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|Title: ||Paleoproterozoic late-orogenic and anorogenic alkaline granitic magmatism from northeast Brazil|
|Other Titles: ||Precambrian Research|
|Authors: ||Plá Cid, J.|
Bitencourt, M. F.
Nardi, L. V. S.
Lafon, J. M.
|Keywords: ||Alkaline granites;Geochemistry;Anorogenic;Late-orogenic|
|Issue Date: ||2000|
|Abstract: ||During the Transamazonian cycle (2.090.2 Ga), two silica-saturated alkaline granite suites were intruded along the border of the Sa˜o Francisco craton, northeastern Brazil. The Couro de Onça intrusive suite (COIS) is late tectonic relative to major deformational events, and the Serra do Meio suite (SMS) postdates this event, being interpreted as anorogenic type, deformed during the Brasiliano cycle (0.65–0.52 Ga). The COIS encompasses alkali-feldspar
granites, syenogranites, monzogranites, with dykes of similar composition and age (2.15795 Ma). They are metaluminous rocks of alkaline affinity, whose evolution was probably controlled by mineral fractionation processes involving mainly plagioclase, amphibole, and Fe–Ti oxide. The SMS, whose probable age is 2.01 Ga, is composed
of metaluminous and peralkaline granites, with associated quartz syenites, with Ti-aegirine transformed during the
Brasiliano deformation to riebeckite titanite aenigmatite. The temperatures of two stages of metamorphic transformation, overprinted during the Brasiliano event, are estimated at about 550 and 400–450°C. Both magmatic suites are derived from enriched mantle sources. The metaluminous and peralkaline trends observed in the SMS,
characterized by high concentrations of HFS and RE elements controlled mainly by F-activity, reflect the evolution
of different primary magmas produced by successive melting of the same mantle sources, in an anorogenic setting.|
|Appears in Collections:||Artigos Publicados em Periódicos (IGEO)|
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