Geological, geophysical, and geochemical evidence indicates that a significant portion of the continental mantle lithosphere may be absent in a number of regions near plate boundaries or plate interiors. Delamination and viscous Rayleigh-Taylor instability (“dripping”) are widely cited to account for the missing lithosphere, however these removal processes are poorly constrained. This thesis examines the dynamics of delaminating and dripping mantle lithosphere, in particular focusing on the response of the crust to underlying lithospheric removal. Using forward computational models, I explore whether certain (surface) geological observables may be diagnostic of either removal mechanism. Surface topography associated with delamination has a broad zone of uplift above the lithospheric gap and a mobile zone of subsidence at the delamination hinge, whereas with dripping lithosphere, the topographic expression is symmetric and fixed above the mantle lithosphere downwelling. The pattern of crustal deformation is also distinctly asymmetric with delamination compared to dripping lithosphere. Expanding on these results, I investigate whether present day geological geophysical observables in Eastern Anatolia are consistent with delamination of the mantle lithosphere. Experimental results demonstrate that well-developed plateau uplift, syn-convergent extension, and crustal thinning in the central part of the Anatolian plateau are consistent with a topographic profile at longitude 42ºE and a geologically interpreted zone of syn-convergent extension in eastern Anatolia. With three-dimensional physical scaled analogue modeling experiments, I consider the process of oceanic plate subduction evolving into continental delamination. Model results show that slower plate convergence with retreating ocean lithosphere subduction can develop into delamination,whereas for the experiments with higher plate convergence, the crust above the consumed mantle lithosphere becomes accreted on the retro-plate similar to flake tectonics. The results suggest that delamination is a process analogous to subduction retreat; however, delamination involves decoupling of the retreating mantle lithosphere slab from the buoyant continental crust.
| Identifer | oai:union.ndltd.org:TORONTO/oai:tspace.library.utoronto.ca:1807/26181 |
| Date | 15 February 2011 |
| Creators | Göğüş, Oğuz |
| Contributors | Pysklywec, Russell |
| Source Sets | University of Toronto |
| Language | en_ca |
| Detected Language | English |
| Type | Thesis |
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