Tectono-magmatic evolution of the southern Reykjanes Ridge, North
Atlantic, from ~11 M.y. to present
Abstract
The geology of the Reykjanes Ridge reflects variations in the style of
crustal accretion related to mantle plume processes and tectonic
reconfigurations. Following a ~30° change in spreading
direction, ridge segments progressively reassumed a linear orientation
under the influence of a regional mantle melting anomaly. This process
is incomplete, with ongoing reorganization along the southernmost part
of the ridge. We investigate the ongoing impacts of this reorganization
on ridge propagation, seafloor morphology, and structural fabrics using
a combination of geophysical evidence to inform the regional and
detailed remote-predictive geological mapping over the southernmost
~200 km of the ridge, covering ~11 M.y. of
spreading history. Our results show that this area is more segmented
than previously described, as we identify two new fracture zones. In
this area, transforms evolved to discontinuities between
~8.2 and 4.2 Ma, associated with the evolution of the
segments comprising the southern part of the Reykjanes Ridge. At
~9.7–8.2 Ma, a new segment (S2) forms at the expense of
segment S3. The evolution of southern most part of the Reykjanes Ridge
is related to magma supply associated with buoyant upwelling mantle
cells. The elimination of transform motion coincides with reorientation
of the seafloor fabric from N-trending at the active plate boundary, to
a complex NE-trending fabric in off-axis. This results in dissection of
axial volcanic ridges by the oblique plate boundary zone. The complex
interplay between segment reorganization and short ridge jumps along the
migrating discontinuities results in more crustal accretion to the North
American plate overall.