The clumped and oxygen isotopes of dolomite from ultramafic rocks recovered during ICDP Expedition 5057, Oman Drilling Project Phase II (November 2017 to February 2018) on the Wadi Tayin Massif, Samail Ophiolite, was examined to characterize carbon sources, speciation, and the fate of organic and inorganic carbon during natural large-scale hydration and carbonization. The measurements were performed at the ETH Zurich from 2017 to 2020 using a Kiel IV carbonate device interfaced with a ThermoFisher Scientific MAT253 isotope ratio mass spectrometer.