Petrological features of the Santa Teresa Granitic Complex Southeastern Uruguay

The Santa Teresa Granitic Complex, located in the north-eastern region of the Rocha Department (Eastern Uruguay), is an epizonal Late-Brasiliano granite intruded in the low-grade metasedimentary sequence of the Rocha Group. Twelve different facies types, each with distinctive structural-petrographic features, were recognized during detailed mapping (1:50,000) of the central-eastern part of the granitic complex and form two magmatic suites. The Santa Teresa Calk-alkaline Suite is composed of mostly porphyritic 3a–3b granites with variable amounts of biotite, sphene, allanite, magnetite and microgranular enclaves and belongs to a middle to high potassium calk-alkaline series with high silica contents. In contrast, the Sierra de la Blanqueada Peraluminous Suite has a great variation of grain size, including 3a–3b granitic facies with variable content of muscovite, biotite, tourmaline, ilmenite and monazite. Zircon morphology was studied in both suites and also shows their calk-alkaline and peraluminous nature. The Santa Teresa Calk-alkaline Suite had a Late- to Post-orogenic setting whereas the Sierra de la Blanqueada Peraluminous Suite was formed during the crustal thickening related to a syn-collisional environment.