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Master's Dissertation
DOI
Document
Author
Full name
Gérson Anderson de Carvalho Lopes
E-mail
Institute/School/College
Knowledge Area
Date of Defense
Published
São Carlos, 2019
Supervisor
Committee
Andrade, Marcelo Barbosa de (President)
Ayala, Alejandro Pedro
Silva, Eduardo Granado Monteiro da
Title in Portuguese
Descrição e caracterização cristaloquímica de minerais do grupo da romeíta
Keywords in Portuguese
Difração de raios X
Espectroscopia Raman
Grupo da romeíta
Microssonda eletrônica
Abstract in Portuguese
O supergrupo do pirocloro é composto por óxidos cúbicos e trigonais de fórmula A2-mB2X6-wY1-n. O grupo da romeíta faz parte do supergrupo do pirocloro e é caracterizado pela predominância de Sb5+ na posição cristalográfica B. Atualmente apenas cinco espécies deste grupo foram aprovadas pela Associação Mineralógica Internacional (IMA). Neste trabalho foram analisadas 3 amostras (MC1-3), procedentes das localidades Kalugeri Hill, Vale de Babuna, cordilheira Jakupica, assentamento de Nezilovo, cidade: Veles, país: Macedônia (MC1) e Mina de Prabornaz, comuna de Saint Marcel, Vale de Aosta, país: Itália (MC2 e MC3).As fórmulas empíricas obtidas por microssonda eletrônica são: MC1)(Ca1,28Na0,560,14Ce0,01Pb0,01)(Sb1,70Ti0,30)(O5,87OH0,13)(F0,77OH0,23); MC2)(Ca1,17Ce0,360,21Na0,14Mn0,10Th0,01U0,01)(Sb1,22Ti0,74Fe0,02Nb0,02)O6,00 (OH0,75F0,19O0,06); MC3)(Ca1,070,57Mn0,20Na0,16)(Sb1,84Ti0,15Fe0,01)(O5,55OH0,45)(OH0,65F0,35). Identificou-se MC1 como fluorcalcioromeíta e MC2 e MC3 como hidroxicalcioromeíta. Todas as amostras possuem sistema cristalino cúbico, grupo espacial 3, Z = 8, sendo: MC1) = 10.2881(13) Å, V = 1088.9(4) Å3; MC2) = 10.2970(13) Å, V = 1091.8(4) Å3; MC3) = 10.289(6) Å, V = 1089.3(19) Å3. Os refinamentos estruturais foram finalizados com: MC1) R1 = 0,016, wR2 = 0,042 e GOF = 1,176; MC2) R1 = 0,23, wR2 = 0,049 e GOF = 1,095; MC3) R1 = 0,029, wR2 = 0,090 e GOF = 1,338. As fórmulas estruturais após refinamento foram: MC1)(Ca1,29Na0,550,11Pb0,05)Σ=2,00(Sb1,71Ti0,29)Σ=2,00(O5,73OH0,27)Σ=6,00(F0,77O0,21OH0,02)Σ=1,00; MC2)(Ca1,30Ce0,510,19)=2,00(Sb1,08Ti0,92)Σ=2,00O6,00(OH0,61O0,21F0,18)Σ=1,00; e MC3) (Ca1,610,24Na0,15)Σ=2,00(Sb1,80Ti0,20)Σ=2,00O6,00 (OH0,48F0,35O0,17)Σ=1,00. Os espectros Raman das amostras exibiram as bandas características das ligações presentes em minerais do grupo da romeíta, com abanda mais evidente correspondente ao stretching da ligação Sb-O em torno de510 cm-1.Para a amostra MC3 observaram-se picos em torno de 1600 e 3600 cm-1, confirmando a presença de água na estrutura. Não se observou estas mesmas bandas nos espectros de MC1 e MC2 devido à baixa intensidade das bandas acima de 1600 cm-1, não se distinguindo do ruído.
Title in English
Description and crystallochemical characterization of roméite-group minerals
Keywords in English
Electron microprobe
Raman espectroscopy
Roméite group
X-ray diffraction
Abstract in English
Pyrochlore supergroup is comprised of trigonal cubic oxides of formula A2-mB2X6-wY1-n. Roméite group is part of pyrochlore supergroup and is characterized by the predominance of Sb5+ in crystallographic position B. Only five species of this group have been currently approved by the International Mineralogical Association (IMA). In this work, 3 samples (MC1-3) were analyzed, which comes from Kalugeri Hill, Babuna Valley, Jakupica Mountains, Nezilovo,Veles, Macedonia (MC1) and Prabornaz Mine, Saint Marcel, Valle d‘Aosta, Italy (MC2 and MC3). The empirical formulas obtained by electron microprobe are: MC1) (Ca1,28Na0,560,14Ce0,01Pb0,01)(Sb1,70Ti0,30)(O5,87OH0,13)(F0,77OH0,23); MC2) (Ca1,17Ce0,360,21Na0,14Mn0,10Th0,01U0,01)(Sb1,22Ti0,74Fe0,02Nb0,02)O6,00 (OH0,75F0,19O0,06); MC3) (Ca1,070,57Mn0,20Na0,16)(Sb1,84Ti0,15Fe0,01)(O5,55OH0,45)(OH0,65F0,35). MC1 was identified as fluorcalcioroméite and MC2 and MC3 as hydroxycalcioroméite. All samples have cubic crystalline system, space group 3, Z = 8, where: MC1) = 10.2881(13) Å, V = 1088.9(4) Å3; MC2) = 10.2970(13) Å, V = 1091.8(4)3; MC3) = 10.289(6) Å, V = 1089.3(19) Å3;. The structural refinements were finalized with: MC1) R1 = 0,016, wR2 = 0,042 and GOF = 1,176; MC2) R1 = 0,23, wR2 = 0,049 and GOF = 1,095; MC3) R1 = 0,029, wR2 = 0,090 and GOF = 1,338. The structural formulas after refinement were: MC1)(Ca1,29Na0,550,11Pb0,05)Σ=2,00(Sb1,71Ti0,29)Σ=2,00(O5,73OH0,27)Σ=6,00(F0,77O0,21OH0,02)Σ=1,00; MC2)(Ca1,30Ce0,510,19)=2,00(Sb1,08Ti0,92)Σ=2,00O6,00(OH0,61O0,21F0,18)Σ=1,00; and MC3) (Ca1,610,24Na0,15)Σ=2,00(Sb1,80Ti0,20)Σ=2,00O6,00 (OH0,48F0,35O0,17)Σ=1,00. Raman spectra of all samples exhibited the characteristic bands of the chemical bonds present in roméite group minerals, with the most evident one corresponding to the stretching of Sb-O bond around 510 cm-1. For MC3, peaks around 1600 and 3600 cm-1 were observed, confirming the presence of water in the structure. It was not observed these same bands in the spectra of MC1 and MC2 due to the low intensity of the bands above 1600 cm-1, whichwere not distinguished from noise.
 
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Publishing Date
2019-10-23
 
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