K-Ar AND Rb-Sr AGES OF BIOTITES FROM COLOMBIA, SOUTH AMERICA

Clockwise rotation of the Santa Marta massif and simultaneous Paleogene to Neogene deformation of the Plato-San Jorge and Cesar-Ranchería basins

“…This belt has a signature of two-mica granitoids (Viñasco et al, 2006) with a large component of inherited older crust (Ordoñez, 2001;Viñasco et al, 2006). Previous K-Ar ages in biotite of 100-110 Ma (Pinson et al, 1962) need further scrutiny, as may represent partial resetting due to a Cretaceous event (Toussaint, 1996).…”

“…Existing geochronological data in basement rocks in the Plato-San Jorge basin include a ca. 110 Ma biotite K-Ar obtained in a biotite granitoid from the Cicuco-3 well (Pinson and Hurley, 1962), and several ca. 110 Ma and 60 Ma Rb-Sr, K-Ar ages from low-grade schist and a volcanic rock of the El Cabano-1 and Los Cayos-1 wells (Thery et al, 1977).…”

On the origin and tectonic significance of the intra-plate events of Grenvillian-type age in South America: A discussion

“…The first age dating in this area was produced by Pinson et al (1962), a 1200 Ma biotite age of a granitic rock at San José del Guaviare, Colombia. Later, Priem et al (1982), also in eastern Colombia, dated by the same methods more than 30 biotites, most of them yielding ages near 1200-1300 Ma, more or less synchronous with the regional cooling of the Rondonian-San Ignacio Province.…”

U-Pb zircon ages of rocks from the Amazonas Territory of Colombia and their bearing on the tectonic history of the NW sector of the Amazonian Craton

“…Figure 1 illustrates the interpretation given by Cordani et al (2000), with the location of the study area. The first geochronological ages in that region were determined by Pinson et al (1962), who dated the alkaline rocks of São José del Guaviare by the K-Ar method, back to an ordovician age (about 480 Ma). During the 1970's and the 1980's, the Geological Survey of Colombia, INGEOMINAS, made an extensive reconnaissance geological mapping of the country (PRORADAM 1979).…”