Lithogeochemical and morphostructural evolution of the Paraná Magmatic Province in the Ponta Grossa Arch, Southeastern Brazil

• Ano de defesa: 2024
• Autor(a) principal: Marteleto, Natasha Sarde
• Tipo de documento: Tese
• Tipo de acesso: Acesso aberto
• Idioma: eng
• Instituição de defesa: Biblioteca Digitais de Teses e Dissertações da USP
• Palavras-chave em Português: Corpos intrusivos; Enxame de diques de Ponta Grossa; Evolução magmática; Grandes províncias ígneas; Intrusive bodies; Large Igneous Provinces; Magmatic evolution; Paraná Magmatic Province; Ponta Grossa Dike Swarm; Província Magmática do Paraná
• Link de acesso: https://www.teses.usp.br/teses/disponiveis/44/44143/tde-28012025-133543/

The Paraná-Etendeka Magmatic Province, formed during the Early Cretaceous (approx. 134- 131 Ma), is the second-largest Large Igneous Province, covering around 920,000 km². This thesis investigates the magmatic and structural evolution of the Ponta Grossa Dike Swarm (PGDS) within the Paraná Magmatic Province, focusing on the Guapiara Lineament in southeastern Brazil. A comprehensive approach, including fieldwork, petrographic and geochemical analyses, aeromagnetic mapping, and structural data integration, offers new insights into the magmatic processes shaping this region. Geological mapping reveals distinct dike orientations influenced by pre-existing structural weaknesses and evolving stress regimes during magmatic emplacement. The study area spans three regions along the Guapiara Lineament, encompassing Proterozoic basement units, sedimentary formations within the Paraná Basin, and volcanic flows of various compositions. Geochemical data identify three magma types within the PGDS: Paranapanema, Pitanga, and Ribeira, along with three newly defined chemical groups: LFe (low iron), HSr (high strontium), and ITi (intermediate titanium). The Ribeira type, with high Mg# and low incompatible element content, is recognized as the most primitive magma, distinguished by TiO levels (1.5-2.3 wt%) compared to the more evolved Paranapanema (1.7-3.2 wt%) and Pitanga (>3.0 wt%) types. Rare earth element (REE) patterns, normalized to chondrite, showed higher (La/Yb)N rations (majorly between 6.5 and 8.5) for Pitanga and LFe types, contrasting with lower (La/Yb)N ratios (~ 3,5 to 4,5) for Ribeira and Paranapanema types. Thermodynamic models tested hypotheses of fractional crystallization processes based on three initial compositions: one Ribeira (to generate Paranapanema) and two Pitanga (the most and second-most primitive; to explore fractionation within this unit and the LFe group). The results indicated that fractional crystallization alone cannot fully account for the geochemical diversity observed in Paranapanema compositions. The same applies to the internal variation of Pitanga (+LFe). Instead, Paranapanema could be generated by mixing residual liquids of Ribeira (after 20-40% crystallization) with Pitanga (if more evolved, after 0-20% crystallization) or Pitanga (if less evolved, after 10-30% crystallization). The high Sr/Y ratios in the Pitanga type align with crystallization models involving garnet rather than plagioclase at greater depths (12 kbar), potentially indicating deeper magmatic reservoirs. Aeromagnetic data and structural analyses identified five tectonic trends from the Santos to the Paraná basins that controlled magma ascent and emplacement: one main NE-SW trend reflecting reactivated Proterozoic structures, two NW-SE trend linked to the Ponta Grossa Arch and two E-W trends associated with later magmatic activity. These trends suggest a sequential activation of structural controls influenced by regional stress fields, shaping magmatic pathways and differentiation processes. The study identified distinct areas of crustal tilting and flexure, with the southern portions showing recent uplift and the northern portions subsidence. The integration of structural and geochemical data supports a geodynamic model explaining the temporal evolution of tectonic regimes and their impact on magmatic activity.