Age Progressive Volcanism Opposite Nazca Plate Motion: Insights from Seamounts and Drowned Islands on the Northeastern Margin of the Galápagos Platform.

Sinton, Christopher W., Hauff, Folkmar , Hoernle, Kaj and Werner, Reinhard (2018) Age Progressive Volcanism Opposite Nazca Plate Motion: Insights from Seamounts and Drowned Islands on the Northeastern Margin of the Galápagos Platform. Open Access Lithos, 310-311 . pp. 342-354. DOI 10.1016/j.lithos.2018.04.014.

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Supplementary data:

Abstract

Highlights

• Four of the seven seamounts northeast of the Galápagos Platform are drowned islands
• The ages of the seamounts range from 5.2 Ma to 0.5 Ma
• Seamount morphology changes from conical to elongate at ~1.5 Ma
• The locus of volcanism appears to migrate eastward at the rate of Nazca plate motion

Abstract

We present new geochemical and 40Ar/39Ar analyses from seven seamounts located off the northeastern margin of the shallow Galápagos Platform. Initial volcanism at 5.2 Ma created a small island (Pico) over the current location of the hotspot with geochemically enriched lavas. There is no further record of magmatism in the study area until 3.8 to 2.5 Ma, during which four roughly conical volcanoes (Sunray, Grande, Fitzroy, and Beagle) formed through eruption of lavas derived from a depleted mantle source. Sunray, Fitzroy, and Grande were islands that existed for ~3 m.y. ending with the submergence of Fitzroy at ~0.5 Ma. The youngest seamounts, Largo and Iguana, do not appear to have been subaerial and were active at 1.3 Ma and 0.5 Ma, respectively, with the style of edifice changing from the previous large cones to E-W elongate, composite structures. The progression of magmatism suggests that Pico erupted near 91.5°W near the location of the Galápagos plume while the others formed well east of the plume center. If the locations of initial volcanism are calculated using the eastward velocity of the Nazca plate, there appears to be a progression of younger volcanism toward the east, opposite what would be expected from a fixed mantle plume source. The rate that initial volcanism moves eastward is close to the plate velocity. A combination of higher temperature and geochemical enrichment of the thickened lithosphere of the Galápagos platform could have provided a viscosity gradient at the boundary between the thick lithosphere and the thinner oceanic lithosphere to the northeast. As this boundary moved eastward with the Nazca plate, it progressively triggered shear-driven mantle upwelling and volcanism.

Document Type: Article
Keywords: Galapagos, Ar-Ar age dating, magmatic geochemistry, seamounts, age progressive volcanism
Research affiliation: OceanRep > GEOMAR > FB4 Dynamics of the Ocean Floor > FB4-MUHS
Refereed: Yes
Open Access Journal?: No
Publisher: Elsevier
Date Deposited: 03 May 2018 10:18
Last Modified: 08 Feb 2021 07:38
URI: https://oceanrep.geomar.de/id/eprint/42921

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