Temperatures in ambient mantle and plumes: Constraints from basalts, picrites, and komatiites

Several methods have been developed to assess the thermal state of the mantle below oceanic ridges, islands, and plateaus, on the basis of the petrology and geochemistry of erupted lavas. One leads to the conclusion that mantle potential temperature (i.e., T P ) of ambient mantle below oceanic ridges is 1430°C, the same as Hawaii. Another has ridges with a large range in ambient mantle potential temperature (i.e., T P = 1300–1570°C), comparable in some cases to hot spots (Klein and Langmuir, 1987; Langmuir et al., 1992). A third has uniformly low temperatures for ambient mantle below ridges, ∼1300°C, with localized 250°C anomalies associated with mantle plumes. All methods involve assumptions and uncertainties…