SciELO - Scientific Electronic Library Online

vol.84 issue2Recurring extensional and strike-slip tectonics after the Neoproterozoic collisional events in the southern Mantiqueira provinceU-Pb dating by zircon dissolution method using chemical abrasion author indexsubject indexarticles search
Home Pagealphabetic serial listing  

Services on Demand




Related links


Anais da Academia Brasileira de Ciências

Print version ISSN 0001-3765


PLA CID, Jorge; CAMPOS, Cristiani S.; NARDI, Lauro V.S.  and  FLORISBAL, Luana. Petrology of Gameleira potassic lamprophyres, São Francisco Craton. An. Acad. Bras. Ciênc. [online]. 2012, vol.84, n.2, pp.377-398.  Epub May 08, 2012. ISSN 0001-3765.

Gameleira lamprophyres are dykes and mafic microgranular enclaves associated with the shoshonitic Gameleira monzonite. This association belongs to the Paleoproterozoic alkaline magmatism from Serrinha nucleus, northeast Brazil. The liquidus paragenesis is diopside, pargasite, apatite and mica. Reverse zoning was identified in the groundmass alkali feldspar and was related to the undercooling of lamprophyric magma during the emplacement, with high growth rate of pargasite/edenite inducing disequilibrium between feldspars and liquid. Chemical data indicate that the lamprophyres are basic rocks (SiO2 < 48 wt%), with alkaline character (Na2O + K2O > 3 wt%) and potassic signature (K2O/Na2O ≈ 2). High contents of MgO and Cr are consistent with a signature of a primary liquid, and such concentrations, as well as Al, K, P, Ba, Ni- and light rare earth elements, are consistent with an olivine-free metasomatic mantle source enriched in amphibole, clinopyroxene and apatite. By contrast, the ultrapotassic lamprophyres from Morro do Afonso, contemporaneous alkaline ultrapotassic magmatism in Serrinha nucleus, were probably produced by melting of a clinopyroxene-phlogopite-apatite enriched-source. The identification of different mineral paragenesis in the source of potassic and ultrapotassic lamprophyres from Serrinha nucleus can contribute to the understanding of the mantle heterogeneities and tectonic evolution of this region.

Keywords : potassic lamprophyres; Gameleira lamprophyres; São Francisco Craton; mantle metasomatism; petrology; mineralogy.

        · abstract in Portuguese     · text in English     · English ( pdf epdf )


Creative Commons License All the contents of this journal, except where otherwise noted, is licensed under a Creative Commons Attribution License