Produção de calor radiogênico de granitoides ediacaranos do Extremo Nordeste da Província Borborema

Abstract

The study examines the Ediacaran-Cambrian plutonic magmatism within the Rio Piranhas-Seridó (PSD) and São José do Campestre (JCD) Domains (NE Borborema Province, Brazil), with a focus on the radiogenic heat production (A) of granitoids. This magmatism encompasses a variety of batholiths, plutons, stocks, and dikes, with distinct petrographic and chemical features, grouped into six plutonic suites. The radiogenic heat production was investigated and compared with petrographic and chemical characteristics of the granitoids from the High-K Calc-Alkaline (porphyritic and equigranular) and Shoshonitic suites, encompassing syeno-monzogranites to monzodiorites, and gabbros/diorites, with metaluminous to peraluminous compositions and calc-alkaline to alkaline signatures. The high-K calc-alkaline porphyritic granitesregister higher A values (up to 11.7 μW/m³) due to high concentrations of Th and U, in contrast to the lower values in shoshonitic rocks (up to 3.5 μW/m³). There is a positive correlation between A, SiO2, and the modified alkali-lime index (MALI), suggesting that more evolved and alkaline compositions favor higher heat generation. The mean Th/U ratio for all suites is 8.6, exceeding typical crustal values. The studied rocks were classified into low (LHP), medium (MHP), and high (HHP) heat production groups. The JCD samples mainly correspond to LHP and MHP, whereas those from the PSD include all categories, with HHP restricted to calc-alkaline granites and shoshonites limited to the LHP group. The spatial distribution of A and the concentrations of Th, U, and K indicate areas within the PSD with geothermal potential for further investigations