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- Title
The Effect of Magma Poor and Magma Rich Rifted Margins on Continental Collision Dynamics.
- Authors
Turino, V.; Magni, V.; Kjøll, H. J.; Jakob, J.
- Abstract
The transition between non‐rifted continental lithosphere and oceanic lithosphere in rifted margins can display a wide range of characteristics, depending on the regional tectonic evolution. The velocity and duration of the rifting process as well as the geodynamic setting influence the properties and geometry of the margins, which are often grouped into two main categories: magma‐poor and magma‐rich. We show how different types of rifted margins can influence the dynamics of continental collision, focusing on the time and depth of slab break‐off after collision and the fate of margin material. We find that rifted margins have a noticeable impact on subduction dynamics, as we observe large variability in slab break‐off times and depths. In particular, the presence of a rifted margin can delay slab break‐off to up to 60 Myr after the onset of collision. Our results show that a large portion of the weak crust of magma‐poor margins is likely to detach from the subducting plate and accrete to the upper plate, while the dense and strong mafic and ultramafic component of magma‐rich margins causes most of the margin to subduct and be lost into the mantle, leaving only a small fraction of transitional and oceanic crust at the surface. Therefore, the volume of accreted material is much larger when the margin is magma‐poor than magma‐rich, which is consistent with geological observations that fossil magma‐poor rifted margins are preserved in many mountain ranges, whereas remnants of magma‐rich rifted margins are scarce. Plain Language Summary: The transition between continental and oceanic lithosphere at rifted margins in nature is not a sharp boundary, but it is gradual and often characterized by the presence of altered crust. Such margins can be either magma‐poor or magma‐rich, depending on the volume and timing of magmatism during extension; in nature, we can find traces of rifted margins in collisional mountain belts, with magma‐poor margins being more easily preserved than magma‐rich ones. The available models for continental collision, however, do not often consider the presence of such margins. We model continental collision with the presence of a magma‐poor or magma‐rich rifted margin, aiming to provide an explanation for these observations and to see how the margins can affect the subduction process. We find that the presence of a rifted margin can have a significant impact on the evolution of the subduction system, with slab break‐off being significantly delayed in all cases. In the models, we find that part of the margin is always transferred to the overriding plate, and our results show that magma‐poor margins are more likely to be recovered, matching the observations that magma‐poor margins are more easily preserved than magma‐rich. Key Points: The presence of rifted margins in numerical models of continental collision can significantly delay slab break‐offThe type of margin (magma‐poor vs. magma‐rich) controls the dynamic of collision and the likelihood for the margin to be preservedThe volume of preserved margin material is much higher when to subduct is a magma‐poor margin than a magma‐rich one
- Subjects
CONTINENTAL margins; SUBDUCTION zones; LITHOSPHERE; OCEANIC crust; OROGENIC belts; MAGMAS; MOUNTAINS
- Publication
Journal of Geophysical Research. Solid Earth, 2023, Vol 128, Issue 12, p1
- ISSN
2169-9313
- Publication type
Article
- DOI
10.1029/2023JB027173