Temperature–time relationships and their implications for thermal history and modelling of silica diagenesis in deep-sea sediments

67 Ocean Drilling Program and Deep Sea Project sites were investigated to determine the relationship between temperature time for silica diagenesis. The selected cover a variety of settings where opal-A opal-CT transition zone lies in Cenozoic sediments. leads abrupt changes sediment petrophysics which are used identify diagenetic interval at study sites. This is thin ranging thickness from 10 40 m. Controls on analysed was found be fundamental driver. extends “the time–temperature stability field Hein et al. (1978)” onset precipitation more generally. Active diagenesis persists over long period (>35 m.y.) low temperatures (<30 °C), within 3 m.y. moderate (35–55 much rapidly high (>55 °C) regardless burial depth. Geothermal gradients accumulation rates principal controls rate transformation. Sites 794 795 Japan Sea, as typical cases deep-sea boreholes capturing active transitions, further understanding temperature–time control reconstructed thermal evolution sediments these representative demonstrates that rapid increase Late Miocene onwards occurred response interval. higher achieved under sedimentation steeper gradient led an earlier Site (~5 compared (~8 m.y.). Kinetic-based models formulated illustrate dependence biogenic One main findings based this model although reaches its peak levels across 8 5 after initial deposition 795, respectively, transformation not completed until 14 ca. 9.5 sedimentation. Given elapsed time, allows state opal-containing successfully predicted any depth two