Interpretation of the kinematics of the fragile neo-tectonic faults of the southeast sector of the Sierra de Pachuca

Abstract

Brittle faults in the Sierra de Pachuca are associated with regional geologic events of neotectonic deformation. Due to the above, brittle deformation predominates in the Cenozoic volcanic rocks that outcrop in the southeast sector. The objective of this work is to determine the state of paleostress in this sector of the Sierra de Pachuca, based on structural displacement data in brittle faults.
In Structural Geology, for the study of brittle faults, three stages are considered: data collection, analysis, and interpretation. In the present work, the field data collected are: the attitude of the fault plane, the orientation of the slide, the direction of movement and the degree of confidence in the determination of the direction of movement. For the data analysis, the consistency of the data, the integration of data subgroups, and the determination of the level of quality of the data were observed.
Finally, for the interpretation, the technique of inversion of the stress tensor was applied and the following two assumptions were considered: 1) the displacement in the fault planes occurs in the direction of the solution of the shear stresses and 2) the data reflect a uniform stress field.
The preliminary results of this investigation combined with the geological mapping show the following: 1) the history of brittle neo-tectonic deformation in the study area records at least two stages, 2) the stress state indicates a left-hand rotation of the orientation of the main stresses and 3) the topological arrangement of the brittle faults in the studied region suggests a Riedel arrangement most likely associated with a left lateral regional movement.