HIDROTERMALISMO NO COMPLEXO GRANÍTICO LAVRAS E VULCÂNICAS ASSOCIADAS, RS

Resumo

The gold-sulphide mineralization in the Lavras do Sul region (RS) is associated with propilitization, sericitization, and silicification of host rocks. These hydrothermal alterations are evident in the Lavras Granite Complex: and volcanoclastic rocks. Episyenites and beresites have been identified among the hydrothermal products. Majors and traces elements distribution in granitic rocks have been extensively affected just where the hydrothermal alternation is extremely well-developed, reaching its most advanced stages. Loss on ignition, representing the amount of volatile elements, is the best indicator of hydrothermal alteration intensity, particularly in the propilitized and sericitized materials. In the granitic rocks, Au, Ag, and As are the best pathfinders for lithogeochemical exploration. K₂O and Na₂O show sharp decrease near the mineralized zones in the Merita area . REE had low mobility during the hydrothermal event identified in the Lavras Granite Complex: LREE depletion has been noticed only in deeply altered products as episyenites. REE have been determined in sericite, chlorite, and epidote concentrates. Even though subsurface data are not available, it is possible to suggest a porph yry copper model for this mineralization based upon the possibility of vein mineralization presently known, representing hydrothermal activity in the suprastructure of the main deposit.