Geochronology (U-Pb/Pb-Pb) and isotopic signatures (Rb-Sr/Sm-Nd) of the Paleoproterozoic Guanambi Batholith, southwest Bahia State (NE Brazil)

The Guanambi batholith (GB) is located in south-western Bahia, Brazil, where it forms part of the Urandi-Paratinga mobile belt. The batholith extends over an area of almost 6,000 km2 and is mainly composed of syenites and monzonites, with subordinate granites, mafic syenites and lamprophyric dykes. Two main units can be recognized: the multiple intrusions, being divided into four regions (Paratinga, Laguna, Igapora and Guanambi) and the so-called late-intrusions forming the Cara Suja, Ceraima and Estreito massifs. U-Pb and Pb-Pb isotopic data demonstrate that the batholith was emplaced 2.05 Ga ago. GB has highly negative initial εNd (-7.4 to -10.6), pointing to an enriched source, and Sr initial ratios between 0.704 and 0.707. Both chemical and isotopic signatures suggest that GB formed by fractional crystallization of a lamprophiric magma derived from a Paleoproterozoic enriched mantle source. (author)