A Proposed Deformation Model from An Andesitic Dome in the Trans Mexican Volcanic Belt in Hidalgo

In the south central part of the Mexican State of Hidalgo, the Trans Mexican Volcanic Belt (TMVB) hosts an andesitic North – South trending elongated dome (ca. 1 km long and 0.5 km wide) of gray to light red andesite. The rock has porfidic texture composed by subhedral plagioclase and amphibole phenocrystals embedded in a matrix of microlithic plagioclase. Occasionaly, elliptical to irregular biotite quartz-diorite xenoliths of centimetric scale are present. The texture of these xenoliths is hipidiomorphic and is constitued by zoned plagioclase crystals and unaltered biotite flakes.

The andesitic dome constitutes a 300 m high abrupt hill with two joint systems, the more pervasive has planes trending NNE-SSW that dip 40-60° to the SE and the less pervasive with NW-SE trending planes that steeply dip to the NE. The dome, in its middle section, is intruded by an ENE-WSW trending, 10-15 m wide andesitic dike. The dome and dike are crosscut by a NE-SW trending, south block down, active normal fault. The inferred orientation of the principal stresses in each deformation event, indicate a span of 35-45° in the trend of maximum extension.

Crosscutting relations and the orientation of the maximum extension in each event allows us to propose a deformation model that can be contrasted and correlated with structures present in the Sierra de Pachuca, to the Northwest of the study area, and to the reminder of the Oriental Sector of the TMVB. If the model proves its effectiveness, it will be a significant contribution in the understanding of the tectonic and petrologic evolution of the TMVB in Hidalgo.