DOCSLIB.ORG

Titanium, Fluorine, and Hydroxyl in the Hrrmite Minerals

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Titanium, Fluorine, and Hydroxyl in the Hrrmite Minerals AmericanMineralogist, Volume 64, pages 1027-1035, 1979 Titanium, fluorine, and hydroxyl in the hrrmiteminerals Paul H. RBns Department of Geological Sciences Virginia Polytechnic Institute and State University Blacksburg, Virginia 24061 Abstract In the humite homologousseries, nMrSiO 4' M F,TL,(F,OH)2-2,O2,(where n : I for nor- bergite, 2 for chondrodite, 3 for humite, and 4 for clinohumite, M : Mg >> Fe > Mn > Ca,Zn,Ni and 0 < x < l), x appearsnever to exceed-0.5 Ti atomsper formula unit, because local electrostaticcharge imbalances at the 3-coordinated(F,OH,O) anion and the 4-coordi- nated oxygen atoms increasevery rapidly as Tia* substitutesfor trP*, even with the con- comitant substitutionof 3-coordinated02- for (F,OH)'-. Both electrostaticand geometricar- gumentssuggest that Ti ordersinto the M(F,OH)O "layer" of the humite structures,t.e., into the M(3)OIV(F,OH,O)|I octahedron,which is the smallestof all octahedrain all the humite minerals(cl Fujino and Tak€uchi, 1978). Refractive indices, density, unit-cell dimensions, and volume are dramatically affected by the substitution of OH for F, and this has been studied as chemistry varies from 1.0 < (F,oH)'ill[(F,oH)"' + o''] = 0.0and 0.0< silv/2(F,oH,o) < l,/8 from sellaiteMg(F'oH), (n : 0) through the humitesto forsterite(r : o1. The volume per anion increasesmuch more rapidly as OH substitutesfor F in theseminerals than would be expectedon the basisof ob- serveddifferences in individual M-(F,OH) distances.As Yamamoto (1977)noted, the effec- tive radius of OHIII would be -0.06A larger than that of Fttt based on individual bond lengths.However, if the grand mean M-(F,OH,O) distanceminus the effectiveradius of the M cationis used,OHIII would have to be -0.15A larger, and if the efective anion radius cal- culated from the observedvolume per anion is used,values -0.10A larger are expected.Pro- ton-proton repulsions,which increasedramatically both within a given mineral series(say F- to OH-chondrodite)and as n goesfrom 4 to 0, expandthe unoccupiedpolyhedra for the hcp anion array very much more than the occupiedoctahedra; physical parametersare accord- ingly affected. Introduction crystal structuresof no less than three titanian cli- nohumites(Ti-CD and one titanian chondrodite(Ti- The formula for the homologous seriesof minerals Ch) have been examined. Least-squaressite refine- collectively called "humites" is nMrSiOo' Mr-,Ti, ments have produced somewhat conflicting results, (F,OH)r-r,Or, where n : I for norbergite, 2 for leaving us with two questionsregarding titanium: (l) chondrodite, 3 for humite, 4 for clinohumite, M is Why doesx appearnever to exceed0.5 Ti atoms per Mg >> Fe > Mn,Ca,Zn,Ni, and 0 < x < l. A seriesof formula unit in natural specimens?(2) Is Ti really or- Mn-isotypes for n : 2 (alleghanyite), 3 (mangan- deredinto the M3 octahedralsite, and if so,why? Fu- humite), and 4 (sonolite) also exists in nature, and jino and Tak6uchi (1978) implied answersto these these exhibit a substantial range of solid solution questions with vague referencesto Pauling's elec- with Mg; most are OH-rich. trostatic valencerule. One purposeof this paper is to Titanium-rich clinohumites and chondrodite (x > addressthat matter more specifically. 0.25) have recently attracted attention as possible Another crystal-chemicalproblem has to do with mineralogical sites for water in the earth's upper the nature of the OH e F substitutionin all the hu- mantle (McGetchin et al., l97O; Merrill et al., 1972; mites.The recentsynthesis of OH-Ch and OH-CI by Aoki er al.,1976;Mitchell, 1978),and as a resultthe Yamamoto and Akimoto (1974, 1977),the determi- 0nn3-{0/.X/79/09 l0- 1027$02.00 1028 RIBBE: HUMITE MINERALS nation of the structure of OH-Ch by Yamamoto panciesin Ti-Cl Robinson et al. (1973ab) took dif- (1977),and the synthesisof many F,OH intermediate ferent approachesthan Fujino and Tak6uchi (1978); compounds by Dutry (1977) have provided a data the former report disorderedTi, the latter ordered. basefrom which the systematicsof the OH ? F sub- Kocman and Rucklidge (1973)-perhaps most stitution has beendeduced. wisely-simply assignedTi to M3 and refined Mgl Fe distributions within the constraintsof their chem- Titanium in natural humites ical analysis. Fujino and Tak6uchi's (1978) referenceto Paul- Titanium content ing's electrostaticvalence principle holds the key to Table I lists, anong others, the compositions of both the restrictedTi substitutionand Ti distribution the most Ti-rich humite minerals analyzed to date. among the nonequivalentoctahedral sites in humites. Note that x does not exceed 0.5 Ti atoms per formula Let us consider the hypothetical homologues, unit in any of the humites. Norbergite (No; n: l) is nMg,SiOo'Mg,-"Ti,(F,OH)2_2.O,.with 0 S x S l. rare in nature and apparently is relatively Ti-free. Note that one half of the octahedral sites are filled Ctnohumite (Cl; n :4) commonly is Ti-rich (Jones with cations in the proportion (x)Ti + (2n + l - et al.,1969, Fig. 4), but only one titanian chondrodite x)Mel. (Ch; n: 2) has ever been reported (Aoki er al., 1976), Charge imbalance with Ti disordered.With Ti dis- and it is epitaxially associated with a Ti-Cl which ordered there are only two types of anions as far as contains the same number of Ti atoms per formula local chargebalance is concerned,regardless of min- unit as Ti-Ch. Notably absent from this intergrowth eral species.The averagecharge on all M cations is is the intermediate phase, humite (Hu; n : 3). the same:(zl : alx/(2n + l)l + 2l(2n+ | - x)/(2n + l)1. The oxygensare 4-coordinatedto lSi + 3M and Titanium distribution are all overbondedby [ + 3(zl/61- 2.00esu. The The structures of both Ti-Ch and Ti-Cl have been (F,OH,O) anion is bonded to 3M atoms and is al- determined by Fujino and Tak6uchi (1978) who ways underbondedby an amount 3(zl/6 - (l + x) found by least-squares site refinement that most, if esu, where x : Or,,/(F + OH + Or,). Figure la in- not all, of the Ti is ordered in the M(OH)O layers, dicatesthe imbalancesas a function of x for each of i.e., in the M3 octahedral sites. Of course there are the four humitesin which Ti is disordered. problems associated with determining unambi- Charge imbalance with Ti ordered. If all the tita- guously the cation distribution among the octahedral nium is ordered into M3, there are collectively sites when three species of atom are present, namely among the humite homologuesthree types of 4- : -26) Me 0 l2), Fe * minor Mn,Ni (f and Ti 6f : coordinatedoxygens, Oo, O,, Or, the subscriptsrefer- 22) (J is the atomic scattering factor at snfl/)r: 0.0). ring to the number of M3 atoms to which they are Some basically unsatisfying assumptions must be bonded, plus one (F,OH,O) anion. From the multi- made to obtain convergence: in refining site occu- plicities of M sitesin the humites (Table 2) it can be Table l. Compositional data for humite minerals whose structures have been refined z Mineral (space group) r Ms Fe Mn Nt ca sio4 ri F oH* ori ,#.trTtl]r, I NorbergiEe (Pbm) xx O.42 (36.2) 0.oil 1.99 <.01 <.01 <.01 1 0.01 1.81 0,17 0.02 Jones et aL. (L969) 2 chond,rodite (p21'/b) 9.36 (22.L) ' o.424 3.99 0.57 0.0r 0.01 o.42 0 1.15 0.85 Fujino & Tak6uchi (1978) o.o3 (22.1) <.0r 4.95 0.03 0.01 0.0r 2 <,oL L.27 0.73 <.0r cibbs e, aL. (I91O) 3 Homite (Pbm) 3.25 (15.9) 0. 201 6,49 0.22 0.09 <.01 3 0.20 0.79 0.81 0.40 Joles et aL. (1969)*** 0.10 (15.9) 0.01 6.60 0.35 0.05 <,01 3 0.01 1.06 0.93 0.01 Ribbe & Gibbs (1971) 4 Cllno}rtnite (P2r,/b) 5.59 (L2.4) 0.468 7.33 1.04 0.05 <.01 4 o.47 0 1.06 0.94 Robinson et aL. (1973) " 3.\4 (r2.4) 0.26 7.34 1.36 0.08 4 o,26 0.40 1.08 0.52 KocDao & Rucklidge (1973) 5.O1 (r2.4) o.429 7.44 r.09 0.02 0.02 4 o.43 0 1.14 0.86 Fujino 6 Tak6uchi (1978) o.22 (r2.4) o.o2 8.42 0,s0 0,06 < .01 0.02 1 . 04 0. 93 0. 03 Robinson et aL. (L973) * Calculated by difference: OH = 2 - 1f + Orr), where OT. = O2x. ** Space group convention of Jones (1969), ***Most Ti-rich hunite analysis reported; the structure of this specinea has not been refined. RIBBE: HUMITE MINERALS Ti DISORDEREDIN M Ti ORDEREDINTO M3 dered humites; the proportions of O0, O,, O, and ) o5 (F,OH,O) anionsper formula unit are listed in Table o o2 2 for eachof the structuretypes. C .9 It is clear from Figure I that the more Ti, the c o o vo greater the local charge imbalances, regardlessof o 0 whether Ti is ordered or disordered in any of the o c 0 homologues.Quite likely these imbalancesplace a o o - practical upper limit on Ti substitution. Comparing E o.5 o the two graphs,it is also evident that chargebalance o o is somewhatimproved when Ti is ordered into M3, E o -t.o exceptfor norbergite in which all anions are bonded o.o o.5 r.o r.o o.o o.5 Thus may argue that Ti prefers x = Ti per formulounil x = Ti per formulounil to two M3 sites.
Load more

Recommended publications
  • Optical Properties of Common Rock-Forming Minerals
    AppendixA __________ Optical Properties of Common Rock-Forming Minerals 325 Optical Properties of Common Rock-Forming Minerals J. B. Lyons, S. A. Morse, and R. E. Stoiber Distinguishing Characteristics Chemical XI. System and Indices Birefringence "Characteristically parallel, but Mineral Composition Best Cleavage Sign,2V and Relief and Color see Fig. 13-3. A. High Positive Relief Zircon ZrSiO. Tet. (+) 111=1.940 High biref. Small euhedral grains show (.055) parallel" extinction; may cause pleochroic haloes if enclosed in other minerals Sphene CaTiSiOs Mon. (110) (+) 30-50 13=1.895 High biref. Wedge-shaped grains; may (Titanite) to 1.935 (0.108-.135) show (110) cleavage or (100) Often or (221) parting; ZI\c=51 0; brownish in very high relief; r>v extreme. color CtJI\) 0) Gamet AsB2(SiO.la where Iso. High Grandite often Very pale pink commonest A = R2+ and B = RS + 1.7-1.9 weakly color; inclusions common. birefracting. Indices vary widely with composition. Crystals often euhedraL Uvarovite green, very rare. Staurolite H2FeAI.Si2O'2 Orth. (010) (+) 2V = 87 13=1.750 Low biref. Pleochroic colorless to golden (approximately) (.012) yellow; one good cleavage; twins cruciform or oblique; metamorphic. Olivine Series Mg2SiO. Orth. (+) 2V=85 13=1.651 High biref. Colorless (Fo) to yellow or pale to to (.035) brown (Fa); high relief. Fe2SiO. Orth. (-) 2V=47 13=1.865 High biref. Shagreen (mottled) surface; (.051) often cracked and altered to %II - serpentine. Poor (010) and (100) cleavages. Extinction par- ~ ~ alleL" l~4~ Tourmaline Na(Mg,Fe,Mn,Li,Alk Hex. (-) 111=1.636 Mod. biref.
    [Show full text]
  • Diopside Camgsi2o6 C 2001 Mineral Data Publishing, Version 1.2 ° Crystal Data: Monoclinic
    Diopside CaMgSi2O6 c 2001 Mineral Data Publishing, version 1.2 ° Crystal Data: Monoclinic. Point Group: 2=m: As prismatic crystals with nearly square cross sections, to 50 cm; granular, columnar, lamellar massive. Twinning: Simple or multiple twins on 100 or 010 , common. f g f g Physical Properties: Cleavage: Distinct on 110 , (110) (110) 87±; partings on 100 and probably 010 . Fracture: Uneven to conchofidal.g Tenaci^ty: Britt»le. Hardness = 5f.5{6.g5 D(meas.) = 3.f22{3g.38 D(calc.) = 3.278 Optical Properties: Transparent to opaque. Color: Colorless, white, yellow, pale to dark green, black; colorless in thin section. Streak: White, gray, gray-green. Luster: Vitreous or dull. Optical Class: Biaxial (+). Orientation: Y = b; Z c = 38± on (010); X a = 22±. ^ ¡ ^ ¡ Dispersion: r > v; weak to moderate. ® = 1.664 ¯ = 1.672 ° = 1.694 2V(meas.) = 59± Cell Data: Space Group: C2=c: a = 9.746 b = 8.899 c = 5.251 ¯ = 105:63± Z = 4 X-ray Powder Pattern: Schwartzenstein, Austria. (ICDD 11-654). 2.991 (100), 2.528 (40), 2.893 (30), 2.518 (30), 3.23 (25), 2.952 (25), 1.625 (25) Chemistry: (1) (2) (1) (2) (1) (2) SiO2 54.66 54.09 FeO 0.07 1.47 K2O 0.15 + TiO2 0.28 MnO 0.02 0.09 H2O 0.22 0.22 Al2O3 0.07 1.57 MgO 18.78 16.96 H2O¡ 0.08 Fe2O3 0.68 0.74 CaO 25.85 21.10 rem: 0.49 Cr2O3 2.03 Na2O 1.37 Total 100.35 100.64 3+ (1) Juva, Finland; corresponds to Ca1:00(Mg1:01Fe0:02)§=1:03Si1:98O6: (2) Dutoitspan mine, 2+ Kimberley, Cape Province, South Africa; corresponds to (Ca0:82Na0:05Fe0:04Mg0:04K0:01)§=0:96 3+ (Mg0:88Cr0:06Al0:03Fe0:02Ti0:01)§=1:00(Si1:96Al0:04)§=2:00O6: Polymorphism & Series: Forms two series, with hedenbergite, and with johannsenite.
    [Show full text]
  • A Specific Gravity Index for Minerats
    A SPECIFICGRAVITY INDEX FOR MINERATS c. A. MURSKyI ern R. M. THOMPSON, Un'fuersityof Bri.ti,sh Col,umb,in,Voncouver, Canad,a This work was undertaken in order to provide a practical, and as far as possible,a complete list of specific gravities of minerals. An accurate speciflc cravity determination can usually be made quickly and this information when combined with other physical properties commonly leads to rapid mineral identification. Early complete but now outdated specific gravity lists are those of Miers given in his mineralogy textbook (1902),and Spencer(M,i,n. Mag.,2!, pp. 382-865,I}ZZ). A more recent list by Hurlbut (Dana's Manuatr of M,i,neral,ogy,LgE2) is incomplete and others are limited to rock forming minerals,Trdger (Tabel,l,enntr-optischen Best'i,mmungd,er geste,i,nsb.ildend,en M,ineral,e, 1952) and Morey (Encycto- ped,iaof Cherni,cal,Technol,ogy, Vol. 12, 19b4). In his mineral identification tables, smith (rd,entifi,cati,onand. qual,itatioe cherai,cal,anal,ys'i,s of mineral,s,second edition, New york, 19bB) groups minerals on the basis of specificgravity but in each of the twelve groups the minerals are listed in order of decreasinghardness. The present work should not be regarded as an index of all known minerals as the specificgravities of many minerals are unknown or known only approximately and are omitted from the current list. The list, in order of increasing specific gravity, includes all minerals without regard to other physical properties or to chemical composition. The designation I or II after the name indicates that the mineral falls in the classesof minerals describedin Dana Systemof M'ineralogyEdition 7, volume I (Native elements, sulphides, oxides, etc.) or II (Halides, carbonates, etc.) (L944 and 1951).
    [Show full text]
  • Titanian Clinohumite in the Carbonatites of the Jacupiranga
    American Mineralogist, Volume 77, pages 168-178, 1992 Titanian clinohumite in the carbonatitesof the JacupirangaComplex, Brazil: Mineral chemistry and comparisonwith titanian clinohumite from other environments Josf C. Glspan Departamento de Mineralogia e Petrologia, Instituto de Geoci€ncias,Universidade de Brasilia, 70910 Brasilia DF, Brazil Ansrucr Titanian clinohumite (TiCl) occurs in the carbonatites of the Jacupiranga Complex, Brazil, either as the result of alteration of olivine (Mitchell, 1978) or in the reaction rock developed in the contact ofthe carbonatitesand the host magnetite pyroxenite, where it may not be related to olivine. Lamellae of titanian chondrodite (TiCh) are found, and the presenceof lamellae of polysomesrepresenting n > 4 is inferred. The TiCl samplescontain TiO, up to 3.78 wto/0,FeO up to 3.09 wto/0,and F up to 2.34 wto/o.Fe and Ti show a positive correlation. Complex zoning is always present. The only consistenttrend is that of increasingTiO, toward the margins, but even this trend is only observedin the crystals of the reaction rock. The partitioning of Fe and Mg between TiCl and olivine indicates enrichment of Mg in the TiCl and is different for samples from the three sovites. The characteristicsof the TiCl are thought to derive from a changing metasomatic environ- ment, and all TiCl so far reported from carbonatite complexesis possibly of metasomatic origin. The JacupirangaTiCl is similar in composition to TiCl from marbles, an obser- vation that cannot be extendedto TiCl from carbonatitesin general.Samples of TiCl from kimberlites have compositions similar to those from some Alpine peridotites. Fluorine TiCl is certainly stable in the upper mantle, but becauseof its rarity it is considered a mineral of no importance to mantle geology.
    [Show full text]
  • The Journal of ^ Y Volume 26 No
    Gemmolog^^ The Journal of ^ y Volume 26 No. 8 October 1999 fj J The Gemmological Association and Gem Testing Laboratory of Great Britain Gemmological Association and Gem Testing Laboratory of Great Britain 27 Greville Street, London EC1N 8TN Tel: 020 7404 3334 Fax: 020 7404 8843 e-mail: [email protected] Website: www.gagtl.ac.uk/gagtl. President: Professor R.A. Howie Vice-Presidents: E.M. Bruton, A.E. Farn, D.G. Kent, R.K. Mitchell Honorary Fellows: Chen Zhonghui, R.A. Howie, R.T. Liddicoat Jnr, K. Nassau Honorary Life Members: H. Bank, D.J. Callaghan, E.A. Jobbins, H. Tillander Council of Management: T.J. Davidson, N.W. Deeks, R.R. Harding, I. Mercer, J. Monnickendam, M J. O'Donoghue, E. Stern, I. Thomson, V.P. Watson Members' Council: A.J. Allnutt, P. Dwyer-Hickey, S.A. Everitt, A.G. Good, J. Greatwood, B. Jackson, L. Music, J.B. Nelson, PG. Read, R. Shepherd, P.J. Wates, C.H. Winter Branch Chairmen: Midlands - G.M. Green, North West -1. Knight, Scottish - B. Jackson Examiners: A.J. Allnutt, MSc, Ph.D., FGA, L. Bartlett, B.Sc, MPhiL, FGA, DGA, E.M. Bruton, FGA, DGA, S. Coelho, B.Sc, FGA, DGA, Prof. A.T. Collins, B.Sc, Ph.D, A.G. Good, FGA, DGA, J. Greatwood, FGA, G.M. Howe, FGA, DGA, B. Jackson, FGA, DGA, G.H. Jones, B.Sc, Ph.D., FGA, M. Newton, B.Sc, D.Phil., C.J.E. Oldershaw, B.Sc (Hons), FGA, H.L. Plumb, B.Sc, FGA, DGA, R.D. Ross, B.Sc, FGA, DGA, PA.
    [Show full text]
  • Geology and Geochemistry of the Early Proterozoic Kortejärvi and Laivajoki Carbonatites, Central Fennoscandian Shield, Finland
    GEOLOGY AND GEOCHEMISTRY OF THE EARLY PROTEROZOIC KORTEJÄRVI AND LAIVAJOKI CARBONATITES, CENTRAL FENNOSCANDIAN SHIELD, FINLAND JUHA NYKÄNEN, KAUKO LAAJOKI and JUHA KARHU JUHA NYKÄNEN, KAUKO LAAJOKI and JUHA KARHU, 1997: Geol- ogy and Geochemistry of the Early Proterozoic Kortejärvi and Laivajoki Carbonatites, Central Fennoscandian Shield, Finland. Bull.Geol. Soc. Fin- land 69, Part 1-2, 5-30. This paper provides for the first time extensive petrological, mineralogical and geochemical data on the early Proterozoic Kortejärvi and Laivajoki car- bonatites, northern Finland, which form metamorphosed and highly strained bodies 2 and 4 km long within a Svecokarelian shear zone in central Fennos- candian Shield. They are not exposed, but have been penetrated by a couple of deep drill holes. In terms of modal mineralogy, both intrusions contain calcite carbonatite and dolomite-calcite carbonatite as their main rock types, but Kortejärvi also contains dolomite carbonatite and calcite-dolomite carbonatite, some glim- men te and olivine-magnetite rock and Laivajärvi tremolite-calcite carbonatite, tremolite-dolomite carbonatite, serpentine-talc-dolomite rock and glimmerite. The main country rock is an amphibolite which is not fenitized. No alkaline rocks have been detected in these intrusions. Calcite is most common mineral in both occurrences. Other carbonate minerals include dolomite with minor ankerite and occassional siderite. In addition to low-Ti phlogopite, tetraferriphlogopite is also encountered. Fresh olivine is rare, and its alteration products include titaniferous clinohumite. The amphiboles are mainly calcic amphiboles, including actinolite, tremolite and edenite. The only sodic-calcic amphibole is accessory richterite. Other essen- tial minerals are Ti-poor magnetite with ilmenite exsolutions, fluorapatite (3.95-4.89 wt.
    [Show full text]
  • Winter 2007 Gems & Gemology
    G EMS & G VOLUME XLIII WINTER 2007 EMOLOGY CVD Synthetic Diamonds Canary Tourmaline W Fluorescence Spectroscopy INTER Napoleon Necklace 2007 P AGES 291–408 V OLUME 43 N O. 4 THE QUARTERLY JOURNAL OF THE GEMOLOGICAL INSTITUTE OF AMERICA ® Winter 2007 VOLUME 43, NO. 4 291 LETTERS ________ FEATURE ARTICLES _____________ 294 Latest-Generation CVD-Grown Synthetic Diamonds from Apollo Diamond Inc. Wuyi Wang, Matthew S. Hall, Kyaw Soe Moe, Joshua Tower, and Thomas M. Moses Presents the gemological and spectroscopic properties of Apollo’s latest products, which show significant improvements in size, color, and clarity. 314 Yellow Mn-rich Tourmaline from the Canary Mining Area, Zambia pg. 295 Carat Points Brendan M. Laurs, William B. Simmons, George R. Rossman, Eric A. Fritz, John I. Koivula, Björn Anckar, and Alexander U. Falster Explores the vivid “canary” yellow elbaite from the Lundazi District of eastern Zambia, the most important source of this tourmaline. 332 Fluorescence Spectra of Colored Diamonds Using a Rapid, Mobile Spectrometer Sally Eaton-Magaña, Jeffrey E. Post, Peter J. Heaney, Roy A. Walters, Christopher M. Breeding, and James E. Butler Reports on the use of fluorescence spectroscopy to characterize colored diamonds from the Aurora Butterfly and other collections. NOTES AND NEW TECHNIQUES ________ 352 An Examination of the Napoleon Diamond Necklace Eloïse Gaillou and Jeffrey E. Post pg. 329 Provides a history and gemological characterization of this historic necklace. REGULAR FEATURES _____________________ 358 Lab Notes Apatite in spessartine • Atypical photoluminescence feature in a type IIa diamond • Diamond with “holiday” inclusions • Diamond with large etch channels containing iron sulfides • Black diamond with an oriented etch channel • The pareidolia of diamonds • Notable emerald carving • Gold coated onyx • Double-star sapphire • Imitation turquoise 366 Gem News International Record auction prices for diamonds • Namibian diamond mining pg.
    [Show full text]
  • OH-Bearing Planar Defects in Olivine Produced by the Breakdown of Ti-Rich Humite Minerals from Dabie Shan (China)
    Contrib Mineral Petrol (2007) 153:417–428 DOI 10.1007/s00410-006-0155-7 ORIGINAL PAPER OH-bearing planar defects in olivine produced by the breakdown of Ti-rich humite minerals from Dabie Shan (China) Jo¨ rg Hermann Æ John D. Fitz Gerald Æ Nadia Malaspina Æ Andrew J. Berry Æ Marco Scambelluri Received: 14 August 2006 / Accepted: 23 October 2006 / Published online: 21 November 2006 Ó Springer-Verlag 2006 Abstract The partial breakdown of Ti-chondrodite beyond the breakdown of the hydrous humite minerals and Ti-clinohumite during exhumation from ultra-high and confirms earlier suggestions that Ti plays a key role pressure to amphibolite facies conditions in garnet- in OH incorporation in mantle olivine. We suggest that pyroxenites from Dabie Shan (China) produces coro- olivine containing Ti-clinohumite defects is an impor- nas of olivine coexisting with ilmenite blebs. Fourier tant phase for water transport in subduction zones and transform infrared (FTIR) spectra of this newly formed for the storage of water in cold subcontinental mantle. olivine exhibit absorption bands in the hydroxyl- However, these defects are unlikely to be stable in stretching region. Two intense peaks were observed at hotter parts of the oceanic mantle such as where 3,564 and 3,394 cm–1, identical in energy to peaks in Ti- basaltic magmas are generated. clinohumite. Transmission electron microscopy (TEM) of the same olivine domains revealed the presence of a Keywords Ti-chondrodite Á Ti-clinohumite Á complex (001) planar intergrowth. These interlayers OH in olivine Á Transmission electron microscopy Á have a 1.35 nm repeat distance, which is characteristic Infrared spectroscopy Á UHP metamorphism of clinohumite.
    [Show full text]
  • Spinel from Mogok, Myanmar—A Detailed Inclusion Study by Raman
    FEATURE ARTICLE Spinel from Mogok, Myanmar—A Detailed Inclusion Study by Raman Microspectroscopy and Scanning Electron Microscopy Myint Myat Phyo, Eva Bieler, Leander Franz, Walter Balmer and Michael S. Krzemnicki ABSTRACT: Mineral inclusions within 100 gem-quality spinels from both primary marble and secondary alluvial mining sites within Myanmar's Mogok Valley were analysed using Raman microspectroscopy and scanning electron microscopy (including backscattered-electron imaging and energy-dispersive spectroscopy). The samples ranged from pink to red, orangey pink to orangey red, and grey to purplish grey. We identified a number of inclusions that are reported here for the first time in Mogok spinel: amphibole (presumably pargasite), anatase, baddeleyite, boehmite, brucite, chlorite, clinohumite, clinopyroxene, diaspore, geikielite, goethite, halite, marcasite, molybdenite, periclase and pyrrhotite. We also found several minerals that were previously known as inclusions in Mogok spinel, including anhydrite, apatite, carbonates (calcite, dolomite and magnesite), chondrodite, elemental sulphur, graphite, iron oxides or iron hydroxides, phlogopite and zircon. We further differentiated the occurrence of inclusions in spinel from different mining sites in Mogok to assess whether these mineral assemblages can enhance our understanding of the geological origin of these gems and whether the inclusions can help separate Mogok spinels from those of other marble-related deposits worldwide. The Journal of Gemmology, 36(5), 2019, pp. 418–435, http://doi.org/10.15506/JoG.2019.36.5.418 © 2019 Gem-A (The Gemmological Association of Great Britain) ince ancient times, gem-quality spinel (ideally imperial jewels, two of which were later integrated into MgAl2O4) has been appreciated for its range British royal jewels (the Black Prince’s ‘Ruby’ and the of colour and often exceptional clarity, and Timur ‘Ruby’; see also Pardieu & Hughes 2008; Yavorskyy today spinel is the second most important and & Hughes 2010; Truong 2017).
    [Show full text]
  • Titanian Clinohumite-Bearing Peridotite from the Ulamertoq Ultramafic Body in the 3.0 Ga Akia Terrane of Southern West Greenland
    geosciences Article Titanian Clinohumite-Bearing Peridotite from the Ulamertoq Ultramafic Body in the 3.0 Ga Akia Terrane of Southern West Greenland Ikuya Nishio 1, Tomoaki Morishita 2,3,* , Kristofer Szilas 4 , Graham Pearson 5, Ken-Ichiro Tani 6, Akihiro Tamura 2, Yumiko Harigane 7 and Juan Miguel Guotana 1 1 Graduate School of Natural Science and Technology, Kanazawa University, Kanazawa, Ishikawa 920-1192, Japan; [email protected] (I.N.); [email protected] (J.M.G.) 2 Faculty of Geosciences and Civil Engineering, Institute of Science and Engineering, Kanazawa University, Kanazawa, Ishikawa 920-1192, Japan; [email protected] 3 Lamont-Doherty Earth Observatory, Columbia University, New York, NY 10027, USA 4 Department of Geosciences and Natural Resource Management, University of Copenhagen, 10, 1165 Copenhagen, Denmark; [email protected] 5 Department of Earth and Atmospheric Science, Univesity of Alberta, Edmonton, AB T6G 2B4, Canada; [email protected] 6 National Museum of Nature and Science, Tokyo 110-8718, Japan; [email protected] 7 Institute of Geology and Geoinformation Geological Survey of Japan/AIST, Tsukuba, Ibaraki 305-8560, Japan; [email protected] * Correspondence: [email protected]; Tel.: +81-(0)76-264-6513 Received: 27 December 2018; Accepted: 28 March 2019; Published: 1 April 2019 Abstract: A titanian clinohumite-bearing dunite was recently found in the Ulamertoq ultramafic body within the 3.0 Ga Akia Terrane of southern West Greenland. Titanian clinohumite occurs as disseminated and discrete grains. Titanian clinohumite contains relatively high amounts of fluorine, reaching up to 2.4 wt.%. The high-Fo content of olivine (Fo93) coupled with low Cr/(Cr + Al) ratio of orthopyroxene implies that the dunite host is not of residual origin after melt extraction by partial melting of the primitive mantle.
    [Show full text]
  • Cretaceous Carbonatites of the Southeastern Brazilian Platform
    DOI: 10.1590/2317-4889201820170123 ARTICLE Cretaceous carbonatites of the southeastern Brazilian Platform: a review Celso de Barros Gomes1*, Piero Comin-Chiaramonti2, Rogério Guitarrari Azzone1, Excelso Ruberti1, Gaston Eduardo Enrich Rojas1 ABSTRACT: This paper reviews general aspects of alkaline-carbonatitic rocks of Brazilian, Paraguayan and Bolivian terrains. Although 30 such oc- currences are known in literature, only the major ones have been thoroughly investigated. The carbonatites are of Cretaceous age, with two well-defined Lower Cretaceous and Upper Cretaceous generation episodes. A clear tectonic control by ancient structural features such as archs, lineaments and faults characterizes most cases. The rocks exhibit a large compositional variation, in decreasing orders of abundance from calciocarbonatites to magnesiocar- bonatites to ferrocarbonatites. In some complexes, they form multistage intrusions. C-O isotopes indicate that, in general, the carbonatites were affected by post-magmatic processes associated with the topographic level of emplacement and low-temperature H2O-CO2 rich fluids responsible for the increased amount of heavy carbon and oxygen. Sr-Nd isotopic compositions similar to those of coeval alkaline silicate rocks, ranging from depleted to enriched mantle sources, have been influenced by two distinct metasomatic events in Proterozoic at 2,0-1.4 Ga and 1.0-0.5 Ga. Sr-Nd-Pb-Os data seem related to an isotopically enriched source, their chemical heterogeneities reflecting a depleted mantle that was metasomatized by small-volume melts and by fluids rich in incompatible elements. Fractional crystallization and liquid immiscibility are believed to be the most effective processes in the formation of the Cretaceous carbonatites, with minor contribution of crustal contamination.
    [Show full text]
  • Gemstone Deposits of the Four Corners Region, USA Robert W
    New Mexico Geological Society Downloaded from: http://nmgs.nmt.edu/publications/guidebooks/61 Gemstone deposits of the Four Corners region, USA Robert W. Eveleth and Virgil W. Lueth, 2010, pp. 221-229 in: Geology of the Four Corners Country, Fassett, James E.; Zeigler, Kate E.; Lueth, Virgil W., [eds.], New Mexico Geological Society 61st Annual Fall Field Conference Guidebook, 246 p. This is one of many related papers that were included in the 2010 NMGS Fall Field Conference Guidebook. Annual NMGS Fall Field Conference Guidebooks Every fall since 1950, the New Mexico Geological Society (NMGS) has held an annual Fall Field Conference that explores some region of New Mexico (or surrounding states). Always well attended, these conferences provide a guidebook to participants. Besides detailed road logs, the guidebooks contain many well written, edited, and peer-reviewed geoscience papers. These books have set the national standard for geologic guidebooks and are an essential geologic reference for anyone working in or around New Mexico. Free Downloads NMGS has decided to make peer-reviewed papers from our Fall Field Conference guidebooks available for free download. Non-members will have access to guidebook papers two years after publication. Members have access to all papers. This is in keeping with our mission of promoting interest, research, and cooperation regarding geology in New Mexico. However, guidebook sales represent a significant proportion of our operating budget. Therefore, only research papers are available for download. Road logs, mini-papers, maps, stratigraphic charts, and other selected content are available only in the printed guidebooks. Copyright Information Publications of the New Mexico Geological Society, printed and electronic, are protected by the copyright laws of the United States.
    [Show full text]