Tectonic Setting of the Late Proterozoic Lavalleja Group (Dom Feliciano Belt), Uruguay |
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Affiliation: | 1. Department of Geology and Geography, 330 Brooks Hall, West Virginia University, Morgantown, WV 26506-6300, USA;2. Department of Earth and Environmental Sciences, 121 Trowbridge Hall, University of Iowa, Iowa City, IA 52242, USA;1. The Development Center of Water Treatment Technology, State Oceanic Administration, Hangzhou 310012, China;2. Zhejiang Sci-Tech University, Hangzhou 310018, China |
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Abstract: | The Lavalleja Group exposed along the Dom Feliciano orogenic belt is located in the southeast of Uruguay. This group consists of volcano-sedimentary rocks, developed during the Neoproterozoic Brasiliano cycle. The geochemical signature of the igneous rocks of the Lavalleja Group, mainly metagabbros and basic and acidic metavolcanic rocks, indicates a back-arc basin tectonic setting. The metamorphic grade increases to the southeast, from very low grade, lower green-schist facies, in the Minas Formation, to a medium grade, amphibolite facies, in Fuente del Puma and Zanja del Tigre Formations. The metamorphic mineral assemblages correspond to a low-pressure regional metamorphism associated with a high thermal gradient. A compressive deformational event that probably corresponds to the closure of the Lavalleja basin during a continental collision, was recognized. The petrology, geochemistry, metamorphic grade, and tectonic setting are consistent with a back-arc basin setting for the Lavalleja Group. |
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