Abstract
Anomalies concerning the litho-stratigraphic, geomorphic and hydrogeologic contexts were detected on the region north of Itapororoca-PB. These anomalies are concentrated in the area coined as "Cretacic volcanics" by the system DNPM-CPRM (1974), in the basement of the Barreiras Group. In this region, two classic terranes of the Borborema Province were recognized: S. José do Campestre (SJC, Paleoproterozoic) and Alto Pajeú (TAP, Eoneoproterozoic, respectively to the north and to the south of the Patos Lineamment (LP). Along LP there is preserved part of the cover rocks of the SJC, phyllonitized and drastically folded, of the Seridó Group. These terranes and cover rocks are pierced by Brasiliano plutons that display very distinct petrogenetic and isotopic characteristics. The fist case of of juvenile tonalitic plutonism of the Province is there recorded. A silicious duricrust, with many textural facies is present in the area, as relicts of previous plateau, between LP and the Mamanguape River (aligned by an E-NE normal fault). Anomalies of F, Cr and Ni were detected in this duricrust, in which some sparce fractions of ultramafic and alkaline rocks could be identified. Besides the geological mapping, a gravity survey of 548 new gravity stations was performed for the purpose in addition to 452 prexisting stations of the Observatório Nacional and of the UFRN, so covering the area of the duricrust as well as the area of some circular structures, in the surroundings.
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