Lead isotope constraints on the mantle sources involved in the genesis of Mesozoic high-Ti tholeiite dykes (Urubici type) from the São Francisco Craton (Southern Espinhaço, Brazil)

Abstract

ABSTRACT:The first results of Pb isotope compositions of the high-Ti Mesozoic dykes of the Southern Espinhaço are presented. The results do not show large variations and are significantly more radiogenic than the Pb isotope compositions of the high-Ti tholeiites from the Paraná Continental Flood Basalts. The data combined with published geochemical and Sr-Nd isotope results rule out crustal contamination processes in the genesis of the dykes, requiring magma generation in metasomatized subcontinental lithospheric mantle with the involvement of HIMU-type and carbonatite components. The magmas may have been also derived from a mantle source containing ~4 -5% of pyroxenite and ~1% of carbonatite melts, agreeing with published Os isotope compositions of high-Ti rocks from the Paraná Continental Flood Basalts. These metasomatizing agents could be responsible for mantle source refertilization, as was also proposed in the literature to explain the characteristics of xenoliths of the Goiás Alkaline Province, which also occurs in the border of the São Francisco Craton. Additionally, to evaluate the risks of Pb contamination during sample preparation for analysis, several experimental tests were accomplished, which indicate the need of sawed surface removal and a careful washing of small-sized rock fragments before powdering, especially for rocks with [Pb] < 7 μg/g.

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

“…and occur in the northern and southern PCMP, respectively. Recent studies have shown that some Urubici flows are present in the border region between Minas Gerais and São Paulo states (Machado 2005), as well as dikes crosscutting rocks of the São Francisco Craton, Minas Gerais (Seer et al 2011, Marques et al 2016. The age of the main phase of the volcanic activity is concentrated at 134 to 132 Ma, according with data obtained by Renne et al (1992), Thiede and Vasconcelos (2010), and Janasi et al (2011).…”

Geochemistry of basaltic flows from a basalt ring structure of the Serra Geral formation at Água Vermelha dam, Triângulo Mineiro, Brazil: implications for the magmatic evolution of the Paraná-Etendeka Province

“…1). The Southern Paraná Magmatic Province hosts the Urubici rocks (HTi) (Piccirillo & Melfi 1988, Peate 1997, although some scarce flows (Machado et al 2007) and dykes (Seer et al 2011, Marques et al 2016 are found in the northern area.…”

Composition and P-T conditions of the lithospheric mantle beneath the Azimuth 125º Lineament, Northern and Southeastern Brazil: constraints from peridotite xenoliths enclosed in diamond-bearing kimberlites

“…The composition of the subcontinental lithospheric mantle (SCLM) beneath igneous provinces is closely related to the chemical and isotopic signatures inherited by magmas and related mineral deposits (e.g., Marques et al 2016;Holwell et al 2019;Hutchison et al 2021). The igneous provinces in Brazil include one of the largest mafic-potassic provinces in the world (Alto Paranaíba Igneous Province, APIP), with the presence of mantle xenoliths enclosed in ultramafic rocks brought up by rapid ascension magmas (e.g., kimberlites, kamafugites).…”