Assessment of Surface Radiogenic Heat Flow in Volcanic Rocks of Trindade Island, South Atlantic Ocean, Brazil.

Abstract

Heat loss from Earth's interior, driven by conduction and convection, influences lithospheric thermal regimes. This heat originates from mantle convection, primordial planetary accretion, and the decay of radioactive heat-producing elements (RHPE: U-238, U-235, Th-232 and K-40), which contribute around 98% of Earth's radiogenic heat production, crucial for surface radioactive heat flux (SRHF). Understanding RHPE is key to studying geothermal dynamics, especially in volcanic regions like Trindade Island, Brazil. This study aims to: Quantify U, Th, and K concentrations in volcanic soils; map their spatial distribution, detect anomalies and evaluate radiogenic heat production and flux. Three methods were used: whole-rock ICP analyses for geochemical characterization, laboratory gamma spectrometry (LabGRS), and in situ gamma spectrometry (surfGRS) for spatial coverage. A total of 77 samples and 481 measurement points were analyzed and SRHF was measured. Results show that the thorium contributes most to SRHF, providing insights into heat generation and mantle-crust volcanic interactions. This study provides critical insights into radiogenic heat generation and its role in lithospheric thermal evolution, offering a refined understanding of heat production in oceanic volcanic settings. The findings enhance geophysical and geochemical models of heat flux, contributing to broader studies on mantle-crust interactions and geothermal energy potential.