Peraluminous leucogranites generation during different stages of the Brasiliano Orogeny in the Borborema Province, NE Brazil

Abstract

The Mamanguape pluton comprises muscovite, biotite syeno-to monzogranite intruded in metasedimentary rocks. Geochemically, the studied samples of the Mamanguape pluton peraluminous granites are ferroan and alkali-calcic. Furthermore, trace element distribution diagrams are characterized by troughs at Ba, Nb, Sr, P and Ti. The REE patterns are fractionated showing (Ce/Yb)N ratios ranging from 12 to 15, and deep negative Eu anomalies, with Eu/Eu* ratios varying between 0.18 and 0.25. The geochemistry of the two-mica granites of the Mamanguape pluton shows similarities with peraluminous leucogranites from the Borborema Province with crystallization ages related to the contractional (640–600 Ma) and transcurrent (590–545 Ma) stages of the Brasiliano/Pan-African Orogeny. Peraluminous, two-mica and biotite-leucogranites were emplaced through all Borborema Province with ages within 640–600 Ma and 590–545 Ma intervals. Their generation is interpreted as the result of partial melting of metasedimentary rocks involving muscovite dehydration. The crystallization age (574 ± 2 Ma) of the Mamanguape two-mica granites suggest intrusion related to the transcurrent stage of the Brasiliano Orogeny. Zircon grains extracted from two samples of a two-mica leucogranites of the Jurema and Jupi Plutons, Pernambuco-Alagoas Domain, show a large variation of εHf(t) values (−45 to −5) and Hf TDM model age between 1.2 and 3.9 Ga. Archean Hf TDM model ages were recorded in Cryogenian/Ediacaran zircon grains as well as Paleoproterozoic grains, suggesting contribution of an Archean component in the source of the granites. One sample of the Mamanguape Pluton, Transversal subprovince, have εHf(t) values ranging between −13.7 and + 1.4 and Hf TDM model age between 1.4 and 2.2 Ga, suggesting that the magma was generated by partial melting of metasedimentary rocks that received a large contribution of Neoproterozoic and Paleoproterozoic igneous sources. Small amount of mantle melt contributing to the source of the two-mica granites is supported by the presence of mafic enclaves and positive εHf(t) values.