http://hdl.handle.net/2122/252 Search the Channel search http://www.earth-prints.org/simple-search http://hdl.handle.net/2122/3621 Title: Relations between faulting and continuous deformation on the continents <br/> <br/>Authors: Jackson, J.; Bullard Laboratories, Madingley Road, Cambridge, CB3 OEZ, UK http://hdl.handle.net/2122/2722 Title: Images of a lower-crustal oceanic slab: Direct evidence for tectonic accretion in the Archean western Superior province <br/> <br/>Authors: White, D. J.; GSC(Ottawa, ON-CANADA); Musacchio, G.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Milano-Pavia, Milano, Italia; Helmstaedt, H. H.; Queen's University (Kingston, ON-CANADA); Rarrab, R. M.; Queen's University (Kingston, ON-CANADA); Thurston, P. C.; OGS (Sudbury, ON-CANADA); Van der Velden, A.; University of Calgary (Calgary, AL-CANADA); Hall, L.; University of Calgary (Calgary, AL-CANADA) <br/> <br/>Abstract: The Archean western Superior province in Canada is the type area for proposed Archean plate tectonics. Seismic images from this region provide direct evidence for assembly of the craton by terrane accretion and for a large slab of remnant oceanic crust preserved at the base of the crust. This slab, with inferred garnet amphibolite composition, adds a critical piece of evidence to previous suggestions that Archean subduction was at a shallow angle and that some Neoarchean tonalite-trondhjemite-granodiorite suites, distinct from most modern-day suprasubduction magmas, are melts primarily derived directly from subducted slabs. http://hdl.handle.net/2122/2407 Title: Mapping mantle flow during retreating subduction: Laboratory models analyzed by feature tracking <br/> <br/>Authors: Funiciello, F.; Dipartimento di Scienze Geologiche, Universita` Roma Tre; Moroni, M.; Dipartimento di Idraulica, Trasporti e Strade, Universita` degli Studi di Roma ‘‘La Sapienza,’’ Rome, Italy.; Piromallo, C.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia; Faccenna, C.; Dipartimento di Scienze Geologiche, Universita` Roma Tre; Cenedese, A.; Dipartimento di Idraulica, Trasporti e Strade, Universita` degli Studi di Roma ‘‘La Sapienza,’’ Rome, Italy.; Bui, H. A.; Dipartimento di Scienze Geologiche, Universita` Roma Tre <br/> <br/>Abstract: Three-dimensional dynamically consistent laboratory models are carried out to model the large-scale mantle circulation induced by subduction of a laterally migrating slab. A laboratory analogue of a slab–upper mantle system is set up with two linearly viscous layers of silicone putty and glucose syrup in a tank. The circulation pattern is continuously monitored and quantitatively estimated using a feature tracking image analysis technique. The effects of plate width and mantle viscosity/density on mantle circulation are systematically considered. The experiments show that rollback subduction generates a complex three-dimensional time-dependent mantle circulation pattern characterized by the presence of two distinct components: the poloidal and the toroidal circulation. The poloidal component is the answer to the viscous coupling between the slab motion and the mantle, while the toroidal one is produced by lateral slab migration. Spatial and temporal features of mantle circulation are carefully analyzed. These models show that (1) poloidal and toroidal mantle circulation are both active since the beginning of the subduction process, (2) mantle circulation is intermittent, (3) plate width affects the velocity and the dimension of subduction induced mantle circulation area, and (4) mantle flow in subduction zones cannot be correctly described by models assuming a two-dimensional steady state process. We show that the intermittent toroidal component of mantle circulation, missed in those models, plays a crucial role in modifying the geometry and the efficiency of the poloidal component http://hdl.handle.net/2122/1518 Title: Rheology of the Indian and Tarim plates in the Karakoram continent-to-continent collision zone <br/> <br/>Authors: Caporali, A.; Dipartimento di Geologia, Paleontologia e Geofisica, Università di Padova, Italy <br/> <br/>Abstract: Bouguer gravity anomalies in the region of Western Himalayas, Karakoram and Tien Shan show large negative values, but classical isostatic models are insufficient to account for the detailed pattern of the observed anomalies. In the past years the gravimetric surveys in the Karakoram done by Marussi, Caputo and others in 1954 have been extended and intensified. The full body of available gravimetric data, including the pendulum observations by De Filippi and Hedin at the beginning of this century, have been re-analyzed. Terrain corrections have been computed systematically for all available data using a unique algorithm and Digital Terrain Model. The isostatic anomalies along a profile from the Indo-Gangetic foredeep, across the Karakoram range and terminating in the Tarim basin show the oscillating values already noted by Marussi. It is here proposed that this oscillatory pattern can be explained by a model in which the convergent boundaries of the Indian and Tarim plates deform by elastic flexure, besides isostasy. The gravity data constrain the numerical values of the model parameters, particularly the flexural rigidity of the plates. For the Indian plate the best fitting value of the flexural rigidity is D = 5 1024 N m, a value very similar to those reported in Central Himalaya. The flexural rigidity of the Tarim plate turns out to be considerably larger D = 7 1025 N m, which makes the Tarim more rigid than the neighboring Central Tibet. Both plates are loaded by an estimated shear stress of 7 1012 N m-1 located in a region corresponding to the Nanga Parbat Haramosh syntaxis. It is concluded that the Indo-Asian continental collision in the Western Himalaya and Karakoram resulted in the development of flexural basins on both sides, unlike the Central Himalaya where the collision produced a flexural basin, the Ganga basin, to the south and, to the north, the indentation of an isostatically supported Tibetan block with possible rheological layering and eastward lateral extrusion.