Registro dos primeiros corpos com afinidade kimberlítica na Província Borborema, NE do Brasil

Abstract

Two kimberlitic bodies were recognized and studied on northern Rio Grande do Norte state during fieldworks of the Diamond Brazil Project. These intrusions have been named Santa Fé-1 and Santa Fé-2 and are located in the Rio Piranhas-Seridó domain, Borborema Province. The Santa Fé-1 and Santa Fé-2 pipes have areas of 27 ha and 9 ha, respectively, and exhibit a volcaniclastic kimberlite breccia texture containing ilmenite, garnet, spinel and clinopyroxene in abundance. Eclogite garnet contains Na2O >0.07 wt.% and has been classified as G3"D" and G4"D". According to ground magnetic and gravity survey data, these kimberlitic intrusions are cylindrical bodies, magnetically stratified and discordantly hosted into highly magnetic and dense rocks, which correspond to granodioritic and tonalitic orthogneisses and migmatites of the Arabia Complex (2546 ± 4.2 Ma, SHRIMP U-Pb zircon). The recognition of kimberlitic pipes with expressive dimensions in a previously not prospective setting opens new horizons to exploration of primary sources for diamonds in the Borborema Province and especially in the Rio Grande do Norte state.