Main Article Content
The northeastern Roraima state (Brazil), located in the north-central portion of 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. Meanwhile, recent papers interpreted that transpressional deformation, related to a distal effect of a Late Mesoproterozoic tectonics (K’Mudku Event), reactivated some basement structures and generated drag folds in the supracrustal successions. This paper presents a multi-scale approach to the best-exposed sector of this geological framework, gathering and analyzing
new data from the regional photointerpretation to the thin section scales. The structural data reveal the fractal character and the rheological control on the E-W- and ESE-WNW-trending compressional structures. The southern domain presents sub-vertical shear zones with down-dip to oblique lineation, which are related to the uplift of the shallow-granitoids in relation to the coeval volcanic successions. The central domain, where the volcanic succession crops out, exhibits ubiquitous E-W- to ESE-WNWtrending sub-vertical foliation parallel to the axial plane of the folds. The southern border of the northern domain (Arai Formation) shows spaced cleavage and gentle folds, besides sub-horizontal thrust faults. The structures reveal a fold-and-thrust belt that presents a transition from thick- to thin-skinned tectonics with mass transport to the north. These geometric relations do not match with the K’Mudku lineaments,
usually following a NE-SW direction in the north-central Guiana Shield. However, the southward Middle Orosirian structural framework (Uatumã-Anauá Domain) shows similar geometric relations with nearly E-W-trending lineaments and parallel sub-vertical foliation.
This work is licensed under a Creative Commons Attribution 4.0 International License.
The papers are published in the open access format, being freely available to any user, under a CC-BY Creative Commons license.
By submitting this manuscript for evaluation, the authors are aware of the CC-BY Creative Commons license. In the case of manuscript approval, the author responsible for the manuscript (corresponding author), hereinafter referred to as CEDENTE (ASSIGNOR), hereby assigns and transfers to CPRM-Serviço Geológico do Brasil, holder of the JGSB, free of charge, on his behalf and on behalf from all co-authors, the right of the first publication. This includes the rights of editing, publication, translation into another language and reproduction by any process, worldwide, today and in the future.
After the first publication by the JGSB, authors hold the copyright without restrictions and are allowed to disclose and distribute their work through personal website pages and institutional repositories.
At the same time, the ASSIGNOR declares that the content of the manuscript is of sole responsibility of the authors and that this content does not infringe the copyrights and/or other property rights of third parties, that is, that any contents of the manuscript and its attachments, if taken from other publications, are duly referenced and, when necessary, the permissions for publications of such contents were requested by the authors from the copyright holders; that the disclosure of images (if any) has been authorized and that it assumes full moral and/or patrimonial responsibility, due to its content, before third parties.