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Ophiolite hosted chromitite formed by supra-subduction zone peridotite–plume interaction

Geoscience Frontiers 2020年第6期11卷 2083-2102页

作者： Júlia Farré-de-Pablo Joaquín A.Proenza JoséMaría González-Jiménez Thomas Aiglsperger Antonio Garcia-Casco Javier Escuder-Viruete Vanessa Colás francisco longo Departament de Mineralogia Petrologia i Geologia AplicadaUniversitat de BarcelonaC/Martíi Franquess/n08028BarcelonaSpain Departamento de Mineraloga y Petrologa Universidad de GranadaFacultad de CienciasFuentenueva s/n18002GranadaSpain Department of Civil Engineering and Natural Resources LuleåUniversity of TechnologySE 97187LuleåSweden Instituto Andaluz de Ciencias de la Tierra(CSIC-UGR) Avda.de las Palmeras 4E-18100ArmillaGranadaSpain Instituto Geologico y Minero de Espana C/La Calera 1Tres Cantos28760MadridSpain Instituto de Geología Universidad Nacional Autonoma de MéxicoCiudad Universitaria04510Ciudad de MéxicoMexico Facultad de Ingeniería Universidad Catòlica de CibaoLa VegaDominican Republic

Chromitite bodies hosted in peridotites typical of suboceanic mantle(***)are found in the northern and central part of the Loma Caribe peridotite,in the Cordillera Central of the Dominican *** chromitites are massive pods of small size(less than a few meters across)and veins that intrude both dunite and ***,they are high-Cr chromitites[Cr#=Cr/(Cr+Al)atomic ratio=0.71-0.83]singularly enriched in TiO2(up to 1.25 wt.%),Fe2 O3(2.77-9.16 wt.%)as well as some trace elements(Ga,V,Co,Mn,and Zn)and PGE(up to 4548 ppb in whole-rock).This geochemical signature is unknown for chromitites hosted in oceanic upper mantle but akin to those chromites crystallized from mantle plume derived ***,the melt estimated to be in equilibrium with such chromite from the Loma Caribe chromitites is similar to basalts derived from different source regions of a heterogeneous Caribbean mantle *** mantle plume is responsible for the formation of the Caribbean Large Igneous Province(CLIP).Dolerite dykes with back-arc basin basalt(BABB)and enriched mid-ocean ridge basalt(E-MORB)affinities commonly intrude the Loma Caribe peridotite,and are interpreted as evidence of the impact that the Caribbean plume had in the off-axis magmatism of the back-arc basin,developed after the Caribbean island-arc extension in the Late *** propose a model in which chromitites were formed in the shallow portion of the back-arc mantle as a result of the metasomatic reaction between the supra-subduction zone(SSZ)peridotites and upwelling plume-related melts.

关键词： Chromitite Ophiolite Plume Mantle Back-arc basin Dominican Republic

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Rietveld refinement and optical properties of SrWO_4:Eu^(3+) powders prepared by the non-hydrolytic sol-gel method

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Journal of Rare Earths 2015年第2期33卷 113-128页

作者： P.F.S.Pereira I.C.Nogueira E.longo E.J.Nassar I.L.V.Rosa L.S.Cavalcante Chemistry Institute University of the State of Sao Paulo Julio de Mesquita Filho-UNESP Francisco DegniAraraquara-SP 14800-900 Brazil LIEC-Chemistry Department Federal University of Sao Carlos Via Washington Luis Km 235Sao Carlos-SP 13565-905 Brazil University of Franca-UNIFRAN Via Dr.Armando Sales de OliveiraNo.201 Franca-SP 14404-600 Brazil CCN-DQ-GERATEC University of the State of Piauí Joao Cabral 2231 P.O.Box 391Terezina PI 64002-150 Brazil

We investigated the effect of annealing time on the structure and optical properties of Sr WO4：Eu^3＋ powders prepared by the non-hydrolytic sol-gel method and heat treated at 800 ℃ for 2,4,8 and 16 *** and differential thermal analyses revealed that Sr WO4：Eu^3＋ powders were obtained at about 800 ℃.X-ray diffraction patterns and Rietveld refinement data confirmed that all powders had a scheelite-type tetragonal ***-Raman and Fourier transform infrared spectra indicated structural order at short range and anti-symmetric stretching vibrations of O-W-O bonds associated with tetrahedral[WO4]*** properties were investigated by ultraviolet-visible（UV-vis）diffuse reflectance,and photoluminescence（PL）data which provided the evolution of quantum efficiency（η）and lifetime（τ）.UV-vis spectroscopy evidenced intermediate energy levels within the band gap of Sr WO4：Eu^3＋ *** properties validated that the Eu^3＋ electric-dipole（^5D0→^7F2）transition in PL emission spectra was dominant which proved that Eu^3＋ ions were positioned in a site without an inversion center.[（^5D0→^7F2）/（^5D0→^7F1）]band ratios showed that Eu^3＋ ions were located in a low symmetry *** PL emission,ηandτproved the dependence on the annealing time in the behavior of Sr WO4：Eu3＋powders with a higher relative emission PL intensity as well as higherηandτvalues related to other samples when heat treated at 800℃ for 8 h.

关键词： SrWO4 Rietveld refinement optical band gap Eu^(3+) +-rare earth luminescence

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Effect of different starting materials on the synthesis of Ba_(0.8)Ca_(0.2)TiO_(3)

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Journal of Advanced Ceramics 2015年第1期4卷 65-70页

作者： P.N.MEDEIROS V.D.ARAÚJO A.P.A.MARQUES R.L.TRANQUILIN C.A.PASKOCIMAS M.R.D.BOMIO J.A.VARELA E.longo F.V.MOTTA DEMAT CTUFRNAv.Sen.Salgado Filho3000CEP 59072-970 NatalRNBrazil UACSA UFRPEBR 101 Sul5225CEP 54510-000 Cabo de Santo AgostinhoPEBrazil UNIFESP Rua Prof.Artur Riedel275CEP 09972-270 DiademaSPBrazil dLIECIQUNESPRua Francisco Degni s/nCEP 14801-907 AraraquaraSPBrazil LIEC IQUNESPRua Francisco Degni s/nCEP 14801-907 AraraquaraSPBrazi

Literature has reported the synthesis of barium calcium titanates by various synthesis methods such as solid state reaction,co-precipitation and polymer *** compounds are usually obtained using calcium carbonate(CaCO_(3)),barium carbonate(BaCO3)and titanium oxide as starting *** study investigated the effect of different starting reagents on the synthesis of Ba_(0.8)Ca_(0.2)TiO_(3)(BCT)by complex polymerization method(CPM).Two sets of starting precursors were used:titanium citrate,CaCO_(3)and BaCO3,and titanium citrate and Ba1-xCaxCO3 solid solution *** were crystallized at a temperature range from 400℃to 700℃for different *** obtained powders were characterized by X-ray diffraction(XRD),thermogravimetry(TG)and differential thermal analysis(DTA),and Raman and infrared *** infrared spectroscopy indicated that the chelation processes of Ba,Ca,Ti and CA ions are very *** results showed that the use of CaCO_(3)and BaCO3 or Ba1-xCaxCO3 solid solution as precursors does not affect the final properties of BCT powders obtained by CPM.

关键词： ceramic synthesis Ba_(0.8)Ca_(0.2)TiO_(3)(BCT) complex polymerization method(CPM)

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