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

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doi: 10.1029/1999GC000018
Author(s): Geldmacher, Jörg; van den Bogaard, Paul; Hoernle, Kaj; Schmincke, Hans-Ulrich
Author Affiliation(s): Primary:
GEOMAR Wischofstrass, Kiel, Federal Republic of Germany
Volume Title: Geochemistry, Geophysics, Geosystems - G<sup>3</sup>
Source: Geochemistry, Geophysics, Geosystems - G>3`, 1(2). Publisher: American Geophysical Union and The Geochemical Society, United States. ISSN: 1525-2027
Note: In English. Accessed on August 29, 2001; 31 p.. 62 refs.; illus., incl. sketch maps, 4 tables, strat. col.
Summary: 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 (>4.6-0.7 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, Ampere (31 Ma), Coral Patch and Ormond (65-67 Ma [Feraud 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.
Year of Publication: 2000
Key Words: 03 Geochronology; Absolute age; African Plate; Ampere Seamount; Ar/Ar; Argon; Atlantic Ocean; Atlantic Ocean Islands; C-14; C-14/C-12; Carbon; Cenozoic; Charcoal; Desertas Islands; Hot spots; Isotope ratios; Isotopes; Madeira; Motions; Neogene; Noble gases; North Atlantic; Northeast Atlantic; Plate tectonics; Porto Santo Island; Quaternary; Radioactive isotopes; Stable isotopes; Tertiary
Coordinates: N300000 N400000 W0050000 W0200000
Record ID: 2002009178
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