The Soca intrusion: a rapakivi granite of Uruguay

The Soca granite, emplaced in the Rı́o de la Plata Craton, is located 65 km east of Montevideo. It is a homogeneous porphyritic leucogranite, with almost 75 km2 of exposed area. Petrographically, the Soca granite is characterized by the occurrence of quartz, plagioclase and alkaline feldspar in two generations, ferrous pyroxene, mica, amphibole, and relic fayalite; with zircon, allanite and apatite as abundant accessory minerals. Its main geochemical features are high K2O/Na2O, low CaO, Al2O3 and P2O5, high total alkali values (average K2O+Na2O around 7.98), high FeO∗/[FeO∗+MgO] (average 0.93), and high Nb, Y, and LREE concentrations (except for Eu). The petrographic and geochemical evidence allow us to classify the Soca granite as an A-type Proterozoic granite, related to the saturated alkaline association, specifically to the rapakivi type granites. The Soca granite has features similar to the typical rapakivi granites from Scandinavia and Central Amazonia.