Multiple sources and multi-stage emplacement of the Esperanca Granitic Complex and its relationship with the Patos - Campina Grande shear zone system, Borborema Province - NE Brazil

Expressive granitic magmatism and a complex system of transcurrent shear zones are the main features associated with the Ediacaran evolution of the Borborema Province (northeastern Brazil). Their petrogenesis and relationships with tectonic structures can provide important insights into lithospheric processes during the collisional to post-collisional stages of the Brasiliano Orogeny. The Esperanca Complex is a NE-trending elongated granitic batholith with ca. 650 km(2) comprising five plutons emplaced between the Patos and Campina Grande dextral shear zones in the central-eastern part of the Borborema Province. An integrated study of the complex was carried out using U-Pb zircon SHRIMP and LA-ICPMS geochronology, mineral and whole-rock geochemistry, and Nd-Hf isotope geochemistry (whole-rock and zircon). The plutons are metaluminous to slightly peraluminous with geochemical and isotopic signature reflecting different sources. The Remigio and Areial plutons have Paleoproterozoic to Neoarchean Nd and Hf T-DM model ages and strong negative epsilon Nd(t) (-15.29 to -16.71) and epsilon Hf (-12.20 to -21.03) values. Their geochemistry is compatible with derivation through partial melting of mafic to intermediate metaigneous sources like the Paleoproterozoic basement (Areial pluton) and metasedimentary sources (Remigio pluton). The Puxinana, Serrote da Cobra and Pocinhos plutons show higher epsilon Nd (-5.90 to -7.35) and epsilon Hf (-2.83 to -6.91) values, and Statherian to Calymmian Nd and Hf TDM model ages, ranging from 1.4 to 1.7 Ga and from 1.6 to 1.8 Ga, respectively. They have geochemical affinity with A-type ferroan granites. The geochemical and isotopic signature are similar to those of Tonian orthogneiss that constitute part of the plutons' host rocks, suggesting derivation from Tonian crustal sources. Evidence of magma mixing and the presence of inherited zircon grains with ages like those of metasedimentary host rocks suggest contribution of the lithospheric mantle and sedimentary sources in different proportions in their petrogenesis. The reported data are compatible with building of the Esperanca Complex by multiple intrusive events. The Pocinhos and Serrote da Cobra plutons are the oldest (similar to 600 Ma) and their genesis is probably associated with heat input resulting from crustal thickening at the end of a long contractional period (ca. 630-600 Ma). The genesis of the Puxinana and Areial plutons (similar to 585 to 565 Ma) involved interactions of crustal and mantle mafic melts, with magma transport and emplacement controlled by the Campina Grande shear zone at the beginning of the transcurrent regime. The Remigio pluton is the youngest intrusion (similar to 565 Ma) and its genesis can be related to a high geothermal gradient resulting from emplacement of the older plutons, possibly enhanced by strain heating related to displacement along the Patos shear zone.

Automated summary

The Ediacaran evolution of the Borborema Province in northeastern Brazil is characterized by expressive granitic magmatism and a complex system of transcurrent shear zones. The Esperanca Complex, consisting of five plutons, was formed between two shear zones in the central-eastern part of the province. Study of the complex using various geochronological and geochemical methods revealed different sources and processes involved in the formation of the plutons.