Neoproterozoic tectonometamorphic history of the exotic Cuchilla Dionisio Terrane, Uruguay and its possible links with and continuation into SW Africa

• Applicant: Professor Dr. Thomas Michael Will, Ph.D.
• Subject Area: Mineralogy, Petrology and Geochemistry
• Term: from 2016 to 2023
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 318297424

The planned project is the result of work carried out within the DFG-funded SPP 1375 South Atlantic margin processes and links with onshore evolution. There, we could demonstrate (i) that the main Pan-African collisional suture lies in South America and, (ii) that the South Atlantic did not open along this suture but followed the long axis of a Neoproterozoic back-arc basin, located to the east of the suture. Remnants of this back-arc basin occur on both sides of the modern South Atlantic, including the allochthonous Cuchilla Dionisio Terrane in eastern Uruguay. Many workers agree that this terrane is exotic to South America and may represent a splinter of the Kalahari Craton. However, its connection with and continuation into SW Africa remains controversial and different links have been proposed: (1) the Angola Block, (2) the Coastal Terrane of the Kaoko Belt in NW Namibia, (3) the Marmora Terrane of the Gariep Belt and, (4) the Malmesbury Terrane in the Saldania Belt in South Africa. Each link has a different implication for the palaeogeographic reconstruction of Rodinia and the amalgamation of SW Gondwana. In this project we plan to determine the tectonothermal history of the Cuchilla Dionisio Terrane and compare it with that of its possible counterparts on the other side of the South Atlantic. This requires a thorough knowledge of the metamorphic and magmatic evolution of the respective terranes, which, at present, is only available at a reconnaissance level for the Cuchilla Dionisio Terrane. Therefore, we aim at resolving (i) the pressure-temperature conditions and paths experienced by high- and medium-grade metasedimentary and metavolcanic rocks, (ii) the tectonic settings in which the metamorphic events occurred and, (iii) the tectonic environments in which the pre-metamorphic magmatic protoliths of the Cuchilla Dionisio Terrane formed. By reconciling the expected results with known information on the geological evolution of SW Gondwana we expect to be able to identify the continuation of the Cuchilla Dionisio Terrane into SW Africa and also its most plausible position during Rodinia dispersion and SW Gondwana assembly. The results are likely to be significant for reconstructing the configuration of the assembled Rodinia supercontinent and the palaeogeographic positions of the various cratonic blocks of Rodinia and SW Gondwana during the Neoproterozoic.

• DFG Programme: Research Grants
• International Connection: China, South Africa, Uruguay
• Cooperation Partners: Professor Dr. Claudio Gaucher; Professor Dr. Qiuli Li; Dr. Xiaoxiao Ling; Dr. Petrus Le Roux
• Co-Investigators: Professor Dr. Hartwig E. Frimmel; Privatdozent Dr. Jörg Pfänder