Yazar "Ballı, Açelya" ile AYBE- Katı Yer Bilimleri Lisansüstü Programı - Yüksek Lisans'a göz atma
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ÖgeEclogite İnduced Deformation of the Siberian Craton(Eurasia Institute of Earth Sciences, 2019-05-03) Ballı, Açelya ; Göğüş, Oğuz Hakan ; 602171001 ; Solid Earth Sciences ; Katı Yer Bilimleri Anabilim DalıThe deformation of the cratons, whose roots are approximately 250 km deep is very difficult. The removal of the mantle lithosphere, which is one of the proposed mechanisms for the deformation of the craton that is stable for long periods, is carried out by many different processes. Deformation of the craton as a result of a gravitational instability is one of the most likely mechanisms. According to isopycnic hypothesis, lithospheric mantle of cratons thought to be buoyant due to their depleted composition, even though most of them Archean in age and cold. Since the mantle lithosphere of the craton is lighter in density than asthenosphere, an additional force is required for a gravitational instability to occur. This thermo - mechanical force causes deformation of the roots of the craton by creating an instability between the mantle lithosphere and the asthenosphere. The Siberian craton is one of the world's largest Archean - Proterozoic cratons. The Siberian craton has approximately 100 - 1300 m surface topography, 35 - 53 km MOHO thickness, and a maximum depth of 350 km LAB which are acquired from petrological studies, seismic tomography and gravity anomalies. Specifically, the LAB varies among 170-350 km and such depth change is not well understood. Until the formation of the Siberian craton is completed, it hosts many tectonic and magmatic events. These include active margin zones, continent collisions, and rift zones. As a result of pressure change in the active boundary regions, the transformation of basalt to eclogite takes place. Therefore, it creates a gravitational instability in the environment. Gravity anomalies observed near kimberlite fields, reflect the possibility of denser eclogitic bodies under the crust of Siberian craton. Our study focuses on testing potential deformation of the Siberian continental lithosphere with the presence of these eclogitic bodies. We performed 2D numerical experiments to investigate the effects of eclogite blocks that are varying in size and density. Crust rheology was prepared in accordance with Siberian craton. The density of the mantle lithosphere (3330 kg / m3 - 3410 kg / m3 +20 kg / m3) is changed to observe its effect on the system, and eclogite blocks of different size (5 km x 500 km, 10 km x 250 km, 25 km x 100 km) are added to the lower crust base to start a gravitational instability. According to model results, depending on the deformation of the mantle lithosphere, eclogite block can either stay attached to the lower crust, or it can be detached from it. In the case where the eclogite block attached to the lower crust, two different conditions: localized deformation (do not occur the drip mechanism) and non-localized deformation occurs due to the small-scale convection movement. Also, two different removal mechanism for the case where eclogite becomes detached are also observed: high degree deformation of mantle lithosphere, and the eclogite block pierce through the mantle lithosphere. Comparison of experimental results with geophysical data for MOHO and LAB depths showed that, the most convenient models for Siberian craton are the models where the dripping were not observed. Mantle lithosphere densities of 3350 kg / m3 or less yields the most consistent results. While the width of the eclogite block causes high-degree deformation, it is observed that with increasing thickness it leads to formation of viscous drips. Taking MOHO and LAB depths into account obtained from the model results, it has been observed that the model #A1, #A2 and #A3 agrees well with the BB' cross-section at 20.92 Ma, 25.36 Ma and 20.92 Ma, respectively. Experimental results indicate that, eclogite block(s) under the Siberian craton may still be there and craton itself does not undergo any significant deformation.