The Archean Eon was a time of geodynamic changes.Direct evidence of these transitions come from igneous/metaigneous rocks,which dominate cratonic segments worldwide.New data for granitoids from an Archean basement inl...The Archean Eon was a time of geodynamic changes.Direct evidence of these transitions come from igneous/metaigneous rocks,which dominate cratonic segments worldwide.New data for granitoids from an Archean basement inlier related to the Southern S?o Francisco Craton(SSFC),are integrated with geochronological,isotopic and geochemical data on Archean granitoids from the SSFC.The rocks are divided into three main geochemical groups with different ages:(1)TTG(3.02–2.77 Ga);(2)mediumto high-K granitoids(2.85–2.72 Ga);and(3)A-type granites(2.7–2.6 Ga).The juvenile to chondritic(Hf-Nd isotopes)TTG were divided into two sub-groups,TTG 1(low-HREE)and 2(high-HREE),derived from partial melting of metamafic rocks similar to those from adjacent greenstone belts.The compositional diversity within the TTG is attributed to different pressures during partial melting,supported by a positive correlation of Dy/Yb and Sr/Zr,and batch melting calculations.The proposed TTG sources are geochemically similar to basaltic rocks from modern island-arcs,indicating the presence of subduction processes concomitant with TTG emplacement.From~2.85 Ga to 2.70 Ga,the dominant rocks were K-rich granitoids.These are modeled as crustal melts of TTG,during regional metamorphism indicative of crustal thickening.Their compositional diversity is linked to:(i)differences in source composition;(ii)distinct melt fractions during partial melting;and(iii)different residual mineralogies reflecting varying P–T conditions.Post-collisional(~2.7–2.6 Ga)A-type granites reflect rifting in that they were closely followed by extension-related dyke swarms,and they are interpreted as differentiation or partial melting products of magmas derived from subduction-modified mantle.The sequence of granitoid emplacement indicates subduction-related magmatism was followed by crustal thickening,regional metamorphism and crustal melting,and post-collisional extension,similar to that seen in younger Wilson Cycles.It is compelling evidence that plate tectonics was active in this segment of Brazil from~3 Ga.展开更多
In PCAC(Po?os de Caldas Alkaline Complex),in southeastern Brazil,it is observed a polyphase mineralization related to Zr-,U-,Th-,Mo-,and REE-enrichment due to hydromethermal processes which affected alkaline primary r...In PCAC(Po?os de Caldas Alkaline Complex),in southeastern Brazil,it is observed a polyphase mineralization related to Zr-,U-,Th-,Mo-,and REE-enrichment due to hydromethermal processes which affected alkaline primary rock.Primary Zr-minerals were leached and concentrated as“caldasite”,a rock composed mainly by zircon and baddeleyite in different proportions.Several techniques of mineralogical characterization were applied and results indicated zircon,baddeleyite,magnetite and iron-oxyhydroxides,mainly.Magnetic separation by WHIMS(Wet High-Intensity Magnetic Separation)was performed in order to indicate the efficiency for Fe-concentration removal for potential application in refractory industry.展开更多
The Pocos de Caldas Plateau is formed by the alkaline intrusion of Pocos de Caldas and surrounding metamorphic basement. It is characterized as a remnant of the South American Planation Surface resulted from erosional...The Pocos de Caldas Plateau is formed by the alkaline intrusion of Pocos de Caldas and surrounding metamorphic basement. It is characterized as a remnant of the South American Planation Surface resulted from erosional events from Late Cretaceous-Paleogene transition. Pocos de Caldas Alkaline Massif (PCAM) was formed during alkaline volcanism event from the Late Cretaceous. It is located on the west side of the Mantiqueira Mountain Range, characterized by alkaline rocks and topography reaches over 1700 m high. A major feature of denudation is the development of the “circular drainage”, a particular feature of some caldera and other circular or concentric structural features. Recent tectonic movements may critically affect regional geomorphology by influencing river patterns and orientations. The morphometric analysis shows that some rivers are controlled by reactivated faults, however, in some regions the lithology has major influence in the rivers development.展开更多
Ni WO4 was prepared using the polymeric precursor method and studied in terms of physical and chemical properties to verify its stability for industrial applications as pigments.The characterization was accomplished u...Ni WO4 was prepared using the polymeric precursor method and studied in terms of physical and chemical properties to verify its stability for industrial applications as pigments.The characterization was accomplished using thermal analyses,X-ray diffraction(XRD),scanning electron microscopy(SEM),photoluminescence(PL)and UV–Vis spectroscopies,colorimetric coordinates,and Raman spectra.Increasing the temperature,successive exothermic reactions were observed and they are related with thermal decomposition of the organic compound.The stability was reached at^700℃.The material is verified to become completely free of second phase at^800℃.The end Ni WO4 powders showed an intense charge transfer(CT)-related tail centered in the ultraviolet region,resulting in a yellow product.In addition,the powders exhibited broad excitation band and broad deep blue–green emission band,which were enhanced with increasing powders’crystallinity.展开更多
基金Fundacao Carlos Chagas de AmparoàPesquisa do Estado do Rio de Janeiro(FAPERJ),for providing him a post-doctoral fellowship(E-26/202.084/2020 and 2020.03701.1).the National Council for Scientific Development(CNPq)for financial support.CNPq for his Productivity on Research grant(#311106/2020-0)。
文摘The Archean Eon was a time of geodynamic changes.Direct evidence of these transitions come from igneous/metaigneous rocks,which dominate cratonic segments worldwide.New data for granitoids from an Archean basement inlier related to the Southern S?o Francisco Craton(SSFC),are integrated with geochronological,isotopic and geochemical data on Archean granitoids from the SSFC.The rocks are divided into three main geochemical groups with different ages:(1)TTG(3.02–2.77 Ga);(2)mediumto high-K granitoids(2.85–2.72 Ga);and(3)A-type granites(2.7–2.6 Ga).The juvenile to chondritic(Hf-Nd isotopes)TTG were divided into two sub-groups,TTG 1(low-HREE)and 2(high-HREE),derived from partial melting of metamafic rocks similar to those from adjacent greenstone belts.The compositional diversity within the TTG is attributed to different pressures during partial melting,supported by a positive correlation of Dy/Yb and Sr/Zr,and batch melting calculations.The proposed TTG sources are geochemically similar to basaltic rocks from modern island-arcs,indicating the presence of subduction processes concomitant with TTG emplacement.From~2.85 Ga to 2.70 Ga,the dominant rocks were K-rich granitoids.These are modeled as crustal melts of TTG,during regional metamorphism indicative of crustal thickening.Their compositional diversity is linked to:(i)differences in source composition;(ii)distinct melt fractions during partial melting;and(iii)different residual mineralogies reflecting varying P–T conditions.Post-collisional(~2.7–2.6 Ga)A-type granites reflect rifting in that they were closely followed by extension-related dyke swarms,and they are interpreted as differentiation or partial melting products of magmas derived from subduction-modified mantle.The sequence of granitoid emplacement indicates subduction-related magmatism was followed by crustal thickening,regional metamorphism and crustal melting,and post-collisional extension,similar to that seen in younger Wilson Cycles.It is compelling evidence that plate tectonics was active in this segment of Brazil from~3 Ga.
文摘In PCAC(Po?os de Caldas Alkaline Complex),in southeastern Brazil,it is observed a polyphase mineralization related to Zr-,U-,Th-,Mo-,and REE-enrichment due to hydromethermal processes which affected alkaline primary rock.Primary Zr-minerals were leached and concentrated as“caldasite”,a rock composed mainly by zircon and baddeleyite in different proportions.Several techniques of mineralogical characterization were applied and results indicated zircon,baddeleyite,magnetite and iron-oxyhydroxides,mainly.Magnetic separation by WHIMS(Wet High-Intensity Magnetic Separation)was performed in order to indicate the efficiency for Fe-concentration removal for potential application in refractory industry.
文摘The Pocos de Caldas Plateau is formed by the alkaline intrusion of Pocos de Caldas and surrounding metamorphic basement. It is characterized as a remnant of the South American Planation Surface resulted from erosional events from Late Cretaceous-Paleogene transition. Pocos de Caldas Alkaline Massif (PCAM) was formed during alkaline volcanism event from the Late Cretaceous. It is located on the west side of the Mantiqueira Mountain Range, characterized by alkaline rocks and topography reaches over 1700 m high. A major feature of denudation is the development of the “circular drainage”, a particular feature of some caldera and other circular or concentric structural features. Recent tectonic movements may critically affect regional geomorphology by influencing river patterns and orientations. The morphometric analysis shows that some rivers are controlled by reactivated faults, however, in some regions the lithology has major influence in the rivers development.
基金the financial support from Brazilian research funding agencies,namely,FAPESP(Grant Nos.2013/07909-4 and 2013/07296-2)CAPESCNPq(Grant No.470069/2013-9)。
文摘Ni WO4 was prepared using the polymeric precursor method and studied in terms of physical and chemical properties to verify its stability for industrial applications as pigments.The characterization was accomplished using thermal analyses,X-ray diffraction(XRD),scanning electron microscopy(SEM),photoluminescence(PL)and UV–Vis spectroscopies,colorimetric coordinates,and Raman spectra.Increasing the temperature,successive exothermic reactions were observed and they are related with thermal decomposition of the organic compound.The stability was reached at^700℃.The material is verified to become completely free of second phase at^800℃.The end Ni WO4 powders showed an intense charge transfer(CT)-related tail centered in the ultraviolet region,resulting in a yellow product.In addition,the powders exhibited broad excitation band and broad deep blue–green emission band,which were enhanced with increasing powders’crystallinity.
