Alto Moxotó Terrane, a fragment of Columbia supercontinent in the Transversal Zone interior: Borborema Province, Northeast Brazil

Abstract

Abstract In the central part or central subprovince of the Borborema Province, in the so-called Transversal Zone, an assemblage of Paleoproterozoic (predominantly Rhyacian) rocks occurs together with sparsely distributed Neoarchean nuclei. These rocks constitute the main basement of the Tonian (Cariris Velhos Cycle) and Ediacaran (Brasiliano Cycle) mobile belts. They are older tectonostratigraphic terranes and par excellence ramifying elements (as “inliers”) of the Neoproterozoic orogenic constructions. This tectonostratigraphic terrane known as Alto Moxotó composes a litho-structural context typical of accretionary orogens, with the presence of granitic, granodioritic, and trondhjemitic orthogneisses (≈ arc-type associations) that stretch out for some hundreds of kilometers (Floresta Suite) and are partially covered by medium-grade pelitic-psammitic sequences (Sertânia Supergroup). This basement outline (Floresta Suite + Sertânia Supergroup) depicts an irregular sigmoidal shape, from the interior of Pernambuco (meridian 39ºW) to the Paraíba coastal area (meridian 34º45'W), along about 450 km, varying from 40 to 80 km in width, resulting in a total area of ca. 28,000 km2. This Rhyacian petrotectonic scenario is conditioned and delimited by extensive (shear + thrust) faults that configure a tectonostratigraphic terrane. Moreover, there are pieces of continuity evidence of this tectonostratigraphic terrane not only in the basement of the adjacent Neoproterozoic mobile belts to the North and South of the TAM in Brazil, but also in Northern Cameroon, in Africa. Within this broader predominantly Rhyacian belt, some small Neoarchean gneissic and migmatitic nuclei were identified. The Rhyacian lithologies reveal evidence (TDM ages) of sources from a Neoarchean paleosubstrate. During the Statherian, the whole Rhyacian context was affected by a series of small-scale magmatic manifestations of varied petrologic composition: syenitic, granitic, granodioritic, and gabbro-anorthositic. In this paper, a synthesis of the bibliographic data is presented, including a series of unpublished (geologic and geochronologic) data that together validate our conviction that we are dealing with an extensive (reworked) fragment (TAM) derived from the basement of a Paleoproterozoic supercontinent (Columbia).

Keywords

• Transversal Zone
• Borborema Province
• Rhyacian accretion
• Cariris Velhos Fold System
• Brasiliano