Isotopic data from various locations within the Mid-Atlantic Ridge indicates the presence of mafic-to-felsic intrusive igneous rocks, including gabbro, diorite, and plagiogranite. These rocks showed high-grade metamorphism because of the presence of magmatic water, exceeding 600 °C. This deformation depleted host rocks of O, leading to further analysis of the ratio of O to O (δO).
Water in equilibrium with igneous melts should bear the same isotopic signature for O and δH. However, isotopic studies of magmatic water have demonstrated similarities to meteoric water, indicating circulation of magmatic and meteoric groundwater systems.
Isotopic analyses of fluid inclusions indicate a wide range of δO and δH content. Studies within these environments have shown an abundance of O and depletion in H relative to SMOW and meteoric waters. Within ore deposits, fluid inclusion data showed that the presence of δO vs δH are within the expected range.