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The Late Cretaceous to Paleogene Laramide orogen in the North American Cordillera involved deformation >1,000 km from the plate margin that has been attributed to either plate-boundary end loading or basal traction exerted on the upper plate from the subducted Farallon flat slab. Prevailing tectonic models fail to explain the relative absence of Laramide-aged (ca. 90–60 Ma) contractional deformation within the Cordillera hinterland. Based on Raman spectroscopy of carbonaceous material thermometry and literature data from the restored upper 15–20 km of the Cordilleran crust we reconstruct the Late Cretaceous thermal architecture of the hinterland. Interpolation of compiled temperature data (n = 200) through a vertical crustal column reveals that the hinterland experienced a continuous but regionally elevated, upper-crustal geothermal gradient of >40 °C/km during Laramide orogenesis, consistent with peak metamorphic conditions and synchronous peraluminous granitic plutonism. The hot and partially melted hinterland promoted lower crust mobility and crust-mantle decoupling during flat-slab traction. Researchers test geodynamic models for far-field continental deformation during the Laramide orogeny. New and existing thermal data show that the hot hinterland crust promoted lower crust mobility and crust-mantle decoupling during flat-slab traction. [ABSTRACT FROM AUTHOR]

In cordilleran-type orogens, subduction geometry exerts a fundamental control on the tectonic behavior of the overriding plate. An integrated low-temperature, large thermochronological data set is used in this study to investigate the burial and exhumation history of the overriding plate in northern Patagonia (40°-45°S). Thermal inverse modeling allowed us to establish that a ~2.5-4-km-thick section originally overlaid the Jurassic-Lower Cretaceous successions deposited in half-graben systems that are presently exposed in the foreland. Removal of the sedimentary cover started in the late Early Cretaceous. This was coeval with an increase of the convergence rate and a switch to a westward absolute motion of the South American Plate that was accompanied by shallowing of the subducting slab. Unroofing was probably further enhanced by Late Cretaceous to early Paleogene opening of a slab window beneath the overriding plate. Following a tectonically quiescent period, renewed exhumation occurred in the orogen during relatively fast Neogene plate convergence. However, even the highly sensitive apatite (U-Th)/He thermochronometer does not record any coeval cooling in the foreland. The comparison between Late Cretaceous and Neogene exhumation patterns provides clear evidence of the fundamental role played by inter-plate coupling associated with shallow slab configurations in controlling plate-scale deformation. Our results, besides highlighting for the first time how the whole northern Patagonia foreland was affected by an exhumation of several kilometers since the Late Cretaceous, provide unrivalled evidence of the link between deep geodynamic processes affecting the slab and the modes and timing of unroofing of different sectors of the overriding plate. [ABSTRACT FROM AUTHOR]

In this study, we present an estimate of the gravity signal of the slabs beneath the Alpine mountain belt. Estimates of the gravity effect of the subducting slabs are often omitted or simplified in crustal-scale models. The related signal is calculated here for alternative slab configurations at near-surface height and at a satellite altitude of 225 km. We apply three different modelling approaches in order to estimate the gravity signal from the subducting slab segments: (i) direct conversion of upper mantle seismic velocities to density distribution, which are then forward calculated to obtain the gravity signal; (ii) definition of slab geometries based on seismic crustal thickness and high-resolution upper mantle tomography for two competing slab configurations – the geometries are then forward calculated by assigning a constant density contrast and slab thickness; (iii) accounting for compositional and thermal variations with depth within the predefined slab geometry. Forward calculations predict a gravity signal of up to 40 mGal for the Alpine slab configuration. Significant differences in the gravity anomaly patterns are visible for different slab geometries in the near-surface gravity field. However, different contributing slab segments are not easily separated, especially at satellite altitude. Our results demonstrate that future studies addressing the lithospheric structure of the Alps should have to account for the subducting slabs in order to provide a meaningful representation of the geodynamic complex Alpine area. [ABSTRACT FROM AUTHOR]

A series of ancient Tethys ocean basins have been consumed beneath the Indian Ocean and are hard to observe due to their subduction below the southern Eurasian margin. The presence of the delaminated Gondwana fragments beneath the Indian Ocean also has long been suspected. These microplate tectonics lead to a fairly complex shallow crust and deep mantle configuration, which makes it difficult to reconstruct East Gondwana and discuss the geodynamics of continental rift-drift-collision in the Tethyan Realm. Lithospheric or crustal thinning due to the dehydration of the underlying stagnant slab is a good tracer of the subducted plate. Using the gravity-derived oceanic crust and Euler rotation method, we obtained an asymmetric crustal thickness across the Indian Ocean ridges. Areas of anomalous intra-plate crustal thinning were revealed and applied to track the possible subducted slabs. Then, combined with other geophysical data, two Meso-Tethyan slabs, one Neo-Tethyan slab, and two Indian slabs were delimited. From north to south, the slabs beneath India and the Northeast Indian Ocean constitute a south-dipping and step-shaped architecture. It requires a double subduction zone or a two-stage India-Eurasia collision model to be driven by the slab pull, which is still open for debate. [ABSTRACT FROM AUTHOR]

The slab dynamic processes, such as roll-back during oceanic subduction and break-off during collision orogenesis, would affect the movement of mantle material and the interaction between crust and mantle, accompanied by significant amounts of magmatism. Providing accurate depictions for these processes are extremely difficult, especially in the case of ancient orogens. Here, we present an integrated study of petrology, geochronology, geochemistry and Sr–Nd–Hf isotopes for Early Paleozoic granitoids from the Duojielaka, Ledu and Binglingsi plutons of the southeastern Qilian orogen. Our LA-ICP-MS U Pb zircon data show that these granitoids were emplaced at 476–432 Ma. The petrological and geochemical data suggest that the ~476 Ma Duojielaka porphyritic syenogranites formed by feldspar-dominated fractionation from relatively K-rich basaltic rock-derived adakitic parental magma. The ~454 Ma Duojielaka biotite monzogranites are highly fractionated I-type granites and were derived from basement orthogneisses mixed with minor mafic rocks. The Ledu fine- and medium-grained quartz diorites (~446 and ~452 Ma) are high-K calc-alkaline to shoshonitic and were produced by partial melting of relatively old K-rich mafic crust followed by minor mixing with mantle-derived magmas. The ~432 Ma Binglingsi biotite monzogranites with adakitic characteristics most likely originated by partial melting of thickened mafic lower crust. Based on the new data, in combination with previously published data, we suggest that the roll-back of the South Qilian oceanic slab occurred during the Middle Cambrian to early Middle Ordovician. The Duojielaka porphyritic syenogranites represented crustal anatexis in an arc front associated with slab roll-back. The Late Ordovician–early Middle Silurian intrusive rocks probably resulted from diachronous slab break-off in the post-collisional stage. The rocks record the opening of the break-off window from east to west and the gradual heat propagation from the central part to the southern and northern margins of the eastern Central Qilian due to the widening of break-off window and asthenospheric upwelling. We propose that complex geodynamic processes and their thermal effects can be traced by a comprehensive consideration of the petrogenetic, temporal and spatial evolution of related magmatism. • Genesis of Early Paleozoic granitoids (476–432 Ma) in the eastern Qilian orogen. • Magmas were predominantly derived from diverse crustal sources. • Magma generations were related to slab roll-back and diachronous break-off. • Orogenic geodynamic processes and their thermal effects can be traced by magmatism. [ABSTRACT FROM AUTHOR]

Understanding how long-term subduction dynamics relates to the short-term seismicity and crustal tec tonics is a challenging but crucial topic in seismotectonics. We attempt to address this issue by linking long-term geodynamic evolution with short-term seismogenic deformation in the Northern Apennines. This retreating subduction orogen displays tectonic and seismogenic behaviors on various spatiotemporal scales that also characterize other subduction zones in the Mediterranean area. We use visco-elasto-plastic seismo-thermo-mechanical (STM) modeling with a realistic 2D setup based on available geological and geophysical data. The subduction dynamics and seismicity are coupled in the numerical modeling, and driven only by buoyancy forces, i.e., slab pull. Our results suggest that lower crustal rheology and lithospheric mantle temperature modulate the crustal tectonics of the Northern Apennines, as inferred by previous studies. The observed spatial distribution of upper crustal tectonic regimes and surface displacements requires buoyant, highly ductile material in the subduction channel beneath the internal part of the orogen. This allows protrusion of the asthenosphere in the lower crust and lithospheric delamination associated with slab retreat. The resulting surface velocities and principal stress axes generally agree with present-day observations, suggesting that slab delamination and retreat can explain the dynamics of the orogen. Our simulations successfully reproduce the type and overall distribution of seismicity with thrust faulting events in the external part of the orogen and normal faulting in its internal part. Slab temperatures and lithospheric mantle stiffness affect the cumulative seismic moment release and spatial distribution of upper crustal earthquakes. The properties of deep, sub-crustal material are thus shown to influence upper crustal seismicity in an orogen driven by slab retreat, even though the upper crust is largely decoupled from the lithospheric mantle. Our simulations therefore highlight the effect of deep lower crustal rheologies, self-driven subduction dynamics and mantle properties in controlling shallow deformation and seismicity. • Simulation links crustal tectonics, seismicity with long-term geodynamics driven solely by slab pull. • Lithospheric delamination allowed by a ductile lower crust is needed for a realistic stress pattern. • Deep material properties (e.g., slab temperature, stiffness) significantly affect crustal seismicity. [ABSTRACT FROM AUTHOR]

Compartmentalized or broken foreland basins are fundamental components of many convergent margins. Partitioning of collisional and retroarc foreland basins by basement-involved uplift has been linked commonly to flat-slab subduction, with an emerging appreciation for the important influence of: (1) regional and local inheritance of stratigraphic, structural, and crustal rheological heterogeneities; and (2) variations in climate, erosion, and sediment accumulation budgets. Shortening and basement uplift in broken foreland provinces greatly disrupts sediment routing patterns and preconditions vast regions for later phases of intracontinental deformation. Despite the wide range of settings in which broken foreland basins are recognized, there is limited understanding of the processes and controls on the common temporal transition from a single regionally integrated flexural foreland basin to a broken or compartmentalized foreland basin. We explore the stratigraphic, structural, sediment routing, and geodynamic evolution of several broken foreland systems to identify the key elements involved in the development of ancient and modern examples and to better assess the competing influences of flat-slab subduction, crustal inheritance, climate, erosion, and sedimentation. Broken foreland basin systems in ocean-continent convergent systems include the modern Central Andes of South America and the Late Cretaceous-Paleogene Laramide province of North America. In continent-continent collisional systems, broken foreland basins have been reported for both the downgoing and overriding plates (pro- and retro-wedge basins), including the Cenozoic Duero basin associated with the Spanish Pyrenean orogenic system and Mesozoic-Cenozoic basins of the Tibetan plateau within the India-Asia collision zone. A review of proposed broken foreland basins identifies some common stratigraphic and structural elements as well as some potential pitfalls, including the misinterpretation of ancient broken forelands in cases where foreland shortening was insufficient to generate positive topographic features capable of disrupting a contiguous (unbroken) foreland basin. [ABSTRACT FROM AUTHOR]