Ancient Antarctic Magmatism: Heat Flux within the Ferrar Large Igneous Province Sill Complex

Large igneous provinces (LIPs) are massive areas of predominantly mafic magmatism, often 10⁵ -10⁷ km² in area with volumes greater than 10⁵ km³, emplaced over a short period (1-5 m.y.). Field studies examining heat transfer processes acting within LIP sill complexes are relatively rare, despite the potential for contribution towards understanding LIP emplacement dynamics and overall interconnectivity of intrusive magmatic systems. This study uses paleomagnetic techniques (alternating field (AF) and thermal demagnetisation) to assess the magnitude of heat transfer associated with the Ferrar LIP sill complex, emplaced 183 Ma across the Transantarctic Mountains and through Tasmania and South Australia. Sampling was carried out through 3000 m of stratigraphy across four sites within the McMurdo Dry Valleys, South Victoria Land, Antarctica, in which 200 m thick Ferrar dolerite sills intrude the Beacon Supergroup sedimentary sequence. Our results quantify the vertical extent of magmatic heating from the Ferrar LIP sill complex, revealing an asymmetry in contact aureoles surrounding sills, which suggests contribution of differing heat transfer mechanisms above and below intrusions. Estimated contact aureole volumes also indicate increased heat flux with depth in the stratigraphy, suggesting more long-lived magma flux through deeper intrusions compared to those further up the sequence. This study has implications for understanding magma and heat fluxes during sill complex emplacement and the potential for these systems to liberate extinction-level volumes of carbon through crustal heating.