The ⁴⁰Ar/³⁹Ar age dating of the Madeira Archipelago and hotspot track (eastern North Atlantic)

Abstract

The 40Ar/39Ar ages for 35 volcanic rocks and 14C ages for two charcoal samples from the Madeira Archipelago and Ampère Seamount (eastern North Atlantic) are presented. The volcanic evolution of Madeira can be divided into a voluminous shield stage (>4.6–0.7 Ma) and a subsequent low‐volume posterosional stage (<0.7–0 Ma). 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 (5500 km3/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, Ampère (31 Ma), Corral Patch and Ormond (65–67 Ma [Féraud et al., 1982, 1986]) Seamounts, and the Serra de Monchique (70–72 Ma [McIntyre and Berger, 1982]) 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.

Gravitational spreading causes en-echelon diking along a rift zone of Madeira Archipelago: an experimental approach and implications for magma transport

“…1). The Desertas ridge is interpreted as either an abandoned rift arm of Madeira (Geldmacher et al 2000) or a separate volcanic system (Schwarz et al 2004). Smith and Sandwell (1997) and nautical maps.…”

“…Madeira Archipelago comprises the volcanic islands of Porto Santo (14.3-11.1 Ma subaerial age), Madeira (5.3 Ma to <10 ka) and the three Desertas Islands Chao, Deserta Grande and Bugio (5.1-1.9 Ma) (Geldmacher et al 2000;Schwarz et al 2005). It is located on Cretaceous oceanic crust between magnetic anomalies M4 and M16 (Klitgord and Schouten 1986;Roest et al 1992) and marks the end of a >70 Ma old hotspot chain.…”

Dated historical biogeography of the temperate Loliinae (Poaceae, Pooideae) grasses in the northern and southern hemispheres

“…The first colonization event involved the relict diploid Drymanthele line that gave rise to the vicariant continental species F. lasto and F. drymeja (4.9 My), and the new founder Madeiran endemic F. donax (3.6 My) (BVI). The volcanic origin of the island of Madeira (5.3 My; Geldmacher et al, 2000) predated the estimated age of the colonization.…”

Probing the Earth’s Deep Interior Through Geochemistry

“…Rejuvenescent volcanism has so far been identified on only a single volcano each in the Marquesas and Society Islands, but both examples follow the Hawaiian pattern in that the lavas are more alkalic with more depleted isotopic characteristics than the shield stage (Brousse et al, 1986;White and Duncan, 1996;Guillou et al, 2014). Madeira may be just entering a rejuvenescent phase with the eruption of several Holocene lavas that follow this same pattern (Geldmacher et al, 2000).…”