Texture of quartzite pebbles in metaconglomerates: strain paths across an extensional detachment

The shape of pebbles in metamorphosed conglomerates has been used as an indicator of strain during tectonic deformation. Here we analyze deformed quartzite pebbles from metaconglomerates across the Salamanca detachment shear zone (SDSZ),  with variations of strain and deformation temperature. This structure is related to the late Variscan gravitational collapse in the Iberian Massif, Central Spain and has significant control on mineral resources. Strong preferred orientation is documented with time-of-flight neutron diffraction measurements and EBSD. The c-axes are in an asymmetric maximum perpendicular to the pebble elongation direction and there is considerable variation between samples. The oblique c-axis maximum relative to the elongated shape axis can be explained as a result of extension, combined with simple shear and dominant basal and rhombohedral slip, based on polycrystal plasticity modeling. It may also be influenced by recrystallization resulting in orientation patterns that resemble single crystals. The role of inherited textures is discussed and seems to be dominant in lower temperature segments on the base of the SDSZ hanging-wall.

Funding: grant PID2020-117332GB-C21 funded by MCIN/ AEI /10.13039/501100011033; SA084P20 from the JCyL government, and TED2021-130440B-I00 funded by MCIN/AEI/10.13039/501100011033.