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1.
Some of the most vanadium-rich silicate minerals known are present in green mica schist from the Hemlo gold deposit, Ontario, Canada. Vanadium-rich silicate minerals include green mica (up to 17.6 wt. % V2O3), phlogopite (10.1 wt. % V2O3), pumpellyite (25.7 wt. % V2O3), garnet (18.5 wt. % V2O3), epidote-group minerals (9.1 wt. % V2O3), antimonian vesuvianite (4.3 wt. % V2O3), and titanite (18.5 wt. % V2O5). In addition, minor amounts of V (<2 wt. % V2O3) are present in tourmaline, chlorite, talc and tremolite in other lithologies of the Hemlo deposit. The principal substitution that incorporates V into most of these silicate minerals is Al3+=V3+ in octahedral positions. Vanadium is incorporated into phlogopite mainly by the two substitutions: 3Mg2+ =2V3++ and VIMg2++IVSi4+=VIV3+ +IVAl3+, and all of the three substitutions Ti4++O2- =V3++(OH,F)-, Ti4+=V4+, and 5Ti4+=4V5+ + may have operated in titanite.Vanadium-enriched green mica schist from the Hemlo gold deposit is characterized by uniform Ti/Zr ratios, systematically low Ti, Ni, Co and Sc abundances, and low levels of incompatible elements Th, U, Hf and Zr and is distinct in these respects from its Cr-enriched counterpart. These geochemical features, along with textural evidence (relict quartz and oligoclase phenocrysts), indicate that the V-enriched green mica schist from Hemlo was most likely derived mainly from quartz-oligoclase porphyry. However, its anomalously high V and Cr contents were probably introduced metasomatically from local maficultramafic sources and were fixed in green mica and oxides during the waning of a second regional metamorphism. Vanadium was further remobilized, and its concentration probably enhanced, during the late hydrothermal alteration, which resulted in the formation of the characteristic V-rich calc-silicate minerals.  相似文献   

2.
Equilibria between plagioclase, calcic amphibole and quartz can be described, in part, by the relation among mineral components: NaAlSi3O8+Ca2Mg5Si8O22(OH)2 = NaCa2Mg5AlSi7O22(OH)2+4SiO2; this relation governs the partitioning of Na between plagioclase and the A-site of coexisting amphibole. Data from natural amphibolites reveal that this partitioning is systematic and sensitive to metamorphic grade. The ideal portion of the equilibrium constant (K id = X Na, A/X, A · X Ab) derived from natural samples is sensitive to bulk composition, inasmuch as both plagioclase and amphibole are highly non-ideal. Samples from a single outcrop have values ranging from 0.5 (X Ab=0.74) to 4.1 (X Ab=0.10). The continuous reaction, NaAlSi3O8+Ca2Mg5Si8O22(OH)2 = NaCa2Mg5AlSi7O22(OH)2+4SiO2, proceeds to the right with increasing grade of metamorphism and for a given bulk composition, K id increases with increasing temperature. Two related discontinuous reactions, actinolite+albite=hornblende+oligoclase+quartz and actinolite+oligoclase=hornblende+anorthite+quartz, also proceed to the right with increasing metamorphic grade and result in changes in the topology of a phase diagram that describes the partitioning of Na between plagioclase and amphibole A-site. A Schreinemakers' net is presented that is consistent with natural occurrences. The results of this study should aid in the delineation of metamorphic facies within amphibolites.  相似文献   

3.
Summary Switzerite has the following schematical chemical formula Mn 4 2+(VI) (Me 3+,2+,1+,)(VI) (Me 3+,2+,1+,)(V) (PO4)4. 8 H2O, whereMe is mainly iron; the mineral is monoclinic, space groupP21/c, Z=4; lattice parameters area=8.496,b=13.173,c=17.214 Å, -96.65°. The atomic arrangement was determined by direct methods and refined by least-squares method. FinalR index is 0.077 for 3038 observed reflections. The crystal structure of switzerite can be described as built up by octahedral sheets parallel to (001), with formula [Mn4O10(H2O)4]2.Me coordination bipyramidal dimers link these units in thec direction whileMe coordination octahedra stick out from the sheets to which they are connected through a vertex. The atomic arrangement of switzerite is compared with that in ludlamite, Fe3(PO4)2·4H2O, and in whitmoreite, Fe2+Fe 2 3+ (OH)2(PO4)2·4 H2O. The only analogy in all these structures is the presence of octahedral slabs exhibiting, however, different shapes.
Switzerit: Chemische Formel und Kristallstruktur
Zusammenfassung Switzerit hat die schematische chemische Formel Mn 4 2+(VI) (Me 3+,2+,1+,)(VI) (Me 3+,2+,1+,)(V) (PO4)4·8 H2O, wobeiMe hauptsächlich Eisen ist. Das Mineral ist monoklin, RaumgruppeP21/c,Z=4; Gitterkonstanten:a=8,496,b=13,173,c=17,214 Å, =96,65°. Die Atomanordnung wurde mit direkten Methoden bestimmt und nach der Methode der kleinsten Quadrate verfeinert. Es wurde für 3038 beobachtete ReflexeR=0,077 erreicht. Man kann die Kristallstruktur des Switzerits als aus Oktaederschichten der Formel [Mn4O10(H2O)4]2, die parallel zu (001) liegen, beschreiben. Dimere aus trigonalen Dipyramiden umMe verbinden diese Einheiten in Richtung derc-Achse, während Koordinationsoktaeder umMe aus diesen Schichten, an die sie über eine Ecke verknüpft sind, hervorragen. Die Atomanordnung des Switzerits wird mit denen des Ludlamits, Fe3(PO4)2·4 H2O und des Whitmoreits, Fe2+Fe 2 3+ (OH)2(PO4)2·4 H2O verglichen. Die einzige Analogie zwischen allen diesen Strukturen ist die Anwesenheit von Oktaederschichten, die aber verschiedene Gestalt haben.

With 3 Figures  相似文献   

4.
Zusammenfassung Die chemische Zusammensetzung eines Ti–Zr-Granats (Schorlomit) mit bis zu 32 Mol.-% Kimzeyit-Komponente wurde zusätzlich zu den chemischen Analysen mittels Mössbauer-Spektrum auf die Fe2+/Fe3+-Verteilung im Granat untersucht. Der Granat hat folgende Zusammensetzung: (Ca2,85Na0,01Mg0,1Mn0,004Y0,001)2,97(Zr0,542 Ti0,68 Al0,065Fe 0,41 3+ Fe 0,05 2+ Mg0,246Cr0,003)2,0(Si2,002Al0,556Ti0,163Fe 0,240 2+ Fe 0,029 3+ )3,0O12. Die Dichte beträgt 3,85 g·cm–3, die Brechzahln=1,92. Die Röntgendiffraktometer-Peaks sind aufgespalten ina 0=1,229 und 1,225 nm. Der Granat stammt aus Kalksilikatfels-Einschlüssen im Gabbro des Radautals, Harz.
The titanium-zirconium garnet of calc-silicate rock inclusions of the gabbro of Radautal, Harz Mountains, F.R.G.
Summary The chemical composition of a Ti–Zr-garnet (schorlomite) with up to 32 mol-% kimzeyite component was investigated additionally to chemical analyses by means of the Mössbauer spectrum for the Fe3+/Fe2+ distribution in the garnet. The composition is: (Ca2,85Na0.01 Mg0.1Mn0.004Y0.001)2.97(Zr0.542Ti0.68Al0.065Fe 0.41 3+ Fe 0.05 2+ Mg0.246Cr0.003)2.0(Si2.002 Al0.556Ti0.163Fe 0.240 2+ Fe 0.029 3+ )3.0O12. Spec. gr. 3.85 g·cm–3,n=1.92. The x-ray peaks are splitted witha 0=1.229 and 1.225 nm. The garnet occurs in calc-silicate rock inclusions of the gabbro of Radautal, Harz Mountains, F. R. G.

Mit 2 Abbildungen

Herrn Prof. Dr.H. Meixner zur Erreichung seines 70. Lebensjahres gewidmet.  相似文献   

5.
A series of amphiboles along the magnesioriebeckite—Na2Mg3Fe3+ 2Si8O22(OH)2– ferri-clinoholmquistite—Li2Mg3Fe3+ 2Si8O22(OH)2 - join, defined by the BLiB Na–1 exchange vector, were hydrothermally synthesized at 700°C, 0.4 GPa, NNO + 1 redox conditions. Powder XRD and SEM-EDAX showed a very high (> 90%) amphibole yield for all samples. X-ray patterns were indexed in the C2/m space group; refined cell-parameters show a linear decrease of a and as a function of chemistry. IR spectra in the OH-stretching region show four main and rather sharp bands; these are assigned to Mg and Fe2+ at M(1,3), and indicate that the obtained amphiboles depart from the nominal octahedral composition (M1,3Mg3). The IR spectra also show that there is an increasing filling-up of the A-site for increasing Na in the system (increasing solid-solution toward, arfvedsonite). Mössbauer spectra show four well-defined quadrupole doublets which are assigned to Fe3+ at M2 and to Fe2+ at M1, M3 and M4, respectively. The Fe3+/Fe2+ content derived from fitted peak areas show variable Fe3+ concentration along the series. Mössbauer spectra also show a distinct alteration of 57Fe hyperfine parameters with changing Na–Li at M4. The most evident variation is observed for the quadrupole splitting of Fe3+ at M2, which increases by 50% from ferri-clinoholmquistite to magnesio-riebeckite; this suggest that the M2 octahedron in ferri-clinoholmquistite is much closer to the ideal geometry than the M2 octahedron in magnesio-riebeckite. Mössbauer spectra show also a well-defined increase in the Fe2+ quadrupole splitting of the M1 and M3 octahedra, which is attributed to the Na–Li distribution at the B-sites.  相似文献   

6.
Summary IR spectra of phenakite single crystals from different localities show a distinct variability in the region of the OH stretching fundamental. Minute hydrous mineral phases (tourmaline, bertrandite) are included in Piracicaba phenakite. Structural OH, ranging up to 0.005 equivalent wt.% H2O, is characterized by two extremely pleochroic bands centered at 3380 and 3120 cm–1. On the basis of their pleochroic scheme it is proposed that (O2(OH)2) and (O3(OH)) tetrahedra occur as structural elements, assuming that the vacancies are on Be sites.
Das Auftreten von OH Absorptionen in Phenakit—eine IR spektroskopische Untersuchung
Zusammenfassung Die IR Spektren von Phenakit-Einkristallen verschiedener Vorkommen zeigen im Bereich der OH-Streckschwingungen eine deutliche Variabilität. Piracicaba Phenakit enthält feinste Einschlüsse von OH-hältigen Mineralphasen (Turmalin, Bertrandit). Strukturell gebundene OH-Gruppen (bis 0,005 äquivalente Gew.% H2O) sind durch zwei extrem pleochroitische Banden bei 3380 und 3120 cm–1 charakterisiert. Unter der Annahme von Be-Leerstellen werden aufgrund des Pleochroismus dieser Banden (O2(OH)2) und (O3(OH)) Tetraeder als strukturelle Baueinheiten vorgeschlagen.

With 3 Figures  相似文献   

7.
This work reports the synthesis of ferri-clinoholmquistite, nominally Li2(Mg3Fe3+2)Si8O22(OH)2, at varying fO2 conditions. Amphibole compositions were characterized by X-ray (powder and single-crystal) diffraction, microchemical (EMPA) and spectroscopic (FTIR, Mössbauer and Raman) techniques. Under reducing conditions ( NNO+1, where NNO = Nickel–Nickel oxide buffer), the amphibole yield is very high (>90%), but its composition, and in particular the FeO/Fe2O3 ratio, departs significantly from the nominal one. Under oxidizing conditions ( NNO+1.5), the amphibole yield is much lower (<60%, with Li-pyroxene abundant), but its composition is close to the ideal stoichiometry. The exchange vector of relevance for the studied system is M2(Mg,Fe2+) M4(Mg,Fe2+) M2Fe3+–1 M4Li–1, which is still rather unexplored in natural systems. Amphibole crystals of suitable size for structure refinement were obtained only at 800 °C, 0.4 GPa and NNO conditions (sample 152), and have C2/m symmetry. The X-ray powder patterns for all other samples were indexed in the same symmetry; the amphibole closest to ideal composition has a = 9.428(1) Å, b = 17.878(3) Å, c = 5.282(1) Å, = 102.06(2)°, V = 870.8(3) Å3. Mössbauer spectra show that Fe3+ is strongly ordered at M2 in all samples, whereas Fe2+ is disordered over the B and C sites. FTIR analysis shows that the amount of CFe2+ increases for increasingly reducing conditions. FTIR data also provide strong evidence for slight but significant amounts of Li at the A sites.  相似文献   

8.
Summary The crystal structure of sigloite, Fe3 [(H2O)3OH] [Al2(PO4)2(OH)2(H2O)2]- 2 H2O, triclinic, a 5.190 (2), b 10.419 (4), c 7.033 (3) Å, 105.00 (3), 111.31(3), 70.87 (3)°, V 330.5 (2) Å3, Z = 1, space group P , has been refined to anR index of 5.3% using 1713 observed (I > 2.5 1) reflections collected with graphite-monochromated MoK X-rays. Sigloite is isostructural with the laueite-group minerals. Corner-linked [A15] chains (: unspecified ligand) are cross-linked by (PO4) tetrahedra to form a mixed corner-linked tetrahedral-octahedral sheet of composition [A12(PO4)2(OH)2(H2O)2]2-. These sheets are linked by (Fe3+O2(OH, H2O)4) octahedra and two (H2O) groups that participate in a hydrogen-bonding network. Sigloite is the oxidized equivalent of paravauxite, Fe2+(H2O)4[Al2(PO4)2(OH)2(H2O)2]-2 H2O, and detailed comparison of the two structures shows that the oxidation mechanism involves loss of hydrogen from one of the (H2O) groups coordinating the Fe3+, and positional disorder of both the Fe3+ and (OH) and (H2O) ligands.
Siggloit: Der Oxidationsmechanismus in (M 2 3 + (PO4)2(OH)2(H2O)2]2- Strukturen
Zusammenfassung Die Kristallstruktur von Sigloit, Fe3+ [(H2O)3OH] [Al2(PO4)2(OH)2(H2O)2].2 H2O, triklin, a 5,190 (2), b 10,419 (4), c 7,033 (3) Å, 105,00 (3), 111,31 (3), 70,87 (3)°, V 330,5 (2) Å3,Z = 1, Raumgruppe P , wurdefür 1713 beobachtete Reflexe (I > 2,5 I), die mit MoKa-Röntgenstrahlung (Graphit-Monochromator) gesammelt wurden, auf einen R-Wert von 5,3% verfeinert. Sigloit ist isotyp mit den Mineralen deer Laueit-Gruppe. Über Ecken verknüpfte [A15]-Ketten (: nicht spezifizierter Ligand) werden über (P04)-Tetraeder zu ebenfalls über Ecken verknüpfte Tetraeder-OktaederSchichten der Zusammensetzung [A12(PO4)2(OH)2(H2O)2]2- verbunden. Diese Schichten werden über (Fe3+O2(OH, H2O)4)-Oktaeder und zwei (H2O)-Gruppen, die amWasserstoffbrücken-Netzwerk beteiligt sind, verbunden. Sigloit ist das oxidierte Analogon zu Paravauxit, Fe2+(H2O)4[A12(PO4)2(OH)2(H2O)2] - 2 H2O; ein detaillierter Vergleich dieser beiden Strukturen zeigt, daß der Oxidationsmechanismus sowohl den Verlust eines Wasserstoffatoms (H2O)-Gruppe, welche ein Fe3+-Atom koordiniert, als auch eine Fehlordnung der Punktlagen von Fe3+ und von den (OH) und (H2O) Liganden bedingt.
  相似文献   

9.
Summary Baotite occurs in the Garaoulére orebody, at Pierreftte, France, as an accessory mineral, included in alstonite and celsian, and associated with sphalerite, galena, pyrite, siderite and calcite in hydrothermal veins crosscutting calcareous, rutile-bearing, siltstones. Microprobe analyses revealed high W03 concentrations (up to 6 wt.%) in baotite. The empirical formula of W-rich baotite is Ba3.959Ti4(Ti3.169W0.393Fe0.116Al0.073 Cr0.048Nb0.024)3.823 Si4.05O28Cl1.166. The excess of charges due to the presence of W6+ and Nb5+ is compensated by the introduction of M3+ (Fe, Al, Cr) into Ti-octahedra, by the appearance of Al in Si-tetrahedra (for W-poor baotite) and by the appearance of vacancies in Ti-octahedra (3Ti4 -> 2W6+ + and in Ba-sites (Ti4+ Ba2+ W6+, ). The unit-cell parameters of W-rich baotite are: a = 19.92(2), c = 5.930(8) Å. Niobium-rich baotites (Baiyun-Obo,Semenov et al., 1961; Karlstein,Nmec, 1987) are characterized by substitutions: Ti4+(VI), Si4+(IV)Nb5+(VI), Al3+(IV) and 2Ti4+, Ba2+ 2Nb5+, .
Wolfram führender Baotit von Pierrefitte, Pyrenäen, Frankreich
Zusammenfassung Baotit kommt in dem Garaoulére Erzkórper in Pierrefitte, Frankreich als ein akzessorisches Mineral in Einschlÿussen in Alstonit und Celsian vor. Er ist mit Zinkblende, Bleiglanz, Pyrit, Siderit und Calcit assoziiert. Diese Paragenese ist an hydrothermale Gänge gebunden, die kalkige rutil-führende Siltsteine durchsetzen. Mikrosondenanalysen zeigen hohe W03 Gehalte (bis zu 6 Gew.%) in Baotit. Die empirische Formel von wolfram-reichem Baotit ist: Ba3.959Ti4(Ti3.169W0.393Fe0.116Al0.073Cr0.048Nb0.024)3.823 Si4.05O28Cl1.66. Der durch die Anwesenheit von W6+ und Nb5+ erforderliche Ladungsausgleich ergibt sich durch das Eintreten von M3+ (Fe, Al; Cr) in Ti-Oktaeder, und von Al in Si-Tetraeder (für W-armen Baotit) und schließlich durch das Erscheinen von Leerstellen in Ti-Oktaedern (3Ti4+ 2W6+ + und in Ba-Stellen (Ti4+, Ba` W6+, Die Zellparameter von ldW-reichem Baotit sind: a = 19.92(2), c = 5.930(8) Å. Niob-reiche Baotite (Baiyun-Obo, Semenov et al., 1961; Karlstein, Nmec, 1987) sind durch Substitutionen charakterisiert: Ti4+(VI), Si4+(IV)Nb5+(VI), Al3+(IV) und 2Ti4+, Ba2+ 2Nb5+, .
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10.
Summary In 1961–63 the Czechoslovakian Geological Survey drilled a 1596 m deep borehole in the Sn-W-mineralized Cinovec (Zinnwald) granite cupola. The hole traversed zinnwaldite granite (ZG) to 730 m, then protolithionite granite (PG). The boundary between the two granites is a transition zone (TZ) about 10 m thick. The oxides of Nb, Ta and Ti, present in accessory amounts, are columbite, ilmenorutile, rutile and pyrochlore. The columbite occurs in both granites, but in the PG only below 1558 m depth. Its crystals are strongly zoned, the zoning representing variations in Nb/(Nb + Ta) on the one hand, and non-uniform distribution of W on the other. The columbite in the TZ is strongly enriched in W, up to 32.6 wt% WO3. The columbites with W < M4+ show the substitutions W6+ + M4+ 2(Nb, Ta)5+, where (M4+ = Ti, Sn, Th, U, Zr) and 6M4+ + 3M3+ 4Fe2+ 5(Nb, Ta)5+, where (M3+ = Sc, Y). In columbites with W > M4+, tungsten is introduced by the substitution W6+ + M4+ 2(Nb, Ta)5+, but also through the appearance of Fe3+ in the B site according to the replacement 2W6+ + Fe3+ 3(Nb, Ta)5+. The ratio Fe/(Fe + Mn + Ca) increases with depth, and Nb/(Nb + Ta) is higher in the PG.The ZG is characterized by the presence of ilmenorutile, which does not occur in the PG, where rutile contains at most only 4 wt% Nb2O5. Two types of substitution have been found in the ilmenorutile: Fe3+ + (Nb, Ta)5+ 2Ti4+; (Fe, Mn)2+ + 2(Nb, Ta)5+ 3Ti4-. For the ilmenorutiles studied, the ratio [Fe3+/(Fe, Mn)2+]at is near 1.AU- and Nb-rich phase, containing up to 36.2 wt% UO2, included in protolithionite, and missing from the ZG, has the composition of a defect pyrochlore, A2+ 2 5+(O6), and forms a solid solution with U4+B2 4+(O6]), where B4-= Ti, Si, Zr, Sn. Electron microprobe analyses indicate that this phase is strongly hydrated.The crystal chemistry of Nb-, Ta- and Ti-oxides in the Cinovec cupola reflects the complex geochemistry of its component granites and the interaction of the minerals with an F- and CO2-rich fluid phase. Among the thermodynamic parameters, fO2 plays a predominant role in the early evolutionary stages.
Résumé Un sondage profond (jusqu'à -1596m), a été réalisé en 1961–63 par le Service géologique tchécoslovaque, dans la coupole granitique, minéralisée en Sn-W, de Cinovec (Zinnwald), République tchèque. Ce sondage a recoupé un granite à zinnwaldite (ZG), relayé en profondeur (–730 m) par un granite à protolithionite (PG). Le contact entre ces deux granites est matérialisé par une zone de transition (TZ) puissante de 10 m environ. Les oxydes de Nb, Ta et Ti, présents en quantité accessoire, sont représentés par: columbite, ilménorutile, rutile et pyrochlore.La columbite apparaît tant dans ZG que dans PG, mais dans ce dernier uniquement dans la zone profonde (-1558.0 m). Ses cristaux sont fortement zonés. Le zonage reflète des variations du rapport Nb/(Nb + Ta) d'une part et une distribution hétérogène de W, d'autre part. La columbite de la zone de transition ZG-PG est très enrichie en W (jusqu'à 32.6 wt.~/ 0 W03). Les coiumbites à W < SM4+ présentent des substitutions W6+ + M4+ 2(Nb, Ta)5+, où (M44+ = Ti, Sn, Th, U, Zr) et 6M4+ + 3M3+ 4Fe2+ + 5(Nb, Ta)5-, où (M3+ = Se, Y). Dans celles à W > EM4+, outre la substitution W6+ + M4+ 2(Nb, T)5+, le tungstène est introduit grâce à l'apparition de Fe 3+ sur le site B suivant le schéma: 2W6+ + Fe3+ 3(Nb, Ta)5+. Le rapport Fe/(Fe + Mn + Ca) croit avec profondeur; celui Nb/(Nb + Ta) augmente dans PG.Le ZG est caractérisé par la présence de l'ilménorutile; par contre, celui-ci est absent dans PG, oú le rutile ne contient que 4 wt.% Nb205 au maximum. Deux types de substitution sont mis en évidence dans l'ilménorutile: Fe3+ + (Nb, Ta)5+ 2Ti4+; (Fe, Mn)2+ + 2(Nb, Ta)5+ 3Ti4+. Pour les ilménorutiles étudiés, le rapport [Fe3+/(Fe, Mn)2+]à, est proche de 1.Une phase riche en U (jusqu'à 36.2 wt.% UO2) et Nb, incluse dans la protolithionite et absente dans ZG, a composition d'un pyrochlore lacunaire A2+[B2 5+(06), formant une solution solide avec U4+E:B24+(O6), où B4+ = Ti, Si, Zr, Sn. Les analyses à la microsonde électronique indiquent que cette phase est fortement hydratée.La cristallochimie des oxydes de Nb, Ta et Ti dans la coupole de Cinovec reflète tant la complexité géochimique des granites qui la composent que l'interaction des minéraux avec une phase fluide riche en F et CO,. Parmi les paramètres thermodynamiques, fO2 joue un râle prépondérant lors des stades d'évolution précoces.
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11.
This contribution is finalized at the discussion of the magnetic structure of two samples, belonging to phlogopite–annite [sample TK, chemical composition IV(Si2.76Al1.24) VI(Al0.64Mg0.72 $ {\text{Fe}}_{1.45}^{2 + } $ Mn0.03Ti0.15) (K0.96Na0.05) O10.67 (OH)1.31 Cl0.02] and polylithionite–siderophyllite joints [sample PPB, chemical composition IV(Si3.14Al0.86)VI(Al0.75Mg0.01 $ {\text{Fe}}_{1.03}^{2 + } $ $ {\text{Fe}}_{1.03}^{3 + } $ Mn0.01Ti0.01Li1.09) (K0.99Na0.01) O10.00 (OH)0.65F1.35]. Samples differ for Fe ordering in octahedral sites, Fe2+/(Fe2+?+?Fe3+) ratio, octahedral composition, defining a different environment around Fe cations, and layer symmetry. Spin-glass behavior was detected for both samples, as evidenced by the dependency of the temperature giving the peak in the susceptibility curve from the frequency of the applied alternating current magnetic field. The crystal chemical features are associated to the different temperature at which the maximum in magnetic susceptibility is observed: 6?K in TK, where Fe is disordered in all octahedral sites, and 8?K in PPB sample, showing a smaller and more regular coordination polyhedron for Fe, which is ordered in the trans-site and in one of the two cis-sites.  相似文献   

12.
The mineral chemistry of cordierites from three different sanidinite facies localities-1) volcanic xenoliths from the Eifel, Germany; 1) buchites of the Blaue Kuppe, Germany; 3) paralavas from the Bokaro coalfield, India-is characterized by unusually high potassium contents up to 1.71 wt%, equivalent to 0.22 K atoms per formula unit (p.f.u.) based on 18 oxygens. Significantly, these cordierites are either hexagonal highcordierites (indialites) with =0 or exhibit intermediate -values 0<<0.20 relative to well Al,Si-ordered orthorhombic low-cordierite. Based on microprobe analyses, the predominant substitutional mechanism for alkali incorporation is Alk[Channel]+Al[4] for +Si[4], thus leading to Al/Si-ratios deviating considerably from the value 4:5 in ideal cordierite M2[Al4Si5O18]. The most highly substituted cordierite from Blaue Kuppe is about (K0.22Na0.07)[Ch](Mg1.33Fe 0.66 2+ )[6][Al4.16Si4.79O18]. Bokaro cordierites are further characterized by obvious (Al+Si)-deficiencies against the ideal value of 9.0 p.f.u., a tendency of which is apparent in most Blaue Kuppe analyses as well. As the tetrahedral deficiencies are often equivalent to excess cations in the octahedra, we assume that ferric iron fills up the remaining tetrahedral sites, again linked with the introduction of potassium according to K+Fe3+ for +Si. In comparison with the available experimental data, these natural potassic cordierites are considered stable high-temperature phases regarding their compositions, but not their structural states. Although the substitution KAl for Si in Mg-cordierite is known to lower the maximum -value to be attained, the hexagonal nature of the cordierites must be due to very rapid crystallization and subsequent quenching. The higher -values of the Blaue Kuppe cordierites might be caused by their topotactic origin from preexisting biotite. The complicated twin and domain patterns of the hexagonal Eifel and Bokaro cordierites as observed in thin section could perhaps be attributed to structural modulations as postulated recently for hexagonal cordierite shortly after its growth.  相似文献   

13.
Coupled substitutions in the tourmaline group   总被引：2，自引：0，他引：2  
Statistical analysis of 136 natural tourmaline compositions from the literature reveals the presence and extent of coupled substitutions involving several cations and structural sites. In schorls and dravites these are a dehydroxylation type substitution (1) (OH)–+R2+ = R3++O2– and an alkali-defect type substitution (2) R++R2+ = R3++, Al3+ being the predominant R3+ action. Substitution (1) which represents solid solution towards a proton-deficient end-member, R+ R 3 3+ R 6 3+ (BO3)3 Si6O18O3(OH), accounts for three times as much of the observed compositional variability as does (2) which represents substitution toward a hypothetical alkali-free end-member, (R 2 2+ R3+) R 6 3+ (BO3)3Si6O18(OH)4. The occurrence of both of these substituions produces intermediates between end-member schorl/ dravite, R+ R 3 2+ R 6 3+ (BO3)3Si6O18(OH)4, and a new series within the tourmaline group, R 1–x + R 3 3+ R 6 3+ (BO3)3Si6O18O3–x (OH)1+x.In addition to dehydroxylation type, 2(OH)–+Li+ = R3++202–, and possibly alkali-defect type, 2R++Li+ = R3++2, substitutions, a third type Li++O2– = (OH)–+, occurs in the elbaites giving rise to Li-poor, proton-rich species. All three substitutions serve to reduce the Li-content of natural elbaite which, as a result, does not attain the composition of the ideal end-member, Na(Li1.5Al1.5)Al6(BO3)3Si6O18(OH)4. Substitution from elbaite and schorl/dravite toward R 1–x + R 3 3+ R 6 3+ (BO3)3Si6O18O3–x(OH)1+x is very extensive and may be complete.Substitution toward R 1–x + R 3 3+ R 6 3+ (BO3)3Si6O18O3–x(OH)1+x results in improved local charge balance. The mean deviation from oxygen charge saturation is at a maximum in end-member schorl, dravite and elbaite. Substitutions (1) and (2) progressively decrease but substitution (1) does so more effectively, which may explain its predominance in nature. However, alkali-defective end-members appear to be unstable regardless of . Substitution (3) in the elbaites cannot be discussed on the basis of charge balance considerations at present due to the lack of structural information on proton-rich species.  相似文献   

14.
Summary Yoderite with compositions close to those of the natural purple variety were synthesized from gels at high water pressures (15–16 kbar) and temperatures (650, 800°C) at the oxygen fugacities of the Mn2O3/MnO2-buffer with yields up to 95%. Chemical formulae based on microprobe data and water analyses are Mg1.90(Al6.01Fe3+ 0.28Mn3+ 0.11)=6.40Si3.8O18.21(OH)1.79 and Mg1.86(Al5.77Fe3+ 0.36Mn3+ 0.04)=6.17Si4O18.20(OH)1.80. Manganiferous, but iron-free yoderite with the formula Mg1.85(Al6.26Mn3+ 0.10)=6.36Si3.91O18.15(OH)1.85 was also obtained and proves that Mn3+ alone may stabilize the yoderite structure, although this does not necessarily imply thermodynamic-stability. All these synthetic yoderites exhibit the typical purple color known from the natural mineral with pleochroism of dark blue b to colorless b, which confirms the earlier spectroscopic conclusion that Mn is responsible for the purple color of yoderite. Compared to ferric iron, Mn3+ is incorporated into yoderite in much smaller amounts, although the maximum attained here (0.11 p.f.u.) is still below the 0.15 found in new analyses of natural yoderite from Tanzania.In some runs yoderite coexisted with kornerupine containing Mn and Fe as well and showing spectacular pleochroism from dark green b to light red c. Relative to yoderite Mn is fractionated into kornerupine. The analytical data suggest that most of the manganese is incorporated as Mn2+, although some Mn3+ may be the reason for the color. Coexisting braunite contains high amounts of Mg and Al substituting for Mn2+ and Mn3+, respectively. Garnet obtained from the Fe-free gel contains only Mn2+ and has the end member composition Pyrope79Spessartine21 despite high oxygen fugacity.
Synthese und Eigenschaften von Mn-haltigem Yoderit und Mn-haltigem Kornerupin als Nebenprodukt
Zusammenfassung Die Synthese von Yoderiten mit chemischen Zusammensetzungen nahe denjenigen der natürlichen, blau gefärbten Varietät gelang in Ausbeuten bis zu 95% aus Gelen bei hohen Versuchsdrücken (15, 16 kbar) und Temperaturen von 650 bzw. 800°C. Die Sauerstoffugazität wurde durch den Puffer Mn2O3/MnO2 kontrolliert. Aus Mikrosondenanalysen und Wasserbestimmungen wurden folgende chemische Formeln von Yoderit bestimmt: Mg1.90(Al6.01Fe3+ 0.28Mn3+ 0.11)=6.40Si3.80O18.21(OH)1.79 and Mg1.86(Al5.77Fe3+ 0.36Mn3+ 0.04)=6.17Si4O18.20(OH)1.80. Die Stabilisierung der Yoderitstruktur allein durch Mangan wurde durch die Synthese manganhaltigen, aber eisenfreien Yoderits, Mg1.85(Al6.26Mn3+ 0.10)=6.36Si3.91O18.15(OH)1.85 belegt. Sämtliche synthetisierten Yoderite besitzen die typische dunkelblaue Farbe, wie sie vom natürlichen Mineral bekannt ist, und zeigen einen Pleochroismus von dunkelblau b zu farblos b. Dies unterstützt die ursprüngliche auf spektroskopischen Untersuchungen basierende Vermutung, daß Mangan für die blaue Farbe von Yoderit verantwortlich ist. Im Vergleich zu Eisen wird Mn3+ in geringerem Ausmaß in die Yoderit-struktur eingebaut, wobei die hier erreichte maximale Menge von 0.11 Mn3+ p.F.E. unter derjenigen der natürlichen Yoderite von Mautia Hill, Tansania, liegt (dort 0.15 Mn3+ p.F.E.).In einigen Versuchsprodukten koexistierte mit Yoderit auch Fe-Mn haltiger Kornerupin, der einen ausgeprägten Pleochroismus von dunkelgrün b zu hellrot c besitzt. Kornerupin enthält im Vergleich zu Yoderit mehr Mangan. Chemische Analysen dieser Phase belegen den Einbau von zweiwertigem Mangan, obwohl wahrscheinlich Spuren von Mn3+ die Farbe von Kornerupin verursachen. Mit Yoderit koexistierender Braunit besitzt Mg und Al, die für Mn2+ bzw. Mn3+ substituiert wurden. Trotz hoher Sauerstoffugazität enthält Granat, der aus einem Fe-freien Gel erhalten wurde, ausschließlich zweiwertiges Mangan und stellt einen Mischkristall zwischen Pyrop und Spessartin dar (Py79Spess21).

With 2 Figures  相似文献   

15.
Zusammenfassung Röntgenographische Untersuchungen an Einkristallen von Arsenbrackebuschit, Pb2(Fe, Zn)(OH, OH2) (AsO4)2 (mit FeZn21), ergaben die RaumgruppeP21/m mita 0=7,763(1) Å,b 0=6.046(1) Å,c 0=9.022(1)Å, =112,5(1)°,V=391,2(1) Å3,Z=2 und x =6,54 g/cm3. Dreidimensionale Fouriersynthesen und Verfeinerungen nach der Methode der kleinsten Quadrate bis zu einemR-Wert von 0,073 zeigten, daß das neue Mineral strukturell einer Gruppe von Blei-Mineralen der allgemeinen Formel Pb2 Me(Z) (XO4) (YO4) — mitMe=Cu2+, Mn2+, Zn2+, Fe3+;X=S, Cr, V, As;Y=P, As, V;Z=OH, OH2 — zuzuordnen ist. Vertreter dieser Gruppe sind z. B. Tsumebit Pb2Cu(OH) (SO4) (PO4), Vauquelinit Pb2Cu(OH) (CrO4) (PO4) und auch Brackebuschit Pb2(Mn, Fe) (OH2) (VO4)2. Strukturelle Verwandtschaft besteht mit Tsumcorit Pb(Zn, Fe)2(OH, OH2)2(AsO4)2, einem weiteren Blei-Arsenat der gleichen Lagerstätte.
Structural investigation of arsenbrackebuschite
Summary X-ray single crystal work on arsenbrackebuschite, Pb2(Fe, Zn) (OH, OH2) (AsO4)2 (with FeZn21), gave space groupP21/m witha 0=7.763(1),b 0=6.046(1),c 0=9.022(1) Å, =112.5(1)°,V=391.2(1) Å3,Z=2 and x =6,54 g/cm3. 3-dimensional Fourier syntheses and least-squares refinement (finalR=0.073) showed that the new mineral belongs to a group of lead minerals with the general formula Pb2 Me(Z) (XO4) (YO4)Me=Cu2+, Mn2+, Zn2+, Fe2+, Fe3+;X=S, Cr, V, As; Y=P, As, V;Z=OH, OH2. Members of this group, are for example tsumebite, Pb2Cu(OH) (SO4)(PO4), vauquelinite, Pb2Cu(OH) (CrO4) (PO4), and brackebuschite, Pb2 (Mn, Fe) (OH2) (VO4)2. A structural relationship exists to tsumcorite, Pb(Zn, Fe)2(OH, OH2)2 (AsO4)2, another lead-arsenate from Tsumeb.

Mit 2 Abbildungen  相似文献   

16.
Zirconolite, allanite and hoegbomite are present as accessory phases in a metasomatically altered spinel-calcite-marble from the contact with the Bergell intrusives (Switzerland/Italy). Textural relationships indicate a step-wise alteration of spinel to 1) hoegbomite or corundum + magnetite, 2) margarite and 3) chlorite. Replacement of spinel by hoegbomite can be described by the substitution 1.94(Mg2+, Fe2+, Zn2+, Mn2+, Ca2+)Ti4+ +0.12(OH–) where Al3+ and Fe3+ are held constant. The average composition of the Bergell hoegbomites is given by the formula Fe 0.97 2+ Mg0.69Zn0.04Ti0.17Al3.94Fe 0.06 3+ O7.98(OH)0.02 and seems to be imposed by the composition of pre-existing spinel. During the first two steps of spinel alteration, calcite was replaced by anorthite+phlogopite, and the rare earth element(REE)-bearing minerals zirconolite, allanite and sphene were formed. Allanites have characteristic chondrite-normalized REE patterns with enrichment in the light REE. The zirconolite patterns show a marked increase in concentration from La to Ce, followed by an almost constant section. Sphene lacks detectable La, and its REE patterns vary from grain to grain. Contemporaneous formation of phlogopite, REE-bearing minerals and hoegbomite during replacement of the spinel-calcite-marble indicates that the metamorphic fluid introduced potassium along with REE and other high valence cations (Ti4+, Zr4+, U4+, Th4A3804265, Nb5A3804265, Y3A3804265) possibly as polynuclear complexes. The abundance of fluorine-bearing phlogopite and fluor-apatite as well as their close association with REE-bearing minerals and hoegbomite suggests F– and PO 4 3– as likely ligands for complexing of the above mentioned elements.  相似文献   

17.
Summary Ardennite of complex composition: (Mn2+ 3.488Ca0.509Ba0.002)=4(Mg0.916916 Fe3+ 0.165 Mn3+ 0.099Cu0.033Ni0.009Zn0.006 Ti0.008Al4.764)=6(As5+ 0.823V5+ 0.022P0.005B0.069Al0.042Si5.039)=6O21.81(OH)6.17 occurs in crack-seal quartz veins in quartz-albite-piemontite-spessartine-phengitehematite-chlorite-rutile-tourmaline ± calcite schist of the Haast Schist Group near Arrow Junction, western Otago, New Zealand. The Mn2+/Mn3+-ratio is sensitive to calculations and to accuracy of analyses. Boron is detected in ardennite for the first time. Other properties include = 1.734(3), = 1.735(3), = 1.751(3), 2VZ = 30(2)°;a = 8.721(1),b = 5.816(1),c = 18.545(3) Å,V = 940.7(2) Å3. Associated mineral phases are spessartine, hematite, piemontite containing 0.7% SrO and 0.06% PbO, and phengite. Later-stage vein minerals comprise chlorite, albite, and manganoan calcite which were deposited under less highly oxidizing conditions. Digenite with minor intergrown covellite occurs in small amount with manganoan calcite and quartz in a cross-cutting late-stage veina chalcopyrite and native copper occur in other late-stage veins. Arsenic and other components of the ardennite and associated minerals are derived from highly oxidized ferromanganese oxide- and hydroxide-bearing siliceous pelagic sediments that formed the protolith for the piemontite schist. The veins formed at a relatively early stage after metamorphism peaked in the chlorite zone of the greenschist facies under conditions that have been estimated at about 4.5 kbar, 390 °C.
Vorkommen von Ardennit in Quarzgängen aus Piemontit-Schiefern, West-Otago, Neuseeland
Zusammenfassung Ardennit mit der Zusammensetzung (Mn2+ 3.488Ca0.509Ba0.002)=4(Mg0.916Fe3+ 0.165Mn3+ 0.099Cu0.033Ni0.009Zn0.006 Ti0.008Al4.764)=6(As5+ 0.823V5+ 0.022P0.005B0.069Al0.042Si5.039)=6O21.81(OH)6.17 tritt in Crack-seal-Quarzgängen in Quarz-Albit-Piemontit-Spessartin-Phengit-Hämatit-Chlorit-Rutil-Turmalin ± Calcit-Schiefern der Haast Schiefer-Gruppe nahe der Arrow Junction, West-Otago, Neuseeland, auf. Die Proportionen von Mn2+/Mn3+ hängen von der Kalkulation und der Genauigkeit der Analyse ab. Bor wird zum ersten Mal im Ardennit bestimmt. Andere Eigenschaften sind: = 1.734(3), = 1.735(3), = 1.751(3), 2Vz = 30(2)°; a = 8.721(1), b = 5.816(1), c = 18.545(3) Å, V = 940.7(2) Å3. Assoziierte Mineralphasen sind Spessartin, Hämatit, Piemontit, der 0.7% SrO und 0.06% PbO enthält und Phengit. Spät gebildete Gangmineralien, wie Chlorit, Albit und Mn-Calcit, sind unter geringer oxidierenden Bedingungen entstanden. Digenit mit etwas Covellin tritt in kleinen Mengen zusammen mit Mn-Calcit und Quartz in einem querschlägigen Gang auf, Chalcopyrit und gediegenes Kupfer kommen in anderen späten Gängen vor. Arsen und andere Komponenten des Ardennites and der assoziierten Minerale können von hochoxidierten, Fe-Mn-Oxid- und Hydroxyd-führenden, Sireichen, pelagischen Sedimenten hergeleitet werden, die das Ausgangsgestein für den Piemontit darstellen. Die Gänge wurden in einem relativ frühen Stadium, nach dem Metamorphosehöhepunkt, innerhalb der Chloritzone der Grünschiefer-Fazies, unter ungefähr 4.5 kbar und 390°C, gebildet.

With 4 Figures  相似文献   

18.
The synthesis and the chemical, structural, magnetic, and Mössbauer spectral characterization of three synthetic alluaudites, Na2Mn2Fe(PO4)3, NaMn Fe2(PO4)3 and Na2MnFeIIFeIII(PO4)3, and a natural sample with the nominal composition of NaMn Fe2(PO4)3, collected in the Buranga pegmatite, Rwanda, are reported. All four compounds have the expected alluaudite monoclinic C2/c structure with the general formula [A(2)A(2)][A(1)A(1)A(1)2]M(1)M(2)2(PO4)3 in which manganese(II) is on the M(1) site and manganese(II), iron(III) and, in some cases, iron(II) on the M(2) site. The X-ray structure of Na2Mn2Fe(PO4)3 also indicates a partially disordered distribution of NaI and MnII on the M(1) and A(1) crystallographic sites. All four compounds are paramagnetic above 40 K and antiferromagnetically ordered below. Above 40 K the effective magnetic moments of NaMnFe2(PO4)3 and Na2MnFeIIFeIII(PO4)3 are those expected of high-spin manganese(II) and iron(III) with the 6A1g electronic ground state and high-spin iron(II) with the 5T2g electronic ground state. In contrast, the effective magnetic moment of Na2Mn2Fe(PO4)3 is lower than expected as a result of enhanced antiferromagnetic exchange coupling by the manganese(II) on the M(2) site. The Mössbauer spectra of all four compounds have been measured from 4.2 to 295 K and have been found to be magnetically ordered below 40 K for Na2Mn2Fe(PO4)3 and 35 K for the remaining compounds. The Mössbauer spectra of Na2Mn2Fe(PO4)3 exhibit the two expected iron(III) quadrupole doublets and/or magnetic sextets expected for a random distribution of manganese(II) and iron(III) ions on the M(2) site. Further, the Mössbauer spectra of Na2MnFeIIFeIII(PO4)3 exhibit the two iron(II) and two iron(III) quadrupole doublets and/or magnetic sextets expected for a random distribution of iron(II) and iron(III) on the M(2) site. Surprisingly, the synthetic and natural samples of NaMnFe2(PO4)3 have 19 and 10% of iron(II) on the M(2) site; apparently the presence of some iron(II) stabilizes the alluaudite structure through the reduction of iron(III)–iron(III) repulsion. The temperature dependence of the iron(II) quadrupole splitting yields a 440 to 600 cm–1 low-symmetry component to the octahedral crystal field splitting at the M(2) site. The iron(II) and iron(III) hyperfine fields observed at 4.2 K are consistent with the presence of antiferromagnetic ordering at low temperatures in all four compounds.  相似文献   

19.
Summary Kutnohorite-quartz veins penetrate through a weakly metamorphosed Late Proterozoic sedimentary rhodochrosite carbonate in pyrite shales. Kutnohorite is pleochroic ranging from colourless () to pinkish grey (), =1.735, =1,543,d=3.066g·cm–3;a 0=4.852(1),c 0=16.219(7) Å. A quantitative chemical analysis leads to the formula (Ca0.95Mn0.05)1.00(Mn0.64Mg0.23Fe0.13)1.00(CO3)2.04. An electron microprobe scanning reveals considerable microscale inhomogeneity in cleavage rhombohedrons taken from a coarsely grained aggregate. It is mostly of the character of periodic fluctuations of the main element contents around an average value. There is a strong prevalence of an Fe+Ca–Mn+Mg antagonism, the extremes of compositonal differences lying in distances of 0.0X mm. The fluctuation maxima amount to about 9% for FeO, 6% for MnO, 3% for CaO, and 1.5% for MgO. In one of the samples even a two phase character with the above antagonism between the two phases was detected by X-rays. The inhomogeneities are due, partly at least, to the Fe-metasomatic processes that followed the formation of the kutnohorite by Alpine-paragenesis hydrothermal metamorphism.
Kutnohorit aus der Pyrit-und Manganlagerstätte von Chvaletice (Ostböhmen)
Zusammenfassung Kutnohorit-Quarzgänge durchdringen ein schwach metamorphes jungproterozoisches sedimentäres Rhodochrositkarbonat in pyritischen Schiefern. Der Pleochroismus von Kutnohorit liegt zwischen farblos () und rosagrau (), =1,735, =1,543;d=3,066 g·cm–3;a 0=4,852(1),c 0=16,219(7) Å. Die quantitative chemische Analyse des Minerals ergibt Formel (Ca0,95Mn0,05)1,00(Mn0,64Mg0,23Fe0,13)1,00(CO3)2,04. Elektronenmikrosondenuntersuchungen zeigen eine starke mikroskopische Inhomogenität in den Spaltrhomboedern von einem grobkörnigen Kutnohoritaggregat. Sie ist meistens durch periodische Schwankungen der Hauptelementgehalte um einen Mittelwert hervorgerufen. Antagonistische Beziehungen von Fe+Ca und Mn+Mg überwiegen, die extremen Werte von Elementgehalten liegen in Abständen von 0,0X mm. Die höchsten Schwankungen erreichen etwa 9% für FeO, 6% für MnO, 3% für CaO und 1,5% für MgO. In einer Probe konnten röntgenographisch sogar zwei Kutnohoritphasen mit dem erwähnten Antagonismus zwischen den Phasen bewiesen werden. Die Inhomogenitäten wurden wahrscheinlich meistens durch Fe-metasomatische Vorgänge nach der Kristallisation des Kutnohorits während der hydrothermalmetamorphen Prozesse der Alpinen Paragenese hervorgerufen.

With 4 Figures  相似文献   

20.
Summary Phosphates of compositions (Na1–xLix)1.5Mn1.5Fe1.5(PO4)3 were synthesized by solid state reactions in air, and pure alluaudite-type compounds were obtained for x=0.00, 0.25, and 0.50. Rietveld refinements of X-ray powder diffraction data indicate the occurrence of Mn2+ in the M(1) site, and of Fe3+ and Mn2+ in the M(2) site. For x=0.25 and 0.50, A(1) is occupied by Li+ and Na+, whereas A(2) is occupied by Na+ and vacancies. A careful examination of the number of electrons occurring in the A sites of the alluaudite-type compounds (Na1–xLix)MnFe2(PO4)3 and (Na1–xLix) CdIn2(PO4)3 confirms that lithium occupies only the A(1) crystallographic site of the alluaudite structure.  相似文献   

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