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Activities involving other projects

IGCP638 works closely with these different Task groups like WAXI (West African Exploration Initiative), AMEDEE (Activité Minières, Environnement, Développement Economique, Ethique) and AVG (Association Vision Géologie, Sénégal) and now with ECOS-Sud-CONICYT (research project on Precambrian mineralizations on the Rio de la Plata Craton, Uruguay, link).

As an example, recently a mining research program (Ecos-sud Conicyt: 2017-2020) [Leaders: Tahar Aïfa (France); Henrique Masquelin (Uruguay)] was developed on mineralizations of the area of “Polanco - Arroyo del Soldad” in the Nico Pérez Terrane, Rio de la Plata Craton (Uruguay). This block, composed mainly of Precambrian rocks, is rich in base metal deposits, particularly in native gold associated with Cu-Zn-Pb-As within quartz dykes. Potential methods (magnetism, gravity and radiometry), combined with the structural data, will be used to investigate the mechanism(s) of ore deposits and estimate the reserves through modeling of the near subsurface structures.

This will be a good opportunity for the involved PhD and MSc students to work on aeromagnetic, radiometric and gravity data combined with observation data (structural, petrophysical data mainly) to investigate properly the mechanism(s) of ore deposit traps.

 

Geological Abstract

South of the Paraná Basin, the study area is divided into three terranes: (i) Piedra Alta, (ii) Nico Perez, and (iii) Punta del Este (Bossi and Campal, 1992) (Fig. 1). Piedra Alta Terrane (PAT) is entirely composed of Paleoproterozoic granites (2.06-2.10 Ga). Nico Pérez Terrane (NPT), central field, separates from the PAT by the shear zone of Sarandí del Yí (Oyhantçabal et al., 2011; Oriolo et al., 2016a) and are divided into various minor tectonic blocks with Archaean and Paleoproterozoic rocks, as well as Neoproterozoic granites (Hartmann et al., 2001; Santos et al., 2003; Gaucher et al., 2008; Peçoits et al., 2016; Oriolo et al., 2016b; Masquelin et al., 2017). Punta del Este Terrane (PET) is separated from the NPT by the shear zone of Ballena Sierra. It is composed of gneisses and meta-tonalites whose magmatic age goes back to 800 Ma (Lenz et al., 2011; Masquelin et al., 2012), as well as Neoproterozoic granites (650-540 Ma).

The area of interest is located in the central part of the NPT. This crustal block contains most mineralizations of economic interest of the Uruguayan Precambrian Shield (gold, iron, limestone with cement, metallic ores, etc). The rocks of the basement are here mafic and felsic orthogneisses, pegmatites, amphibolites, paragneisses with muscovite and tourmaline, chlorito-schists, quarzites with fuchsite, deformed meta-conglomerates and banded iron formation (BIF). The cover is a Proterozoic meta-sedimentary succession of low metamorphic degree which recovers uncomformably the basement, being even tectonically inserted and is composed of dolomitic marbles, sericitic schists, rhythmic metapelites (shales), quarzites with brands of waves and polygenic conglomerates (Mac Millan, 1933; Midot, 1984; Fesefeldt, 1988).

The study area shows the recutting by a series of fractures resulting from a brittle deformation probably reactivated during the general exhumation of the block, as of half of the Lower Paleozoic (Hueck et al., 2016). This phenomenon would result from the redistribution of Proterozoic faults during their Phanerozoic long story. The structural analysis shows the occurrence of WE, NS normal faults as well as N70°E and N20°E shears (Masquelin et al., 2017).

Fig.1

Fig. 1

References

Fesefeldt, K. 1988. Asesoramiento Geológico y yacimentológico a la Dirección Nacional de Minería y Geología (DINAMIGE) - Misión Geofísica Alemana. Bund. für Geowiss. und Rohstoffe, 102, 131: 1-186.

Gaucher, C., Finney, S.C., Poiré, D.G., Valencia, V.A., Grove, M., Blanco, G., Pamoukaghlián, K., Gómez Peral, L. 2008. Detrital zircon ages of Neoproterozoic sedimentary successions in Uruguay and Argentina: Insights into the geological evolution of the Río de la Plata Craton. Precambrian Research, 167, 150-170.

Hartmann L.A., Campal N., Santos J.O., Mac Naughton N.J., Schipilov A. 2001. Archaean crust in the Río de la Plata Craton, Uruguay: SHRIMP U–Pb reconnaissance geochronology. Journal of South American Earth Sciences, 14:557–570.

Lenz C., Fernandes L.A.D., McNaughton N.J., Porcher C.C., Koester E., Masquelin H. 2011. Magmatic and metamorphic U-Pb SHRIMP ages in zircons for the Cerro Olivo Gneissic complex orthogneisses – Dom Feliciano Belt in Uruguay. Precambrian Research, 185:149-163.

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Masquelin H., Fernandes L.A.D., Lenz C., McNaughton N.J., Porcher C.C. 2012. The Cerro Olivo complex: A Pre-Collisional Neoproterozoic Magmatic Arc in Eastern Uruguay. International Geology Review, 54(10):1161-1183.

Masquelin H., Silva Lara H., Sánchez Bettucci L., Núñez Demarco P., Pascual S., Muzio R., Peel E., Scaglia F. 2017. Lithologies, structure and basement-cover relationships in the schist belt of the Dom Feliciano Belt in Uruguay. Brazilian Journal of Geology, 47(1): 21-42.

Midot, D. 1984. Étude géologique et diagnostique métallogénique pour l'exploration du secteur de Minas, Uruguay. Thèse Doctorat 3ème Cycle, Univ. Paris VI, 24(1984), 3 cartes, Paris, 175p.

Oriolo S., Oyhantçabal P., Basei M.A.S., Wemmer K., Siegesmund S. 2016a. The Nico Pérez Terrane (Uruguay): from Archean crustal growth and connections with the Congo Craton to late Neoproterozoic accretion to the Río de la Plata Craton. Precambrian Research, 280: 147-160.

Oriolo S., Oyhantçabal P., Wemmer K., Heidelbach F., Pfänder J., Basei M.A.S., Hueck M., Hannich F., Sperner B., Siegesmund S. 2016b. Shear zone evolution and timing of deformation in the Neoproterozoic transpressional Dom Feliciano Belt, Uruguay. Journal of Structural Geology, 92: 59-78.

Oyhantçabal P., Siegesmund S., Wemmer K. 2011. The Río de la Plata Craton: a review of units, boundaries, ages and isotopic signature. International J. Earth Sciences (Geol. Rundschau), 100:201-220.

Peçoits E., Aubet N., Heaman L.M., Philippot P., Rosière C.A., Veroslavsky G., Konhauser K.O. 2016. U-Pb detrital zircon ages from some Neoproterozoic successions of Uruguay: Provenance, stratigraphy and tectonic evolution. Journal of South American Earth Sciences, DOI: 10-1016/j.jsames.2016.07.003.

Santos, J.O.S., Hartmann, L.A., Bossi, J., Campal, N., Schipilov, A., Piñeiro, D. 2003. Duration of the Trans-Amazonian Cycle and Its Correlation within South America Based on U-Pb SHRIMP Geochronology of the La Plata Craton, Uruguay. International Geology Review, 45, 27-48.