Portal de Periódicos da CAPES

IDADE RADIOMÉTRICA DO GRANITO DE CAMPO FORMOSO, BA - UMA IDADE MÍNIMA PARA O GRUPO JACOBINA

1978; Sociedade Brasileira de Geologia; Volume: 8; Issue: 3 Linguagem: Inglês

10.25249/0375-7536.1978171179

2177-4382

TORQUATO JOAQUIM RAUL, OLIVEIRA MARIA ALBA FARIAS TANNER DE, BARTELS RICHARD LESTER,

Geochemistry and Geologic Mapping

The Campo Formoso granite represents the magmatic phase of the remobilized Pre-Jacobina basement, located within an arc defined by the Serra de Jacobina, north of Campo Formoso, Bahia. Intrusive relationships between this granite and the Jacobina Group metasediments, gradational changes in textures and compositions between the granite and basement rocks, and the general structural-topographic expression of this arc suggest a mantled gneiss dome model for this area. This work establishes a Rb/Sr whole rock isochron age of 1911 ± l3 m.y. for the Campo Formoso granite. This date is interpreted as the age of the development of the structure, as well as a minimun age for the Jacobina Group metasediments. K/Ar dates on muscovites from the Campo Formoso granite are concordant with the Rb/Sr isochron. It is suggested that a lower regional thermal gradient in the Campo Formoso area during Transamazonic time is the cause for a more rapid cooling environment.