Autochthonous and allochthonous strata of the El Callao greenstone belt: Implications for the nature of the Paleoproterozoic Trans-Amazonian orogeny and the origin of gold-bearing shear zones in the El Callao mining district, Guayana shield, Venezuela

East-northeasterly trending folds of both the allochthon and the autochthon, coupled with the northerly thickening of the quartzite, suggest that the allochthon was part of an unknown craton that formerly lay to the north. A second regional fold set, which trends northerly, refolds the earlier structures. It is possibly related to collision of the San Carlos terrane with the amalgamated Imataca-Supamo-Pastora terranes. The unconformably overlying 1.98 Ga Cuchivero arc terrane provides a minimum age for the two collisional events.