High‐Resolution 40Ar/39Ar Geochronology of the Louisville Seamounts IODP Expedition 330 Drill Sites: Implications for the Duration of Hot Spot‐related Volcanism and Age Progressions

Abstract

AbstractThe Louisville Seamounts display age progressive volcanism and are thought to have formed as the Pacific Plate moved over a long‐lived primary hot spot. Here we present 70 new 40Ar/39Ar age results from the Integrated Ocean Drilling Program (IODP) Sites U1372, U1375, U1376, and U1377 drilled and cored during Expedition 330 to the northern, older end of the Louisville Seamounts. The five seamounts drilled are flat‐topped guyots with ages ranging from ∼74 Ma (Canopus Guyot) to ∼51 Ma (Hadar Guyot) recovering up to ∼510 m of basaltic material beneath thin sediment interfaces. Our 40Ar/39Ar measurements reveal that throughout each drill hole, most dates are constant within ∼500‐900 kyr at the 2σ confidence interval. In this study we use the new Louisville age information to compare against the Hawaiian‐Emperor trail on the Pacific Plate. The Louisville hot spot trail is low volume, dominantly alkali basalt, and seamounts have a relatively short lifespan up to ∼4 Myr, whereas the Hawaiian hot spot trail is high volume, has a tholeiitic shield‐building stage capped by an alkalic post‐shield stage, and has a lifespan up to ∼6‐7 Myr. Here we show a new approach to estimating a seamount's inception age based on the known cumulative age distributions for seamounts in the Louisville Seamount and Hawaii‐Emperor Seamount trails. Based on our new 40Ar/39Ar analyses, we conclude that existing absolute plate motion models misrepresent the age progression of Louisville Seamounts and that the timing of the Hawaiian‐Emperor Bend and the 169°W bend in the Louisville Seamounts are asynchronous by ~3.7 Myr.