Banca de DEFESA: Lucas Santos Batista Teles

Uma banca de DEFESA de DOUTORADO foi cadastrada pelo programa.
STUDENT : Lucas Santos Batista Teles
DATE: 10/11/2023
TIME: 14:00
LOCAL: Sala de videoconferência e Teams
TITLE:

 

AGROMINERAL DEPOSITS IN THE BRASÍLIA FOLD BELT: GEOLOGY, CHARACTERIZATION AND POTENTIAL

KEY WORDS:

Agrominerals, Brasília Fold Belt, Sedimentary Deposits.

PAGES: 108
BIG AREA: Ciências Exatas e da Terra
AREA: Geociências
SUMMARY:

Agrobusiness is one of the main components of the Brazilian Gross Domestic Product, internationally recognized for its strength and expectations of continuous growth. However, the external dependence on inputs, especially on phosphorus (P) and potassium (K) elements for fertilizer production represents a vulnerability that imposes the current need for the evolution of research and exploration in the agromineral sector. Currently, national phosphate production is mainly derived from carbonatite alkaline complexes, and the real potential of sedimentary deposits remains uncertain, contrary to global trends. Regarding potassium, the scenario is even more drastic, considering that all southern hemisphere basins are naturally deficient in this element due to their geological evolution. Within this problem, there is interest in the rocks of the Vazante and Bambuí groups, located in the External Portion of the Brasília Fold Belt, which host wellrecognized deposits of P and K. Despite these deposits being discussed in the literature, there is a limited number of works focused on the geological characterization of these areas, lacking new data and models that can stimulate the discussion and evolution of knowledge about sedimentary agromineral deposits. With the primary goal of filling this gap, this doctoral thesis proposes a detailed description of the rocks, facies associations, depositional environments, and genetic models of sedimentary phosphate deposits of the Coromandel and Campos Belos types, and of the potassic deposit of Cedro do Abaeté. The Coromandel Type deposit is found within the Retiro Formation, at the base of the Vazante Group, and exhibits an intrinsic relationship between a Rudaceous Unit, composed of polymictic diamictites, conglomeratic sandstones, and fine arkoses, and the Phosphatic Unit. The phosphatic facies comprise Laminated Phosphorites, Brecciated Phosphorites, and Phosphatic Siltstones with P2O5 contents ranging from 2% to 34%. Due to field correlations and the evolution of the Vazante basin, these rocks were interpreted as the result of sedimentation in a glacimarine environment, where physicochemical conditions favorable for phosphate precipitation were directly controlled by terminal glaciers, in a mechanism classified as "cap phosphorites" deposition due to similarities with widely discussed glacial dolomites (cap dolomite). Similarly, the Campos Belos Type deposit, situated within the context of the Sete Lagoas Formation, at the base of the Bambuí Group, also exhibits an inherent relationship between the Phosphatic Unit and the diamictite of the Jequitaí Formation. This unit is subdivided into Stratified/Laminated Phosphorite, Brecciated Phosphorite, Pedogenic Phosphorite, and Phosphatic Siltstone facies, with P2O5 values ranging from 4% to up 30%. Although the genetic models between the Coromandel and Campos Belos Type deposits share similarities, crucial genetic factors distinguish them. The influence of paleorelief, such as paleochannels incised in the granitic rocks of the Aurumina Suite or arkoses at the top of the Araí Group, plays a fundamental role in the deposition and, together with simpler mineral assemblages, ore facies, and environmental interpretations, distinguishes the two models. The potassic deposit of Cedro do Abaeté, located within the context of the Serra da Saudade Formation at the top of the Bambuí Group, is composed of exotic greenish-colored pelite known as verdetes and has reported P2O5 contents averaging 8%, with occasional areas reaching up to 34%. However, the economic significance of the deposit lies in the presence of 7% to 14% K2O content spatially distributed within a massive volume of verdetes. Based on magnetometry, gamma spectrometry, and mineralogy data, it is possible to relate the genesis of verdetes to deep alkaline intrusions of the Mata da Corda Group and interpret the mineralization as a result of potassic metasomatism of primary pelitic sediments due to the circulation of fluids from these intrusions. Finally, the new data added with the new genetic interpretations and their respective exploration vectors are powerful tools for expanding both knowledge and exploration in the context of supplying the domestic agromineral market.

COMMITTEE MEMBERS:
Externo à Instituição - DANIEL BEZERRA DAS CHAGAS - UFG
Externo à Instituição - FARID CHEMALE JUNIOR - UNISINOS
Externo ao Programa - 1170677 - JOSE ELOI GUIMARAES CAMPOS - nullExterno ao Programa - 3340609 - MARCIO VINICIUS SANTANA DANTAS - nullInterno - 2339865 - MARTINO GIORGIONI