Produção Nacional
PETROLOGIA MAGNÉTICA DO GRANITO SÃO JORGE ANTIGO, PROVÍNCIA AURÍFERA DO TAPAJÓS
2003; Sociedade Brasileira de Geologia; Volume: 33; Issue: 2 Linguagem: Inglês
10.5327/rbg.v33i2.1036
ISSN2317-4889
AutoresMarco Aurélio Figueiredo, Roberto Dall’Agnol, Cláudio Nery Lamarão, Davis Carvalho de Oliveira,
Tópico(s)Geomagnetism and Paleomagnetism Studies
ResumoThe Paleoproterozoic Older Sao Jorge Granite is a high-K calc-alkaline, magnetite-series granite of the Tapajos Gold Province. The different facies of the pluton display titanomagnetite and individual ilmenite as primary magmatic phases. These minerals generated, respectively, magnetite-ilmenite and ilmenite-hematite intergrowths during the subsolidus stage. Magnetite was later altered in different degrees to martite; ilmenite was sometimes severely oxidized and replaced by assemblages dominated by titanite and rutile. There is a good correlation between magnetic susceptibility (MS) and magmatic differentiation of the facies forming the pluton. MS decreases from biotite-amphibole quartz monzodiorites to amphibole-biotite monzogranites and, finally, to biotite leucogranites. Opaque minerals, amphibole, total mafic, biotite, and titanite modal contents show a positive correlation with MS. Chlorite and MS display a negative correlation in the leucogranites. High MS, significant modal contents of magnetite, and the magmatic assemblage quartz-magnetite-titanite demonstrate that the Older Sao Jorge Granite evolved in relatively oxidizing conditions estimated as situated near those of the HITMQ buffer and a little above those of the NNO buffer. The general characteristics of the Older Sao Jorge granite indicate that it has a good metalogenic potential for gold and sulfide deposits.
Referência(s)