Alteração hidrotermal e mineralização na Mina Caneleira, Lavras do Sul, RS

Abstract

The Caneleira Mine, located west of the city of Lavras do Sul, central portion of Rio Grande do Sul state, comprises granitoids (monzogranite and granite perthite) U-Pb zircon age of 594 ± 5 Ma (Ediacaran). The rocks that occur in the mine present hydrothermal alterations with auriferous occurrences and other metals such as copper, silver, lead, zinc and molybdenum. The objective of this work was to determine the types of hydrothermal alterations and to discuss the petrographic and structural framework of the study area. The methods used were beyond the geological mapping, the macroscopic and microscopic study of samples from drill core, mineral chemistry (Diffraction X-ray) and whole rock geochemistry. The hydrothermal and mineralized zones in the Caneleira Mine have strong structural control and suggest to be related to the tensile fractures generated during the sinistral regime of the Palmas Jaques Fault Zone. The intersections of the northwest-southeast direction lineaments with the northeastsouthwest direction lineages inferred by remote sensing showed a positive correlation with the areas with hydrothermal alteration and gold mineralization. Three main sets of hydrothermal alterations were identified: type 2 and type 2.1 alterations with mineral assembly composed of chlorite, illite, epidote, calcite, sulfides and sometimes hematite. Hydrothermal alterations of type 3 and 3.1 with mineral composition by ilite, quartz, epidote, calcite, sulfides and sometimes chlorite, kaolinite and hematite. Hydrothermal alterations of type 4 and 4.1 with mineral assembly composed of ilite, chlorite, quartz, calcite, epidote and sulfides. The mineral assemblies that occur in rocks with alterations in the Caneleira Mine are similar to mineral assemblies that occur in some types of alterations in the porphyry copper model deposit. Alterations in the type 2 and 2.1 would be equivalent to propylitic alteration. Alterations of type 3 and 3.1 would be equivalent to phyllic alteration. Alterations in the type 4 and 4.1 would be equivalent to silicática potassic alteration. The exploration of new hydrothermal and possibly gold mineralized areas at the Caneleira Mine can be based on structures identified by remote sensing together with the processing and interpretation of geophysical data of aerogamaespectrometry.