DOCSLIB.ORG

Field Relations and Chemistry Of

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text

Load more

Canadian Mineralogist Yol. 22, pp. 417421 (1984) FIELDRELATIONS AND CHEMISTRYOF SAPPHIRINE.BEARING ROCKSFROM THE R'@RNESUNDAREA. FISKENESSET,WESTERN GREENLAND HOWARD R. WILLIAMS Dewrtnent of Geologicol Sciences,Brock University, St. Catharines, Ontario L2S 3Al ABSTRACT (1910),has sincebeen found worldwide in hig[-grade met?morphic rocks of diverse composition and his- Two contrasting sapphirine-bearing assemblagesare tory (Hiegins et al. 1979).This paper dessribestlree described: a higbly maguesianone, developed sporadical- more sapphirine-bearing localities some 50 kn east ly at the upper contact of the FisketrEssetComplex in as- of the tlpe locality. Herd et al. (1969) and Herd sociation with layeredultramafic rocks, and the other, more (1973) reinvestigated the Fiskenaessetlocality, iron-rich, in the amphibolite bordering the Complex. Miner- describing it in detail; the sapphirine was found to al assemblagesdescribed (1) are oftwo kincls: iron-poor: be associatedwitl rocks marginal to the Fiskenas- enstatite - phlogopite - olivine - pargasite - - sapphirine (Windley spinel, gedrite - sapphirine - spinel, and enstatite - gedrite set Complex et al. 1973). - phlogopite - sapphirine - spi4el; (2) iron-rich: magnesio- The tlree occurrencesdescribed in this paper have hornblende - sapphirine - spinel - anorthite. Only the iron- similar field relations to the classicFiskenasset lo- poor sapphirine-bearing assemblagesand their associates cality Gig. l). The local geologyis dominatedby a are characterizedby the presenceof accessoryapatite, ru- high-eradequartzofeldspathic gneiss terrane contain- tile and zircon, which may indicate a possible sedimentary ing intercalated layers of amphibolite and outlying origin for at least some of the sapphirine-bearing materi- parts of the Fiskenessetgemplex. Petrographic evi- al. The iron-rich assemblageis found within rocks consi- dence indicates that these rocks failed to enter dered to be entirely of igneous origin. eranulite-facies conditions during late Archean (Williams Keywords: sapphirine, west Greenland, chemistry, petrol- met?morphism 1973). ogy, Fiskenesset Complex. Two types of sapphirine-bearing lithology are described,with contrasting mineralogy and minsl{ chemistry. Both fit into the classification systempro- Souuarnr posed by Herd et al. (L969). On d6crit deux assemblagese sapphirine du complexe PETRocRAPHY AND MINERALOGY oF SAPPHIRN.IE. de Fiskenesset (Groilnland occidental). Le premier, trts BEARING LITHOLOGIES AND ASSOCIATED ROCKS magndsien, apparalt par ci, par li au contact supdrieur, associ€aux roches ultramafiques stratifides. L'autre, plus Iron-poor assemblages riche en fer, setrouve d4ns les amphibolites en bordure du Two examplesof an iron-poor sapphirine-bearing complexe. On note les assemblagessuivants: (l) dans les between the roches i faible teneur etr fer: enstatite - phlogopite - oli- assemblage occur at the contact vine - pargasite - sapphirine - spinelle, gedrite - sapphi- Fiskenesset Complex and amphibolite (Fig. lb). rine - spinelle,et enstatite- gedrite - phlogopite - sapphirine Four distinct parageneseshave beenrecopized (Ia- - spinelle; (2) dans les roches riches en fer, magn6sio- ble 1). Where present, sapphirine oscurs as rims hornblende - sapphirine - spinelle - anorthite. Seuls les around spinel blasts up to l0 mm acrossin a matrix assemblagesd sapphirine pauvres en fer, et les assembla- containingrelics of olivine and enstatitewithin ged- gesqui leur sont associds,contiennent apatite, rutile et zir- rite and phlogopite. The gedrite and enstatiteare g6a ggmms min6raux accessoires,ce qui fait penser d une straw-colored in hand specimen and predominate origine s6dimentaire pour partie au moins une des roches over oliyine, pargasite and phlogopite, which are ir- d sapphirine. L'assemblage riche en fer, par contre, se and spinel trouve dans desroches dont I'origine est considdrdecomme regularly distributed. Where sapphirine purement ign6e. are present, amphibole and mica commonly radiate from them. Clraduit par la R€daction) In thin section, amphibole and sapphirine are colorless; the spinel is palest blue and phlogopite is Mots-clds: sapphirine, Groihland oocidental, chimisme, pale brown. Grains of amphibole and nica clearly p6trologie, complexe de Fiskenesset. replace olivine and enstatite. However, spinel may be intergrown symplectitically with gedrite, and is commonly rimmed by both gedrite and phlogopite. INTRoDUcTIoN Spinel and olivine are found as large blasts with in- Sapphirine, first described from the Fiskenasset clusions of rutile, zircon and apatite. Anorthitic district of western Greenland in 1809 by Giesecke plagioclaseis rarely found but occurs enclosing eu- 4t7 Downloaded from http://pubs.geoscienceworld.org/canmin/article-pdf/22/3/417/3713708/417.pdf by guest on 26 September 2021 THE CANADIAN MINERALOGIST Ftc. l. (a) Map showing sapphirine localities; inset left indicates position of (a) within Greenland. Positions of Figure lb and lc are indicated. Stipple: amphibolite and anorthosite in the Bjdrnound area only. O) Ceological map of tle two iron-poor sapphirineoccurrences. Insets indicate detailedrelationships. (c) Geologicalmap of relatively iron-rich sapphirine occurrence. Downloaded from http://pubs.geoscienceworld.org/canmin/article-pdf/22/3/417/3713708/417.pdf by guest on 26 September 2021 SAPPHIRINE.BEARING ROCKS FROM WESTERN GREENLAND 4t9 'I. hedral gedrite needlespoikiloblastically. In general, TABLE MINERALASSEI4BLAGES AND HERD CLASSIFICATION SAPPHIRINE-BEARINGAND ASsOCIATED ROCKS these four lithologies show abundant textural evi- OF IRON-POOR dence for rnineral disequilibrium, with particularly Sample Paraqenesls Herd Class complicated textural relationships. 106619 Enstatl te-ph] ogopite-o l i vl ne-pargaslte- AlBn The four lithologies are developedoverlying and sapphirine-sp I nel -zl rcontanorthlte within magnetite- and pleonaste-rich dunites and 'l I nel -ruti e-apatl te C peridotites, which occur as well-layered, discontilu- 106622 Gedrite-sapphi ri ne-sp 106625 Gedrlte-phlogoplte-anorthite No sapph. ous lensesalong the upper anorthositic contact. In- Type 3 terlayered with these ultramafic units are thin lay- 106626 Enstati te-gedrite-ph l ogopi te-sapphirine- AlC ers of marble. High chromium and niqkel splnel -zl rcon-ruti l e concentrations in the ultramafic rocks suggestanl ig- Sanples are ldentified by thelr GreenlandGeological survey neous origin. Locally derived pegmatites of div$rse (G.G.U.)number. Material is housedat the Unlversity of 'granitic' compositions are comm.only associaited Exeter, U.K. with the zoneof contact betweenthe ulhamafic rd,cks and the amphibolite. They range in compositiion from true granite through syenite to subsilicic robks Anorthite-rich plagioclase,magnetite and corundum containing only albite and corundum (plumasife). occur as accessories,in bands parallel to the folia- tion. Corundu'n and magnetite appear to have Iron-rich assembloge formed from the breakdown of spinel, whereaszoi- site formed from the degradation of anorthite. The An exampleof an iron-rich sapphirine-bearingas- generaltexture of amphibole, spinel, sapphirine and (GGU semblage 10479) is found near the nortlbrn anorthite is one of mineral equilibrium, with simple parag(ne- end of Bjdrnesund (Fig. lc), and has the grain-boundaries and triple-point contacts. sis magncio-hornglende - sapphirine- spinel - a4or- thte a magnetite t corundum t zoisite QIerdt[pe B). The sapphirine is contained within a sacchafoi- MINERAL CHEMISTRY OF THE SEPPHNTNS-SEARTNIC dal hornblende-rich rock found withiu fine-grained LITHOLOGIES amphibolites lying structurally above the Fiskenas- set Complex. Composed chiefly of slightly foliated The sapphirine-bearinglithologies and associated pale green granoblastic magnesio-hornblende, the rocks have been analyzed (Table 2). Except for rock contains medium blue, pleochroic sapphirine 106619,there is little evidenceof compositional zon- and olive green aluminous spinel as elongate grains ing; therefore, the compositionsare consideredto up to 1 mm asross.Sapphirine commonly includes represent the typical chemistry of each phase. The spinel and, in some instances, perhaps replaces it. composition of olivine, enstatite and phlogopite in TABLE2. COI4POSITIONOF SAPPHIRINE AND ASSOCIATED MINERALS n6a2z1 I 066261 I 066191 rc47gg2 Spr # Spl Opx Ged Spr Spl Opx Ged Phl Hbl Opx 0l Spr SPI Hbl si02 tr. 56.1 46,4 14.0 56.4 5l.5 40.3 50.7 58.6 42.7 13.3 tr' 45.7 Ti02 tr. 0.02 0.1 0.3 0.04 tr. 0.03 - 0.6 0.77 0.07 0.01 0.02 0.02 0.2 Al^0^ 66.I 68.3 3,47 17.4 62,5 68.5 3.01 16.4 17.2 9.09 2.11 tr. 63.5 65.0 15.? 18.8 7.16 Fe0 J.l t 0.I 6.54 5.5 ?.4 8.1 6.31 5.27 2.13 1.62 3.82 4.M 5.91 Mn0 0.03 0.03 u.uo 0.03 0.lI 0.06 0.06 0.09 0.12 .16.0 Mso t 9.4 21,9 34.8 25.7 20.4 23.6 35.0 26.8 24.5 21.3 37.3 53.6 17.6 15.5 Ca0 o_ou 0.63 tr. 0.03 0.46 tr. 12.9 0.0s 0.03 0.01 0.02 IL6 Na20 : 1.84 tr. - u.v4 l.1 l tr. tr. l.l4 Kr0 u.uJ 0.02 - 7.8 - 0'16 fnO 0.02 tr. tr. 0.16 0.28 0.05 "'2-3 0.12 0.02 0.02 .l01.0 Tota l 101.8loo.4 97.7 99.3 100.0100.7 100.4 93.4 97.4 101.9 100.8 100.4 99.6 97,1 Mg/(l,tg+Fe)0.92 0.78 0.90 0.89 0.94 0.84 0.91 0.90 0.9s 0.96 0.95 0.96 0.84 0.60 0.80 l. SeeTable I for iron-poor assemblages.2. Iron-rich assenblage..# Analyst,..J.C..Bevan..Abbreviations: ollvlne' Spr sapphlrine, Spl splnel, Opx orthopyroxene,Ged gedrite, Phl -phlogopJte'Hbl hornblende'ul ti.. trirte. foiat'jron'calculaLed as Feb-. Prob6 condilions ts t<v, 2b nA, torrection program"MAGlc" adapted by R.N. t^lilson. Downloaded from http://pubs.geoscienceworld.org/canmin/article-pdf/22/3/417/3713708/417.pdf by guest on 26 September 2021 420 TI{E CANADIAN MINERALOGIST the iron-poor lithologies is extremely magnesian,in tribution coefficient Kp for both is gimilu, 6d contrast to the adjacent ultramafis rocks, which are identical to that determined by Lal et al.
Recommended publications
  • New Minerals Approved in 1998 by The

    New Minerals Approved in 1998 by The

    247 The Canadian Mineralogist Vol. 37, pp. 247-252 (1999) NEW MINERALSAPPROVED IN 1998 BY THE COMMISSIONON NEW MINERALS AND MINERALNAMES. INTERNATIONAL MINERALOGICAL ASSOCIATION JOEL D. GRICE* CanadianMuseum of Nttture,P.O. Box 3443A,Station "D", Ottawa,Ontario KIP 6P4 GIOVANNI FERRARISX* Dipanimentodi ScienzeMineralogiche e Petrologiche,Universitd di Torino,Via ValpergaCaluso 35, I-10125Torino, Italy The information given here is provided by the Commission on New Minerals and Mineral Names (CNMMN), Intemational Mineralogical Association (IMA), for comparative purposesand as a service to mineralogists work- ing on new species.Each mineral is described in the following format: IMA Number Chemical Formula (any relationship to other minerals; structure analysis) Crystal system, spacegroup unit-cell parameters Color; luster; diaphaneity Optical properties Strongestlines in the X-ray powder-diffraction pattern td in A(I)l The namesof these approved speciesare consideredconfidential information until the authors have published their descriptions or releasedinformation themselves.No other information will be releasedby the Commission. 1998Pnoposers IMA No. 98-002 Ca:Ge(OH)6(SO+XCO:).12HzO A memberof IMA No. 98-001 the ettringitegroup; Cu3(AsOa)2.4H2O New structure-type structure OrthorhombiciPnma Hexagonal:P63/m a 5.6906.b t7.06I.c 9.82 A, a 11.056,c 10.629A Bottle green;vitreous; transparent White; vitreous;transparent Biaxial(-), u 1.745,B 1.755,1 1.760,2V(meas)11", Uniaxial(-), to 1.509,e 1.479 2V (calc)70" 8.52(100),3.721(60), 3.221(90), 9.57 (vs), 5. 5 3 (s), 3. 8 3 (s), 3. 56(ms), 3.44(m), 2.7 4(ms), 3.ro2(40), 2.8 r7 (3 5), 2.79 s (3 s), 2.3s0(25) 2.53(m) \ * Chairman, CNMMN.
  • Chemographic Exploration of Amphibole Assemblages from Central Massachusetts and Southwestern New Hampshire

    Chemographic Exploration of Amphibole Assemblages from Central Massachusetts and Southwestern New Hampshire

    Mineral. Soc. Amer, Spec. Pap. 2, 251-274 (1969). CHEMOGRAPHIC EXPLORATION OF AMPHIBOLE ASSEMBLAGES FROM CENTRAL MASSACHUSETTS AND SOUTHWESTERN NEW HAMPSHIRE PETER ROBINSON AND HOWARD W. JAFFE Department of Geology, University of Massachusetts, Amherst, Massachusetts 01002 ABSTRACT Fourteen wet chemical and forty electron-probe analyses were made of amphiboles from critical assemblages in the kyanite and sillimanite zones of central Massachusetts and southwestern New Hampshire. The rocks studied in- clude plagioclase amphibolites that are metamorphosed mafic lavas and tuffs, aluminous anthophyllite rocks of uncertain derivation, quartz-garnet-amphibole granulites that are metamorphosed ferruginous cherts, and pods of ultramafic amphibolite. The rocks contain the following associations: hornblende-anthophyllite, hornblende-cummingtonite, anthophyllite-cummingtonite, hornblende-anthophyllite-cummingtonite, anthophyllite-cordierite, and anthophyllite- kyanite-sillimanite-staurolite_garnet. The following generalizations are made: 1) The cummingtonites are compositionally simple, containing neither sig- nificant AI/AI, NaJAI, nor Ca substitution. 2) The hornblendes are high in AI/AI substitution. Those coexisting with cummingtonite in the kyanite zone or in retrograded rocks have a higher Al content than those coexisting with cum- mingtonite in the sillimanite zone, in close agreement with the prograde reaction tschermakitic hornblende -7 cumming- tonite + plagioclase + H20 proposed by Shido. The Na content of hornblende is considerably less than that of the theoretical edenite end member and is relatively insensitive to variation in the Na content of coexisting plagioclase. 3) Anthophyllites coexisting with hornblende contain about 1as much AI/AI substitution and 1as much Na substitution as coexisting hornblendes. Ca is negligible. Anthophyllites with cordierite, aluminosilicates, or garnet equal or surpass hornblende in AI/AI and Na substitution.
  • The Rutile Deposits of the Eastern United States

    The Rutile Deposits of the Eastern United States

    THE RUTILE DEPOSITS OF THE EASTERN UNITED STATES. By THOMAS L. WATSON. INTRODUCTION. The titanium-bearing minerals comprise more than 60 distinct species, grouped under a variety of mineral and chemical forms, chiefly as oxides, titanates, titano-silicates, silicates, columbates, and iantalates. These minerals are widely distributed in a variety of associations and in such quantity as to make titanium a relatively abundant element. Clarke* estimates the. amount of titanium in the solid crust of the earth to be 0.44 per cent, equivalent in oxide to 0.73 per cent, the element thus standing in the ninth place in the scale of abundance, next to potassium. Most of the titanium-bearing minerals, however, are rare and are only of scientific interest. The largest concentrations of the element are as oxide (rutile), as iron titanate (ilmenite), and in iron ferrate (magnetite) as intergrown ilmenite. Of these three forms the prin­ cipal source of the element at present is rutile. The known workable deposits of rutile, however, are extremely few and widely sepa­ rated, and as the demand for titanium has greatly increased in the last few years it has been necessary for some uses to turn to ilmenite or highly titaniferous magnetites. This paper briefly summarizes present knowledge of the geology of the rutile deposits in the eastern United States and for the sake of comparison discusses several foreign deposits, each of which has produced some rutile. Of the known deposits in the United, States only those in Virginia are of commercial importance. These have been made the subject of a special report 2 by the Virginia Geological Survey, which was preceded by a preliminary paper on the rutile deposits of Amherst and Nelson counties.3 1 Clarke, F.
  • Optical Properties of Common Rock-Forming Minerals

    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.
  • Khmaralite, a New Beryllium-Bearing Mineral Related to Sapphirine: a Superstructure Resulting from Partial Ordering of Be, Al, and Si on Tetrahedral Sites

    Khmaralite, a New Beryllium-Bearing Mineral Related to Sapphirine: a Superstructure Resulting from Partial Ordering of Be, Al, and Si on Tetrahedral Sites

    American Mineralogist, Volume 84, pages 1650–1660, 1999 Khmaralite, a new beryllium-bearing mineral related to sapphirine: A superstructure resulting from partial ordering of Be, Al, and Si on tetrahedral sites JACQUES BARBIER,1,* EDWARD S. GREW,2 PAULUS B. MOORE,3 AND SHU-CHUN SU4 1Department of Chemistry, McMaster University, Hamilton, Ontario, L8S 4M1 Canada 2Department of Geological Sciences, University of Maine 5790 Bryand Center Orono, Maine 04469, U.S.A. 3P.O. Box 703, Warwick, New York,10990, U.S.A. 4Hercules Research Center, 500 Hercules Road, Wilmington, Delaware 19808, U.S.A. ABSTRACT 3+ 2+ Khmaralite, Ca0.04Mg5.46Fe 0.12Fe 1.87Al14.26Be1.43B0.02Si4.80O40, is a new mineral closely related to sapphirine from Khmara Bay, Enderby Land, Antarctica. It occurs in a pegmatite metamorphosed at T ≥ 820 °C, P ≥ 10 kbar. The minerals surinamite, musgravite, and sillimanite associated with khmaralite at Casey Bay saturate it in BeO, and thus its BeO content could be close to the maximum possible. Optically, khmaralite is biaxial (–); at λ = 589 nm, α = 1.725(2), β = 1.740(2), γ = 1.741(2), 2Vmeas = 34.4 (1.8)°, v > r strong, and β b. The weak superstructure reported using electron diffraction has been confirmed by single-crystal X-ray diffraction. The superstructure corresponds to a doubling of the a axis in monoclinic sapphirine-2M (P21/c setting) with the following unit-cell parameters: a = 3 19.800(1), b = 14.371(1), c = 11.254(1) Å, β = 125.53(1)°, Z = 4, Dcalc = 3.61 g/cm .
  • List of Abbreviations

    List of Abbreviations

    List of Abbreviations Ab albite Cbz chabazite Fa fayalite Acm acmite Cc chalcocite Fac ferroactinolite Act actinolite Ccl chrysocolla Fcp ferrocarpholite Adr andradite Ccn cancrinite Fed ferroedenite Agt aegirine-augite Ccp chalcopyrite Flt fluorite Ak akermanite Cel celadonite Fo forsterite Alm almandine Cen clinoenstatite Fpa ferropargasite Aln allanite Cfs clinoferrosilite Fs ferrosilite ( ortho) Als aluminosilicate Chl chlorite Fst fassite Am amphibole Chn chondrodite Fts ferrotscher- An anorthite Chr chromite makite And andalusite Chu clinohumite Gbs gibbsite Anh anhydrite Cld chloritoid Ged gedrite Ank ankerite Cls celestite Gh gehlenite Anl analcite Cp carpholite Gln glaucophane Ann annite Cpx Ca clinopyroxene Glt glauconite Ant anatase Crd cordierite Gn galena Ap apatite ern carnegieite Gp gypsum Apo apophyllite Crn corundum Gr graphite Apy arsenopyrite Crs cristroballite Grs grossular Arf arfvedsonite Cs coesite Grt garnet Arg aragonite Cst cassiterite Gru grunerite Atg antigorite Ctl chrysotile Gt goethite Ath anthophyllite Cum cummingtonite Hbl hornblende Aug augite Cv covellite He hercynite Ax axinite Czo clinozoisite Hd hedenbergite Bhm boehmite Dg diginite Hem hematite Bn bornite Di diopside Hl halite Brc brucite Dia diamond Hs hastingsite Brk brookite Dol dolomite Hu humite Brl beryl Drv dravite Hul heulandite Brt barite Dsp diaspore Hyn haiiyne Bst bustamite Eck eckermannite Ill illite Bt biotite Ed edenite Ilm ilmenite Cal calcite Elb elbaite Jd jadeite Cam Ca clinoamphi- En enstatite ( ortho) Jh johannsenite bole Ep epidote
  • The Crystal Structure of Aenigmatite E

    The Crystal Structure of Aenigmatite E

    THE AMERICAN MINERALOGIST, VOL. 56, MARCH-APRIL, 1971 THE CRYSTAL STRUCTURE OF AENIGMATITE E. CANNILLO AND F. MAZZI, Centro di studio del C.N.R. per la cristal- lografia struturale, Istituto di Mineralogia dell' Universita di Pavia, Italy. AND J. H. FANG, PAUL D. ROBINSON, AND Y. OHYA, Department of Geology, Southern Illinois University, Carbondale, Illinois, U.S.A. ABSTRACT Aenigmatite, Na2Fe.TiSi602Q, is triclinic PI, with a= 10.406(13), b = 10.813(14), c=8.926(6) A, <>= 104° 56'(9), ~=96°52'(11), 1'= 125°19'(6), and Z = 2. The structure was solved, independently and simultaneously, by Patterson syntheses and by the symbolic addition procedure. Three-dimensional refinement with 921 "observed" reflections (photo- graphic data) from a Naujakasik, Greenland, crystal gave RhkZ=0.075 and with 1501 "observed" reflections (counter data) from a Kola, Greenland crystal gave Rhkl=O.072. A distinct pseudo-monoclinic symmetry, based on a cell with parameters: 11m= 12.120, b1O=2X14.815, c1O=1O.406 A, <>10=90°4', ~1O=127°9', 1'10=89°44' (matrix of transforma- tion [011jI22/100j), Z = 8, emphasizes the similarity of its crystal structure with that of sapphirine [(Mg, Alh02(Si, Al)6018, a=11.266, b=14.401, c=9.929 A, ~=125 °46', Z=4, space group P2i!a]. The crystal structure consists of two sets of polyhedral layers parallel to the pseudo- monoclinic (100) plane which alternate along the x*-direction. The first layer is formed by Fe-octahedra, Ti-octahedra and distorted Na-square antiprisms and the second by [Si601s]" chains connected by Fe-octahedra.
  • The Effects of Composition Upon the High-Pressure Behaviour of Amphiboles: Compression of Gedrite to 7 Gpa and a Comparison with Anthophyllite and Proto-Amphibole

    The Effects of Composition Upon the High-Pressure Behaviour of Amphiboles: Compression of Gedrite to 7 Gpa and a Comparison with Anthophyllite and Proto-Amphibole

    Mineralogical Magazine, August 2012, Vol. 76(4), pp. 987–995 The effects of composition upon the high-pressure behaviour of amphiboles: compression of gedrite to 7 GPa and a comparison with anthophyllite and proto-amphibole 1,2, 1 3 4 F. NESTOLA *, D. PASQUAL ,M.D.WELCH AND R. OBERTI 1 Dipartimento di Geoscienze, Universita`di Padova, via Gradenigo 6, 35131 Padova, Italy 2 CNR Istituto di Geoscienze e Georisorse, UOS Padova, via Gradenigo 6, 35131 Padova, Italy 3 Department of Mineralogy, The Natural History Museum, Cromwell Road, London SW7 5BD, UK 4 CNR Istituto di Geoscienze e Georisorse, UOS Pavia, via Ferrata 1, 27100 Pavia, Italy [Received 10 February 2012; Accepted 23 March 2012; Associate Editor: G. Diego Gatta] ABSTRACT A single-crystal X-ray diffraction study of a sample of natural gedrite from North Carolina, USA, with A B 2+ C 2+ 4+ the crystal-chemical formula Na0.47 (Na0.03Mg0.97Fe0.94Mn0.02Ca0.04) (Mg3.52Fe0.28Al1.15Ti0.05) T W (Si6.31Al1.69)O22 (OH)2, up to a maximum pressure of 7 GPa, revealed the following bulk and axial moduli and their pressure derivatives: K0T = 91.2(6) GPa [K0T’ = 6.3(2)]; K0T(a) = 60.5(6) GPa [K0T(a)’ = 6.1(2)]; K0T(b) = 122.8(2.6) GPa [K0T(b)’ = 5.7(8)]; K0T(c) = 119.7(1.5) GPa [K0T(c)’ = 5.1(5)]. Gedrite has a much higher bulk modulus than anthophyllite (66 GPa) and proto-amphibole (64 GPa). All of the three axial moduli of gedrite are higher than those of these two other ortho- amphiboles.
  • KYANITE-GARNET GEDRITITE NEAR OROFINO, IDAHO* ANNI Hrbranrn, U

    KYANITE-GARNET GEDRITITE NEAR OROFINO, IDAHO* ANNI Hrbranrn, U

    THE AMERICAN MINERAIOGIST, VOL. 44, MAY_JUNE, 1959 KYANITE-GARNET GEDRITITE NEAR OROFINO, IDAHO* ANNI HrBraNrN, U. S. GeologicalSuraey, Menlo Park, Californio. ABSTRACT In Clearwater County, Idaho, kyanite is found with amphibole in two rock types, (1) in kyanite-garnet gedritite near Orofino and (2) in hornblende-bearing iayers of anorthosite in the Boehls Butte quadrangle. The associated rocks near Orofilo are garnetiferous biotite gneisses,hornblende-biotite gneiss, garnet amphibolites, quartzites, and lime-silicate rocks of sedimentary origin. The major constituents in the kvanite-garnet gedritite are gedrite (38 per cent), quartz (26 per cent), oligoclase (16 per cent), and garnet (14 per cent). One to two per cent of kyanite in light bluish crystals is scattered throughout the rock. The formula of the gedrite calculated from the chemical analysis is (K6 s1Na6eoCao ooMg:.soFe 1.57Mn 6.6aTi" e.e7Pe.61Feo olAlno)>:z ca (Sie.nA1r.or)>-r. oo(On.ro(OH)r.s0) >:2a. 00. The garnet consists of about 49 per cent almandite and 43 per cent pyrope with some spessartite, grossularite, and andradite The texture suggests that gedrite and garnet crystallized later than the other minerals. The chemical analysis of the gedritite shows more than 15 per cent Al:Or, about 8.5 per cent each of FeO and MgO, but only 0.2 per cent K2O and 1.7 per cent CaO. The hornblende- and kyanite-bearing layers of the anorthosite are described briefly for comparison. The kyanite in these layers is a relict mineral, inherited from the schist that formerly occupied the area now covered by anorthosite.
  • Ruby- and Sapphirine-Bearing Mineral Occurrenc- Es in the Fiskenaesset, Nuuk and Maniitsoq Re- Gions, West Greenland Peter W

    Ruby- and Sapphirine-Bearing Mineral Occurrenc- Es in the Fiskenaesset, Nuuk and Maniitsoq Re- Gions, West Greenland Peter W

    Ruby- and sapphirine-bearing mineral occurrenc- es in the Fiskenaesset, Nuuk and Maniitsoq re- gions, West Greenland Peter W. U. Appel & Martin Ghisler 1 cm G E U S 3 Contents Summary 6 Introduction 7 Geological setting 10 Mineralogy of the ruby/sapphirine-bearing rocks 12 Exploration history 14 Mineral licenses in Greenland 17 Description of localities in the Fiskenaesset area 19 1. Akunnaq/Lichtenfels ..................................................................................................... 20 2. Qeqertarssuatsiaat/Fiskenaesset ................................................................................. 21 3. Nunaqarfinguaq ............................................................................................................ 23 4. Sungaasa Nuaat ........................................................................................................... 24 5. Taseq East ................................................................................................................... 26 6. Pikiniq ........................................................................................................................... 27 7. Tuk ................................................................................................................................ 27 8. Ivnaarssuunguaq .......................................................................................................... 28 9. Iterdlaq fault .................................................................................................................
  • GEOLOGY of CORUNDUM and EMERALD GEM DEPOSITS : a R EVIEW Gaston Giuliani and Lee A

    GEOLOGY of CORUNDUM and EMERALD GEM DEPOSITS : a R EVIEW Gaston Giuliani and Lee A

    FEATURE ARTICLES GEOLOGY OF CORUNDUM AND EMERALD GEM DEPOSITS : A R EVIEW Gaston Giuliani and lee A. Groat The great challenge of geographic origin determina - processes), and alluvial (deposited by rivers). Today, tion is to connect the properties and features of indi - most sapphires are produced from gem placers related vidual gems to the geology of their deposits. Similar to alkali basalts, as in eastern Australia or southern geologic environments can produce gems with similar Vietnam, while placers in metamorphic environments, gemological properties, making it difficult to find such as in Sri Lanka (Ratnapura, Elahera) and Mada - unique identifiers. Over the last two decades, our gascar (Ilakaka), produce the highest-quality sap phires. knowledge of corundum and emerald deposit forma - The colluvial Montepuez deposit in Mozam bique pro - tion has improved significantly. vides a huge and stable supply of clean and very high- quality rubies. The mineral deposits are classically separated into pri - mary and secondary deposits. Primary corundum de - Primary emerald deposits are subdivided into two posits are subdivided into two types based on their types based on their geological environment of forma - geological environment of formation: (1) magmatic and tion: (1) tectonic-magmatic-related (Type I) and (2) (2) metamorphic. Magmatic deposits include gem tectonic-metamorphic-related (Type II). Several sub - corundum in alkali basalts as in eastern Australia, and types are defined and especially Type IA, hosted in M- sapphire in lamprophyre and syenite as in Montana UMR, which accounts for about 70% of worldwide (United States) and Garba Tula (Kenya), respectively. production (Brazil, Zambia, Russia, and others).
  • In the Piên Area, Paraná, Southern Brazil

    In the Piên Area, Paraná, Southern Brazil

    2A[' n"*t" arasileira d.e Geociênciæ VolmeS, 1978 A SAPPH I RIN E-ORTHOPYROXEN E-SPI N EL OCCU RR ENCE IN THE PIÊN AREA, PARANÁ, SOUTHERN BRAZIL VICENTE A.V. GIRARDI* and H.H.GJ. ULBRICHT ABSTRACT A minor ourcrop of a sapphirine-bearing rock within migmatites is geologi- cally associated with the largcmafic-ultramafic complex at Piên, State'of Paraná, S, nrazit. The rock, petrographycally classified as a sapphirine meta-norite, is characterized by a fine-grained equiliÈrium mosaic texture, with plagioclase (An 60/s), btonzite, qapphi- ìnter- rine and þeen spinel as main ininerals. The sapphirine is observed as ¡fmPl_ectitic growths with orihopyroxene and as isolated grains associated with_ plagioclase..and.or- Accessory minerals, not associated texgur¿lly with sapphirine crystallization, 'are-garnetihopyto*.tr.. and some retrograde minerals. Chemically, the rock presents high AlrO, and MgO contents and low SiO, ratios. with a strongly undersaturated_normative mineralogy' Itis suggested that the original material was a spinel-rich ultramafic rock. The sapphirine prribably crystallized by a combination of reaction-s involving mainly Al-pyroxenes, olivi- äe and ipinêt. A 2-pyroxene geothelmometer,_ applied to associated mafic and ultramafic rocks, inãicates for tñe granulitic metamorphism a temperature of crystallization between ?50 and 880"C and minirnum pressures of 7 Kb, while temperatures estimated from the.{l' content of orthopyroxenes coexisting with sapphirine are much too high. Similar conclu- sions are drawn irom the coexistence of sapphirine, bronzite and spinel, which suggests a crystallization temperature of about 800oC or more, at a minimum Pressure of 4 Kb. RESUMO O presente trabalho descreve ocorrência de safirina na região de Piên, Para- ná.