Volcanic passive margins and Phanerozoic foldbelts – a causal relationship?
1Geological Survey of Norway, Leiv Erikssons
vei 39, 7491 Trondheim, NORWAY
A broad empirical relationship is observed between the South, Central, and North Atlantic volcanic passive margins and re-opened Late Proterozoic – Phanerozoic fold belts. In contrast, non-volcanic margins occur where: a) cratons were separated, b) Archean mobile belts were followed, or c) Phanerozoic fold belts were transacted at a high angle. It appears that the natural outcome of the Wilson Cycle, when applied to the reactivation of Late Proterozoic - Phanerozoic belts, is volcanic passive margins.
We speculate that remnants of eclogitized orogenic roots may provide a fertile source for melt generation when mixed with mantle peridotite. Tectonically unroofed eclogites, from lower portions of the Caledonian Orogen, are well known in the Western Gneiss Region, SW Norway and are found throughout the Caledonian-Appalachian Orogen, in the Mauritanides of NW Africa, and more sparsely in the Pan-African fold belts. Thus, the re-opened Atlantic fold belts appear to have contained eclogitized roots. Another factor that can be of importance for volcanic margin development is build-up of heat beneath the Pangean supercontinent prior to break-up (see abstract by Daniel Praeg).
The volcanic or non-volcanic nature of the Arctic margins is poorly known. However, it is possible that the Barentsian Caledonide fold belt influenced the Early Cretaceous magmatism in the Arctic (Svalbard, Franz Josef's Land, Sverdrup Basin, North Greenland, Bennett Island, and the Alpha-Mendeleev Ridge). The Alpha – Mendelev Ridge in the Canada Basin is strikingly analogous to the Greenland – Faroes Ridge, and a similar origin appears likely. The Arctic is a natural choice for further testing of the concept of a relationship between re-opened eclogitized fold belts and volcanic margins.