3. The Rio Boba mafic-ultramafic plutonic sequence: field relations and petrography
The Rio Boba mafic-ultramafic plutonic sequence is a lenticular massif, whose approximate dimensions are 30 km long and 15 km wide, composed of gabbroic rocks and subordinate lenses of pyroxenite (Fig. 2 and Appendix A). Cross-sections show that the southern Rio San Juan complex is folded by late WNW–ESE trending, subvertical antiforms and synforms of kilometer wavelength, which fold on a regional scale the main foliation in the different units, the tectonic contact between Jobito and Guaconejo assemblages, and the magmatic and solid-state deformation fabrics in the overlying Rio Boba plutonic sequence (Escuder-Viruete et al., 2013a). The plutonic sequence is overprinted by late thrust, reverse and strike-slip faults related to Neogene transpressive tectonics.