Sample records for gadolinite
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Minasgeraisite, a new member of the gadolinite group from Minas Gerais, Brazil.
Foord, E.E.; Gaines, R.V.; Crock, J.G.; Simmons, W.B.; Barbosa, C.P.
1986-01-01
Minasgeraisite, Y2CaBe2Si2O10, a 9.833(2), b 7.562(1), c 4.702(1) A, beta 90.46(6)o, P21/a, Z = 2, is a new member of the gadolinite group. Found in quantities of only several hundred mg in the Jaguaracu pegmatite, Minas Gerais, Brazil, it occurs as 0.2 to 1.0 mm-diameter rosettes, coating and intergrown with milarite, albite, quartz and muscovite. The mineral is lavender to lilac purple and has a sheaf-like habit, with a grain size of 4.25, D(calc.) 4.90 g/cm3, lustre is earthy to subvitreous and the streak is pale purple. Minasgeraisite is slowly soluble in common acids. The mineral has one excellent cleavage, (100) by analogy with gadolinite, and another good cleavage (001). Minasgeraisite is biaxial positive with alpha (colourless) 1.740(4), beta (pale greyish yellow) 1.754(4), gamma (lavender purple) 1.786(4), 2Vgamma 68o. Strongest powder XRD lines include 3.11(100), 2.830(100), 2.540(90), 1.768(35) A.-J.A.Z.
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NASA Astrophysics Data System (ADS)
Guastoni, Alessandro; Nestola, Fabrizio; Schiazza, Mariangela
2017-06-01
CaCeAl2(Fe3+ 2/3□1/3)[Si2O7][SiO4]O(OH), allanite-(Ce) and rare earth element (REE)-bearing epidote occur as globular aggregates and platy prismatic crystals in miarolitic cavities in a niobium, yttrium, fluorine (NYF) granitic pegmatite at Baveno, Verbania, Southern Alps, Italy. These samples were investigated by means of an electron probe micro-analyser (EPMA) and single-crystal X-ray diffraction. Our EPMA results show that the globular aggregates have the highest REE content in the core portion and decreases to REE-bearing epidote towards the rim whereas the prismatic crystals are characterized by marked oscillatory zoning that have the highest REE contents at the rim of the crystal. The unit-cell parameters of "allanites" have an intermediate unit-cell between CaCeAl2(Fe3+ 2/3□1/3)[Si2O7][SiO4]O(OH), allanite-(Ce) and REE-free epidote, because reflect the strong chemical heterogeneity of the samples which form complete solid solutions. Hydrothermal fluids control the activity and precipitation of incompatible elements like high field strength elements (HFSE), Sc and REE by hydrous F-rich fluids below the critical temperature which allow to deposit accessory minerals in the cavities with decreasing temperature. The source of REE and Y are the sheet and REE-silicates like siderophyllite-annite, and gadolinite-(Y) which underwent partial to complete decomposition by the activity of aggressive F-rich hydrothermal fluids.
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Slack, John F.
2012-01-01
Mineralogical and geochemical studies of strata-bound Fe-Co-Cu-Au-Bi-Y-rare-earth element (REE) deposits of the Idaho cobalt belt in east-central Idaho provide evidence of multistage epigenetic mineralization by magmatic-hydrothermal processes in an iron oxide copper-gold (IOCG) system. Deposits of the Idaho cobalt belt comprise three types: (1) strata-bound sulfide lenses in the Blackbird district, which are cobaltite and, less commonly, chalcopyrite rich with locally abundant gold, native bismuth, bismuthinite, xenotime, allanite, monazite, and the Be-rich silicate gadolinite-(Y), with sparse uraninite, stannite, and Bi tellurides, in a gangue of quartz, chlorite, biotite, muscovite, garnet, tourmaline, chloritoid, and/or siderite, with locally abundant fluorapatite or magnetite; (2) discordant tourmalinized breccias in the Blackbird district that in places have concentrations of cobaltite, chalcopyrite, gold, and xenotime; and (3) strata-bound magnetite-rich lenses in the Iron Creek area, which contain cobaltiferous pyrite and locally sparse chalcopyrite or xenotime. Most sulfide-rich deposits in the Blackbird district are enclosed by strata-bound lenses composed mainly of Cl-rich Fe biotite; some deposits have quartz-rich envelopes.Whole-rock analyses of 48 Co- and/or Cu-rich samples show high concentrations of Au (up to 26.8 ppm), Bi (up to 9.16 wt %), Y (up to 0.83 wt %), ∑REEs (up to 2.56 wt %), Ni (up to 6,780 ppm), and Be (up to 1,180 ppm), with locally elevated U (up to 124 ppm) and Sn (up to 133 ppm); Zn and Pb contents are uniformly low (≤821 and ≤61 ppm, respectively). Varimax factor analysis of bulk compositions of these samples reveals geochemically distinct element groupings that reflect statistical associations of monazite, allanite, and xenotime; biotite and gold; detrital minerals; chalcopyrite and sparse stannite; quartz; and cobaltite with sparse selenides and tellurides. Significantly, Cu is statistically separate from Co and As
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NASA Astrophysics Data System (ADS)
Gysi, Alexander P.; Williams-Jones, Anthony E.
2013-12-01
Petrological and geochemical observations of pegmatites in the Strange Lake pluton, Canada, have been combined with numerical simulations to improve our understanding of fluid-rock interaction in peralkaline granitic systems. In particular, they have made it possible to evaluate reaction paths responsible for hydrothermal mobilization and mineralization of rare earth elements (REE) and Zr. The focus of the study was the B-Zone in the northwest of the pluton, which contains a pegmatite swarm and is the target of exploration for an economically exploitable REE deposit. Many of the pegmatites are mineralogically zoned into a border consisting of variably altered primary K-feldspar, arfvedsonite, quartz, and zirconosilicates, and a core rich in quartz, fluorite and exotic REE minerals. Textural relationships indicate that the primary silicate minerals in the pegmatites were leached and/or replaced during acidic alteration by K-, Fe- and Al-phyllosilicates, aegirine, hematite, fluorite and/or quartz, and that primary zirconosilicates (e.g., elpidite) were replaced by gittinsite and/or zircon. Reaction textures recording coupled dissolution of silicate minerals and crystallization of secondary REE-silicates indicate hydrothermal mobilization of the REE. The mobility of the light (L)REE was limited by the stability of REE-F-(CO2)-minerals (basnäsite-(Ce) and fluocerite-(Ce)), whereas zirconosilicates and secondary gadolinite-group minerals controlled the mobility of Zr and the heavy (H)REE. Hydrothermal fluorite and fluorite-fluocerite-(Ce) solid solutions are interpreted to indicate the former presence of F-bearing saline fluids in the pegmatites. Numerical simulations show that the mobilization of REE and Zr in saline HCl-HF-bearing fluids is controlled by pH, ligand activity and temperature. Mobilization of Zr is significant in both saline HF- and HCl-HF-bearing fluids at low temperature (250 °C). In contrast, the REE are mobilized by saline HCl-bearing fluids
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Saintilan, N.J.; Creaser, R.A.; Bookstrom, Arthur A.
2017-01-01
-Os systematics with evidence for a linear trend of mixing with (metamorphic?) fluids.The new Re-Os ages and extremely high initial 187Os/188Os ratios of cobaltite reported here favor a magmatic-hydrothermal genetic model for a multi-stage REE-Y-Co-Cu-Au mineralization occurring at ca. 1370 to 1349 Ma, and related to the emplacement of the Big Deer Creek granite pluton at ca. 1377 Ma. In our model, deposition of paragenetically early xenotime and gadolinite was followed by an influx of Mesoproterozoic evaporitic brines and magmatic-hydrothermal fluids containing metals and reduced sulfur derived from mafic and oceanic island-arc Archean to Paleoproterozoic rocks in the Laurentian basement. Cobaltite mineralization occurred upon cooling of these fluids at an inferred temperature of 300 °C or below.
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O'Neill, J. Michael
2007-01-01
-central Idaho are integrated and summarized by Bookstrom and others (chapter B, this volume). In particular, their field investigations and analysis of evidence and previous arguments for synsedimentary versus epigenetic mineral deposit types, both of which have been postulated by earlier workers, led them to conclude that both processes were likely instrumental in forming the ore deposits of the Blackbird district. Finally, this report supplies new data on isotopic ratios of sulfur, oxygen, carbon, and helium in minerals associated with cobalt-bearing ores of the cobalt belt. Slack (chapter C, this volume) identified several previously unrecognized rare-earth-element minerals in Blackbird ores: monazite (Ce,La,Y,Th)PO4, xenotime (YPO4), allanite (CaCe)2(Al,Fe)3Si3O12(OH), and gadolinite (Be2FeY2Si2O10). Light rare-earth elements reside mostly in monazite, whereas yttrium and heavy rare-earth minerals reside mostly in xenotime. Dated monazite, which in the Blackbird district is interstitial to cobaltite, is Cretaceous. This date brings into question the otherwise geologically convincing interpretation of Blackbird ores as being of Mesoproterozoic age and synsedimentary origin. This volume consists of three summary articles: A. Great Divide megashear, Montana, Idaho, and Washington: An intraplate crustal-scale shear zone recurrently active since the Mesoproterozoic by J. Michael O'Neill, Edward T. Ruppel, and David A. Lopez B. Blackbird Fe-Cu-Co-Au-REE deposits by Arthur A. Bookstrom, Craig A. Johnson, Gary P. Landis, and Thomas P. Frost C. Geochemical and mineralogical studies of sulfide and iron oxide deposits in the Idaho cobalt belt by John F. Slack
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NASA Astrophysics Data System (ADS)
Lyalina, L. M.; Zolotarev, A. A.; Selivanova, E. A.; Savchenko, Ye. E.; Krivovichev, S. V.; Mikhailova, Yu. A.; Kadyrova, G. I.; Zozulya, D. R.
2016-12-01
Batievaite-(Y), Y2Ca2Ti[Si2O7]2(OH)2(H2O)4, is a new mineral found in nepheline syenite pegmatite in the Sakharjok alkaline massif, Western Keivy, Kola Peninsula, Russia. The pegmatite mainly consists of nepheline, albite, alkali pyroxenes, amphiboles, biotite and zeolites. Batievaite-(Y) is a late-pegmatitic or hydrothermal mineral associated with meliphanite, fluorite, calcite, zircon, britholite-group minerals, leucophanite, gadolinite-subgroup minerals, titanite, smectites, pyrochlore-group minerals, zirkelite, cerianite-(Ce), rutile, behoite, ilmenite, apatite-group minerals, mimetite, molybdenite, and nickeline. Batievaite-(Y) is pale-cream coloured with white streak and dull, greasy or pearly luster. Its Mohs hardness is 5-5.5. No cleavage or parting was observed. The measured density is 3.45(5) g/cm3. Batievaite-(Y) is optically biaxial positive, α 1.745(5), β 1.747(5), γ 1.752(5) (λ 589 nm), 2 V meas. = 60(5)°, 2 V calc. = 65°. Batievaite-(Y) is triclinic, space group P-1, a 9.4024(8), b 5.5623(5), c 7.3784(6) Å, α 89.919(2), β 101.408(2), γ 96.621(2)°, V 375.65(6) Å3 and Z = 1. The eight strongest lines of the X-ray powder diffraction pattern [ d(Å)(I)( hkl)] are: 2.991(100)(11-2), 7.238(36)(00-1), 3.061(30)(300), 4.350(23)(0-1-1), 9.145(17)(100), 4.042(16)(11-1), 2.819(16)(3-10), 3.745(13)(2-10). The chemical composition determined by electron probe microanalysis (EPMA) is (wt.%): Nb2O5 2.25, TiO2 8.01, ZrO2 2.72, SiO2 29.96, Al2O3 0.56, Fe2O3 0.43, Y2O3 11.45, La2O3 0.22, Ce2O3 0.33, Nd2O3 0.02, Gd2O3 0.07, Dy2O3 0.47, Er2O3 1.07, Tm2O3 0.25, Yb2O3 2.81, Lu2O3 0.45, CaO 24.98, MnO 1.31, MgO 0.01, Na2O 1.13, K2O 0.02, F 2.88, Cl 0.19, H2O 6.75 (determined on the basis of crystal structure data), O = (F,Cl) -1.25, total 97.09 wt.%. The empirical formula based on the EPMA and single-crystal structure analyses is (Y0.81Ca0.65Mn0.15Zr0.12Yb0.11Er0.04Fe3+ 0.04Ce0.02Dy0.02Lu0.02La0.01Tm0.01)Σ2.00((H2O)0.75Ca0.70□0.55)Σ2.00Ca2.00(□0.61Na0
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Beryl-bearing pegmatites in the Ruby Mountains and other areas in Nevada and northwestern Arizona
Olson, Jerry C.; Hinrichs, E. Neal
1960-01-01
Pegmatite occurs widely in Nevada and northwestern Arizona, but little mining has been done for such pegmatite minerals as mica, feldspar, beryl, and lepidolite. Reconnaissance for beryl-bearing pegmatite in Nevada and in part of Mohave County, Ariz., and detailed studies in the Dawley Canyon area, Elko County, Nev., have shown that beryl occurs in at least 11 districts in the region. Muscovite has been prospected or mined in the Ruby and Virgin Mountains, Nev., and in Mohave County, Ariz. Feldspar has been mined in the southern part of the region near Kingman, Ariz., and in Clark County, Nev. The pegmatites in the region range in age from Precambrian to late Mesozoic or Tertiary. Among the pegmatite minerals found or reported in the districts studied are beryl, chrysoberyl, scheelite, wolframite, garnet, tourmaline, fluorite, apatite, sphene, allanite, samarskite, euxenite, gadolinite, monazite, autunite, columbite-tantalite, lepidolite, molybdenite, and pyrite and other sulflde minerals. The principal beryl-bearing pegmatites examined are in the Oreana and Lakeview (Humboldt Canyon) areas, Pershing County; the Dawley Canyon area in the Ruby Mountains, Elko County, Nev.; and on the Hummingbird claims in the Virgin Mountains, Mohave County, Ariz. Beryl has also been reported in the Marietta district, Mineral County; the Sylvania district, Esmeralda County; near Crescent Peak and near Searchlight, Clark County, Nev.; and in the Painted Desert near Hoover Dam, Mohave County, Ariz. Pegmatites are abundant in the Ruby Mountains, chiefly north of the granite stock at Harrison Pass. In the Dawley Canyon area of 2.6 square miles at least 350 pegmatite dikes more than 1 foot thick were mapped, and beryl was found in small quantities in at least 100 of these dikes. Four of these dikes exceed 20 feet in thickness, and 1 is 55 feet thick. A few pegmatites were also examined in the Corral Creek, Gilbert Canyon, and Hankins Canyon areas in the Ruby Mountains.The pegmatite dikes