GRANITOIDS MARKING THE END OF THE BRASILIANO (PAN - AFRICAN) OROGENY WITHIN THE CENTRAL TECTONIC DOMAIN OF THE BORBOREMA PROVINCE

IGNEZ DE PINHO GUIMARÃES, CÍCERA NEYSI DE ALMEIDA, ADEJARDO FRANCISCO DA SILVA FILHO, JOÃO MARIA MARTINS DE ARAÚJO

Resumo


The studied syenogranite and granodiorite intrusions have a similar U-Pb zircon age (ca 570 Ma). They are intruded in the Central Tectonic Domain of the Borborema Province, forming an S-type belt in relation to the Patos and Pernambuco Lineaments. The studied granitoids are clinopyroxene biotite leuco-syenogranites of the Solidão Pluton; amphibole biotite sienogranites from the Queimadas Pluton; biotite granodiorite and amphibole biotite granodiorite, which occur as dikes cutting the Itapetim Complex and leuco-syenogranites from the Serra Branca Pluton. They show geochemical data transitional between shoshonitic and alkaline series. Deep troughs at Nb, Sr, P and Ti and high LILE/HFSE ratios characterize the spiderdiagram patterns. The ÎNd (0.6 Ga) values are extremely negative (- 11 to -16; except for the Itapetim dykes ~-3) and Nd model ages (TDM) range from 2.0 Ga to 2.5 Ga (the Itapetim dykes ~1.4Ga). Biotites of the studied granitoids are Fe-rich with Fe/(Fe+Mg) ratios in the 0.62 to 0.84 range. Biotites from older granitoids (640 Ma -580 Ma) of the Pajeú - Paraíba Terrane, have Fe/(Fe+Mg) ratios < 0.60. The isotopic and geochemical data suggest that the studied granitoids correspond to a trans-alkaline, ferro-potassic plutonism, originated by partial melting of Paleoproterozoic and Mesoproterozoic crusts, emplaced during the final stage of the Brasiliano Orogeny in the Central Tectonic Domain of the Borborema Province.

Palavras-chave


Granites; Brasiliano; Post-collision.

Texto completo:

PDF (English)

Apontamentos

  • Não há apontamentos.