The opencast gold mine of Boinás, has allowed to outcrops the contact between the variscan basement
and the Cenozoic sediments. It is observable that the contact is a post - Lower Oligocene thrust, with a
N40ºE trend. From a macrostructural point of view, Boinás thrust spreads along more than 10 km with a
constant orientation, a vertical gap that reaches 400 m, and a NW vergence. Northwestwards another
Alpine thrust develops (Tineo, A l o n s o y Pulgar , 2004) with a parallel orientation an opposite vergence.
Between both thrusts a tectonic pop-down appears (Narcea Pop-down). The dynamic analysis shows that
this structure was activated by a paleostress tensor with an horizontal s1 trending N139ºE, with a stress regime close to uniaxial compression (R=0.06). This stress allows the geometrical interchanges between s2 and s3. The outcrop also allows to observe a secondary population of normal faults, that fits to an extensional stress tensor (R=0.01) with s3 trending N146ºE, that is coaxial with the main compressive stress tensor. We interpret both fault populations as generated by the tectonic thrust emplacement
