New Heat Flow Measurements Offshore Montserrat: Advective Heat Flow Detected via MeBo Borehole Temperature Logging

Abstract

New heat flow measurements collected at the Lesser Antilles Arc using a Hybrid Lister-Outrigger probe and a new logging-while-tripping MeBo70 drilling approach provide the first high-resolution (meter-to-cm-scale) temperature-depth measurements across the Lesser Antilles volcanic arc and offer new insight into heat and fluid transfer at a convergent oceanic margins. At multiple sites where logging-while-tripping MeBo temperature measurements were made, temperature increases linearly with depth in shallowly buried hemipelagic sediment but is isothermal or significantly hotter in deeper, courser-grained sediments associated with mass flows. We interpret these isothermal zones as regions where advective heat flow—perhaps caused by convection or pressure-driven advection—dominates. The implication is that apparently conductive heat flow regimes observed in the shallowest upper 5–10 m of hemipelagic sediment across the Lesser Antilles Arc measured using standard lister-type probes may often unknowingly be influenced by deeper, advective flow along buried mass transport deposits at this site. Since mass transport deposits are ubiquitous on convergent margins, higher permeability mass transport deposits may play a fundamental and previously unrecognized role in fluid and heat transport.