The soil of the Brazilian Cerrado is poor in macro and micronutrients. Although Brazil is one of the most important countries in agribusiness, there is only one potash mine in production, more than 90% of which has to be imported. This dependence also has a significant impact on the country's trade balance. Due to relative high potash prices on the market it is unlikely that any significant new production capacity will be developed in Brazil from the local potassium salt deposits. The need for alternative sources led Terrativa Minerais to a series of geological surveys in search of ultrapotassic rocks in different regions of Brazil, searching for sites near agricultural areas such as the Cerrado and favorable geology and logistics. Due to this, in 2013, field research in the area of Santa Cruz das Lajes, in the Alkali Province of Goiás, SW of the State of Goiás, mapped ultrapotassic rocks with kamafugite affinities. These rocks are marked by a series of volcanic magmatic manifestations installed during the Upper Cretaceous, representing one of the largest occurrences of ultrapotassic and Kamafugite rocks in Brazil. From then on, these rocks deserved special attention, being the object of this work where petrochemical and geochemical characterization of their occurrences in the Santa Cruz of Lajes region, was evaluated the potassium, K+, in the profile of weathering, its mineralogical transformations along the The degree of soil fertility for the development of agriculture was determined to verify the agronomic efficiency of this type of rock and its wheatering products. In order to reach the mentioned objectives, field campaigns were carried out over the course of one year aiming the mapping and sampling of the research area. The collected rock and channel samples were analyzed by X-Ray Fluorescence by the SGS GEOSOL laboratory in Goiânia. The channel samples were also analyzed by the Esalq USPlaboratory in Belo Horizonte for later identification of the soil fertility generated by the weathering of the ultrapotassic rocks. The mineralogical analysis, petrography allied to X-ray diffraction, characterized the ultrapotassic rocks in three types such as Mafuritos, Uganditos and tefrifonolites. The Mafuritos have dark coloration, are aphanitic with olivine and pyroxene phenocrysts and fine polycrystalline matrix, composed of pyroxenes, analcima, sanidine, nepheline and smectite. The Ugandites are light gray, phaneritic with aphanitic matrix, when altered they show light brown to yellowish coloration, frequently present amygdas filled with calcite and zeolites. Its mineralogy is marked by the presence of rare crystals of olivine, pyroxenes, usually euhedral, prismatic, zoned and sometimes fractured, occurring at random and sometimes describing a foliation of magmatic flow. Tefrifonoliths are aphanitic, light gray in color, with rare tonsils filled by carbonaceous material and / or zeolites. The sampling of the weathering profile on these rocks was carried out at different points. The profiles are shallow and generally, about one meter deep, one arrives at the mother rock. It is interesting to observe the distribution of the K2O values in a profile on the Ugandite, where the top soil is clayey dark brown, and in the XRD it still presents sanidine and pyroxene, besides hematite and a great amount of smectite and zeolites, in a diffraction pattern of Very low crystallinity. This reveals that the primary minerals bearing K are still present, and that together with the smectite, zeolites, are responsible for the high levels of K available in soils, increasing their fertility.
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