Mid-Ocean Ridges and Their Geomorphological Features

Origin of Fe‐Ca‐Metasomatism in Exhumed Mantle Rocks at the MARK Area (23°N, ODP Leg 153) and Implications on the Formation of Ultramafic‐Hosted Seafloor Massive Sulfide Deposits

“…(2000)) and interpreted depth velocity‐profile considering high geothermal gradient. The depth range of maximum micro‐seismicity at Mid‐Oceanic Ridge sites having a similar spreading rate than the MARK area is also displayed (after Escartín and Olive (2022)). (b) Interpreted geothermal gradient curves and depth field for Fe‐Ca metasomatism.…”

“…Microseismicity has been used as a proxy to estimate this brittle thickness, as indicated by the maximum depth of the seismic activity. At MOR sections with comparable spreading rates (e.g., ∼2–3, ∼2.5 cm/yr at the MARK area), the maximum depth of seismic studies ranges between 4 and 11 km below seafloor (DeMartin et al., 2007; Grevemeyer et al., 2013; Horning et al., 2018; Parnell‐Turner et al., 2017; Tilmann et al., 2004; Wolfe et al., 1995; see Escartín & Olive, 2022 for a review); this range in depth of seismicity is shown in Figure 11a, and used to constrain the range of thermal gradients in Figure 11b to temperatures of ∼750°C. Considering the thermal gradients in Figure 11b and the temperatures between 350° and 600°C for Fe‐Ca metasomatism, we propose that this results from fluid circulations at depths that may range from ∼2 to ∼6.5 km below seafloor.…”

“…Hydrothermal circulation requires fluid paths and hence a brittle lithosphere, that may reach temperatures of up to ∼750°C (e.g., Escartín & Olive, 2022). Microseismicity has been used as a proxy to estimate this brittle thickness, as indicated by the maximum depth of the seismic activity.…”