Abstract We quantify the redox capacity (dO2) by redox titration—defined as the quantity of oxygen required to fully oxidize a sample—for rocks spanning Earth’s upper mantle to surface sediments. The values span three orders of magnitude, with the greatest variability in metamorphic and surface rocks that host both highly reduced (rich in carbon and sulfur) and oxidized materials. In contrast, exhumed lower‐crustal and mantle rocks display more uniform values of dO2. This distribution reflects not a progressive net planetary oxidation, but active redox partitioning, shaped by far‐from‐equilibrium biological chemistry, surface processes, and tectonic cycling. Unlike thermodynamic potentials such as μO2, the compositional variable dO2 directly constrains the redox structure of Earth’s shallow lithospheric reservoirs. This framework provides an experimentally grounded and physically intuitive metric for quantifying redox transfers and assessing their geophysical consequences.
Observations from the Little Bunker
Last updated: December 20, 2025 06:13 PM
Atmospheric CO₂
427.2 ppm
+17.9
ppm/year
Atmospheric CH₄
1930.95 ppb
+-3.5
ppb/year
Global Temperature
+1.48 °C
Peak: +1.73°C
World Population
8.1 billion
+67
million/year