Was the Hercynian Orogenic Belt of Europe of the Andean Type ?

Abstract

THE Hercynian orogenic belt has distinctive features with regard to the preceding and subsequent orogenies, as demonstrated by Zwart¹ and others². It appears to have formed on a continental basement. There is no evidence for a large eugeosyncline, but rather small subsiding basins or troughs with a shallow type of sedimentation. It is characterized by clastic volcano-sedimentary formations often represented in the Culm facies, pointing to a chiefly submarine or aerial intermediate and acid volcanism of explosive style. From North Britain to the Urals, they form an almost continuous belt (Fig. 1). which could have been a line of volcanic eruptions, active from late Devonian till the end of the lower Carboniferous. The syn- or post-tectonic magmatism is emphasized by intensive granitization (granites and granodiorites) which are, in turn, followed by rhyolitic volcanism during the Permian. The Hercynian metamorphism is rather weak, usually covering the green schist facies and reaching locally the amphibolite facies in the low pressure high temperature series. The tectonic style as it is best observed in the external northward zones appears to be the result of weak compressions and, in contrast, of block faulting which might be partially responsible for passive shear folding in the sedimentary cover, with axial planes parallel to the faults in the basement.