40Ar/39Ar ages for the alkaline volcanism and the basement of Gorringe Bank,North Atlantic ocean |
| |
Authors: | Gilbert Féraud Janine Gastaud Jean-Marie Auzende Jean-Louis Olivet Guy Cornen |
| |
Institution: | 1. Laboratoire de Géologie et Géochimie, E.R.A. C.N.R.S. 888, Facultédes Sciences, Parc Valrose, 06034 Nice Cedex France;2. Centre Océanologique de Bretagne, B.P. 337, 29273 Brest Cedex France;3. Laboratoire de Pétrologie et de Minéralogie, U.E.R. des Sciences de la Nature, Universitéde Nantes, F-44072 Nantes Cedex France |
| |
Abstract: | Gorringe Bank is situated on the Europe-Africa plate boundary at the eastern end of the Azores-Gibraltar fracture zone. It has two summits, Gettysburg Bank to the Southwest and Ormonde Bank to the northeast.We applied the40Ar/39Ar stepwise heating method to date six samples of the alkaline volcanic rocks, two gabbros from the Ormonde Bank and a dolerite from the Gettysburg Bank. The results that the alkaline volcanism lasted probably for less than 6 Ma(66-60 Ma).Although the nature of this volcanism precludes any subduction feature during its setting, the alkaline volcanism of Ormonde is probably linked to Upper Cretaceous/Eocene compressive tectonic events.The basement rocks of Gorringe Bank reveal distrubed40Ar/39Ar age spectra. One plagioclase and one biotite from a gabbro give evidence for a thermic event whose age is tentatively estimated at about 75 Ma, and related to a variation in the direction of the relative movement between Europe and Africa. The more probable age given by a plagioclase of another gabbro and by a dolerite (110 Ma) corresponds to tilting northeastward of the Gorringe massif. |
| |
Keywords: | |
本文献已被 ScienceDirect 等数据库收录! |
|