Mega-scale sheath fold of southern copper belt, Canaã shear zone, Carajás Province, Brazil

Abstract

Sheath folds are highly non-cylindrical folds frequently linked with shear zones. ln cross-sections perpendicular to the stretching direction they display eye-structures, commonly recognized in the field and remote sense images. ln this work, using airborne geophysical images and field geology information, we investigate the crustal architecture of the Canaã shear zone, Carajás Province, Brazil. This area is also known as the Southem copper belt, hosting several Neoarchean lron-Oxide-Copper-Gold (IOCG) deposits. The locations of lOCG deposits in this area delineate an elliptical distribution near the boundary of basement rocks and younger metavolcano-sedimentary sequence. We interpreted that the structural architecture of the Southem copper belt may be reflecting a large-scale upwardly convex sheath-like fold cored by older granulitic basement rocks. This interpretation may bring some contributions to understanding the regional structural control of IOCG deposits in this area, for example, elucidating how the deep-seated (ca. 20 km depth) IOCG deposits (e.g., GT-34 deposit) are now exposed close by to same-aged IOCG deposits of upper crustal levels (1 to 2 km depth).