Rosely Aparecida Liguori Imbernon

Weathering alteration and related REE concentration in the Catalao I carbonatite complex, central Brazil

Abstract REE geochemistry and mineralogy was investigated in a lateritic profile derived from the weathering alteration of the Catalao I complex. From bottom to top of the weathering profile the fresh rock (FR) changes gradually into an altered rock, an isalteritic saprolite (IS) and an alloteritic saprolite (AS). The FR is a phoscorite cut by abundant carbonatitic veins. In the IS apatite is the most abundant mineral, occurring together with goethite, quartz, and small amounts of a secondary Al-phosphate belonging to the plumbogummite-group minerals. AS is formed of goethite, plumbogummite-group minerals, and quartz. Within the FR, carbonatitic veins are richer in REE (REE2O3=0.32%) than phoscorite (REE2O3=0.13%). Both parent rocks are characterized by LREE enrichment, but LREE/HREE ratio is higher for carbonatite. REE concentration tends to intensify with weathering, being REE2O3=0.6–0.8% for IS and 1.3–1.9% for AS. REE fractionation in the vertical direction is very weak, being the general pattern of REE distribution essentially inherited from the fresh rock. In addition to the REE-laterites, an extremely REE rich silicified facies within the IS (REE2O3=2.48–4.83%) was also investigated.

Mössbauer spectroscopic study of iron oxides and oxyhydroxides in gossans

Abstract Two sets of gossan samples derived from the oxidation of sulphides of a NiCu and a PbZn deposit, respectively, have been investigated by Mossbauer spectroscopy. For the first set of samples all spectra consisted of one magnetically split sextet with parameters similar to those of goethite, except for one sample that presented an additional sextet typical of hematite. The magnitude of the magnetic hyperfine field in goethite was found to decrease linearly with increasing (Ni + Cu)/(Ni + Cu + Fe) mole fraction, suggesting that Ni and Cu could be structurally incorporated in the goethite lattice, in an analogous way to previously reported Al substitution. The PbZn gossan samples yielded spectra with two sextets that could be assigned to goethite and hematite. One sample, in addition, presented a doublet that was attributed to jarosite. No correlation was observed between the goethite hyperfine fields and the (Zn + Pb)/(Zn + Pb + Fe) mole fractions. Reasons for such behavior are discussed.

Caractérisation par analyse thermique de la constitution cristallochimique de diverses chlorites zincifères

Characterization of the crystallochemical composition of some Zn-chlorites by means of differential analysis. Thermal decomposition of tlie liydrox- ide layer of Zn-chlorites shows a broad endotlierniic peak and a high loss of OH. This phenomenon occurs between 510 and 555 OC for sonie Zn-chlorites (franltlinfuriiaceite, Ixdeyclilore and Vazante Zii-chlorite). For Canoas Zii-chlorite, this decomposition takes place at a lower temperature (< 450 OC). This low teniperature of hydroxide layer deliy- droxilation depends on tlie Zn content of the hydroxide layer, and H,O+ is related to atomica1 amount of Zn in tlie cell. Dehydroxilation of tlie 21 layer takes place around 620-680 OC and 750-780 OC, with small endothermic peaks and low loss of OH. Thermal analysis may show Zn location in the hydroxide layer. O 2000 Academie des sciences / Editions scientifiques et medicales Elsevier SAS Zii-chlorite / DTA-GTA

An Interdisciplinary Approach to Teach Geoscience

Music is the central theme of the interdisciplinary approach presented in this chapter. The interdisciplinary approach of this teaching proposal focuses on using the construction of a lithophone (from Greek lithos = stone), a percussion instrument with rock plates, for teaching geoscience. Lithophones are similar to the more common xylophones, but with unique musical characteristics which reflect their peculiar design. The main aims of this chapter focus on how to build a lithophone in order to use it as education tool and as an appealing educational resource. When designing a lithophone, the teacher and his/her students should characterize the chosen lithotype (rock type) and the relationship between the length of the plates and the vibration frequency in order to select the musical notes. When the lithophone has been constructed, the teacher should use the sound of the rock plates as a tool to discuss the elastic characteristic of materials. The amazing results obtained through this interdisciplinary approach illustrate the importance of this educational resource in teaching and disseminating geosciences.

Biogeochemical coefficients as indicators of nutrient element sorption in jerivá (Syagrus romanzoffiana (Chamisso) Glassman), a palm tree species from Brazil

The absorption coefficients usually applied to biogeochemical prospection may provide information on the substrate (soil) in natural and contaminated ecosystems, since the chemical composition of the plants tends to reflect the availability of the elements. The biogeochemical coefficients could be a parameter to assess the bioaccumulation potential of a flora species, interactions involving the soil–plant system, and presence or absence of contaminants, such as metals. This study applies the biological absorption coefficient, the temporal absorption coefficient, and the acropetal coefficient as parameters to evaluate the differential absorption in the selected representative species. The Syagrus romanzoffiana (Chamisso) Glassman chosen as a representative species in this study is a palm tree species commonly known in Brazil as “palmeira jerivá” (jerivá palm tree). The representative species is widely used in landscaping and vegetation restoration in urban areas. It shows major regional dispersion and is endemic in South America. The results indicate that jerivá palm tree could be a useful indicator of soil contamination in tropical areas.