EarthRef.org Reference Database (ERR) -- Dalrymple et al. 1981

The samples recovered from Northampton Bank demonstrate that tholeiitic basalt similar to modern Hawaiian tholeiite is present along the western Hawaiian Ridge. The volcanic cobbles from Laysan are hawaiite and mugearite chemically similar to the flows erupted during the late (alkalic) stage of Hawaiian volcanoes. In addition, the Laysan samples represent at least two discrete fractionation trends and thus were probably derived by crystal fractionation of two parental alkalic magmas in shallow chambers. These and previously published results show that the volcanoes of the Hawaiian-Emperor chain resemble those of the principal Hawaiian Islands, as predicted by the hot spot hypothesis. The abundance of differentiated alkalic lavas along the chain further suggests that many, if not most, of the volcanoes have evolved to the alkalic eruptive stage and that extinction of a Hawaiian-Emperor volcano during the tholeiitic stage is uncommon. The new radiometric data bring to 29 the number of Hawaiian-Emperor volcanoes for which K-Ar ages are available. Plotted as a function of distance from Kilauea (Fig. 2), the K-Ar ages show a remarkably consistent increase that substantiates the age-distance corollary and the general hot spot hypothesis for the origin of the Hawaiian-Emperor chain. A least-squares linear fit to the radiometric data forced through the origin yields a volcanic propagation rate of 8.2+0.2 cm/yr. The data of Figure 2 demonstrate, however, that the increase in measured age with distance is not exactly linear. As pointed out by Jackson (1976), the observed scatter in the age-distance data may be due to errors in the ages, to the fact that different stages of volcanism have been dated on the different volcanoes, to real changes in the volcanic propagation rate, or to some combination of these factors. The first two factors probably cannot account for all of the scatter evident in Figure 2, much of which may be due to real short-term changes in the rate of propagation of volcanism along the chain (Jackson and others, 1972). The strongest evidence for this interpretation is the concave upward curvature of the data for the volcanoes of the principal Hawaiian Islands, especially from Mauna Kea to Waianae, and the large age differences in volcanoes with nearly equal distances from Kilauea, especially Northampton Bank and Laysan Island (Fig. 2). Nonlinear volcanic propagation has been disputed by McDougall (1979), who argued that all of the deviations in the age-distance data can be explained by dating errors and differences in the volcanic stage dated. We think, however, that there is at present sufficient evidence for departures from linearity to warrant retention of short-term, nonlinear volcanic propagation as a working hypothesis.

Keywords
absolute age; age; alkali basalts; basalts; Cenozoic; Cretaceous;, data; dates; East Pacific; Emperor Seamounts; evolution;, geochemistry; Hawaiian Ridge; hawaiite; hot spots; igneous rocks;, island arcs; K/Ar; lava; Laysan Island; major elements; Mesozoic;, mugearite; North Pacific; Northampton Bank; Northeast Pacific;, Northwest Pacific; Pacific Ocean; petrology; plate tectonics;, tectonophysics; tholeiitic basalt; trace elements; Upper, Cretaceous; volcanic rocks; volcanism; volcanoes; volcanology;, West Pacific, 18, Solid-earth geophysics