A Double Hotspot Model for the Origin of Line Islands Ridge

Abstract:

The origin of the various seamount chains in the central Pacific is often difficult to reconstruct due to the number of potential volcanic sources and the criss-crossing patterns associated with plate motion history. One particularly difficult seamount chain to reconstruct is the Line Islands Ridge and the possibly-related Mid-Pacific Mountains and Tuamotu Chain. While the general geographic and age-progressive trends of these features resemble the predicted pattern for Pacific plate motion over the past 120 to 130 My, the relative ages of volcanism along the Line Islands Ridge are not consistent with a conventional hotspot model. To explore potential models of the origin of the Line Islands Ridge, we use GPlates software in conjunction with published seamount dates and known hotspot locations to constrain tectonic reconstructions. Our primary results suggest the Line Islands Ridge was formed by at least two different volcanic sources. The initial source formed the southern section of the Line Island Ridge (4˚N to 1˚S) around 95 to 83 Ma and corresponds to the present-day Crough hotspot. The hotspot also likely generated the linear Boudeuse Ridge (a.k.a. Southern Line Islands) volcanic chain (5˚S to 13˚S) from about 70 to 50 Ma. The second volcanic source, which we call the Larson Hotspot in memory of Roger Larson, formed the northern section of the Line Islands Ridge (7˚N to 4˚N) around 77 to 64 Ma and corresponds to a new “hotspot” region centered on 17˚S and 125˚W near the eastern extension of the Pukapuka Ridge. This source may also account for the formation of the Mid-Pacific Mountains (130 to 105 Ma), the Necker Ridge (105 to 90 Ma), and the later volcanism on the southern section of the Line Island Ridge (65 to 55 Ma). This volcanic source also roughly coincides with the Pukapuka Ridge and more recent volcanism along the same trend, but closer to the East Pacific Rise.