Estudo gravimétrico 2D dos diatremas da porção sul das Minas do Seival

Abstract

The Seival Mines (MS) are located 54 km from the city of Caçapava do Sul-RS, SW direction, where rocks from the Hilário Formation (Bom Jardim allogroup, second oldest unit of the Camaquã Basin), with important copper mineralizations. The Hilário Formation is part of a period belonging to the first volcanic cycle of the Camaquã Basin, which corresponds to flows of basaltic to andesitic composition. In the southern portion of the MS, two twinned circular structures are found, with approximately 1 km in diameter each, presenting internally, pyroclastic breccias formed by blocks similar to the surrounding andesite. The present work is focused on twinned circular structures, whose origin is attributed to magmatic processes, were formed during volcanic episodes and have an important explosive component. With the aim of creating a 2D subsurface modeling and complementing studies already carried out regarding these features, a gravimetric work was developed to investigate the shape of these structures, based on variations in the Earth's gravitational field caused by differences in density of rocks in the area. The results acquired in addition to the 2D modeling include maps of the Bouguer anomaly, residual and upward continuation (100, 200, 300, 400 and 500m). A radial power spectrum was also generated, in order to qualitatively estimate the estimated depth in sources. Data integration proved to be consistent with previous work already carried out in the area. The results were satisfactory regarding the composition of the model based on gravimetric data and on the data collected for the laboratory density test. With 2D modeling, it was possible to confirm the presence of two bodies in the subsurface, which have two different breaches, with different densities. The presence of four breccias with lower density, diameter and depth was later associated as rooted zones of the two diatremes.