THE SIERRA DE LAS ANIMAS MAGMATIC COMPLEX, SOUTHERN URUGUAY, REVISITED: NEW PALEOMAGNETIC AND PRECISE GEOCHRONOLOGIC DATA

RAPALINI, AUGUSTO E.; TOHVER, ERIC; SANCHEZ BETTUCCI, LEDA; BARCELONA, HERNÁN

Tandil

Congreso; LatinMag 2011; 2011

LatinMag (Latin American Association of Geomagnetism and Paleomagnetism)

A new paleomagnetic study was carried out on 15 sites of the Sierra de Animas Complex, exposed in SE Uruguay. Preliminary results show that six sites carry a likely pre-tectonic characteristic remanence. Mean directions from five of these sites are consistent with those six published previously that led to the SA2 paleomagnetic pole. On the basis of 11 virtual geomagnetic poles a new preliminary paleomagnetic pole was computed for the Sierra de Animas Complex (SAn, 12.2°S, 258.9°E, A95: 14.9°). This falls slightly displaced respect to the original SA2 pole, but is consistent with the Los Barrientos pole from the Rio de la Plata craton and poles of ca. 550 Ma from Arabia and Congo. A geochronologic study based on U/Pb (SHRIMP) dating in zircons was also carried out. Two samples, obtained in a microsyenite and a rhyolite provided well defined ages of  573±2 and 585±4 Ma, respectively, confirming the Early Ediacaran age of the complex and precisely dating the new paleopole and this segment of the APWP for the Rio de la Plata craton. These ages also cast serious doubts on the extension of this magmatic event into the Cambrian.