Mapeamento Litoestrutural de rocha ornamental da Mina Amazon, Vieirópolis-Pb

Abstract

The Northeast region of Brazil is recognized as having great potential for the growth of the ornamental stone market, since a large part of the rocks are exposed in the surface, which makes easier the geological research work to request new areas. The study area is related to the one required by Granistone S.A company, being inserted in the county of Vieirópolis, belonging to the state of Paraíba, there the company mine an amazonite pegmatite dyke and benefits the blocks for sale. Geologically the area is inserted in the Rio Piranhas-Seridó Land, belonging to the Rio Grande do Norte Domain of the Borborema Province. In order to understand the geological association and the structural controls of the amazonite pegmatite, a lithostructural mapping was performed in the area of application concerning the Amazon Mine. It is also the purpose of the this paper explain the system of production and sale of the blocks produced by the company. The premapping stage allowed knowledge about the geomorphology, geology and structure of the study area, while in the mapping stage were perfomed the lithostructural mapping and the understanding of the production and sale processes, later, in the post-mapping stage, the petrography study provided the correct definition of the names of the mapped rocks as well as an understanding of the active metamorphic processes, while the creation of the rose diagrams and stereographic projections provided an understanding of the structural aspects represented by the ductile and brittle stages. The results show that the amazonite pegmatite dyke is generated from the final fluids of the Ediacaran magmatism which filled T - type extension fractures controlled by the Portalegre shear zone. Two other occurrences of amazonite pegmatite were mapped, as well as areas of old shorlite tourmaline mines. The processes of production and sale of amazonite pegmatite as ornamental rock were understood in detail. The lithostructural mapping allows to conclude that the area was subjected to metamorphic processes of upper amphibolite facies that generated ortho-derived rocks of the Complex Caicó during the transamazonic orogeny, which later were reworked and metamorphosed by the Brasilian orogeny that also generated the Ediacaran granitoids, and these allowed the amazonite pegmatite generation.