Newly formed oceanic crust interacts with penetrating seawater, resulting in the formation of secondary minerals. Sediment cover can potentially change the redox conditions of underlying basaltic crusts, significantly affecting the types of secondary minerals and element transfer during alteration. However, previous studies have not revealed the quantitative regional variation and controlling factors of seafloor alteration using altered samples taken from different sites. We present a novel approach for the quantitative analyses of element mobility related to seafloor alteration based on a regional dataset of altered basalt bulk compositions and highlights the effects of the redox state and duration on alteration. The protolith reconstruction models (PRMs), machine learning-based element mobility analyses, were applied to the compositional data of the basaltic crusts from the South/Northwest Pacific region. The analyses revealed that altered basalts with older ages showed higher element mobility, particularly characterized by an enrichment of Rb and K, which were associated by up to 100 times with the formation of secondary minerals. In the oxidative settings of the South Pacific region, enrichment of Ba, U, and Pb and depletion of P were observed in samples with intense alteration. In contrast, under reductive conditions in the Northwest Pacific region, alterations associated with carbonate veins caused U enrichment. Our research suggests that sediment thickness is a key factor in the redox conditions during alteration, which changes the characteristics of element transfer and secondary minerals. Additionally, seafloor alteration likely persisted for at least 30 Myr, irrespective of whether the environment was oxidative or reductive.