Geology, geochemistry and petrology of basalts from Paraná Continental Magmatic Province in the Araguari, Uberlândia, Uberaba and Sacramento regions, Minas Gerais state, Brazil

Lucia Castanheira De Moraes,Leila Soares Marques,Hildor José Seer

doi:10.1590/2317-4889201820170091

Abstract

This study covers the region between the cities of Sacramento and Araguari/Uberlândia (Minas Gerais State, Brazil), where basalt flows from the Parana Continental Magmatic Province outcrop. The investigated rocks present tholeiitic signature, with high titanium content, and are classified as Pitanga magma-type. The preserved basalt thickness is between 10 and 200 meters and individual flows do not exceed 15 meters thick. Flows were identified as sheet lobes, smaller and thinner flows units — stacked laterally and vertically forming compound lavas —, or frontal, centimetric lobes. The basalt flows show decimetric to metric intercalations of clastic sedimentary rock, with depositional characteristics that can vary from aeolian to lacustrine, and are important markers on prevailing environmental conditions. The plagioclases are dominantly labradorite and pyroxene is augite, whereas olivine can be hyalosiderite or hortonolite/ferrohortonolite. The behavior of the major, minor and trace elements is compatible with the presence of at least two parental magmas, which were subjected to fractional crystallization mainly of plagioclase, clinopyroxene, ilmenite and magnetite. There is a chemistry distinction between basalts from Sacramento to those from Araguari/Uberlândia region, the former one showing more evolved than the last one. The high (La/Lu)N values are indicative of partial melting of a garnet peridotite, while the Rare Earth Elements (REE) values are indicative of fractional crystallization.

Highlights

Continental flood basalt provinces are huge eruptive events characterized by their phenomenal volumes of tholeiitic basalts erupted in a very short time range and in a continental environment from fissure systems in the Earth’s crust (Hooper 2000)
The petrographic studies were performed on 28 polished thin sections at the Centro de Pesquisas Professor Manoel Teixeira da Costa of the Geoscience Institute of the Universidade Federal de Minas Gerais (UFMG)
The minerals were analyzed by electronic microprobe in the laboratories of the Universidade Federal de Goiás (UFG) (153 analyses) and the Universidade Estadual Paulista “Júlio de Mesquita Filho” (UNESP) (252 analyses), of which 113 in pyroxene, 184 in plagioclase, 88 in oxides, 9 in olivine and 11 in alteration minerals

Summary

Introduction

Continental flood basalt provinces are huge eruptive events characterized by their phenomenal volumes of tholeiitic basalts erupted in a very short time range and in a continental environment from fissure systems in the Earth’s crust (Hooper 2000). The Brazilian portion of the PEP volcanic rocks (Serra Geral Group; Rossetti et al 2017) was formed in the final phase of the Paraná Basin This was an intracratonic and polyhistoric basin, which was part of the Gondwana Continent, dominated in its interior, at that time, by the arid climate (Scherer 2002, Jerram & Stollhofen 2002). These volcanic rocks are mainly of basaltic composition and overlap the aeolian deposits of the Botucatu Formation, and, in some places, they are intercalated. Mainly located in the northern area, as well as the mafic dyke swarms of Ponta Grossa, Serra do Mar and Florianópolis, are associated to Brazilian Journal of Geology, 48(2): 221-241, June 2018

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