Sodalite Syenite Research Articles

Büyük Kuluncak (Malatya) Nb-U-NYE-Zr-Li Yatağının Cevherleşme Özellikleri ile Alterasyon ilişkisi

Rare Earth Elements (REE) + Niobium (Nb) + Uranium (U) + Zircon (Zr) + Lithium (Li) formations are investigated which are related with alkaline Upper Cretaceous - Lower Paleocene Kuluncak Syenitoid that settled by cutting the Kuluncak ophiolite in the north of Kuluncak (Malatya) town. The alkaline magma-related Büyük Kuluncak REE - Nb - U deposit, which is enriched with regard to rare metals (Nb, Zr, and Rb), is the first economic deposit of our country. The deposit formed related to alkaline characterized foid syenite, sodalite syenite, syenite, alkaline feldspar syenite rocks which intruded into Triassic - Lower Cretaceous limestones of the Domuzdağı Nappe. The REE and fluorites with related elements formed in magmatic rocks, the contact zone of these rocks with limestones, in pegmatitic intrusions and in fluorites formed with the effect of the contact metasomatism. The purpose of this study is to interpret ore properties and the alteration grade of the rocks which formed the deposit. The REE are enriched in argillized and highly argillized samples. However, the REE composition of fresh samples are relatively low. Therefore, the REE are enriched twice or three times due to the effects of alteration and argillization of the hydrothermal fluids in the parent rock and contact metasomatism and alterations that occur both syn- and post-emplacement of syenite.

Chemistry and Sr-Nd isotope signature of amphiboles of the magnesio-hastingsite–pargasite–kaersutite series in Cenozoic volcanic rocks: Insight into lithospheric mantle beneath the Bohemian Massif

Amphibole phenocrysts, xenocrysts and cumulate xenoliths from Cenozoic volcanic rocks of the Bohemian Massif (BM) belong to the magnesio-hastingsite–pargasite–kaersutite series. Their host rocks are mostly basaltic lavas, stocks, dykes and breccia pipe fills, less commonly also felsic rocks. Felsic rocks with amphibole cumulate xenoliths represent differentiated magmas which have undergone polybaric fractionation of the mafic minerals. The calculated p–T conditions suggest that almost all amphiboles crystallized in a relatively narrow temperature range (1020–1100 °C) at depths of ~20–45 km (0.7–1.2 GPa) during the magma ascent. These p–T estimates are compatible with the published experimental data on the stability of kaersutite. We therefore suggest the presence of a deep magma chamber situated close to the crust–mantle boundary where amphibole xenoliths to megacrysts could have formed. Nevertheless, crystallization of rare amphibole rims during the magma ascent was observed in a hornblendite cumulate in sodalite syenite from “Giegelberg”. The lowest concentration of incompatible elements in the amphiboles was found in xenocrysts in alkaline basaltic rocks and mantle xenoliths and megacrysts, followed by phenocrysts/xenocrysts in lamprophyric rocks, xenocrysts of cumulates in felsic rocks, and phenocrysts in subvolcanic rocks. Amphibole compositional and Sr-Nd isotope characteristics resemble those of amphiboles from metasomatic clinopyroxene/amphibole veins in mantle peridotites. The initial 143Nd/144Nd and 87Sr/86Sr ratios of amphiboles (0.51266–0.51281 and 0.70328–0.70407, respectively) are similar to those of their whole rocks (0.51266–0.51288 and 0.70341–0.70462, respectively). Amphiboles of the magnesio-hastingsite–pargasite–kaersutite series of the BM are mostly chemically homogeneous, with no pronounced Mg-Fe fractionation and zoning. The amphiboles are characterized by relatively homogeneous εNd(i) = +1.4 to +3.8 values: only a single sample from the České Středohoří Volcanic Complex (CSVC) yielded a negative εNd(i) (−0.6). This testifies to locally elevated proportions of recycled Variscan crustal material during melting of mantle peridotites rich in clinopyroxene–amphibole veins. These veins were formed by metasomatic fluids enriched in High Field Strength Elements (HFSE) and are isotopically similar to Enriched Mantle1 (EM1)-type mantle. Amphibole host rocks occur in areas with a significant concentration of basaltic magmas in rift zones along lithospheric block boundaries of the BM. Lithospheric mantle beneath such zones was probably strongly influenced by metasomatic fluids during the formation of clinopyroxene–amphibole veins in mantle peridotite that facilitated the generation of basaltic magma with amphibole.

Nolzeite, Na(Mn,□)2[Si3(B,Si)O9(OH)2]·2H2O, a new pyroxenoid mineral from Mont Saint-Hilaire, Québec, Canada

AbstractNolzeite, Na(Mn,□)2[Si3(B,Si)O9(OH)2]·2H2O, is a new mineral found in altered sodalite syenite at the Poudrette quarry, La Vallée-du-Richelieu, Montérégie (formerly Rouville County), Québec, Canada. Crystals are colourless to pale green and are acicular with average dimensions of 5 μm × 8 μm × 55 μm. They occur as radiating to loose, randomly oriented groupings within vugs associated with aegirine, nepheline, sodalite, eudialyte-group minerals, analcime, natron, pyrrhotite, catapleiite, steedeite and the unidentified mineral, UK80. Nolzeite is non-pleochroic, biaxial, withnmin= 1.616(2) andnmax= 1.636(2) and has a positive elongation. The average of six chemical analyses gave the empirical formula: Na1.04(Mn1.69□0.24Fe0.05Ca0.02)∑=2.00(Si2.96S0.04)∑=3.00(B0.70Si0.30)∑=1.00O9(OH)2·2H2O based on 13 anions. The Raman spectrum shows six distinct bands occurring at ∼3600–3300 cm–1and 1600–1500 cm–1(O–H and H–O–H bending), 1300–1200 cm–1(B–OH bending), 1030–800 cm–1(Si–O–Si stretching) as well as 700–500 cm–1and 400–50 cm–1(Mn–O and Na–O bonding, respectively). The FTIR spectrum for nolzeite shows bands at ∼2800 –3600 cm–1(O–H) stretching, a moderately sharp band at 1631 cm –1(H–O–H) bending, strong, sharp bands at ∼650 –700 cm–1, ∼800 –840 cm–1, and ∼900–1100 cm–1(Si–O and B –O) bonds. Nolzeite is triclinic, crystallizing in space groupPwitha= 6.894(1),b= 7.632(2),c= 11.017(2) Å, α= 108.39(3), β= 99.03, γ = 103.05(3)°,V= 519.27 Å3, andZ= 2. The crystal structure was refined toR= 12.37% and wR2= 31.07% for 1361 reflections (Fo> 4σFo). It is based on chains of tetrahedra with a periodicity of three (i.e. adreierchain) consisting of three symmetrically independent SiO4tetrahedra formingC-shaped clusters closed by BO2(OH)2tetrahedra, producing single loop-brancheddreierborosilicate chains. The chains are linked through shared corners to double chains of edge-sharing MnO5(OH) octahedra. Nolzeite is a chain silicate closely related to steedeite and members of the sérandite–pectolite series. Paragenetically, nolzeite is late-stage, probably forming under alkaline conditions and over a narrow range of low pressures and temperatures.

Garronite-Na, A New Zeolite Species From Mont Saint-Hilaire, Québec

Abstract Garronite-Na, ideally Na 6 (Al 6 Si 10 O 32 ) · 7–10H 2 O, a new mineral species, was found in the Mont Saint-Hilaire quarry, Quebec. It occurs in vugs in sodalite syenite. The crystals are transparent to translucent, pale yellow in color, with a white streak and vitreous luster. Crystal aggregates are botryoidal masses up to 1.5 mm in size. The mineral is brittle with a good {011} parting. Associated minerals include aegirine, natrolite, gmelinite, and gonnardite. Garronite-Na is monoclinic, space group I 2, with unit-cell parameters refined from single crystal X-ray diffraction data: a 9.990(2), b 10.032(2), c 10.036(2) A, β 90.11(3)°, V 1005.8(7) A 3 , and Z = 1. Electron microprobe analyses give (average of eight with ranges): Na 2 O 14.28 (10.38–18.55), K 2 O 1.10 (0.51–3.07), CaO 0.04 (0.01–0.11), MnO 0.02 (0.00–0.09), BaO 0.09 (0.00–0.44), FeO 0.02 (0.00–0.07), Al 2 O 3 26.89 (25.71–28.96), Nb 2 O 5 0.04 (0.00–0.10), SiO 2 46.71 (42.65–49.32), TiO 2 0.00 (0.00–0.02), H 2 O 10.73 (10.22–11.22) (determined by crystal structure analysis), total 99.92 wt.%. The empirical formula, based on the crystal-structure analysis and ideally showing 16 (Si + Al) and 32 O atoms in the framework and 7.3 H 2 O groups is: (Na 5.650 K 0.286 Ca 0.009 Ba 0.007 Mn 0.003 Fe 0.003 Nb 0.004 ) ∑5.960 (Al 6.468 Si 9.532 ) ∑16 O 32 ·7.3H 2 O + (O 0.67 ). Garronite-Na is biaxial positive, α = 1.489 ± 0.001, β = 1.492 ± 0.001, γ = 1.496 ± 0.001, 2 V meas. = 75(3)°, 2 V calc = 82(7)°. The strongest eight reflections of the X-ray powder-diffraction pattern [ d (obs.) in A ( I ) ( hkl )] are: 7.098 (79) (011, 110), 5.026 (32) (002, 200), 4.101 (77) (112, , , 121), 3.172 (013, 031, 130, 310), 2.904 (14) (, 222), 2.685 (64) (123, ), 1.9669 (14) (015, , 341, 510), 1.7213 (11) (, 053, 350, 433). The Mohs hardness is ∼4; D (meas.) = 2.19(2) and D (calc.) = 2.071 g/cm 3 . The structure has been refined to an R index of 0.056 for 2952 unique, observed reflections. The structure is a Si/Al–O framework like that of gismondine with Na atoms and H 2 O groups in the cages.

STEEDEITE, NaMn2[Si3BO9](OH)2: CHARACTERIZATION, CRYSTAL-STRUCTURE DETERMINATION, AND ORIGIN

Steedeite, ideally NaMn 2 Si 3 BO 9 (OH) 2 , is a new mineral discovered in altered sodalite syenite at the Poudrette quarry, La Vallee-du-Richelieu, Monteregie (formerly Rouville County), Quebec, Canada. Crystals of steedeite are colorless to pale pink, and acicular with average dimensions of 0.006 × 0.011 × 0.51 mm. They occur as radiating to loose, randomly oriented groupings within vugs associated with aegirine, nepheline, sodalite, eudialyte-group minerals, analcime, natron, pyrrhotite, catapleiite, and two other unidentified minerals temporarily designated UK78 and UK80. Steedeite is transparent to translucent with a vitreous luster and has a weak pale green to pale yellow fluorescence under medium-wave radiation. No partings or cleavages were observed, although crystals exhibit an uneven fracture. The calculated density is 3.106 g/cm 3 . Steedeite is nonpleochroic, biaxial with n min = 1.636(2) and n max = 1.656(2) and a positive elongation. Chemical analyses (n = 14) from seven crystals gave an average (range, standard deviation) of: Na 2 O 7.51 (6.78–8.32, 0.44), CaO 0.17 (0.08–0.22, 0.03), MnO 31.02 (29.91–32.83, 0.93), FeO 0.86 (0.76–1.01, 0.07), SiO 2 46.34 (40.39–49.29, 2.56), S 0.39 (*b.d.– 2.36, 0.71) (*b.d. = below detection), B 2 O 3 (calc.) 8.73, and H 2 O (calc.) 4.52, total 99.53 wt.%. The empirical formula is: Na 0.97 (Mn 1.75 Fe 0.05 Ca 0.01 ) ∑1.83 (Si 3.07 S 0.02 ) ∑3.09 BO 9 (OH) 2 , or ideally NaMn 2 Si 3 BO 9 (OH) 2 . The presence of both B and OH in steedeite were inferred from the refinement of the crystal structure. The Raman spectrum for steedeite show bands at 3250–3500 cm –1 attributed to O–H stretching, strong sharp bands at 575–750 cm −1 and 825–1075 cm −1 attributed to Si–O bonds and possibly B–O bonding, as well as weak to strong bands at 50–500 cm −1 attributed to Na–O/Mn–O bonds. Steedeite crystallizes in space group P 1 ¯ (#2) with a 6.837(1), b 7.575(2), c 8.841(2) A, α 99.91(3), β 102.19, γ 102.78(3)°, V 424.81 A 3 , and Z = 2. The strongest six lines on the X-ray powder-diffraction pattern [ d in A (I) ( hkl )] are: 8.454 (100) (00 1 ¯ ), 7.234 (39) (00 1 ¯ ), 3.331 (83) (1 2 ¯ 1, 0 1 ¯ 2 ¯ , 20 1 ¯ , 1 1 ¯ 2), 3.081 (38) (0 2 ¯ 1 ¯ ), 2.859 (52) (0 1 ¯ 3), and 2.823 (80) (21 1 ¯ ). The crystal structure of steedeite was refined to R = 1.68% and wR 2 = 4.96% for 2409 reflections ( F o > 4σ F o ). It is based on silicate chains with a periodicity of three (i.e., dreier chain) consisting of four-membered borosilicate rings of composition [BSi 3 O 9 (OH) 2 ] 5− . The borosilicate chains are classed as single loop-branched dreier chains that are linked together through shared corners to bands of edge-sharing MnO 5 (OH) octahedra. Steedeite is a chain silicate mineral closely related to the serandite-pectolite series of the pyroxenoid group and is the first mineral found to contain single loop-branched dreier silicate chains.

Tertiary alkaline Roztoky Intrusive Complex, České středohoří Mts., Czech Republic: petrogenetic characteristics

The Ceske středohoři Mts. is the dominant volcanic center of the Ohře (Eger) rift zone. It hosts the Roztoky Intrusive Complex (RIC), which is made up of a caldera vent and intrusions of 33–28-Ma-old hypabyssal bodies of essexite–monzodiorite–sodalite syenite series accompanied by a radially oriented 30–25-Ma-old dike swarm comprising about 1,000 dikes. The hypabyssal rocks are mildly alkaline mostly foid-bearing types of mafic to intermediate compositions. The dike swarm consists of chemically mildly alkaline and rare strongly alkaline rocks (tinguaites). The geochemical signatures of the mildly alkaline hypabyssal and associated dike rocks of the RIC are consistent with HIMU mantle sources and contributions from lithospheric mantle. The compositional variations of essexite and monzodiorite can be best explained by fractional crystallization of parent magma without significant contributions of crustal material. On the other hand, the composition of monzosyenite, leuco-monzodiorite and sodalite syenite reflects fractional crystallization coupled with variable degrees of crustal assimilation. It is suggested that the parent magmas in the Ohře rift were produced by an adiabatic decompression melting of ambient upper mantle in response to lithospheric extension associated with the Alpine Orogeny.

Petrology and geochemistry of the Tertiary alkaline intrusive rocks at Doupov, Doupovské hory Volcanic Complex (NW Bohemian Massif)

*Corresponding author Field observations, petrography, geochemical data and the results of K–Ar dating are presented for Oligocene (c. 30–29 Ma) alkaline intrusions at the former township of Doupov (Duppau) in the central part of the Doupovske hory Volcanic Complex (DHVC). The Doupov Intrusive Complex (DIC) is a very limited in area (< 2 km 2 ) but is petrographically highly variable. Several phaneritic rock types have been identified, including clinopyroxenite (both the clinopyroxenite-dominated breccia and xenoliths in younger intrusive phases), essexite, sodalite-bearing monzodiorite, sodalite monzosyenite to nepheline–sodalite syenite, and highly mafic to felsic nephelinolites (melteigite–ijolite–urtite). These rocks are accom panied by vent breccias, and a thermal and metasomatic aureole with zones of pervasive phlogopitization. Phaneritic intrusions and their host rocks are cut by thin aphanitic dykes ranging from mafic alkaline lamprophyres to felsic trachytes and phonolites. All the intrusions are characterized by undersaturated alkaline compositions with high abundances of incompatible elements. Geochemical variations and also subtle differences in the isotopic compositions of Sr and Nd suggest that the less undersaturated essexitic rocks and sodalite syenitoids do not form a common evolutionary line with highly undersaturated nephelinolites. Nephelinolites are isotopically close to the “European Asthenospheric Reservoir” or the “Common Mantle Reservoir” compositions and interaction of their parental magmas with the continental crust was negligible. Magmatic evolution of nephelinolites with “dry” mineral assemblages was dominated by fractionation of clinopyroxene accompanied at the early stage by olivine, and later by titanite, magnetite and apatite. Essexite is isotopically more different though still within the field of mafic lavas from DHVC and other volcanic complexes in Central and Western Europe. Either its parental magma originated in heterogeneous mantle with more distinct lithospheric signature or this magma reacted with the continental crust during its ascent and fractionation. Sodalite monzosyenite displays significantly higher 87 Sr/ 86 Sr ratios and its parental magma probably interacted even more intensively with the crustal rocks. The K–Ar ages of phaneritic intrusive rocks from Doupov are c. 30–29 Ma. Intrusions are older than the tephrite–basanite and foidite lavas forming the upper parts of the DHVC. The rock association resembles that accompanying many carbonatite intrusions around the world. However, brecciation and high-temperature metasomatic overprint including the extensive phlogopitization may be related to ijolitic magma. Nevertheless, the presence of carbonatite at some deeper level cannot be excluded.

Reverse age zonation of zircon formed by metamictisation and hydrothermal fluid leaching

Understanding the stability of radiation-damaged zircon is crucial to the application of zircon to U–Pb geochronology, especially for zircons rich in radioactive nuclides. Electron microprobe and laser Raman spectral analyses show that zircons from the Ejinao sodalite syenite in Southeast China are composed of cores without zonation and oscillatory rims. The cores are rich in uranium and have experienced increased metamictisation. An internal sieved structure and radial cracks were formed by radiation damage and radiation-induced volume expansion. Infrared spectral analyses show that zircon from the Ejinao sodalite syenite contains large amounts of OH and H2O. This finding suggests that the zircon crystals experienced hydrothermal alteration.The Pb loss of zircons is ascribed to their interaction with a hydrothermal fluid derived from the Ejinao syenite. Radiogenic Pb4+ situated in α-recoil damaged sites has been significantly reduced to Pb2+ by the hydrothermal fluid, becoming incompatible in the crystal lattice and highly mobile in solution; consequently, it has been leached out from the zircon. This Pb loss leads to diverse 206Pb/238U ages from 134Ma to 147Ma, and severe Pb loss from the inner core even produces reverse age zonations, with cores approximately 5Ma younger than the rims. The real crystallisation age for zircons from the Ejinao sodalite syenite should be approximately 145Ma, considering the entire range of analytical data obtained by both the SHRIMP and LA-ICPMS methods.

The Banhadão Alkaline Complex, Southeastern Brazil: source and evolution of potassic SiO2-undersaturated high-Ca and low-Ca magmatic series

The Cretaceous Banhadao alkaline complex in southeastern Brazil presents two potassic SiO2-undersaturated series. The high-Ca magmatic series consist of initially fractionated olivine (Fo92-91) + diopside (Wo48-43En49-35Ae0-7), as evidenced by the presence of xenocrysts and xenoliths. In that sequence, diopside (Wo47-38En46-37Ae0-8) + phlogopite + apatite + perovskite (Prv>92) crystallized to form the phlogopite melteigite and led to the Ca enrichment of the magma. Diopside (Wo47-41En32-24 Ae3-14) continued to crystallize as an early mafic mineral, followed by nepheline (Ne74.8-70.1Ks26.3-21.2Qz7.6-0.9) and leucite (Lc65-56) and subsequently by melanite and potassic feldspar (Or85-99Ab1-7) to form melanite ijolites, wollastonite-melanite urtites and melanite-nepheline syenites. Melanite-pseudoleucite-nepheline syenites are interpreted to be a leucite accumulation. Melanite nephelinite dykes are believed to represent some of the magmatic differentiation steps. The low-Ca magmatic series is representative of a typical fractionation of aegirine-augite (Wo36-29En25-4Ae39-18) + alkali feldspar (Or57-96Ab3-43) + nepheline (Ne76.5-69.0Ks19.9-14.4Qz15.1-7.7) + titanite from phonolite magma. The evolution of this series from potassic nepheline syenites to sodic sodalite syenites and sodalitolites is attributed to an extensive fractionation of potassic feldspar, which led to an increase of the NaCl activity in the melt during the final stages forming sodalite-rich rocks. Phonolite dykes followed a similar evolutionary process and also registered some crustal assimilation. The mesocratic nepheline syenites showed interactions with phlogopite melteigites, such as compatible trace element enrichments and the presence of diopside xenocrysts, which were interpreted to be due to a mixing/mingling process of phonolite and nephelinite magmas. The geochemical data show higher TiO2 and P2O5 contents and lower SiO2 contents for the high-Ca series and different LILE evolution trends and REE chondrite-normalized patterns as compared to the low-Ca series. The 87Sr/86Sr, 143Nd/144Nd, 206Pb/204Pb and 208Pb/204Pb initial ratios for the high-Ca series (0.70407–0.70526, 0.51242–0.51251, 17.782–19.266 and 38.051–39.521, respectively) were slightly different from those of the low-Ca series (0.70542–0.70583, 0.51232–0.51240, 17.758–17.772 and 38.021–38.061, respectively). For both series, a CO2-rich potassic metasomatized lithospheric mantle enriched the source with rutile-bearing phlogopite clinopyroxenite veins. Kamafugite-like parental magma is attributed to the high-Ca series with major contributions from the melting of the veins. Potassic nephelinite-like parental magma is assigned to the low-Ca series, where the metasomatized wall-rock played a more significant role in the melting process.

ARISITE-(Ce), A NEW RARE-EARTH FLUORCARBONATE FROM THE ARIS PHONOLITE, NAMIBIA, MONT SAINT-HILAIRE AND THE SAINT-AMABLE SILL, QUEBEC, CANADA

Arisite-(Ce), ideally NaCe2(CO3)2[(CO3)1– x F2 x ]F, is a new layered, rare-earth fluorcarbonate mineral from the Aris phonolite (Namibia), Mont Saint-Hilaire (Quebec), and the Saint-Amable sill (Quebec). At the Aris phonolite, arisite-(Ce) occurs as vitreous, transparent, beige, beige-yellow, light lemon yellow to pinkish, tabular, hexagonal plates and prisms up to 1.5 mm in miarolitic cavities. At Mont Saint-Hilaire, arisite-(Ce) occurs in alkaline pegmatite veins, sodalite syenite and sodalite syenite xenoliths as pale pink, silvery or very pale brown, micaceous plates with a rough hexagonal outline, as thin fibers (5 μm thick), as isolated crystals, as irregular clusters, rosettes or spherical aggregates 0.1 to 2 mm in diameter. In the Saint-Amable phonolite sill, arisite-(Ce) occurs as thin, flexible, pearly to silvery white, rounded to irregular micaceous plates (0.3 to 0.5 mm) in spherical aggregates or rosettes. Arisite-(Ce) is brittle, has a conchoidal fracture, poor cleavage perpendicular to (001), and a Mohs hardness of approximately 3–3½; it is non-fluorescent under either long- or short-wave UV radiation, dissolves slowly in room-temperature dilute HCl, and sinks in methylene iodide. Its density D calc is 4.126 g/cm3 for Z = 1 (Aris). Arisite-(Ce) is uniaxial negative, has a sharp extinction, with both ω and e exhibiting a range of values within each grain: 1.696 < ω < 1.717(4) and 1.594 < e < 1.611(3), a result of chemical zoning attributed to both Ce-for-La and Na-for-Ca substitutions. The average empirical formula for arisite-(Ce) from the Aris phonolite is (Na0.97Ca0.03)∑1.00(Ce0.92La0.80Nd0.11Pr0.04Sm0.01Ca0.09)∑1.97(CO3)2[(CO3)0.71F0.59] F. The mineral is hexagonal, P 6 m 2, a 5.1109(2), c 8.6713(4) A, V 196.16(6) A3. The strongest 11 lines of the powder X-ray-diffraction patterns [ d hkl NAM/ d hkl MSH in A( I obsNAM/ I obsMSH, hkl )] are: 4.439/4.428(100/100,100), 4.352/4.317(52/60,002), 3.103/3.097(87/80,102), 2.561/2.558(38/50,110), 2.424/2.415(21/40,103), 2.171/2.162(12/30,004), 1.9748/1.969(42/60,202), 1.9501/1.941(16/30,104), 1.9169/1.910(12/20,113), 1.6547/1.650(11/30,114) and 1.5640/1.560(13/20,212). Arisite-(Ce) is a late-stage, postmagmatic to hydrothermal mineral at all three localities. It is a member of the flat-lying layered REE fluorcarbonate group that includes lukechangite-(Ce), cordylite-(Ce), huanghoite-(Ce), cebaite-(Ce), kukharenkoite-(Ce) and kukharenkoite-(La). All these fluorcarbonates have crystal structures characterized by separate layers of carbonate, F, REE and alkali or alkaline-earth elements. The mineral’s name recalls the type locality, the Aris phonolite, Namibia.

MARTINITE, A NEW HYDRATED SODIUM CALCIUM FLUORBOROSILICATE SPECIES FROM MONT SAINT-HILAIRE, QUEBEC: DESCRIPTION, STRUCTURE DETERMINATION AND GENETIC IMPLICATIONS

Martinite, ideally (Na,□,Ca) 12 Ca 4 (Si,S,B) 14 B 2 O 38 (OH,Cl) 2 F 2 ·4H 2 O, is a new mineral species from the Poudrette quarry, Mont Saint-Hilaire, Quebec. The mineral arose through the interaction of highly fractionated, hyperagpaitic fluids with sodalite syenite xenoliths. Martinite develops both as single crystals and as rosettes of triangular to roughly hexagonal plates varying from 50 μm to a maximum of about 1 mm across. Individual crystals are typically 2− x S minerals (UK55 group), UK53a, UK73, UK82, UK91 and a lollingite-like mineral. The mineral has a vitreous luster, is transparent, has a white streak and shows no fluorescence in either short- or long-wave ultraviolet radiation. It has a Mohs hardness of 4; the crystals are inelastic, and have a perfect cleavage on {001}. It is brittle with an uneven fracture. The calculated density is 2.51 g/cm 3 . Martinite is non-pleochroic, optically biaxial (−), with α 1.529(1), β 1.549(1), γ1.551(1) (for λ = 590 nm), 2 V meas = 38(1)°, 2 V calc = 35(1)°; no dispersion was noted. The optical orientation is X ≈ c . On average, 19 electron-microprobe analyses gave: Na 2 O 17.70, MgO 0.03, CaO 16.71, MnO 0.07, B 2 O 3 (calc.) 5.02, SiO 2 48.85, TiO 2 0.06, SO 3 2.30, F 2.18, Cl 1.09 and H 2 O (calc.) 4.44, O=F+Cl −1.17, total 97.28 wt.%. The empirical formula (based on 46 anions) is: (Na 9.19 □ 1.99 Ca 0.82 ) ∑12 (Ca 3.97 Mn 0.02 Mg 0.01 ) ∑4 (Si 13.08 S 0.46 B 0.45 Ti 0.01 ) ∑14.00 B 2 O 38 (OH 1.50 Cl 0.50 ) ∑2.00 (F 1.84 OH 0.16 ) ∑2 ·4H 2 O. The principal absorption bands in the infrared spectrum include 3437, 1634 and 1011 cm −1 (shoulders at 1137, 1081, 898 and 862 cm −1 ) and five bands in the region 786–498 cm −1 . The mineral is triclinic, space group P 1, a 9.5437(7), b 9.5349(6), c 14.0268(10) A, α 108.943(1), β 74.154(1), γ119.780(1)°, V 1038.1(1) A 3 , Z = 2. The strongest seven lines in the X-ray powder-diffraction pattern [ d in A( I )( hkl )] are: 13.18(100)(001), 6.58(43)(002), 2.968(37)(130), 3.29(34)(004,220), 2.908(27)(323), 3.02(17)(211), 2.800(17)(212). The structure of martinite has been refined to R = 6.30, wR 2 = 13.82%. The mineral is strongly layered, with sheets of tetrahedra ( T ), octahedra ( O ) and interlayer cations ( X ). The T layers are composed of six-membered rings of SiO 4 tetrahedra linked by [(Si,B)]O 4 and (BO 4 ) tetrahedra. The sheets of octahedra are composed of edge-sharing M ϕ 6 octahedra ( M : Na,Ca; ϕ: unspecified ligand) arranged in a closest-packed arrangement. The O sheets are effectively sandwiched between two symmetrically equivalent T layers ( T 2 , & T macr; 2 ), producing a strongly bonded T – O – T unit. The interlayer component ( X ) houses poorly ordered Na polyhedra and H 2 O molecules. Stacking of these principal components perpendicular to [001] results in a OT 2 X & T macr; 2 O module. Martinite is a member of the reyerite–gyrolite group. It represents the first B-bearing mineral of the group and the first mineral known to possess the OT 2 X & T macr; 2 O module. The name honors Robert Francois Martin (b. 1941), Professor of Geology at McGill University and long-time editor of The Canadian Mineralogist .

Mineral thermometry and the composition of fluids of the sodalite syenites of the Lovozero alkaline massif

In order to determine the conditions of mineral formation, a suite of sodalite syenite samples was investigated from the differentiated complex and in part from the eudialyte lujavrite complex of the Lovozero alkaline massif. The compositions of major and accessory minerals were analyzed using an electron microprobe. Various mineral geothermometers (Bt-Cpx, Amph-Cpx, and Amph-Bt) were applied to estimate the temperature of formation of clinopyroxene-bearing assemblages from the sodalite syenites. The temperature varied from ∼990 to 595–630°C, which reflects various stages of crystallization. The temperatures of formation of sodalite assemblages were estimated from the compositions of coexisting sodalite phases as 625–530°C and appeared to be in good agreement with estimates obtained by other mineral geothermometers. Based on the data on the composition and crystallization temperature of sodalites, the minimum concentration of salts (NaCl and Na2SO4) in the mineral-forming fluid was estimated as 10–20 wt % NaCl eq. for the two-sodalite assemblages and 1.5–3.0 wt % NaCl eq. for the nosean-bearing assemblages. The molar fraction of sulfur in the fluid was also estimated: 0.02 for the two-sodalite assemblages and 0.04–0.27 for the nosean-bearing assemblages.

Neoproterozoic anorogenic magmatism in the Southern Bahia Alkaline Province of NE Brazil: U–Pb and Pb–Pb ages of the blue sodalite syenites

Blue sodalite syenite is a rare rock, and the Southern Bahia Alkaline Province (SBAP) is the only place in Brazil where economic deposits are found. This province forms part of the Archaean to Paleoproterozoic São Francisco craton, and contains a few batholiths, a large number of stocks and hundreds of dykes. Its southern part lies close to the tectonic contact between the craton and the Neoproterozoic Araçuaí mobile melt. Blue sodalite-bearing syenites are found in almost all the igneous bodies of the SBAP as dykes or pegmatitic masses hosted by nepheline syenite. Economically viable quantities for the production of dimension stones are found only in the Floresta Azul alkaline complex, the Itaju do Colônia and Rio Pardo stocks and the Itarantim batholith.U–Pb ages obtained for titanite from Itaju do Colônia (732 ± 8 Ma) and Rio Pardo (714 ± 8) and Pb–Pb evaporation ages of zircon from Floresta Azul (696 ± 3 Ma) and Itarantim (722 ± 5 Ma). The geochronology of the SBAP shows that the anorogenic alkaline magmatism persisted for at least 58 Ma, demonstrating an extensional tectonic environment in the southern part of the São Francisco craton at this time. The data show that the rift phase which preceded the formation of the Araçuaí orogen was active until at least 700 Ma. The reported ages are similar to those found for the nepheline syenite host bodies, which supports the conclusions of the previous petrologic study demonstrating that blue sodalite is formed during the crystallization of these bodies. Two different processes are involved. In the magmatic process, sodalite occurs as disseminated and interstitial crystals among alkali feldspar crystals, and is associated with calcite and cancrinite formed by destabilization of nepheline. In the metasomatic process, discontinuous bands of sodalite are in sharp contact with nepheline syenite pegmatite, and its crystal aggregates often contain relict textures of nepheline and albite been replaced by sodalite.

Fe-bearing trioctahedral micas from Mont Saint-Hilaire, Québec, Canada

AbstractWe document the occurrence of Fe-bearing trioctahedral micas in the Poudrette quarry in the Mont Saint-Hilaire alkaline intrusion, characterize them by microprobe analysis, Mössbauer spectroscopy, X-ray diffraction, and optical measurements, describe their mineral chemistry, and discuss their petrological significance. In the nepheline and sodalite syenite, biotite and annite occur as coarse crystals characterized by low Al content (typically 2 atoms per formula unit, a.f.u.), high Mn content (typically 0.2 to 0.8 a.f.u.) and variable Fe/(Fe+Mg) values from 0.61 to 0.97. In the gabbro, biotite is less Fe-rich, has lower Mn content and high Ti content. Phlogopite is found as small metamorphic crystals in marble xenoliths within the syenite and siderophyllite occurs as large crystals in a metasomatized albitite dyke. Fe3+/Fetot values extend from 0.079 in the siderophyllite to 0.282 in a high-Fe3+ annite. All of the micas except for the phlogopite have high contents of (Fe3+)iv (∼0.13 to 0.45 a.f.u.) despite the high availability of Al in the rocks. We suggest that the high (Fe3+)iv amounts are caused by the high Mn abundance via a local structural mechanism. The great variety of mica encountered at Mont Saint-Hilaire reflects the highly heterogeneous conditions that prevailed during magmatic and postmagmatic crystallization in this intrusion.

The Bingo carbonatite-ijolite-nepheline syenite complex, Zaire: geology, petrography, mineralogy and petrochemistry

The Bingo complex, on which little information has been published heretofore, is located in northeastern Zaire, 30 km west of the western branch of the East African rift. Although outcrop is poor, fresh float has enabled construction of a geological map showing that the intrusion consists of ijolites cut and net-veined by nepheline and sodalite syenites. The ijolites include wollastonite-bearing varieties while some feldspathic; urtite also occurs. Calcite carbonatites underline some 8 km 2 and fenites are present. The rocks are described petrographically and microprobe analyses of most mineral phases, including the rare mineral götzenite, are given. The pyroxenes define a complete series in terms of diopside-hedenbergite-aegirine and range from sodic diopside/hedenbergite to aegirine-augite in ijolite pyroxene cores and rims with aegirine-augite and aegirine in the nepheline syenites. The presence of götzenite and eudialyte attests to the high peralkalinity of the nepheline syenites. The analyses, including many trace elements, of igneous silicate rocks and three carbonatites are given. As is typical for intrusions of this type, there is considerable incoherance in the chemical data of the igneous silicate rocks, but they do give some evidence of a continuous series from the ijolites to the nepheline syenites, which, together with the pyroxene data, are taken to indicate a fractionation series. There is no direct evidence of a genetic relationship between the carbonatite and the igneous silicate rocks.

Geochronology and cooling history of the northern part of the Chilwa Alkaline Province, Malawi

The Cretaceous Chilwa Alkaline Province of southern Malawi has an exceptional variety of lithologies ranging from carbonatite to granite. The largest plutons consist of syenite and peralkaline granite, with somewhat smaller intrusions consisting of syenite, nepheline syenite and sodalite syenite. Carbonatite and minor nephelinite occur on Chilwa Island and metamorphosed basanitic/nephelinitic volcanics are preserved in down-faulted blocks. KAr amphibole and titanite fission-track ages were determined for all of the major plutons and from these ages emplacement times were estimated for the various plutons. Apatite fission-track ages and confined track-length measurements in apatite were determined in order to develop a thermal model for the Chilwa Province. KAr amphibole and titanite fission-track ages indicate that igneous activity started at ca 133 Ma with the extrusion of nephelinitic lavas and the emplacement of nepheline and sodalite syenites. An existing KAr date for the carbonatite at Chilwa Island gives a similar age. Nepheline syenites and syenites were intruded at ca 126 Ma followed by the emplacement of large syenite-peralkaline granite plutons at ca 113 Ma. The geochronology suggests that there was a temporal variation in the chemistry of the magmas forming the Chilwa plutons. Apatite fission-track ages and track-length measurements indicate that the intrusions were emplaced at high level (shallow burial depths) and cooled relatively rapidly to near ambient temperatures. The emplacement of the large syenite-granite pluton (Zomba-Malosa) caused local doming, which led to a rapid exhumation rate for Zomba-Malosa. Plutons distal to Zomba-Malosa show a slower cooling rate, suggesting that they were on the flanks of the local uplift and more deeply buried. The Chilwa alkaline magmatism post-dates the Karoo volcanism and has no apparent direct relationship to the Karoo magmatism. It seems most likely that the Chilwa magmatism was caused by crustal extension, which ruptured pre-existing zones of weakness and lead to decompressional melting.

Pyroxene in enclaves and syenites of the Red Hill complex, New Hampshire: an ion and electron microprobe study

The Red Hill complex, New Hampshire, contains both silica-undersaturated and silica-saturated to oversaturated syenites. Ion microprobe analyses of pyroxene from the Nepheline Sodalite Syenite (NSS) and its enclaves reveal that the REE abundances increase in a systematic manner from low values in the enclave pyroxenes to higher values in the NSS host rock pyroxenes. This variation is interpreted to have resulted from differentiation and coupled with previously published mineral and bulk-rock compositions, suggests that the enclaves represent samples of NSS parental liquids that intruded into residual, syenitic liquids in a zoned magma chamber. Pyroxene analyses of the Garland Peak Syenite (GPS) and its enclaves indicate that the enclaves are of several populations: some may be related to the GPS, others are not. The GPS itself is heterogeneous and pyroxene trace element zoning is difficult to explain by fractionation processes. The silica-oversaturated Outer Coarse Syenite (OCS) contains pyroxenes with trace element characteristics that are distinct from the NSS. The low V concentrations suggest that the OCS exprienced magnetite fractionation prior to pyroxene growth. It is proposed that high f O2in the OCS magma caused Fe-Ti oxide crystallization, which in turn, influenced magmatic silica activity. The chondrite normalized REE patterns of OCS pyroxenes are also suggestive of titanite crystallization, another indication of high f O2. In contrast to the influence of magnetite crystallization, the high and rimwardly increasing Y and Yb concentrations in both the NSS and the OCS pyroxenes suggest that amphibole fractionation was not the major influence on silica activity. Therefore, it is unlikely that the OCS was derived by amphibole fractionation from a NSS precursor magma.

The stability of sodalite in the system NaAlSiO 4-NaCl

The reaction sodalite = β-nepheline + NaCl ( s) was reversed in solid-medium apparatus (923 K, 7.6–8.0 kbar; 973 K, 7.4–7.6 kbar; 1073 K, 7.8–8.0 kbar; 1173 K, 8.4–8.6 kbar) and the reaction sodalite = carnegieite + NaCl ( l) was reversed at 1 bar (1649–1652 K). The calculated slope for the first reaction is −11 bar/K compared to the experimentally constrained slope above 973 K of +5 bar/K. This major discrepancy can be eliminated if the entropy of sodalite (Na 8Al 6Si 6O 24Cl 2) is 61.7 J/mol · K greater than the measured value of 848.1 ± 4.0 J/mol · K at 298.15 K. This entropy contribution is equal to that expected from 58% disorder of Al and Si on the tetrahedral sites, but could also be caused by a reversible phase change. The experimental reversals between 923 K and 973 K can be fit with a dP dT of −11 bar/K, suggesting that the excess entropy for sodalite is present only above 923 K. A phase diagram for the NaAlSiO 4-NaCl system that is consistent with the measured thermochemical data and the experiments between 973 and 1650 K can be generated if the 61.7 J/mol · K entropy contribution is included in the S 298 0 of sodalite. This entropy contribution must be removed below 973 K for the experiments to fit with calculations. Previously unreported thermodynamic data estimated in this study are ΔG 298 0 for sodalite (−12697 kJ/mol) and carnegieite (NaAlSiO 4) (−1958 kJ/mol), S 298 0 of carnegieite (129.6 J/mol · K) and compressibility of NaCl liquid ( V 298 P (cm 3) = 31.6 · [1 − 24.7 · 10 −3 · P + 800 · 10 −6 · P 2]) ( T in K; P in kbar). Sodalite is a high-temperature, low-pressure phase, stable well above the solidus in sodic silica-undersaturated magmas enriched in NaCl, and its presence constrains NaCl activities in magmas. Estimates of minimum NaCl ( l) activities in the Mont St-Hilaire sodalite syenites are 0.05 at 1073 K and 0.13 at 1273 K. Density calculations are consistent with the field observations that sodalite phenocrysts will float in a nepheline syenite liquid. This explains the enrichment of sodalite in the upper levels of the sodalite syenites at Mont St-Hilaire and elsewhere.

The Ice River Complex, British Columbia, is Precambrian Basement

ABSTRACT The Ice River complex, in Yoho and Kootenay National Parks, consists of plutonic basement rocks of Precambrian age (Gussow and Hunt, 1959), brought to the surface in two thrust sheets as a result of the Rocky Mountain orogeny. The basement rocks consist of nepheline and sodalite syenite, paragneisses, and crystalline limestones, which unconformably underlie rocks of Upper Cambrian age. The strata immediately overlying the basement are dove-gray limestones containing boulders and pebbles of basement rocks, and locally have a thin basal conglomerate or grit. The limestones thin by onlap on basement topography (, ). In recent years, other workers have postulated carbonatites, magmatic differentiation, and liquid immiscibility for their origin (Gussow, 1977).2 The Ice River controversy is dealt with in detail, by documenting the evidence for the true age of the complex, and reinterpreting the data of others in the light of this evidence.

Hydrocarbon gases and bituminous substances in rocks from the Ilímaussaq alkaline intrusion, South Greenland: (Contribution to the Mineralogy of Ilímaussaq No. 18)

Samples of poikilitic sodalite syenite (naujaite), sodalite foyaite and augite syenite from the Ilímaussaq alkaline intrusion in South Greenland contain hydrocarbons in vacuoles in the minerals and in intergranular micro-pores. Samples of lujavrite and gabbro have very low gas contents. Methane is the predominant hydrocarbon; the contents of CO 2 and CO are insignificant. The carbon of the hydrocarbon gases of naujaite is enriched in C 13. The rocks contain disseminated bituminous substances composed mainly of oil, alcohol-benzol resins and asphaltenes. The hydrocarbon gases and the bituminous substances are thought to be inorganic origin. The methods of examination are described.