Adolf Heinrich Horn

C-, Sr-isotope stratigraphy of carbonate rocks from the Southern Espinhaço Ridge, Minas Gerais, southeastern Brazil

Neoproterozoic carbonate rocks comprise different stratigraphic units in the southern part of the Espinhaço Ridge, Minas Gerais, Brazil. C, O- and Sr-isotope analyses were carried out along four selected stratigraphic sections across these formations. These are: (i) the Rio Pardo Grande Formation in the upper portion of the Espinhaço Supergroup, sampled in section 3; (ii) Macaúbas Group laminated limestones (Tijucuçu Farm) and dolostone layers (Domingas Formation) have been respectively sampled along the so-called sections 1 and 2, and (iii) the lower stratigraphic units of the Bambuí Group, sampled in section 4. Laminated limestone samples from the Macaúbas Group have δ13C values as high as 10.9‰ decreasing up section to -1.1‰ and 87Sr/86Sr values vary from 0.7072 to 0.7076, a range commonly observed in Cryogenian rocks. In section 2, dolomitic samples exhibit 87Sr/86Sr from 0.7076 to 0.7077 while in section 3, 87Sr/86Sr from 0.7074 to 0.7079. In section 4, 87Sr/86Sr values are around 0.7080. The values of 87Sr/86Sr observed in carbonate samples from the Macaúbas Group are similar to those observed in the Sr-isotope secular curve for the Neoproterozoic. Carbonate samples from the base of the Bambuí Group correlate with Ediacaran fingerprints, after the Marinoan (ca. 635 Ma) glaciation.

PEGMATITES IN SOUTHEASTERN BRAZIL

Two pegmatite groups are represented in southeastern Brazil. The first group, resulting from fractional crystallization, is linked to syn-tectonic granites (580 Ma – deformation event D1) and the second one is associated with another partial melting event of the crust which simultaneously produced porphyritic leucogranites [(520-500 Ma)- later deformation event D2 ] and pegmatites themselves. The Fe/Mn ratios of tourmalines, micas and columbite-tantalites decrease continuously from simple pegmatites to gem quality elbaite-rich ones. The Fe/Mn ratio has been used as a qualitative fractionation index which seems to reflect the regional zoning of the first pegmatites group around a hidden granite body. The Fe/Mn ratio values correlate negatively with Na and Li contents in tourmalines and mica. The REE, Nb, Co and Zn contents in tourmalines, micas, and columbite-tantalites are controlled by their mineral assemblages.

Site partitioning of Cr3+ in the trichroic alexandrite BeAl2O4:Cr3+ crystal: contribution from x-ray absorption spectroscopy.

X-ray absorption spectroscopy measurements at the Cr K-edge of a trichroic crystal of alexandrite BeAl(2)O(4):Cr(3+) for different orientations of the crystal with respect to the polarization and direction of the x-ray incident beam have been performed. Analysis of the experimental spectra with the help of first-principles calculations of x-ray absorption spectra allowed us to estimate the proportion of chromium Cr(3+) cations among the two different octahedral sites of the alexandrite structure (70% in the C(s) site-30% in the C(i) site). The methodology presented in this work opens up new possibilities in the field of mineralogy for the study of complex minerals containing several sites potentially occupied by several transition elements or for solid solutions.

Metal Anomaly Prospection at Cerrado. Example for the use of Si-Phytoliths as anomaly indicators at Riacho dos Machado Region, Minas Gerais, Brazil

The target area of this work is a heavy metal anomaly in the surroundings of a gold mine and a lead mining complex. This work investigated the distribution of selected heavy elements in soil samples and Si-Phytoliths from plants. The aim was to verify if metal contents are indicative for metal anomalies in the soil. Plants and soil samples were collected in profiles over granitic-gneissic rocks, which form the basement, in tectonized contact with the overlaying sedimentary units belonging to the Riacho dos Machados Group, part of the Espinhaco Super Group. The whole rock substrate is covered by lateritic to arenitic soils with different exposure depths. Metal-rich fluid invaded these units, forming metal anomalies culming in Zn-Pb-Au deposits, like that of Salobre-Porteirinha. After appropriate preparation, the samples were, analyzed by ICP-OES (Si-Phytoliths) and FRX (soil). Anomalies in the investigated profile are indicated by high metal contents in the Si-Phytoliths of the selected species. Using different species the metal concentration in different depths can be determined in a simple and easy way. The Si-Phytolith concentrations seem to reproduce better the rock metal anomalies than the soil samples.

RELATIONSHIP BETWEEN METAL WATER CONCENTRATION AND ANTHROPOGENIC PRESSURES IN A TROPICAL WATERSHED, BRAZIL

In developing countries, Rivers are used to dispose wastewater from many human activities that may result in an input of metals to the water bodies. The Sao Francisco watershed is of extreme importance to Brazil as it drains large areas most of them with high hydric deficit. Besides being an important water resource to the local population several anthropogenic activities are developed in its watershed and compromise its water quality. The main objective was to address the relationship between metal concentration and anthropogenic pressures in Sao Francisco River. A Principal Component Analysis was used to determine a relationship between human activities and water metal concentration and to verify if there was a seasonal trend. Several metals in particulate and dissolved forms were measured in water from 59 points, collected during a “wet” and “dry” seasons, and analyzed using ICP-OES. The results showed that there was a clear correlation of particulate metal concentration with “wet” season, while the dissolved forms were highest in the “dry” season. The suspended particulate matter also showed clearly higher concentration during the “wet” season indicating important surface runoff input related to agricultural activities. Higher particulate metal concentration was found in areas with agricultural practices where the dissolved metals were the main forms in industrial sites. The results indicate that metals associated with soil particles enter the river with surface runoff. On the other side the treatment of industrial effluents are being successful in retaining metals in particulate but dispose metal in dissolved form in the river.

Brachiaria brizantha growth in amended soil by effluents from the milk industry

he present work had as objective the verification of the effects of the incorporation of organic residues originating from ETE of the milk factory products in the soil and the effects in the development of the Brachiaria brizantha plants. The organic material was collected in the discard area of the factory, and been evaporated, triturated and separated in three granule size: powder, medium particles (with 2.0 mm diameter) and grains (medium particles with 6.0 mm diameter) and incorporate in soil by quantity of 0, 5, 10, 15 and 20 t. ha-1 followed by the planting of the forage. During the development of the plants, three cuts were appraised the dry weight and number of tillers. At the end, analysis of the fertility of soil was executing. The used experimental design was representing by randomized blocks with four repetitions. The application of organic material originating from ETE residual of dairies was have shown highly promising results vin the development of the forage plants, mainly when they are used in the powder form or attached and in higher amounts. Also considering some absorption by the plants during the experiment, the level of the nutrients and available minerals in the soil increas ed, except for the magnesium.

Fonte, distribuição e características geoquímicas dos sedimentos de corrente do Rio do Formoso – MG

POLLINATOR FORAGING STRATEGY IN Galactia peduncularis (BENTH.) TAUB. (LEGUMINOSAE: PAPILIONOIDEA) IN THE PARQUE ESTADUAL DA SERRA DE CALDAS NOVAS BRAZIL The way the animals look for food is an important characteristic of their behavior. The optimal foraging theory is based on the existence of a balance between costs and benefits of these behavioral decisions. The present study aimed to evaluate the behavior of the pollinator in response to increased availability of floral resources. The experiment was conducted in a recently burned Cerrado area (Campo rupestre) in the State Park of Serra de Caldas Novas , located in the municipalities of Caldas Novas and Rio Quente Brazil. The species chosen to test our hypothesis was Galactia peduncularis (Benth.) Taub. (Leguminosae: Papilionoidea). 17 pairs of specimens were selected with a number of flowers, and the individuals of each pair were spaced by about 2m. In these pairs, one of them was considered the focal, and the other, the isolated. To test possible differences in pollination between isolated plants and focus, we performed two randomization tests: a test binary (TB), where all pairs were analyzed and verified the number of times where the focus on the individual floral visits were higher than the number of visits in isolated. According to the data analyzed, floral visitors preferred to use plants that could provide a greater amount of floral resources so that the number of visitors varied positively with the increment of flowers. Plants with many flowers can provide a greater amount of food in one location so that visitors do not need to flower around for long distances in search of meeting their energy needs.