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Lev Vinnik, Sergey Oreshin, Larissa Makeyeva, Dmitriy Peregoudov, Elena Kozlovskaya, Elena Kozlovskaya, Helle Pedersen, Jaroslava Plomerova, Ulrich Achauer, Eduard Kissling, Irina Sanina, Teppo Jämsen, Hanna Silvennoinen, Catherine Pequegnat, Riitta Hurskainen, Robert Guiguet, Helmut Hausmann, Petr Jedlicka, Igor Aleshin, Ekaterina Bourova, Reynir Bodvarsson, Evald Brückl, Tuna Eken, Pekka Heikkinen, Gregory Houseman, Helge Johnsen, Elena Kremenetskaya, Kari Komminaho, Helena Munzarova, Roland Roberts, Bohuslav Ruzek, Hossein Shomali, Johannes Schweitzer, Artem Shaumyan, Ludek Vecsey, Sergei Volosov |
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Title |
Anisotropic lithosphere under the Fennoscandian shield from P receiver functions and SKS waveforms of the POLENET/LAPNET array |
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2014 |
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Tectonophysics |
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628 |
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45-54 |
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Asthenosphere Lithosphere Mantle flow Receiver functions Seismic anisotropy Shear-wave splitting |
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Seismic azimuthal anisotropy is the key evidence of the past and present strains in the upper mantle. The standard analysis of shear-wave splitting with the SKS techniques is useful in mapping lateral variations but it is insensitive to depth of anisotropy and to variations of anisotropy with depth. To retrieve the depth localized anisotropy under the Fennoscandian shield, we inverted P-wave receiver functions of the POLENET/LAPNET array in northern Finland jointly with SKS recordings. Shear-wave anisotropy of ~2.5% with the fast direction of 40°–60° in a depth range from the Moho to ~110km is a robust result of the inversion. The obtained direction is nearly normal to the azimuth of the maximum horizontal compressional stress in the lithosphere, but a recent origin of this anisotropy is in doubt. This anisotropy may be frozen since the Precambrian, but it shows no clear relation with the trends of the Precambrian tectonics. The upper anisotropic layer accounts for ~40% of shear-wave splitting in SKS, and to explain the rest another anisotropic layer is required. The top of the second layer with a practically similar fast direction is found at a depth of 200–240km. This direction is close to the current APM direction of the lithosphere with implication that the inferred anisotropy may be related with the current plate motion, and the anisotropic layer belongs to the asthenosphere. The bottom of this layer is uncertain, but it is at least 320km deep. In a depth range from 160km to 200–240km the fast anisotropy direction is 110–150°. Origin of this direction is unclear. |
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8169 |
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Bergerat F., Angelier J. & Homberg C. |
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Tectonic analysis of the Husavik-Flatey fault (northern Iceland) and mechanisms of an oceanic transform zone, the Tjörnes Fracture Zone. |
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2000 |
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Tectonics |
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19 |
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6 |
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1161-1177 |
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316 |
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0278-7407 |
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322 |
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Callot J.P., Grigne C., Geoffroy L. & Brun J.P. |
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Title |
Development of volcanic passive margins : two-dimensional laboratory models. |
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2001 |
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Tectonics |
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20 |
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148-159 |
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290 |
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0278-7407 |
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yes |
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2399 |
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Geoffroy L., Callot J.P., Scaillet S., Skuce A., Gélard J.P., Ravilly M., Angelier J., Bonin B., Cayet C., Perrot K. & Lepvrier C. |
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Southeast Baffin volcanic margin and the North American-Greenland plate separation. |
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2001 |
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Tectonics |
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20 |
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566-584 |
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290 |
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0278-7407 |
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yes |
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2402 |
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MICHON, L., O. MERLE |
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Title |
Mode of lithospheric extension: conceptual models from analogue modeling |
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2003 |
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Tectonics |
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22 |
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1028 |
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doi:10.1029/2002TC001435 |
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444 |
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0278-7407 |
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yes |
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3886 |
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Author |
Callot, J.-P.; Geoffroy, L.; Brun, J.-P. |
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Title |
Development of volcanic passive margins: Three-dimensional laboratory models |
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Journal Article |
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Year |
2002 |
Publication |
Tectonics |
Abbreviated Journal |
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21 |
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Keywords |
8109 Tectonophysics: Continental tectonics—extensional; 8120 Tectonophysics: Dynamics of lithosphere and mantle—general; 8159 Tectonophysics: Rheology—crust and lithosphere; 8194 Tectonophysics: Instruments and techniques |
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Abstract |
Continental breakup above an anomalously hot mantle may lead to the development of volcanic margins. Volcanic margins are characterized by (1) thick seaward dipping lava flow sequences, (2) central intrusive complexes associated with dyke swarms parallel to the coast, and (3) high seismic velocity bodies in the lower crust attributable to magma underplating. A conceptual model for volcanic margins development has recently been proposed based on onshore studies of the Greenland margins and the British Tertiary Igneous Province. It is proposed that the long-lived central intrusions are genetically linked to underlying persistent zones of mantle fusion. These localized melting domains (or soft spots), equivalent to small mantle diapirs, may locally soften the extending continental lithosphere. The low-viscosity diapirs would (1) localize tectonic strain and (2) feed the volcanic margin with magma. Thus such soft spots can control the along-strike magmatic and tectonic segmentation of volcanic margins. Recent geophysical investigations appear to show that the along-strike structure of volcanic passive margins is compatible with such a segmentation process. Here we present a set of scaled experiments designed to study how such localized rheological heterogeneities in the sub-Moho mantle may have a mechanical effect on continental breakup. Four-layer models were constructed using sand and silicone putties to represent the brittle and ductile layers of both crust and mantle. The soft spots are simulated by low-viscosity silicone putty emplaced within the brittle material. At the scale of the entire breakup zone, the soft spots display an oceanic-type strength profile defining low-strength zones where continental breakup is initiated. The rift orientation and segmentation are strongly controlled by the distribution of the low-viscosity heterogeneities, rather than by the direction of regional extension. The experiments are compared with the geometry and segmentation of the onshore part of the Greenland volcanic margins. |
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290 |
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American Geophysical Union |
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0278-7407 |
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yes |
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IPEV @ Thierry.Lemaire @ |
Serial |
5547 |
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Author |
Garcia, S.; Angelier, J.; Bergerat, F.; Homberg, C.; Dauteuil, O. |
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Title |
Influence of rift jump and excess loading on the structural evolution of northern Iceland |
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Journal Article |
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Year |
2008 |
Publication |
Tectonics |
Abbreviated Journal |
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27 |
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Keywords |
rift jump; structural evolution; lava dip; dyke; fault; flexure zone; Iceland; 8010 Structural Geology: Fractures and faults; 8036 Structural Geology: Paleoseismology; 8178 Tectonophysics: Tectonics and magmatism; 8137 Tectonophysics: Hotspots, large igneous provinces, and flood basalt volcanism; 9325 Geographic Location: Atlantic Ocean |
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Abstract |
New structural data combined with published structural and geochronological data allow reconstruction of the structural evolution that followed the last rift jump across northern Iceland. Tertiary lava flows erupted along the Skagafjördur paleo-rift have been down-bent under the weight of, and in the direction of, Plio-Pleistocene lava flows emitted from the Northern Volcanic Zone and the central part of Iceland. This down-bending process involved development of local flexure zones and a flexural extension along the resulting monoclines. This structural reorganization explains the existence of the Húnaflói-Skagi synform without need for a paleo-rift axis along it, in agreement with previous radiometric dating. The large amount of Plio-Pleistocene lava flows erupted in Central Iceland may have been enhanced by ice cap loading. |
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316 |
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American Geophysical Union |
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0278-7407 |
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yes |
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IPEV @ Thierry.Lemaire @ |
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5497 |
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Author |
Faccenna, C.; Rossetti, F.; Becker, T.W.; Danesi, S.; Morelli, A. |
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Title |
Recent extension driven by mantle upwelling beneath the Admiralty Mountains (East Antarctica) |
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Journal Article |
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Year |
2008 |
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Tectonics |
Abbreviated Journal |
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27 |
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Antarctica; continental tectonics; faulting; mantle dynamics; seismic tomography; 7230 Seismology: Seismicity and tectonics; 8010 Structural Geology: Fractures and faults; 8107 Tectonophysics: Continental neotectonics; 7270 Seismology: Tomography; 8122 Tectonophysics: Dynamics: gravity and tectonics |
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Abstract |
Northern Victoria Land is located at the boundary between an extended, presumably hot, region (West Antarctic Rift System) and the thick, possibly cold, East Antarctic craton. The style and timing of Tertiary deformation along with relationships with the magmatic activity are still unclear, and contrasting models have been proposed. We performed structural and morphotectonic analyses at the NE termination of northern Victoria Land in the Admiralty Mountains area, where the relationship between topography, tectonics, and magmatism is expected to be well pronounced. We found evidence of two subsequent episodes of faulting, occurring concurrently with the Neogene McMurdo volcanism. The first episode is associated with dextral transtension, and it is overprinted by extensional tectonics during the emplacement of large shield alkaline volcanoes. Upper mantle seismic tomography shows that the extensional regime is limited to regions overlying a low-velocity anomaly. We interpret this anomaly to be of thermal origin, and have tested the role of large-scale upwelling on lithosphere deformation in the area. The results of this integrated analysis suggest that the morphotectonic setting of the region and the magmatism is likely the result of upwelling flow at the boundary between the cold cratonic and the hot stretched province (WARS), at work until recent time in this portion of the northern Victoria Land. |
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906 |
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American Geophysical Union |
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0278-7407 |
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yes |
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IPEV @ Thierry.Lemaire @ |
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5551 |
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Author |
Biessy, G.; Dauteuil, O.; Van Vliet-Lanoë, B.; Wayolle, A. |
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Title |
Fast and partitioned postglacial rebound of southwestern Iceland |
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Journal Article |
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Year |
2008 |
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Tectonics |
Abbreviated Journal |
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27 |
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Keywords |
glacio-isostasy; rebound; rheology; 5475 Planetary Sciences: Solid Surface Planets: Tectonics; 5416 Planetary Sciences: Solid Surface Planets: Glaciation; 4556 Oceanography: Physical: Sea level: variations and mean; 8033 Structural Geology: Rheology: mantle |
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Abstract |
Located both on the Mid-Atlantic Ridge and above a mantle plume, Iceland is subject to horizontal and vertical motions. Many studies described these deformations in terms of rifting episodes that have combined both extensional tectonics and magmatism. However, few studies have described the glacio-isostatic response induced by the retreat of the Weichselian ice cap. The melting of this ice cap induced a postglacial rebound for the whole of Iceland that may be controlled by the geodynamic setting and the rheological layering of the lithosphere. This study is devoted to (1) understanding the Holocene rebound on the southwestern coast and (2) estimating the asthenosphere viscosity and depth beneath Iceland. Two stages of holocene evolution were determined by means of GPS profiles, morphological observations, and data compilation. The first stage corresponds to a vertical uplift of 67.5 to 157.5 m. It started at 10,000 years BP and ended at 8500 years BP implying uplift rates between 4.5 and 10.5 cm/a. It was a quick isostatic response to the fast ice retreat. The second stage had vertical motion of tens of meters with a probable tectonic origin and started at 8500 years BP. The uplift rate is 1 to 2 orders of magnitude slower than the one during the first stage. Uplift partitioning during the first stage was controlled by the thermal state of the lithosphere, the highest geothermal flux inducing the maximum uplift rates. The relaxation time for uplift provides a viscosity estimate of 5.4–5.8 × 1019 Pa s for the asthenosphere. This value is similar to those determined for glacial areas in different continental contexts. However, the flexural wavelength indicates a shallower asthenosphere than that occurring in continental domains. Therefore this study highlights a coupling between the thermal structure of the Icelandic asthenosphere and the glacial rebound. |
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316 |
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American Geophysical Union |
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0278-7407 |
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yes |
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IPEV @ Thierry.Lemaire @ |
Serial |
5569 |
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Author |
Homberg, C.; Bergerat, F.; Angelier, J.; Garcia, S. |
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Title |
Fault interaction and stresses along broad oceanic transform zone: Tjrnes Fracture Zone, north Iceland |
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Journal Article |
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Year |
2010 |
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Tectonics |
Abbreviated Journal |
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29 |
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1 |
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TC1002 |
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Keywords |
oceanic transform; fault interaction; stresses; Iceland; slip transfer; 8150 Tectonophysics: Plate boundary: general; 8164 Tectonophysics: Stresses: crust and lithosphere; 8020 Structural Geology: Mechanics, theory, and modeling |
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Abstract |
Transform motion along oceanic transforms generally occurs along narrow faults zones. Another class of oceanic transforms exists where the plate boundary is quite large (∼100 km) and includes several subparallel faults. Using a 2-D numerical modeling, we simulate the slip distribution and the crustal stress field geometry within such broad oceanic transforms (BOTs). We examine the possible configurations and evolution of such BOTs, where the plate boundary includes one, two, or three faults. Our experiments show that at any time during the development of the plate boundary, the plate motion is not distributed along each of the plate boundary faults but mainly occurs along a single master fault. The finite width of a BOT results from slip transfer through time with locking of early faults, not from a permanent distribution of deformation over a wide area. Because of fault interaction, the stress field geometry within the BOTs is more complex than that along classical oceanic transforms and includes stress deflections close to but also away from the major faults. Application of this modeling to the 100 km wide Tjrnes Fracture Zone (TFZ) in North Iceland, a major BOT of the Mid-Atlantic Ridge that includes three main faults, suggests that the Dalvik Fault and the Husavik-Flatey Fault developed first, the Grismsey Fault being the latest active structure. Since initiation of the TFZ, the Husavik-Flatey Fault accommodated most of the plate motion and probably persists until now as the main plate structure. |
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316 |
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AGU |
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0278-7407 |
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yes |
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IPEV @ Thierry.Lemaire @ |
Serial |
6062 |
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