ST. PETER AND ST. PAUL ARCHIPELAGO, EQUATORIAL ATLANTIC: YOUR SURFACE RADIOGENIC HEAT FLOW SUGGEST THAT IS COLDER THAN THE SURROUNDINGS LITHOSPHERIC ATLANTIC OCEAN

This research presents the pioneer radiogenic heat production (RHP) mapping and the radiogenic heat flow (RHF) of the Saint Peter and Saint Paul Archipelago located at 0.55°N 29°20’43”W, in the Equatorial Atlantic Ocean. Using radiogenic heat producing elements, we inferred a radiogenic heat production of these emerse mantle mylonite rocks, that vary between 0.08 to 0.68 μW/m³, showing a Median of 0.21 μW/m³ and Geometric mean of 0.25 μW/m³ by whole-rock chemical analysis and by superficial Gamma radiation spectrometry vary between 0.08 to 0.48 μW/m³ (Median: 0.19 μW/m³; Geometric  mean: 0.19 μW/m³). The mean of radiogenic heat production (0.22 μW/m³) of these rocks is significantly higher than predicted values for ultramafic rocks in the Word. This is due to the pervasive alteration of these rocks and the incorporation of little magma fractions during mylonitization. On the other hand, the average surface radiogenic heat flow (49.7 μW/m²) is lower than that predicted for the oceanic lithosphere, suggesting that the upper mantle contribution to the heat flow is also low in the SPSPA region. Based on the acquired data and the peculiar tectonics of the SPSPA, we propose that the lithospheric mantle around the SPSPA area is colder than the surrounding Atlantic ocean.