Pesquisas em Geociências

Heat treatment of Corundum from Barra Velha Region, SC

Guilherme Tunes Villani — 2025-01-07

Ruby is the variety of corundum with the highest commercial value due to its intense red color caused by the presence of chromium in its chemical composition. The most valuable rubies are pure red, without secondary shades of pink or orange. Due to the rarity of high-quality gemstones, the gem industry has developed various treatment techniques to enhance the appearance and quality of gems, making them more attractive and valuable. Gem treatments are essential to provide quality gems to a broader market. Controlled heating of gems improves the color and transparency of various gem minerals, including ruby, sapphire, and topaz. This form of treatment is widely accepted in the international market. Since discovering the factors that cause color change in minerals, technological advancements have enhanced treatment methods to adhere to certain conditions to make the results increasingly predictable and stable. Originating from the Barra Velha deposits in Santa Catarina, Brazil, these rubies are characterized as low-quality stones. This study aimed to evaluate whether heat treatment of this material could offer the potential for these gems to be included in the national context of producing quality rubies. The treatment was performed on 10 ruby samples in an electric furnace at temperatures of up to 1600°C with controlled heating, cooling rates, and atmosphere to create a unique set of parameters for all treated samples and achieve stable conditions for the creation of crystal defects, oxygen diffusion in the crystal structure, and changes in charge compensation. In addition to conventional thermal treatment, flux healing was performed on two samples, which changed the color and improved the crystals' transparency. The change in color and improvement in the gemological quality of the crystals is visually identified by changes in light absorption patterns quantified through spectrophotometer analysis.

Morphological parameters analysis in landslide scars for spatial resolutions of 1 and 10-meters

Regiane Sbroglia — 2025-01-19

This research analyzed the changes in the hillslopes geometry where landslides occurred in the natural disaster in the state of Santa Catarina in November 2008. The analysis was carried out on two different scales. To do this, maps of the hillslopes morphological parameters hypsometry, slope declivity, aspect, curvature, and contributing area were performed using Digital Elevation Models (DEM) with 10-m and 1-m spatial resolution, using Geographic Information System (GIS). The methodology developed by Gao (1993) was used to analyze the correlation between these morphological parameters and the occurrence of landslides. The results showed that the classes with the highest frequency did not necessarily have the greatest landslides potential. Field works are recommended to validate and help interpret the results. Analyzing the scale, greater relief detail was observed in the higher spatial resolution maps. Finally, the shape of the elevation contours and the curvature have changed inside the scars in the DEM with 1-m grid. This DEM was performed after the natural disaster under study. This shows the potential of using morphological data in slope stability studies. However, it was concluded that the choice of the input topographic data scale and the input topographic data processing date in relation to the event studied are decisive factors in the results obtained.

Potential of atmospheric CO2 capture by enhanced weathering in Mato Grosso: case study

Português — 2025-04-14

The use of soil remineralizers (REM), a practice grounded in ancient agricultural techniques, is experiencing a resurgence as a sustainable and complementary alternative to soluble chemical fertilizers. These REM, rich in multiple nutrients, gradually release essential elements necessary for plant growth, emulating the natural regeneration processes of soil. In addition to their effectiveness, this approach offers lower costs and added benefits, such as enhanced crop quality and maintained or increased agricultural yield. In Brazil, where agriculture is a fundamental pillar of the economy, research and regulation of REM have progressed significantly. As of July 2024, this advancement has registered 66 products with the Ministry of Agriculture. As the impacts of the greenhouse effect intensify, there is an urgent need for strategies to reduce greenhouse gas (GHG) emissions. Agriculture, a significant contributor to CO₂ emissions, is particularly impactful in Brazil. Thus, adopting sustainable management practices is essential for making both competitive and environmentally sustainable agriculture. In this context, using REM within the framework of Enhanced Weathering (EW) emerges as a promising method for capturing atmospheric CO₂, promoting plant growth, and enhancing carbon sequestration in the soil. This study examined two geological sites in the state of Mato Grosso: the Colíder Group and Planalto da Serra Alkaline Complex. The findings indicate that the samples from these sites have substantial potential for atmospheric CO₂ removal, with values ranging from 39.53 kg CO₂ t-1 to 496.16 kg CO₂ t-1. This suggests that EW is an effective climate change mitigation technique and that the rocks studied play a vital role in this process. In the future, EW could be an integral component of a broader strategy to control GHG emissions and combat climate change, focusing on using rocks with properties similar to those analyzed in this research.

Identifying phosphate deposits in the Rio Grande Terrace through the use of echo characters

Maria Eulália Alberton — 2025-04-15

This work presents categories of echo-facies in the Rio Grande Terrace, Pelotas Basin, relating them to the area’s morphology and potential phosphorite deposits. Single-channel seismic records acquired with frequencies between 400 and 1200 Hz and power between 500 and 1200 J were used to identify echo-facies, focusing on their shape, size, and subsurface patterns, compared with multichannel records using the RMS Amplitude attribute. Measurements of features and hyperbolas were taken on vertical and horizontal scales to group echo classes. Five main echo-facies categories were defined. Moreover, a bathymetric surface was interpolated through kriging. The spatial analysis revealed distribution patterns. Small and medium-scale hyperbolic echoes (categories 3A and 3B) and rugged bottoms correlate strongly with phosphorite deposits. Moreover, larger horizontal scales of hyperbolas indicate increased roughness on the bathymetric surface and a tendency toward concentration. Rugged bottoms and small-scale hyperbolic echoes correlate with potential phosphorite deposits.