Leucocratic syenogranites the Macururé Domain, Sergipano Orogenic System, Northeastern Brazil: Glória Sul Stock
ABSTRACT: The Glória Sul Stock (SGS) (41 km2) is a round-shaped pluton, which intrudes the metasediments of the central area of the Macururé Domain, in the Sergipano Orogenic System (SOS). The stock encompasses a number of leucocratic syenogranites, including biotite syenogranite, muscovite-biotite bearing syenogranite and muscovite syenogranite. Mafic microgranular enclaves with syenitic composition are abundant in the biotite syenogranites but very rare in the muscovite-biotite bearing syenogranites. The syenogranites are predominantly metaluminous although the more evolved rocks show a peraluminous character. They can be classified as I-type and high-K calc-alkaline rocks. The syenitic enclaves are metaluminous and show shoshonitic geochemical characteristics. Geochemical modeling suggests that petrological diversity may be explained by considering mixing between peraluminous magma with ca. 73% SiO2 and a mafic shoshonitic magma with ca. 56% SiO2. Trace elements contents (Ba = 1,179 - 319 ppm; Rb = 351 - 55.3 ppm; Y = 16.7 - 1.6 ppm) are higher in the enclaves than in the granites. REE contents range from 38.58 - 299.21 ppm; LaN/YbN = 12.57 - 137.22 and Eu/Eu* = 0.72 - 1.94. The present data indicates that granitogenesis in the Macururé Domain (DM) is complex as well as that the widespread leucocratic syenogranites are post-tectonic, having been generated through interaction between peraluminous rhyolitic magmas and mantellic shoshonitic magmas.