Petrological features of the Santa Teresa Granitic Complex Southeastern Uruguay Rossana Muzio a, *, Antonio Carlos Artur b a Departamento de GeologõÂa, Instituto de GeologõÂa y PaleontologõÂa, Facultad de Ciencias, Igua  4225, CP 11400, Montevideo, Uruguay b Departamento de Petrologia e Metalogenia, Instituto de Geocie Ãncias e Cie Ãncias Exatas, UNESP, Av. 24A 1515, CP 178-CEP 13506-900, Rio Claro, Sa Äo Paulo, Brazil Abstract 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 dierent 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. # 1999 Published by Elsevier Science Ltd. All rights reserved. Keywords: Granite; Petrology; Zircon tipology; Brasiliano Cycle; Uruguay Resumen El Complejo GranõÂtico Santa Teresa esta localizado en la regioÂn noreste del Departamento de Rocha, Uruguay y corresponde a un granito epizonal emplazado en los metasedimentos de bajo grado del Grupo Rocha. El mapeo facioloÂgico a escala 1:50,000 del sector centro-este del complejo permitio el reconocimiento de doce facies granõÂticas diferentes que fueron agrupadas en dos suites magmaÂticas denominadas, respectivamente, como Suite Calco-alcalina Santa Teresa y Suite Peraluminosa Sierra de la Blanqueada. La Suite Calco-alcalina Santa Teresa esta compuesta por seis facies petrogra®cas predominantemente por®rõÂticas, de composicioÂn monzo- a sienogranõÂtica con presencia de esfeno, alanita y magnetita. GeoquõÂmicamente son de naturaleza calco-alcalina, de medio a alto potasio con altos tenores de sõÂlice. La SuõÂte Peraluminosa Sierra de la Blanqueada esta representada por seis faÂcies granõÂticas, inequigranulares y por®rõÂticas, de composicioÂn monzo- y sienogranõÂticas con muscovita, turmalina, ilmenita y monacita como principales accesorios. Los estudios de tipologõÂa del circoÂn con®rman la naturaleza calco- alcalina y peraluminosa de ambas suites. GeotectoÂnicamente, los granitoides calco-alcalinos se encuadran como tardi- a post- orogeÂnicos y mientras que los peraluminosos estarõÂan relacionados al espesamiento crustal de ambientes sincolisionales. # 1999 Published by Elsevier Science Ltd. All rights reserved. Journal of South American Earth Sciences 12 (1999) 501±510 0895-9811/99/$ - see front matter # 1999 Published by Elsevier Science Ltd. All rights reserved. PII: S0895-9811(99)00033-4 * Corresponding author. Fax: +59-82-5258617. E-mail addresses: rossana@fcien.edu.uy (R. Muzio), acartur@ dpm.igce.unesp.br (A.C. Artur).