"TINAQUILLO", Basic Igneous Rocks in

State of Cojedes, Venezuela

Original reference: S. E. Aguerrevere et al., 1937, p. 22

Original description: ibid.

S. E. Aguerrevere, G. Zuloaga and M. Tello (1937, p. 22-30) give a petrographic description of the basic igneous rocks of the region of Tinaquillo, in which they include the following varieties: peridotite porphyry norite (a variety of gabbro), piroxenite, quartziferous monzonite, and The peridotite porphyry outcrops typically in: a) Cerro El Tigre, b) the crossing of the Quebrada Pedernales with the road Tinaquillo-La Montaflita, and c) the Teta de Tinaquillo peak. Said porphyry is one of the rocks that constitute the Tinaquillo sill; it presents a typical blackish color in the outcrops located in the hills and a brownish color in those located in the lower parts, produced by the oxidation of the iron minerals Its granular texture gives to the surface outcrops a typical roughness which permits the rock to be distinguished from the others (p. 22-25).

The norite outcrops in: a) the road to Cerro El Tigre, b) the northern slope of the Cerro El Cachicamo, c) the road from La Montañita to La Pica. The norite also constitutes the Tinaquillo sill. It is more even-grained and less jointed than the former; it is commonly gneissic or banded (p. 25-28).

The piroxenite outcrops in the road from Pedernales to Casupo, some 300 m. from the crossing with the Quebrada Pedernales. The rock forms thin beds within the mass of peridotite porphyry; it has been constituted by extreme magmatic differentiation of the porphyry (p. 28).

The quarziferous monzonite outcrops in the road from Tinaquillo to El Tinaco, in the site called El Topo, in the vicinity of the kilometer 240. It seems to have originated the great amount of acid dikes that cross the igneous and metamorphic rocks from Tinaquillo to El Tinaco and also seems to constitute the edge of a large acid batholith located somewhat near the surface (p. 28-29).

Felix A. Balda