STRATIGRAPHIC INTERPLAYS BETWEEN IGNEOUS AND SEDIMENTARY EVENTS IN THE EARLY PALAEOZOIC JAIBARAS TROUGH (NORTHEAST BRAZIL)

Abstract

The Jaibaras Trough is an example of an intraplate province for which both origin of magmatic manifestations and basin generation mechanisms are coeval. The magmatic suites demonstrate closed spatial and temporal relationships and, in turn, appear to be genetically associated. The simple distribution of igneous bodies occurrence constrains the spatial relationship between the whole magmatic activity during the basin infill. Sequential stratigraphic interplays between sediments and magmatic activities are perfectly constrained through thermal-structural features such as contact aureoles, faulted contacts/abutting and cross-cutting. The basin infill congregates continental immature siliciclastic sedimentary deposits. Deposition took place in areas of instable young shoulder relief and problably totals up to 3 km in thickness. Marked variations in thickness, rapid changes in depositional facies, interbedded thick conglomerates, local unconformities and disconformities of variable extent typify the overall sedimentary deposits making a regional palaeogeographic reconstruction difficult. Probably axial basin filling provided the sedimentation of shale and sandstone, whereas the rift flanks laterally sustained the alluvial fan conglomerates. The magmatic evolution of Jaibaras Trough comprises basically four temporal and spatially separated phases. The early phase involved the Vendian Coreau Dike Swarm, and represents the initial tectonic pulse of rift opening. With continued breakup, reactivation of deeper shear zones gave rise to the emplacement of the Mucambo Pluton during Early Cambrian times, which preceeded the main rift infill. The basin sedimentation was accompanied by a huge volume of volcanism, most of which is composed by flood basalts, dikes and sills. The Meruoca Pluton is the last basin-related igneous manifestation during the Upper Cambrian