GEOCHEMICAL CHARACTERIZATION OF IGNEOUS ROCKS IN CENTRAL CHIHUAHUA, MEXICO

Chihuahua State is located in northern Mexico, and is distinguished by its wide geological settings that have allowed the formation of diverse igneous rocks. We can mention the Sierra Madre Occidental (SMO) to the western part of the state, a large silicic province product of the subduction of the Farallon plate 100 to 42 M.y. ago; and the Basin and Range province, which also has been related to the Rio Grande Rift, located in the central – eastern part, with ages of 30 to 27 M.a.

This project is focused in igneous rocks of central Chihuahua, which are 40 to 42 M.y. old. We include volcanic rocks that are rhyolites and intrusive rocks that are syeno-diorites and syenites. The rhyolites are riched in Co (26 – 258 ppm), Rb (120-243 ppm), Ce (75-250 ppm) and W (400-3000 ppm) compared to the intrusive rocks.

The intrusive rocks, according to the geochemical classification for granitic rocks (Frost et al., 2001), are ferroan, alkalic and metaluminous, which correspond to plutons in cores of alkali volcanoes, the environment which these rocks are located. These plutons are rich in Ba (200-1976 ppm), Eu (0.7-2.43 ppm), and Zr (500-639 ppm), compared to the rhyolites.

A compelling geochemical analyses of these rocks, allow us to characterize and classify them properly, especially those rocks that were collected within Chihuahua City, rocks that have not even appeared in the current geologic map of the city.