Estudo da interação fuido-rocha nos depositos da lavrinha, distrito aurifero de Pontes e Lacerda-MT

AUTOR(ES)
DATA DE PUBLICAÇÃO

1998

RESUMO

Gold deposits of Lavrinha region, Mato Grosso State, are associated to quartz veins in shear zones formed by low angle tangencial compressive tectonics in a ductil-ruptil regim. As a result, the Proterozoic metasediments of the Aguapei group were thrusted above an igneous basement, represented by metagabros, basalts, tonalites and granites. These processes evolved to dextral transcurrences related a ruptile-ductile reglm. The gold can be founded in two structural domains: the lower domain: is represented by deformed igneous rocks, sheared in the contact area with lithotipes of the Aguapei group (metarenites and metaconglomerates); the upper is composed of quartz-sericite xists, magnetite-quartz-sericite xists and sericite xists and has intermediate position in the sediment strata ofthe Fortuna Formation (Aguapei group). The ore paragenesis is composed by pyrite and hematite where gold is c10sely related. The alteration mineral assemblage inc1ude rutile, epidote, chlorite, and carbonates which occurr in a restrict way. Sericitization is the most pervasive hydrothermal alteration. Fluids involved in the hydrothermal processes were identified as aquo-carbonic and low salinity aqueous fluid inc1usions (approximately 5% ofweight correspondent to NaCI), trapped in inc1usions of quartz veins. It is proposed that the gold was transported as a [Au(HS)2] complexo Its precipitation could be related to imiscibility processes of warmer aquo-carbonic fluids with metamorphic origin followed by an interaction with colder aqueous fluids possible from meteoric nature. Temperature conditions ofhydrotermal processes were estimated by the chlorite geothermometer and ranges between 303-335°C

ASSUNTO(S)

alteração hidrotermal ouro geologia estrutural inclusões fluidas

ACESSO AO ARTIGO

Documentos Relacionados