The Structural Framework of the North-Central Guiana Shield: a Fossil Fold-and-thrust Belt in Northeastern Roraima State, Brazil

ACCEPTED MANUSCRIPT - UNCORRECTED PROOF The northeastern Roraima state (Brazil), located in the north-central portion of the Guiana Shield, shows shallow-granitoids and associated volcanic rocks of the Orocaima Igneous Belt (2.00-1.96 Ga) overlaid by the Arai Formation sedimentary succession (1.96-1.87 Ga). Previous authors suggested a compressional event affecting the region, however recent works interpreted that transpressional efforts are related to a distal effect of a Grenvillean-aged tectonics (K’Mudku Event) from reactivation of some basement structures, generating drag folds in the supracrustal successions. The present multi-scale approach to the best-exposed sector of this geological framework shows new data from the regional photointerpretation to the thin section scales. The structural data reveals the fractal character and the rheological control on the widespread east-west-trending compressional structures. The southern domain presents steeply-plunging shear zones related to thrusting of the shallow-granitoids over the volcanic successions. The central domain presents ubiquitous southward steeply-plunging secondary foliation parallel to the folds’ axial plane. The south border of the northern domain shows spaced foliation and gentler folds, besides sub-horizontal thrust faults. The suite of structures reveals an E-W- to ESE-WNW-trending fold-and-thrust belt that presents a transition of thick- to thin-skinned tectonics with mass transport to the north. These geometric relations do not match with the K’Mudku lineaments, being further parallel to the southward Middle Orosirian structural framework (Uatumã-Anauá Domain), opening new possibilities for the timing and meaning of structures in this area.