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Geldmacher et al. 2000

Geldmacher, J., van den Bogaard, P., Hoernle, K. and Schmincke, H. (2000). The ⁴⁰Ar/³⁹Ar age dating of the Madeira Archipelago and hotspot track (eastern North Atlantic). Geochemistry Geophysics Geosystems 1: doi: 10.1029/1999GC000018. issn: 1525-2027.

The 40Ar/39Ar ages for 35 volcanic rocks and 14C ages for two charcoal samples from the Madeira Archipelago and Ampere Seamount (eastern North Atlantic) are presented. The volcanic evolution of Madeira can be divided into a voluminous shield stage (>4.6--0.7Ma) and a subsequent low-volume posterosional stage (<0.7--0Ma) . Volcanism during the shield stage originated from a two-armed rift system, composed of the E-W oriented Madeira rift arm and the N-S oriented Desertas rift arm. Average growth rates for the submarine (5500km3/Ma) and subaerial (100--150 km3/Ma)shield stages on Madeira are among the lowest found for ocean island volcanoes. It is proposed that Madeira represents the present location of a >70 Myr old hotspot which formed Porto Santo Island (11.1--14.3 Ma), Seine, Ampere (31 Ma), Coral Patch and Ormond (65--67 Ma ) Seamounts, and the Serra de Monchique (70--72 Ma ) complex in southern Portugal. Age and spatial relationships result in a calculated absolute African Plate motion above the hotspot of 1.2 cm/yr around a rotation pole located at 43?36'N/24?33'W

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Keywords
Volcanology, Tectonophysics, Plate motions—past, Geochemistry, Geochronology

Journal
Geochemistry Geophysics Geosystems

Publisher
American Geophysical Union
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