PALEO-STRESSES ANALYSIS, BY MEANS OF STRIATED FAILURES IN CHINCHINA-SANTA ROSA STOCK

Silvia Pijao Fault belongs to Romeral Faul system, place in contact rocks from Quebradagrande Complexes (at East) and Arquia (at West). Chinchina-Santa Rosa Stock is a Metagabro unit of oceanic origin, which is disposed with an elongated stripe with N-S direction, on West of Silvia-Pijao Fault; it could be correlated with Arquia Complex, but there is not any certainty about this. This Unit presents a series of friction surface generated by faulting, which were analyzed at different locations through corp, near municipalities of Chinchina, Manizales, Neira and Santa Rosa de Cabal.

Structural data was measured on striated faults, which were used to find paleo-stresses directions, by means of right dihedral and sliding model, which allowed analytic comparison of worked zone.

Paleo-stresses analysis results allow us to deduct two faults populations of striated faults, which correspond to different events. A first deformities event, corresponds to a stress field for which a compression direction tendency is WSW-ENE; the second event is composed by a stresses field in which maximum horizontal stress (σ1) has a E-W direction, intermediate stress tries to go horizontal (σ2) and minimum stress places near a vertical position (σ3), being this stresses field corresponding to an environment mainly compressive. In this work, absolute ages were not determined of researched structural events. Local stress deducted fields, could be generated by activity of Silvia-Pijao Fault.

It follows by the form factor “R” (0.60 to 0.67) associated with the location of nearby σ2 effort to vertical shear regime. A predominant direction NE-SW is obtained through statistical representations to fracture planes measured in the Stock Chinchiná-Santa Rosa, Colombia.