Inter-relationship between tectonic and magmatic processes during hyper-extension and break-up at Atlantic type rifted margins

Long-offset seismic reflection and refraction data coupled with well data on rifted margins show an architecture and evolution in which the volume and distribution of syn-rift magmatism and fault structures vary considerably. Therefore rifted margins were classified as either volcanic or non-volcanic. “Non-volcanic” margins are, however, not necessarily amagmatic, as shown by ODP drilling along the Iberia-Newfoundland rifted margins. On the other hand, magma-rich margins, such as the Norwegian, Northwest Australian and Brazilian rifted margins, show evidence for earlier episodes of hyper-extension, suggesting that there is significantly more deformation before magma emplacement than has previously been proposed. This leads to the question about how magmatic and tectonic processes are interacting before, during and after continental breakup. In my presentation I will hypothesize that the relative timing between degree of extension and excess magma arrival is a major factor in margin architecture variability. Moreover, I will propose that break-up is not necessarily an end-result of hyper-extension. A fundamental trigger for continental break-up is the injection of excess magma into a hyper-extended system that may occur significantly later. Based on a review of results from the South and North Atlantic I will discuss the inter-relationship between hyper-extension and magma input in controlling both the evolution and timing of continental break-up and the architecture of passive continental margins.