Aplicação da técnica de rastreamento de minerais indicadores de kimberlitos na porção central do Estado do Rio Grande do Norte, Nordeste do Brasil

Abstract

The present work addresses the technique of tracing kimberlite indicator minerals applied on the central portion of Rio Grande do Norte (RN) state, Northeast of Brazil, with reference to kimberlitic bodies Santa Fé-1 and Santa Fé-2, recently discovered in the RN, and aims to define new potential areas to contain others kimberlite intrusions. The study area is part of the regional tectonic-geological context of the Rio Piranhas-Seridó Domain, Borborema Province. As crystalline basement, predominantly gneisses and migmatites related to Arábia and Caicó Complexes, with plugs and dykes of Cenozoic olivine basalt intrusive in both complexes. Initially, a sampling stage was performed, on which was collected 30 samples, and then sent for laboratory analysis for counting and description of the grains of kimberlite indicators mineral (KIM), such as Mg-garnet, Mg-ilmenite, Cr-diopside, Cr-spinel, olivine and diamond. As a description of the grains, it was analysed their mineralogy, colour, brightness, fractures, surface textures, the level of abrasion and particle size. The grains were photographed to illustrate the main characteristics for their recognition. With the results of the samples with positive values for KIM, it was possible to determine six target areas with strong mineralogical evidence for the existence of kimberlitic bodies. They have been grouped according to the variety and amount of KIM present as priority 01 and 02, each containing three target areas as following: (I) Target Riacho Maracajá, (II) Target Riacho Salgado, (III) Target Riacho Gaspar Lopes, (IV) Target Riacho das Pombas, (V) Target Riacho do Açude and (VI) Target Riacho Tupã. As recommendation for future works is suggested to apply other prospection techniques - such as: follow-up, soil sampling, chemical analysis (rock and mineral), ground geophysical surveys (magnetics and/or gravimetry), among others - to deepen the study of these target areas and location of the dispersive source of the KIM.