Current and past state of the Reykjanes ridge, from Bight to Langjökull SW Iceland. Magmatic and tectonic evolution

In this presentation, we shall present results from studies of the Reykjanes Ridge (RR). RR is a continuous plate boundary extending some 1200 km from the Bight in the south to the north of Langjökull, Iceland. The boundary is oblique to the current plate motion. The RR has been mapped by multibeam techniques from the Bight fracture zone in the south to the Reykjanes peninsula. On land, however, the part of it that includes Reykjanes and extends to the Langjökull area in SW Iceland has been mapped by satellite techniques and photogrammetry. Thus, we have compiled all data for a morphometric study of its evolution. In this presentation, we shall focus on the past 1 Ma. The southernmost part of RR is characterised by a deep, well-defined rift valley, about 15 km wide, populated by en-echelon AVRs, extending to about 59° north. From there to Reykjanes (63.8° north), rift valleys are discontinuous and shallow, with densely populated and overlapping AVRs. On Reykjanes itself, the plate boundary becomes highly oblique, characterised by en-echelon fissures and AVRs, until it reaches the Hengill area (64° north). From Hengill to Langjökull (64.9° north), the system comprises shallow-to-deep rift valleys that widen to the north (13 → 30 km wide), with parallel AVRs. North of Langjökull, there is no clear evidence of RR continuation. The heading of different segments of the RR varies: from Bight to the Icelandic continental shelf at ~36°, on the continental shelf at ~50°, on the Reykjanes peninsula at ~65°, and from Hengill to its end at ~36°. At the same time, the spreading along the RR is at ~99°. The number of AVRs and thus magma production varies along the RR, being smallest in the south and increasing towards the north.