this LIP.

Bortolanite, a rare mineral of the rinkite group, seidozerite supergroup occurs in two different associations in the Lovozero massif in the Kola Peninsula, Russia: (1) together with ferri-katophorite and phlogopite, it forms porous or mesh aggregates (symplectitic accretions) with euhedral contours in the contact zone of a volcano-sedimentary xenolith and eudialyte lujavrite at Kuamdespakhk Mt. and (2) in intergrowths with titanite and fluorcaphite in the poikilitic feldspathoid syenites at Sengischorr Mt. In both cases, bortolanite was found in association with rosenbuschite that is close to it in chemical composition, but unlike bortolanite, it contains no REEs. The mineral is triclinic, space group P1̄, a = 9.5807(5), b = 5.6943(4), c = 7.2813(4) Å, α = 89.891(5)°, β = 100.959(4)°, γ = 101.241(5)°, V = 382.25(4) Å3 and Z = 1. The Lovozero bortolanite differs from the Brazilian holotype sample from de Caldas alkaline massif, Minas Gerais, due to the presence of (OH)-groups in its composition, which is indicated by Raman data. A combination of single-crystal X-ray diffraction data and electron microprobe data provides the following crystal-chemical formula: (Ca1.97Ce0.01Nd0.01Th0.01)Σ2(Ca1.39Zr0.61)Σ2(Na0.72 Ca0.28) Σ1(Na1.36Ca0.56Mn0.03Zn0.01)Σ1.96(Ti0.78Zr0.08Nb0.0 5Mg0.05 Fe0.04)Σ1Si4O14((OH)0.92O0.87F0.21)Σ2F2.

Fluorsigaiite, ideally Ca2Sr3(PO4)3F, is a new Sr analogue of fluorphosphohedyphane and a new member of the apatite supergroup. It was discovered in lujavrite from the Saima alkaline complex, Liaoning Province, China. Fluorsigaiite commonly occurs as individual prismatic, columnar and platy crystals of 10 to 50 µm in size, associated with microcline, nepheline, aegirine, natrolite, eudialyte, fluorapatite, a fluorstrophite-like mineral, stronadelphite and calcite. Occasionally, crystals of fluorsigaiite form prismatic aggregates in the interstices of lujavrite. Fluorsigaiite is translucent to transparent, colourless to yellowish white with a vitreous lustre and without fluorescence. The estimated Mohs hardness is 5, and the tenacity is brittle with uneven fractures. The calculated density is 3.842 g/cm3. Optically, fluorsigaiite is uniaxial (-) with ω = 1.64(1) and ε = 1.63(1) in white light and without dispersion. The mean chemical composition (in wt.%) of fluorsigaiite is Na2O 0.75, CaO 15.17, SrO 44.44, La2O3 3.64, Ce2O3 2.22, Pr2O3 0.19, Nd2O3 0.13, Sm2O3 0.05, Gd2O3 0.23, P2O5 31.87, F 1.91, H2O 0.46, sum 100.26, giving the empirical formula (Sr2.82Ca1.79Na0.16La0.15Ce0.09Pr0.01Nd0.01Gd0.01)Σ5. 04P2.97O12[F0.66(OH)0.34]Σ1, which is calculated on the basis of 13 total anions and F+(OH) = 1. The strongest eight lines of its powder X-ray diffraction pattern [d, Å (I, %) (hkl)] are: 3.563 (15) (002), 3.275 (15) (102), 3.144 (19) (120), 2.876 (100) (121), 2.861 (96) (112), 2.772 (27) (300), 1.991 (17) (222) and 1.895 (23) (213). Fluorsigaiite is hexagonal, in the space group P63/m and unit-cell parameters refined from single-crystal X-ray diffraction data are: a = 9.6101(2) Å, c = 7.1311(1) Å, V = 570.35(3) Å3 and Z = 2. It is isostructural with hedyphane-group minerals, and contains different prevailing (species-defining) Ca and Sr cations at the Ca1 and Ca2 sites, respectively. Fluorsigaiite was probably formed from Sr-rich fluids at late-magmatic or hydrothermal stage of the Saima lujavrite.

The Soarinho Alkaline Intrusion, southeastern Brazil, makes up part of the Serra do Mar Igneous Province, and it is composed of alkali feldspar syenite, alkali feldspar trachyte, quartz syenite, and monzonite. Geochemical and geochronological analyses of the Soarinho were compared with data from its neighbors, Rio Bonito and Tanguá. Zircon U-Pb Laser Ablation ages show that Soarinho is younger than Rio Bonito and Tanguá. Ages obtained from the monzonite (60 ± 2 Ma), alkali feldspar syenite (58 ± 2 Ma), and quartz syenite (58 ± 2 Ma) are indistinguishable within error. One nepheline syenite sample from Tanguá gives an age equal to those of Rio Bonito already published (65 ± 1 Ma). Petrographic and geochemical data show a clear contrast among Soarinho, Rio Bonito, and Tanguá. Lu-Hf isotopic data for the three alkaline intrusions (all negative) point to some similarities in their sources. The data suggest an enriched mantle source for Soarinho; however, an older continental crust contribution cannot be discarded.

The Moine Thrust Zone forms the Caledonian orogenic thrust front where the Moine Supergroup metamorphic rocks have been thrust westward across the Laurentia plate stable foreland, comprising Archean-Proterozoic granulite and amphibolite facies rocks (Lewisian gneisses), with unconformably overlying Mesoproterozoic and Neoproterozoic Torridonian clastic sediments and Cambrian-Ordovician passive margin sedimentary rocks. Four major thrusts beneath the Moine thrust in the Assynt window include the (i) Ben More Thrust, which places the Loch Ailsh syenite intruded into Lewisian basement and Cambrian-Ordovician sedimentary rocks over the Sole thrust sheet, (ii) Glencoul thrust, which places Lewisian basement and folded cover rocks over Cambrian-Ordovician sedimentary rocks, (iii) Borralan thrust, which carries a large alkaline syenite intrusion beneath the Ben More roof thrust and (iv) the Sole thrust sheet, which carries imbricated Cambrian-Ordovician sedimentary rocks and lamprophyre sills over the stable foreland. Three further thrust sheets within the Lewisian basement gneisses are now recognised through restoration of balanced cross-sections, which were responsible for doming of the Assynt window. Although the Moine thrust is mapped as a single line on the map it encompasses, (a) deep ductile shear zone formed of mylonites derived from hangingwall Moine schists, footwall Cambrian quartzites and Ordovician limestones, and basement Lewisian gneisses, (b) roof thrust of the Glencoul and Ben More Thrust sheets and (c) brittle out-of-sequence motion where the Moine schists have been thrust over mylonites, which directly overlie the stable foreland (Knockan Crag).