Emplacement model for the Cupira Pluton, Borborema Province (NE Brazil)

Abstract

The Cupira pluton, located in the southern domain of the Borborema province in the Garanhuns subdomain, crops out for approximately 300 km². It is oval in shape and is slightly elongated in the E-W direction. In order to establish an emplacement model and to obtain structural-magnetic alignments, an integration of Anisotropy of Magnetic Susceptibility (AMS) and magnetometry data was carried out. AMS data show that total susceptibility ranges from 0.105x10^-3 SI to 34.618x10^-3 SI, indicating a ferromagnetic character. The degree of anisotropy varies from 1.06 to 1.272, with positive correlation with the total susceptibility. The shape parameter varies from -0.802 to 0.897, with predominance of oblate over prolate ellipsoids, reflecting a dominantly planar magnetic fabric. The magnetic lineations are distributed mainly in the NE-SW direction, with gentle to strong plunges to NE and SW. The magnetic foliation trends vary from NE to NNE, with moderate to strong dips (30° to 86°). The central portion of the pluton has concentric inward dipping foliations associated with strongly plunging lineations, suggesting a central magmatic conduct. The magnetic alignments corroborate with the structural trends obtained by AMS. These data favor the proposition of an emplacement model for the Cupira Puton from a central magmatic conduct, with magma flow distributed in a concentric form, characterizing it as a lopolith.