Jardim do Seridó Suite: first example of Ediacaran peraluminous magmatism in the Rio Piranhas-Seridó Domain, Borborema Province, Northeast Brazil

Abstract

Peraluminous granitoids were recently mapped in the Rio Piranhas-Seridó Domain, the northeast portion of the Borborema Province. These bodies occur as stock and intrusive dikes in the metapelites of the Seridó Formation, constituting the Jardim do Seridó Suite. This suite has two facies. The first and most expressive facies consists of a medium-grained and whitish leucocratic monzogranite with muscovite, garnet, and biotite, while the second is represented by fine-grained and greyish leucocratic granodiorites with biotite, cropping out mainly on the edges of the main body. The thermobarometric conditions for the crystallization of the monzogranites were estimated between 2-5 kbar and 690-950 ºC, whereas the lithochemical data indicate a syn-collisional peraluminous signature. Neoproterozoic garnet-biotite schist xenoliths of the Seridó Formation are sometimes observed partially assimilated in the main body (stock). A U-Pb zircon age of 592 ± 2 Ma obtained in the main body is considered as the crystallization age of the Jardim do Seridó Suite, corroborating the proposed existence of peraluminous magmas associated with the Brasiliano Orogenesis in the Rio Piranhas-Seridó Domain. The chemical and petrographic data identified this suite as fertile to that it can generate dikes of rare elements-bearing pegmatites.