OBLIQUE TECTONIC IN THE PRECAMBRIAN SHIELD OF BOLIVIA, SW OF AMAZONIAN CRATON

The geodynamic setting of the Sunsás orogeny of the Precambrian Shield of Bolivia displays transcurrent regime of oblique movements namely transtension and transpression. The San Ramón district displays oblique stress from WSW to ENE. The tectonic style at San Ramón districts provides evidence to transpression as an intermediate between compression and transcurrent regime. The geological mapping, satellite image, airborne geophysical survey, ongoing deformation, s-c structure, veining and geochronology to support our results. These trends represent the mean transported vectors in the area for the amalgamation of Sunsás orogeny to the Paraguá block in the late Mesoproterozoic.

This region with oblique tectonic is characterized by the following features:

1. Strike slip shear zones parallel to the mobile belt, with S-C foliation pattern in the intervening blocks and an internal network of sigmoidal lenticular shearing in all the observation scales.
2. Internal organization of complex branching with different blocks, showing different ages, metasedimentary and metamorphic structural patterns joined by areas of shearing.
3. Folds in "echelon" oblique to the mobile belt, rotated to the direction of main course shearing.
4. Horizontal stretch lineation parallel or oblique to the mobile belt.
5. Granitic intrusions affected by shear zone