Abstract
The origin of rejuvenated volcanism on mantle plume related oceanic islands remains controversial. One commonly cited model is decompressional melting related to plate flexure from the rapid loading of the lithosphere by the formation of a shield volcano above the plume stem. This model provides testable predictions about the timing and subsidence history of the island. Here we evaluate the flexure model by examining the products of three well dated rejuvenation stage eruptions at Kilauea Point, Kaua‘i, (Hawaii) the 2.65 ± 0.35 Ma Mōkōlea Point lava, 1.67 ± 0.11 Ma for Crater Hill tuff cone and 0.69 ± 0.03 Ma for Kīlauea Point lava events. These eruptions record the flexure of the island over a 2 Ma period, the longest sequence of rejuvenated volcanism within the Hawaiian Islands. These three eruptions, including two subaerial flows (the 2.65 ± 0.35 Ma Mōkōlea Point and 0.69 ± 0.03 Ma for Kīlauea Point lavas) and the only phreatomagmatic vent structure on Kaua‘i (the 1.67 ± 0.11 Ma Crater Hill tuff cone), document the progressive sinking and uplift of the island related to sea level as the island drifted away from the Hawaiian hot spot at ~10 cm/yr. The timing of volcanism and the elevation of Kilauea Point relative to sea level are inconsistent with the predicts from the flexural melting model. These new results indicate that decompression melting cannot be the sole driver for rejuvenated volcanism on Kaua‘i. Additional explanations are needed to account for the timing and volume of rejuvenated volcanism in Hawai‘i.
Highlights
Rejuvenated magmatism on Hawaiian and other ocean islands occurs hundreds of kilometers downstream from the stem of the ascending mantle plume following a hiatus of ∼0·5–2 millions of years (Myrs) in volcanism (e.g., Macdonald et al, 1983; Garcia et al, 2010)
The Crater Hill tuff cone sequence and Kılauea Point lava are separated by a 2–3 m thick red paleosol horizon formed by weathering of the tuff cone tephra during sustained surface exposure (Figures 3a, 7)
It is evident, that at the time of the Crater Hill eruption (∼1.7 Ma) the relative sea level was similar to the present, while the overlying ∼0.7 Ma Kılauea Point lava and underlying ∼2.7 Ma Mokolea Point lava were formed when the relative sea level was substantially lower than today (Figure 9)
Summary
Rejuvenated magmatism on Hawaiian and other ocean islands occurs hundreds of kilometers downstream from the stem of the ascending mantle plume following a hiatus of ∼0·5–2 millions of years (Myrs) in volcanism (e.g., Macdonald et al, 1983; Garcia et al, 2010). The Crater Hill tuff cone sequence and Kılauea Point lava are separated by a 2–3 m thick red paleosol (i.e., saprolite) horizon formed by weathering of the tuff cone tephra during sustained surface exposure (Figures 3a, 7). The near-vent deposits are ∼100-m-thick accumulation of spatter and scoria, representing a crater rampart that rests directly on the red paleosol horizon at the top of Crater Hill tuff cone sequence (Figure 7) Down slope, this succession grades into >60-m-thick fountain-fed lava flow that was flowed south and northwest from the erupting fissure (Figure 2). Sample KR-3 is from Kılauea Point lava feeder dyke which yields an unspiked K-Ar eruption age of 0.69 ± 0.03 Ma (Table 1) It is comprised of nearly aphyric basanite (Figure 4a) with
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