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THE CRYSTAL STRUCTURE of a MICROLITE-GROUP MINERAL with a FORMULA NEAR Nacata2o6f from the MORRO REDONDO MINE, CORONEL MURTA, MINAS GERAIS, BRAZIL

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615 The Canadian Mineralogist Vol. 49, pp. 615-621 (2011) DOI : 10.3749/canmin.49.2.615 THE CRYSTAL STRUCTURE OF A MICROLITE-GROUP MINERAL WITH A FORMULA NEAR NaCaTa2O6F FROM THE MORRO REDONDO MINE, CORONEL MURTA, MINAS GERAIS, BRAZIL MARCELO B. ANDRADE§ Instituto de Física de São Carlos, Universidade de São Paulo, Av. Trab. São-carlense 400, 13560-970 São Carlos, SP, Brazil DANIEL ATENCIO Instituto de Geociências, Universidade de São Paulo, Rua do Lago, 562, 05508-080 São Paulo, SP, Brazil LUIZ A.D. MENEZES FILHO Instituto de Geociências, Universidade Federal de Minas Gerais, Avenida Antônio Carlos, 6627, 31270-901 Belo Horizonte, MG, Brazil JAVIER ELLENA Instituto de Física de São Carlos, Universidade de São Paulo, Av. Trab. São-carlense 400, 13560-970 São Carlos, SP, Brazil ABSTRACT We present electron-microprobe and single-crystal X-ray-diffraction data for a microlite-group mineral with a formula near NaCaTa2O6F from the Morro Redondo mine, Coronel Murta, Minas Gerais, Brazil. On the basis of these data, the formula A B X Y is (Na0.88Ca0.88Pb0.020.22)S2.00 (Ta1.70Nb0.14Si0.12As0.04)S2.00 [(O5.75(OH)0.25]S6.00 (F0.730.27)S1.00. According to the new nomenclature for the pyrochlore-supergroup minerals, it is intermediate between fluornatromicrolite and “fluorcalciomicrolite”. The crystal structure, Fd3m, a = 10.4396(12) Å, has been refined to an R1 value of 0.0258 (wR2 = 0.0715) for 107 reflections (MoKa radiation). There is a scarcity of crystal-chemical data for pyrochlore-supergroup minerals in the literature. A compilation of these data is presented here. Keywords: microlite group, “fluorcalciomicrolite”, fluornatromicrolite, crystal-structure refinement, solid solution. SOMMAIRE Nous présentons ici des données acquises avec une microsonde électronique et par diffraction X sur monocristal pour caractériser un minéral du groupe du microlite ayant une formule voisine de NaCaTa2O6F, provenant de la mine Morro A Redondo, Coronel Murta, Minas Gerais, Brésil. Compte tenu de ces données, la formule en serait (Na0.88Ca0.88Pb0.020.22)S2.00 B X Y (Ta1.70Nb0.14Si0.12As0.04)S2.00 [(O5.75(OH)0.25]S6.00 (F0.730.27)S1.00. Selon la nouvelle nomenclature des minéraux du super- groupe du pyrochlore, il s’agit d’une composition intermédiaire entre fluornatromicrolite et “fluorcalciomicrolite”. La structure du cristal, Fd3m, a = 10.4396(12) Å, a été affinée jusqu’à un résidu R1 égal à 0.0258 (wR2 = 0.0715) en utilisant 107 réflexions (rayonnement MoKa). Il y a une pénurie de données cristallochimiques pour les minéraux du supergroupe du pyrochlore dans la littérature. Nous présentons ici une compilation des données disponibles. (Traduit par la Rédaction) Mots-clés: groupe du microlite, “fluorcalciomicrolite”, fluornatromicrolite, affinement de la structure, solution solide. § E-mail address: [email protected] Downloaded from https://pubs.geoscienceworld.org/canmin/article-pdf/49/2/615/3457778/615_vol_49-2_art_14.pdf by USP Universidade de Sao Paulo user on 27 September 2018 616 thE CANADIAN MINERALOGIst INTRODUCTION granitic pegmatites (Lumpkin & Ewing 1992, Ercit et al. 1994, Zurevinski & Mitchell 2004). The pyrochlore Pyrochlore-supergroup minerals have been studied supergroup includes minerals of the pyrochlore, micro- in detail because of their interesting magnetic properties lite, roméite, betafite and elsmoreite groups. and advanced technological applications. The “geomet- There is a scarcity of crystal-chemical data in the rical frustration” concept is related to the incapacity of literature. There are crystal-structure determinations magnetic systems to satisfy simultaneously all the inter- published for only nine pyrochlore-supergroup minerals actions (ferromagnetic and antiferromagnetic) between (Table 1). In this paper, we present results of electron- spins in order to minimize the total energy. The study microprobe and single-crystal diffraction studies of a of frustration among spins in the corner-sharing tetra- microlite-group mineral from the Morro Redondo mine. hedra of pyrochlore-like structures of synthetic origin has contributed to a better understanding of new exotic OCCURRENCE low-temperature states, magnetic ordering (Wang et al. 2006, Normand 2009), and superconductivity, such as in The Morro Redondo pegmatite is located in the RbOs2O6 (Brühwiler et al. 2004). Titanate (CaZrTi2O7) northern part of the Oriental Pegmatite Province of and zirconate (Gd2Zr2O7, Er2Zr2O7) pyrochlores play Minas Gerais (that extends 320 km east to west and 720 an important role in the development of long-term km north to south, reaching the southern part of Bahia geological depositories of high-level radioactive waste and the northwestern part of Espírito Santo state. It such as plutonium (Laverov et al. 2010). Minerals of the was formed during the Brasiliano orogeny (also known pyrochlore supergroup have a formula A2–mB2X6–wY1–n as Araçuaí orogeny), dated from 600 to 450 million (m = 0 to 2, w = 0 to 0.7, n = 0 to 1), in which the A site years ago. The pegmatite is located inside the Coronel is normally occupied by Na, Ca, Ag, Mn, Sr, Ba, Fe2+, Murta pegmatite field, which comprises tens of gem- Pb2+, Sn2+, Sb3+, Bi3+, Y, Ce (and other REE), Sc, U, bearing granitic pegmatites that have been extensively Th, , or H2O. The B site typically accommodates Ta, mined for the production of gem-grade elbaite (green, Nb, Ti, Sb5+, W, and also V5+, Sn4+, Zr, Hf, Fe3+, Mg, blue, red and multi-colored), gem-grade beryl (mostly Al, Si. The X site typically is occupied by O, but can “morganite”), ornamental quartz and perthitic K-feld- include subordinate OH and F. The Y site is occupied spar (raw material for ceramic and glass industries). by OH, F, O, , H2O, K, Cs, Rb. These minerals are Morro Redondo is the largest pegmatite found commonly found in carbonatites, alkaline rocks and in this field: it has a length of 400 meters and an TABLE 1. REFINED CRYSTAL-STRUCTURE DATA: CELL PARAMETER a AND OCCUPANCY OF THE SITES A, B, X AND Y _______________________________________________________________________________________________________________ a (Å) ABX Y Ref. _______________________________________________________________________________________________________________ fluorcalciomicrolite* – 10.4396(12) Na0.88Ca0.88Pb0.02G0.22 Ta1.70Nb0.14Si0.12 O5.75 F0.73G0.27 (1) fluornatromicrolite As0.04 (OH)0.25 intermediate member 3+ hydroxykenomicrolite 10.515(2) G1.09Sb 0.57Bi0.01Na0.31 Ta1.88Nb0.12 O5.69 (OH,F)0.69 (2) (from Vasin–Myl’k Mtn.) Pb0.02 (OH,F)0.31 Cs0.31 3+ hydroxykenomicrolite 10.496(1) G0.93Na0.45Sb 0.39Bi0.02 Ta1.95Nb0.05 O5.78 (OH,F)0.55 (2) (from Tanco, Manitoba) Pb0.14Ca0.06 (OH,F)0.22 Cs0.22K0.01 kenoplumbomicrolite* 10.571(1) Pb1.30Ca0.29G0.30Na0.08 Ta0.82Nb0.62Si0.23 O6 G0.52(OH)0.25 (3) 4+ 3+ U 0.03 Sn0.15Ti0.07Fe 0.10Al0.01 O0.23 fluorcalciopyrochlore* 10.4200(7) Ca0.73Sr0.07Mn0.04Pb0.01 Nb1.72Ta0.02Ti0.16 O5.03 F0.62(OH)0.38 (4) 3+ G0.69Na0.37K0.02Ce0.03 Si0.07Fe 0.03 (OH)0.97 4+ La0.01Nd0.01U 0.02 hydroxycalciopyrochlore* 10.3738(7) Ca0.72Sr0.08Mn0.04Pb0.01 Nb1.48Ta0.04Ti0.16 O4.63 (OH)0.54F0.46 (4) 3+ G0.84Na0.18K0.05Ce0.04 Si0.24Fe 0.08 (OH)1.37 4+ La0.01Nd0.01U 0.02 hydropyrochlore 10.604(1) (H2O)0.99G0.95Sr0.05Ca0.01 Nb1.80Ti0.20 O4.06(OH)0.94 (H2O)0.86K0.14 (5) 5+ fluornatroroméite* 10.265(2) Na1.00Ca0.80Mn0.01G0.19 Sb 2 O5.69(OH)0.31 F0.89(OH)0.05G0.06 (6) 3+ 5+ 3+ hydroxycalcioroméite 10.277(1) Ca1.04Mn0.07Sb 0.65 Sb 0.99Ti0.76Fe 0.19 O6 (OH)0.91G0.09 (7) G0.23Na0.01 Al0.06 3+ 5+ hydroxycalcioroméite 10.311(7) Ca0.91Mn0.06G0.37Sb 0.27 Sb 1.28Ti0.72 O6 OH (8) 3+ Fe 0.19Al0.10Na0.10 4+ oxycalciobetafite* 10.2637(13) Ca1.29U 0.50Na0.18REE0.03 Ti1.09Nb0.79Ta0.01 O6 O0.98F0.02 (9) 3+ Zr0.14Fe 0.04 3+ hydrokenoelsmoreite 10.352(1) G1.33(H2O)0.59Ca0.06Na0.02 W1.46Fe 0.54 O4.70(OH)1.30 (H2O)0.80K0.20 (10) _______________________________________________________________________________________________________________ * Need to be completely described in order to be approved as valid species. References: (1) this work, (2) Ercit et al. (1993), (3) Bindi et al. (2006), (4) Bonazzi et al. (2006), (5) Ercit et al. (1994), (6) Matsubara et al. (1996), (7) Rouse et al. (1998), (8) Zubkova et al. (2000), (9) Cámara et al. (2004), (10) Ercit & Robinson (1994). Downloaded from https://pubs.geoscienceworld.org/canmin/article-pdf/49/2/615/3457778/615_vol_49-2_art_14.pdf by USP Universidade de Sao Paulo user on 27 September 2018 thE stRUCTURE OF A MICROLITE-GROUP MINERAL, MINAS GERAIS 617 average thickness of 30 meters, has a N–S strike and Since then, all attempts at finding more mineralized dips 70°W. It shows a well-developed zoning, with cavities in the deeper parts of the pegmatite were unsuc- a wall zone about 3 m thick, constituted of perthitic cessful. Two subsequent prospecting rotary-drilling feldspar and quartz showing a graphic texture, with campaigns failed to find more mineralized areas, and smaller amounts of dark muscovite plates, schorl and confirmed that the pegmatite has an atypical cross- almandine. The intermediate zone is thick (about 10 section of a parallelogram measuring 30 3 40 meters. m) and is constituted mostly of centimetric microcline After the mining operations were discontinued in and quartz grains, lighter brown centimetric muscovite 1997, intermittent and risky digging has been conducted plates, schorl, albite, montebrasite and beryl crystals. by individual miners, who take the risk of digging The inner zone consists of a discontinuous quartz core, into the safety pillars. One of these miners found the that in some areas can be up to 10 m thick, surrounded microlite crystal that is the object of this study in the by albite-dominant replacement bodies with decimetric vicinity of the cavity of the mined-out tourmaline zone, crystals of schorl.
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  • Crystallization Processes and Solubility of Columbite-(Mn), Tantalite-(Mn), Microlite, Pyrochlore, Wodginite and Titanowodginite in Highly Fluxed Haplogranitic Melts

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    Western University Scholarship@Western Scholarship@Western Electronic Thesis and Dissertation Repository 3-12-2018 10:30 AM Crystallization processes and solubility of columbite-(Mn), tantalite-(Mn), microlite, pyrochlore, wodginite and titanowodginite in highly fluxed haplogranitic melts Alysha G. McNeil The University of Western Ontario Supervisor Linnen, Robert L. The University of Western Ontario Co-Supervisor Flemming, Roberta L. The University of Western Ontario Graduate Program in Geology A thesis submitted in partial fulfillment of the equirr ements for the degree in Doctor of Philosophy © Alysha G. McNeil 2018 Follow this and additional works at: https://ir.lib.uwo.ca/etd Part of the Earth Sciences Commons Recommended Citation McNeil, Alysha G., "Crystallization processes and solubility of columbite-(Mn), tantalite-(Mn), microlite, pyrochlore, wodginite and titanowodginite in highly fluxed haplogranitic melts" (2018). Electronic Thesis and Dissertation Repository. 5261. https://ir.lib.uwo.ca/etd/5261 This Dissertation/Thesis is brought to you for free and open access by Scholarship@Western. It has been accepted for inclusion in Electronic Thesis and Dissertation Repository by an authorized administrator of Scholarship@Western. For more information, please contact [email protected]. Abstract Niobium and tantalum are critical metals that are necessary for many modern technologies such as smartphones, computers, cars, etc. Ore minerals of niobium and tantalum are typically associated with pegmatites and include columbite, tantalite, wodginite, titanowodginite, microlite and pyrochlore. Solubility and crystallization mechanisms of columbite-(Mn) and tantalite-(Mn) have been extensively studied in haplogranitic melts, with little research into other ore minerals. A new method of synthesis has been developed enabling synthesis of columbite-(Mn), tantalite-(Mn), hafnon, zircon, and titanowodginite for use in experiments at temperatures ≤ 850 °C and 200 MPa, conditions attainable by cold seal pressure vessels.
  • November 2004 3/22/17, 1�11 PM

    November 2004 3/22/17, 111 PM

    November 2004 3/22/17, 111 PM Bulletin of the Mineralogical Society of Southern California Volume 74 Number 11 November 2004 The 801st Meeting of The Mineralogical Society of Southern California "Romancing the Stone: Adventures in Brazil" by Dr. Anthony Kampf Friday, November 12 at 7:30 p.m. Geology Department, E-Building, Room 220 Pasadena City College 1570 E. Colorado Blvd. Pasadena Inside this bulletin November 12th meeting Show Report: Thank you! Kid Rock Report Minutes of the October Meeting Report from the Nominating Committee Successful October Field Trip to Arizona Mineral Notes from Italy: The Praborna Mine Calendar of Events November 12th Meeting..... http://www.mineralsocal.org/bulletin/2004/2004_nov.htm Page 1 of 11 November 2004 3/22/17, 111 PM November 12th Meeting Dr. Tony Kampf will present "Romancing the Stone: Adventures in Brazil" at our November 12, 2004 meeting. If you think you've heard this talk, think again. Tony has led 11 tours to the gem and mineral deposits of Minas Gerais, Brazil, and always has something new up his sleve. We will be treated to the latest news out of the Brazilian gem mines by a foremost expert on gem-bearing pegmatite deposits. For those who want to see lots of Brazil, Tony will also show a video of his 1987 tour to Brazil after his talk. Dr. Kampf recieved a Ph.D. in mineralogy from the University of Chicago in 1976 http://www.mineralsocal.org/bulletin/2004/2004_nov.htm Page 2 of 11 November 2004 3/22/17, 111 PM and joined the staff of the Natural History Museum of Los Angeles Co.
  • Unusual Mineral Diversity in a Hydrothermal Vein-Type Deposit: the Clara Mine, Sw Germany, As a Type Example

    Unusual Mineral Diversity in a Hydrothermal Vein-Type Deposit: the Clara Mine, Sw Germany, As a Type Example

    427 The Canadian Mineralogist Vol. 57, pp. 427-456 (2019) DOI: 10.3749/canmin.1900003 UNUSUAL MINERAL DIVERSITY IN A HYDROTHERMAL VEIN-TYPE DEPOSIT: THE CLARA MINE, SW GERMANY, AS A TYPE EXAMPLE § GREGOR MARKL Universitat¨ Tubingen,¨ Fachbereich Geowissenschaften, Wilhelmstraße 56, D-72074 Tubingen,¨ Germany MAXIMILIAN F. KEIM Technische Universitat¨ Munchen,¨ Munich School of Engineering, Lichtenbergstraße 4a, 85748 Garching, Germany RICHARD BAYERL Ludwigstrasse 8, 70176 Stuttgart, Germany ABSTRACT The Clara baryte-fluorite-(Ag-Cu) mine exploits a polyphase, mainly Jurassic to Cretaceous, hydrothermal unconformity vein-type deposit in the Schwarzwald, SW Germany. It is the type locality for 13 minerals, and more than 400 different mineral species have been described from this occurrence, making it one of the top five localities for mineral diversity on Earth. The unusual mineral diversity is mainly related to the large number and diversity of secondary, supergene, and low- temperature hydrothermal phases formed from nine different primary ore-gangue associations observed over the last 40 years; these are: chert/quartz-hematite-pyrite-ferberite-scheelite with secondary W-bearing phases; fluorite-arsenide-selenide-uraninite- pyrite with secondary selenides and U-bearing phases (arsenates, oxides, vanadates, sulfates, and others); fluorite-sellaite with secondary Sr- and Mg-bearing phases; baryte-tennantite/tetrahedrite ss-chalcopyrite with secondary Cu arsenates, carbonates, and sulfates; baryte-tennantite/tetrahedrite ss-polybasite/pearceite-chalcopyrite, occasionally accompanied by Ag6Bi6Pb-bearing sulfides with secondary Sb oxides, Cu arsenates, carbonates, and sulfates; baryte-chalcopyrite with secondary Fe- and Cu- phosphates; baryte-pyrite-marcasite-chalcopyrite with secondary Fe- and Cu-sulfates; quartz-galena-gersdorffite-matildite with secondary Pb-, Bi-, Co-, and Ni-bearing phases; and siderite-dolomite-calcite-gypsum/anhydrite-quartz associations.
  • Mineralogy and Geochemical Evolution of the Little Three

    Mineralogy and Geochemical Evolution of the Little Three

    American Mineralogist, Volume 71, pages 406427, 1986 Mineralogy and geochemicalevolution of the Little Three pegmatite-aplite layered intrusive, Ramona,California L. A. SrnnN,t G. E. BnowN, Jn., D. K. Brno, R. H. J*rNs2 Department of Geology, Stanford University, Stanford, California 94305 E. E. Foono Branch of Central Mineral Resources,U.S. Geological Survey, Denver, Colorado 80225 J. E. Snrcr,nv ResearchDepartment, Gemological Institute of America, 1660 Stewart Street,Santa Monica, California 90404 L. B. Sp.c,uLDrNG" JR. P.O. Box 807, Ramona,California 92065 AssrRAcr Severallayered pegmatite-aplite intrusives exposedat the Little Three mine, Ramona, California, U.S.A., display closelyassociated fine-grained to giant-texturedmineral assem- blageswhich are believed to have co-evolved from a hydrous aluminosilicate residual melt with an exsolved supercriticalvapor phase.The asymmetrically zoned intrusive known as the Little Three main dike consists of a basal sodic aplite with overlying quartz-albite- perthite pegmatite and quartz-perthite graphic pegmatite. Muscovite, spessartine,and schorl are subordinate but stable phasesdistributed through both the aplitic footwall and peg- matitic hanging wall. Although the bulk composition of the intrusive lies near the haplo- granite minimum, centrally located pockets concentratethe rarer alkalis (Li, Rb, Cs) and metals (Mn, Nb, Ta, Bi, Ti) of the system, and commonly host a giant-textured suite of minerals including quartz, alkali feldspars, muscovite or F-rich lepidolite, moderately F-rich topaz, and Mn-rich elbaite. Less commonly, pockets contain apatite, microlite- uranmicrolite, and stibio-bismuto-columbite-tantalite.Several ofthe largerand more richly mineralized pockets of the intrusive, which yield particularly high concentrationsof F, B, and Li within the pocket-mineral assemblages,display a marked internal mineral segre- gation and major alkali partitioning which is curiously inconsistent with the overall alkali partitioning of the system.