Subduction processes play a critical role in introducing heterogeneities in the mantle with major petrological, geochemical and geodynamic consequences at the surface and at depth. Spatial and temporal changes in element recycling during subduction processes are strongly tied to the thermal structure and redox profile of the Earth’s upper mantle. This session provides an opportunity to showcase research focused on subduction induced variability in the chemical and physical properties of the upper mantle and crust throughout time and space. Perspectives from geophysical observations, volatile abundances and speciation, isotopic signatures, multivalent and trace element chemistries of Earth materials at a variety of depths will enable a better understanding of mass transfer throughout the subduction factory. We welcome contributions utilizing diverse approaches including observations of natural systems, laboratory experiments, numerical modelling and others.