Abstract

MUZIO, Rossana; MARTINO, Natalia  and  PEEL, Elena. Petrologic features of mesoproterozoic lamprophyric dykes from Montevideo (Piedra Alta terrane, South Uruguay). Earth Sci. Res. J. [online]. 2021, vol.25, n.2, pp.157-168.  Epub Oct 15, 2021. ISSN 1794-6190.  https://doi.org/10.15446/esrj.v25n2.89652.

Mafic dykes of lamprophyric affinity cropping out along the coastal area of Montevideo city are described. These dykes trend N75°-85° and crosscut 2.1 Ga Paleoproterozoic metamorphic units of the Rio de la Plata craton. They show mainly porphyritic textures with phlogopite and clinopyroxene macrocrysts in a groundmass composed of carbonates, phlogopite, augite, and feldspathoids. Ocellar structures filled with leucite, carbonates, and fibrous alkaline amphibole are present. The mineralogical assembly allows their classification as lamprophyres (minettes), but according to their chemical nature, they can be classified as alkaline lamprophyres. A crystallization age of 1.42 Ga by Ar-Ar method (on biotite/phlogopite) was obtained.

Keywords : lamprophyres; petrology; geochronology; Uruguay.

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