DEGEO - Departamento de Geologia
URI permanente desta comunidadehttp://www.hml.repositorio.ufop.br/handle/123456789/8
Navegar
10 resultados
Resultados da Pesquisa
Item Assessment of the molecular structure of an intermediate member of the triplite-zwieselite mineral series : a raman and infrared study.(2014) Frost, Ray Leslie; Xi, Yunfei; López, Andrés; Moreira, Viviane Amaral; Cipriano, Ricardo Augusto Scholz; Lima, Rosa Malena Fernandes; Gandini, Antônio LucianoThe mineral series triplite-zwieselite with theoretical formula (Mn2þ)2(PO4)(F)-(Fe2þ)2(PO4)(F) from the El Criolo granitic pegmatite, located in the Eastern Pampean Ranges of Cordoba Province, was studied using electron microprobe, thermogravimetry, and Raman and infrared spec- troscopy. The analysis of the mineral provided a formula of (Fe1.00, Mn0.85, Ca0.08, Mg0.06)P2.00(PO4)1.00(F0.80, OH0.20)P1.00. An intense Raman band at 981cm1 with a shoulder at 977cm1 is assigned to the PO3 4 n1 symmetric stretching mode. The observation of two bands for the phosphate symmetric stretching mode offers support for the concept that the phosphate units in the structure of triplite-zwieselite are not equivalent. Low-intensity Raman bands at 1012, 1036, 1071, 1087, and 1127 cm1 are assigned to the PO3 4 n3 antisymmetric stretching modes. A set of Raman bands at 572, 604, 639, and 684 cm1 are attributed to the PO3 4 n4 out-of-plane bending modes. A single intense Raman band is found at 3508 cm1 and is assigned to the stretching vibration of hydroxyl units. Infrared bands are observed at 3018, 3125, and 3358 cm1 and are attributed to water stretching vibrations. Supplemental materials are available for this article. Go to the publisher’s online edition of Spectroscopy Letters to view the supplemental file.Item Vibrational spectroscopy of the phosphate mineral kovdorskite - Mg2PO4(OH)-3H2O.(2013) Frost, Ray Leslie; López, Andrés; Xi, Yunfei; Granja, Amanda; Cipriano, Ricardo Augusto Scholz; Lima, Rosa Malena FernandesThe mineral kovdorskite Mg2PO4(OH)_3H2O was studied by electron microscopy, thermal analysis and vibrational spectroscopy. A comparison of the vibrational spectroscopy of kovdorskite is made with other magnesium bearing phosphate minerals and compounds. Electron probe analysis proves the mineral is very pure. The Raman spectrum is characterized by a band at 965 cm_1 attributed to the PO3_ 4 m1 symmetric stretching mode. Raman bands at 1057 and 1089 cm_1 are attributed to the PO3_ 4 m3 antisymmetric stretching modes. Raman bands at 412, 454 and 485 cm_1 are assigned to the PO3_ 4 m2 bending modes. Raman bands at 536, 546 and 574 cm_1 are assigned to the PO3_ 4 m4 bending modes. The Raman spectrum in the OH stretching region is dominated by a very sharp intense band at 3681 cm_1 assigned to the stretching vibration of OH units. Infrared bands observed at 2762, 2977, 3204, 3275 and 3394 cm_1 are attributed to water stretching bands. Vibrational spectroscopy shows that no carbonate bands are observed in the spectra; thus confirming the formula of the mineral as Mg2PO4(OH)_3H2O.Item Vibrational spectroscopy of the mineral meyerhofferite CaB3O3(OH)5 H2O - an assessment of the molecular structure.(2013) Frost, Ray Leslie; López, Andrés; Xi, Yunfei; Cipriano, Ricardo Augusto Scholz; Costa, Geraldo Magela da; Belotti, Fernanda Maria; Lima, Rosa Malena FernandesMeyerhofferite is a calcium hydrated borate mineral with ideal formula: CaB3O3(OH)5_H2O and occurs as white complex acicular to crude crystals with length up to _4 cm, in fibrous divergent, radiating aggregates or reticulated and is often found in sedimentary or lake-bed borate deposits. The Raman spectrum of meyerhofferite is dominated by intense sharp band at 880 cm_1 assigned to the symmetric stretching mode of trigonal boron. Broad Raman bands at 1046, 1110, 1135 and 1201 cm_1 are attributed to BOH in-plane bending modes. Raman bands in the 900–1000 cm_1 spectral region are assigned to the antisymmetric stretching of tetrahedral boron. Distinct OH stretching Raman bands are observed at 3400, 3483 and 3608 cm_1. The mineral meyerhofferite has a distinct Raman spectrum which is different from the spectrum of other borate minerals, making Raman spectroscopy a very useful tool for the detection of meyerhofferite in sedimentary and lake bed deposits.Item Characterization of the sulphate mineral amarantite - using infrared, Raman spectroscopy and thermogravimetry.(2013) Frost, Ray Leslie; López, Andrés; Cipriano, Ricardo Augusto Scholz; Xi, Yunfei; Silveira, Aléssio Jordan da; Lima, Rosa Malena FernandesThe mineral amarantite Fe3þ 2 (SO4)O _ 7H2O has been studied using a combination of techniques including thermogravimetry, electron probe analyses and vibrational spectroscopy. Thermal analysis shows decomposition steps at 77.63, 192.2, 550 and 641.4 _C. The Raman spectrum of amarantite is dominated by an intense band at 1017 cm_1 assigned to the SO2_ 4 m1 symmetric stretching mode. Raman bands at 1039, 1054, 1098, 1131, 1195 and 1233 cm_1 are attributed to the SO2_ 4 m3 antisymmetric stretching modes. Very intense Raman band is observed at 409 cm_1 with shoulder bands at 399, 451 and 491 cm_1 are assigned to the m2 bending modes. A series of low intensity Raman bands are found at 543, 602, 622 and 650 cm_1 are assigned to the m4 bending modes. A very sharp Raman band at 3529 cm_1 is assigned to the stretching vibration of OH units. A series of Raman bands observed at 3025, 3089, 3227, 3340, 3401 and 3480 cm_1 are assigned to water bands. Vibrational spectroscopy enables aspects of the molecular structure of the mineral amarantite to be ascertained.Item The molecular structure of the borate mineral inderite Mg(H4B3O7)(OH)-5H2O - a vibrational spectroscopic study.(2013) Frost, Ray Leslie; López, Andrés; Xi, Yunfei; Lima, Rosa Malena Fernandes; Cipriano, Ricardo Augusto Scholz; Granja, AmandaWe have undertaken a study of the mineral inderite Mg(H4B3O7)(OH)_5H2O a hydrated hydroxy borate mineral of magnesium using scanning electron microscopy, thermogravimetry and vibrational spectroscopic techniques. The structure consists of ½B3O3ðOHÞ5_2_ soroborate groups and Mg(OH)2(H2O)4 octahedra interconnected into discrete molecules by the sharing of two OH groups. Thermogravimetry shows a mass loss of 47.2% at 137.5 _C, proving the mineral is thermally unstable. Raman bands at 954, 1047 and 1116 cm_1 are assigned to the trigonal symmetric stretching mode. The two bands at 880 and 916 cm_1 are attributed to the symmetric stretching mode of the tetrahedral boron. Both the Raman and infrared spectra of inderite show complexity. Raman bands are observed at 3052, 3233, 3330, 3392 attributed to water stretching vibrations and 3459 cm_1 with sharper bands at 3459, 3530 and 3562 cm_1 assigned to OH stretching vibrations. Vibrational spectroscopy is used to assess the molecular structure of inderite.Item Infrared and Raman spectroscopic characterization of the silicate mineral olmiite CaMn^2+[SiO3(OH)](OH) – implications for the molecular structure.(2013) Frost, Ray Leslie; Cipriano, Ricardo Augusto Scholz; López, Andrés; Xi, Yunfei; Granja, Amanda; Gobac, Željka Žigovečki; Lima, Rosa Malena FernandesWe have studied the mineral olmiite CaMn[SiO3(OH)](OH) which forms a series with its calcium analogue poldervaartite CaCa[SiO3(OH)](OH) using a range of techniques including scanning electron microscopy, thermogravimetric analysis, Raman and infrared spectroscopy. Chemical analysis shows the mineral is purê and contains only calcium and manganese in the formula. Thermogravimetric analysis proves the mineral decomposes at 502 °C with a mass loss of 8.8% compared with the theoretical mass loss of 8.737%. A strong Raman band at 853 cm^-1 is assigned to the SiO stretching vibration of the SiO3(OH) units. Two Raman bands at 914 and 953 cm^-1 are attributed to the antisymmetric vibrations. Two intense Raman bands observed at 3511 and 3550 cm^-1are assigned to the OH stretching vibration of the SiO3(OH) units. The observation of multiple OH bands supports the concept of the non-equivalence of the OH units. Vibrational spectroscopy enables a detailed assessment of the molecular structure of olmiite.Item Thermal analysis and vibrational spectroscopic characterization of the boro silicate mineral datolite - CaBSiO4(OH).(2013) Frost, Ray Leslie; Xi, Yunfei; Cipriano, Ricardo Augusto Scholz; Lima, Rosa Malena Fernandes; Horta, Laura Frota Campos; López, AndrésThe objective of this work is to determine the thermal stability and vibrational spectra of datolite CaBSiO4(OH) and relate these properties to the structure of the mineral. The thermal analysis of datolite shows a mass loss of 5.83% over a 700–775 °C temperature range. This mass loss corresponds to 1 water (H2O) molecules pfu. A quantitative chemical analysis using electron probe was undertaken. The Raman spectrum of datolite is characterized by bands at 917 and 1077 cm^-1 assigned to the symmetric stretching modes of BO and SiO tetrahedra. A very intense Raman band is observed at 3498 cm^-1 assigned to the stretching vibration of the OH units in the structure of datolite. BOH out-of-plane vibrations are characterized by the infrared band at 782 cm^-1. The vibrational spectra are based upon the structure of datolite based on sheets of four- and eight-membered rings of alternating SiO4 and BO3(OH) tetrahedra with the sheets bonded together by calcium atoms.Item The spectroscopic characterization of the sulphate mineral ettringite from Kuruman manganese deposits, South Africa.(2013) Frost, Ray Leslie; López, Andrés; Xi, Yunfei; Cipriano, Ricardo Augusto Scholz; Costa, Geraldo Magela da; Lima, Rosa Malena Fernandes; Granja, AmandaThe mineral ettringite has been studied using a number of techniques, including XRD, SEM with EDX, thermogravimetry and vibrational spectroscopy. The mineral proved to be composed of 53% of ettringite and 47% of thaumasite in a solid solution. Thermogravimetry shows a mass loss of 46.2% up to 1000 ◦C. Raman spectroscopy identifies multiple sulphate symmetric stretching modes in line with the three sulphate crystallographically different sites. Raman spectroscopy also identifies a band at 1072 cm−1 attributed to a carbonate symmetric stretching mode, confirming the presence of thaumasite. The observation of multiple bands in the _4 spectral region between 700 and 550 cm−1 offers evidence for the reduction in symmetry of the sulphate anion from Td to C2v or even lower symmetry. The Raman band at 3629 cm−1 is assigned to the OH unit stretching vibration and the broad feature at around 3487 cm−1 to water stretching bands. Vibrational spectroscopy enables an assessment of the molecular structure of natural ettringite to be made.Item Vibrational spectroscopic characterization of the phosphate mineral series eosphorite-childrenite-(Mn,Fe)Al(PO4)(OH)2 (H2O).(2013) Frost, Ray Leslie; Xi, Yunfei; Cipriano, Ricardo Augusto Scholz; López, Andrés; Lima, Rosa Malena Fernandes; Ferreira, Claudiane MoraesThe phosphate mineral series eosphorite–childrenite–(Mn,Fe)Al(PO4)(OH)2•(H2O) has been studied using a combination of electron probe analysis and vibrational spectroscopy. Eosphorite is the manganese rich mineral with lower iron content in comparison with the childrenite which has higher iron and lower manganese content. The determined formulae of the two studied minerals are: (Mn0.72,Fe0.13,Ca0.01)(Al)1.04(PO4, OHPO3)1.07(OH1.89,F0.02)•0.94(H2O) for SAA-090 and (Fe0.49,Mn0.35,Mg0.06,Ca0.04)(Al)1.03(PO4, OHPO3)1.05(OH)1.90•0.95(H2O) for SAA-072. Raman spectroscopy enabled the observation of bands at 970 cm−1 and 1011 cm−1 assigned to monohydrogen phosphate, phosphate and dihydrogen phosphate units. Differences are observed in the area of the peaks between the two eosphorite minerals. Raman bands at 562 cm−1, 595 cm−1, and 608 cm−1 are assigned to the _4 bending modes of the PO4, HPO4 and H2PO4 units; Raman bands at 405 cm−1, 427 cm−1 and 466 cm−1 are attributed to the _2 modes of these units. Raman bands of the hydroxyl and water stretching modes are observed. Vibrational spectroscopy enabled details of the molecular structure of the eosphorite mineral series to be determined.Item Characterization of the sulphate mineral coquimbite, a secondary iron sulphate from Javier Ortega mine, Lucanas Province, Peru – Using infrared, Raman spectroscopy and thermogravimetry.(2014) Frost, Ray Leslie; Gobac, Željka Žigovečki; López, Andrés; Xi, Yunfei; Cipriano, Ricardo Augusto Scholz; Lana, Cristiano de Carvalho; Lima, Rosa Malena FernandesThe mineral coquimbite has been analysed using a range of techniques including SEM with EDX, thermal analytical techniques and Raman and infrared spectroscopy. The mineral originated from the Javier Ortega mine, Lucanas Province, Peru. The chemical formula was determined as (Fe1.37^3+; Al0.63)Σ2.00(SO4)3. 9H2O. Thermal analysis showed a total mass loss of ~73.4% on heating to 1000 °C. A mass loss of 30.43% at 641.4 °C is attributed to the loss of SO3. Observed Raman and infrared bands were assigned to the stretching and bending vibrations of sulphate tetrahedra, aluminium oxide/hydroxide octahedra, water molecules and hydroxyl ions. The Raman spectrum shows well resolved bands at 2994, 3176, 3327, 3422 and 3580 cm^-1 attributed to water stretching vibrations. Vibrational spectroscopy combined with thermal analysis provides insight into the structure of coquimbite.