H2O in basaltic glasses from the slow-spreading Carlsberg Ridge: Implications for mantle source and magmatic processes

Sea‐Level Fall Driving Enhanced Hydrothermal and Tectonic Activities: Evidence From a Sediment Core Near the Tectonic‐Controlled Tianxiu Vent Field, Carlsberg Ridge

“…Nevertheless, if the depth of melt origin and the melt migration rate are known, then it is possible to estimate the depth of the heat source. We estimated the depth of the decompression melting using the geochemical data of basalts obtained from the Carlsberg Ridge reported by Zong et al (2019) and the empirical equation provided by Niu and Batiza (1991). The results showed that the melting pressures were in the range of 1.51-1.96 GPa with an average of 1.65 GPa (n = 8), that is, 50-64 km (average of 55 km, n = 8) beneath the ridge.…”

“…During the Chinese DY 49th cruise in 2019, a 134 cm long sediment core (core GC06; 63°51′E, 3°42′N, 3,842 m) was acquired from the slope on the south of rift valley, ∼2.2 km northeast of the TVF (Figures 1a and 2). Seafloor observations and studies of the ultramafic rocks, basalts, and surface hydrothermal sediments collected from this area suggest that the TVF is an ultramafic‐hosted high‐temperature hydrothermal field (Cai et al., 2020; Chen, 2019; Chen et al., 2020; Qiu et al., 2015; Zong, 2019). In this paper, we investigate the sedimentology, mineralogy, geochemistry, and chronology of sediment core GC06 to reconstruct the hydrothermal activity history of the TVF and to understand its responses to global glacial–interglacial sea‐level changes, as well as the role of tectonic events on the control of the hydrothermal activity.…”

Geochemical Constraints on Mantle Melting and Magma Genesis at Pohnpei Island, Micronesia

“…They have SiO2 and MgO contents of 44.78-48.24 and 4.46-11.95 wt.%, respectively, and Mg # (100 × mol MgO/(MgO + FeO T )) values of 40-62. The samples have higher total Fe oxide (FeO T ) contents and lower Na2O contents than those of the Carlsberg Ridge MORBs (midocean ridge basalts) [24,25], indicating that they are derived from deeper mantle sources with lower degrees of melting than MORB sources [26,27]. The Pohnpei lavas are enriched in alkali elements (Na2O + K2O) and are classified as basalt, tephrite basanites, and minor trachybasalts in the (Na2O + K2O)-SiO2 plot (Figure 3).…”