Produção Nacional
Química mineral e condições de colocação do batólito trondhjemítico nordestina, Núcleo Serrinha, Bahia
2005; Sociedade Brasileira de Geologia; Volume: 35; Issue: 4 Linguagem: Inglês
10.5327/rbg.v35i4.1210
ISSN2317-4889
AutoresBasílio Elesbão da Cruz Filho, Herbet Conceição, Maria de Lourdes da Silva Rosa, Débora Correia Rios, Moacyr Moura Marinho,
Tópico(s)Geochemistry and Elemental Analysis
ResumoThe Nordestina Trondhjemitic Batholith (NTB; 720 km 2 ) is a ellipsoidal intrusion, exposed in the central part of Serrinha Nucleus, an Archaean-Paleoproterozoic segment of the Sao Francisco Craton at the eastern of the Bahia State. It intrudes the gneissic-migmatitic Archaean- Paleoproterozoic basement along its western margin and the Paleoproterozoic volcano-sedimentary sequences of the Rio Itapicuru Greenstone Belt along the southern and eastern contacts. Its north-south elongated shape, associated with concentric internal foliation, which becomes more intense toward the border, and crystallization age of 2.15 Ga, are interpreted as result of syn-tectonic emplacement during the compressional Transamazonic event and concomitant to the closure of the Rio Itapicuru Basin (2.2-2.1 Ga). The NTB is composed of zoned oligoclase (An 17 -An 26 ), quartz, calcic amphibole (Fe-hornblende and Mg-hornblende), biotite (Fe-rich), microcline, epidote (pistacite Ps 23 mole %), titanite, zircon and apatite. Iron oxides are rare to absent and the epidote occurs as euedral to subhedral magmatic grains included in biotite. Magnetic susceptibility, electron microprobe analyses of Al content in hornblende (aluminumin- hornblende barometry), coexisting hornblende-plagioclase (hornblende-plagioclase thermometry) and the presence of magmatic epidote were used to constrain the oxygen fugacity ( f O 2 ), P and T during the crystallization of the magma. The NTB crystallized from low f O 2 magmas (between NNO and FMQ buffers), at ~ 5kbar pressure under narrow range of temperature (651-673°C).
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