Passive margin subduction and the dynamics of collisional orogenesis

Abstract

Continental passive margins are characterized by a wide variety of geometries and widths. Whether these variations have an influence on subsequent dynamics of orogenesis is unresolved. To investigate, a series of upper mantle numerical experiments were performed with systematically varied continental margin widths and geometries. Results show that the vertical geometry of subducting continental margin crust controls both crustal and mantle lithosphere deformation. On both scales, end‐members can be identified. Namely, break‐off versus delamination of continental mantle lithosphere and double vergence versus single vergence of crustal thrust fronts form as a direct result of passive margin geometry. We find that the subduction of upper crust to depths >100 km promotes lithospheric delamination and is facilitated by an extended passive margin. Modeled orogens show decreasing upper plate deformation with increasing margin width. These results suggest that along‐strike deformational variation within orogens may develop due to precollision passive margin geometry.

Rapid Late Eocene Exhumation of the Sivas Basin (Central Anatolia) Driven by Initial Arabia‐Eurasia Collision

“…This progressive evolution has been documented from low‐temperature thermochronology in a variety of orogens including the Pyrenees (Mouthereau et al, ; Vacherat et al, ), Zagros (Mouthereau et al, ), and Taiwan (Mesalles et al, ). Numerical modeling experiments suggest that the architecture and rheology of rifted margins play a fundamental role in this evolution (Jammes & Huismans, ; Schoettle‐Greene & Pysklywec, ). The earliest stage of collision typically involves the subduction of a ~50‐ to 300‐km‐wide zone of thinned or extremely thinned continental crust (e.g., Brune et al, ) at the distal rifted margins (Figure b).…”

“…In contrast, the progressive collision model involves early soft collision during the Eocene and Oligocene in which a wide, thinned Arabia passive margin was underthrust beneath southern Eurasia (Anatolia) causing diffuse contraction throughout the ATB and Sivas Basin (Figures b and c). Numerical modeling suggests an inverse relationship between passive margin width and the degree of plate coupling, with wider margins leading to a more decoupled collision involving less upper plate strain (Schoettle‐Greene & Pysklywec, ). The rheology of the upper plate is also a key factor controlling deformation style during collision, such that a weak upper crust may promote penetrative retrowedge deformation hundreds of kilometers from the margin (Jammes & Huismans, ).…”

Tectonic Inheritance in Continental Rifts and Passive Margins

“…1.2 Processes of inheritance and its relation with lithospheric layers, strain distribution, rocks/fabrics, rheological control and strength profile of the continental lithosphere. Besides their width and geometry (Schoettle-Greene and Pysklywec 2014), passive margins govern subsequent orogeny (as referred in Chabli et al 2014;Mohn et al 2014;Schoettle-Greene and Pysklywec 2014) and tectonic heterogeneity along the orogenic trend (Jammes et al 2014). This scheme is built for a three-layered lithosphere comprising of a brittle upper continental crust, a ductile lower crust and lithospheric mantle.…”

Partitioning of crustal shortening during continental collision: 2‐D thermomechanical modeling

“…Geological structure and evolution of modern and ancient collisional orogens are highly variable, and physical controls of such variability remain poorly understood [e.g., Burov and Yamato , ; Gerya , ; Jamieson and Beaumont , , and references therein]. In particular, crustal shortening partitioning during continental collision varies dramatically and may either almost entirely localize within the lower plate [ Burov and Yamato , ; Butler et al , ; Li et al , ; Sokoutis and Willingshofer , ; Jammes and Huismans , ; Duretz and Gerya , ; Schoettle‐Greene and Pysklywec , ] or distribute in different proportions between the two colliding plates [ Willett et al , ; Beaumont et al , ; Ellis et al , ; Burov and Yamato , ; Faccenda et al , ; Willingshofer and Sokoutis , ; Butler et al , ; Sokoutis and Willingshofer , ; Jammes and Huismans , ; Jamieson and Beaumont , ; Calignano et al , ] even within a single orogen [ Rosenberg and Kissling , ]. One prominent natural example of such variability is documented in the central Alps, where crustal shortening gradually changes from lower plate localized in the western part to upper plate concentrated in the eastern part [ Rosenberg and Kissling , ].…”