|
|
|
| Registros recuperados: 10 | |
|
| |
|
|
| Moussa, N.; Boiron, M.c-; Grassineau, N.v.; Asael, Dan; Fouquet, Yves; Le Gall, Bernard; Rolet, Joël; Etoubleau, Joel; Delacourt, Christophe. |
| In this paper, the mineralogy, fluid inclusions and stable isotopes of hydrothermal veins from the SE part of the Afar Rift (Djibouti) were studied. Mineralization occurs as gold-silver in quartz/carbonate veins and is mainly associated with felsic volcanism. The morphologies and textures of quartz show crustiform colloform banding, massive and breccias. Microthermometric measurements were made on quartz-hosted two phases (liquid + vapor) inclusions. Mean homogenization temperature ranges from 150°C to 340°C and ice-melting temperatures range from -0.2°C to - 1.6°C indicating that inclusion solutions contain 0.35 to 2.7 eq. wt. % NaCl. Furthermore, δ18O and δ13C values from calcite range from 3.7 to 26.6 ‰ and -7.5 to 0.3 ‰, respectively. The presence of... |
| Tipo: Text |
Palavras-chave: Fluid inclusions; Stable isotopes; Hydrothermal; Epithermal system; SE Afar Rift; Djibouti. |
| Ano: 2019 |
URL: https://archimer.ifremer.fr/doc/00494/60528/63991.pdf |
| |
|
|
| Plasman, Matthieu; Hautot, Sophie; Tarits, Pascal; Gautier, Stephanie; Tiberi, Christel; Le Gall, Bernard; Mtelela, Khalfan; Gama, Remigius. |
| Continental break-up is controlled by several parameters and processes (rheology, inherited structures, magmatism, etc). Their impact, chronology and interactions are still poorly known and debated, particularly when rifting interacts with cratons. In order to better understand the rifting initiation in a cratonic lithosphere, we analysed 22 magnetotelluric (MT) soundings collected along two East-West profiles in two different rift segments of the North Tanzanian Divergence. The North Tanzanian Divergence, where the East African Rift is at its earliest stage, is a remarkable example of the transition between magmatic to amagmatic rifting with two clearly identified segments. Only separated by a hundred kilometers, these segments, Natron (North) and Manyara... |
| Tipo: Text |
Palavras-chave: Magnetotellurics; 3-D inversion; North Tanzanian Divergence; East African rift; Lithospheric structure; CO2 content; Seismology; Joint interpretation. |
| Ano: 2019 |
URL: https://archimer.ifremer.fr/doc/00637/74897/76062.pdf |
| |
|
|
| Authemayou, Christine; Le Gall, Bernard; Caroff, Martial; Bussien Grosjean, Denise. |
| During the Carboniferous collision stage, the West European Variscan orogen was affected by oblique convergence, wrenching, plate-scale oroclinal bending, and widespread exhumation of the deep crust. One of these exhumed units forms the Leon dome located on the northern flank of the Ibero-Armorican Arc in the western part of the Armorican massif. Structural field data from the Ouessant Island reveal kinematic changes between 330 and 300 Ma that affected the northwestern margin of the Leon dome. This margin underwent two ductile deformation phases with opposite strike-slip shear senses. Dextral strike-slip wrenching combined with orogen-normal shortening, orogen-parallel stretching, and local top-to-the-NE shearing occurred during the Leon dome formation... |
| Tipo: Text |
Palavras-chave: Variscan; Armorican massif; Gneiss dome formation; Wrenching; Orogenic syntax; Ouessant Island. |
| Ano: 2019 |
URL: https://archimer.ifremer.fr/doc/00637/74906/75947.pdf |
| |
|
|
| Daoud, Mohamed A.; Le Gall, Bernard; Maury, Rene; Rolet, Joel; Huchon, Philippe; Guillou, Herve. |
| The Tadjoura rift forms the westernmost edge of the westerly propagating Sheba ridge, between Arabia and Somalia, as it enters into the Afar depression. From structural and remote sensing data sets, the Tadjoura rift is interpreted as an asymmetrical south facing half-graben, about 40 km wide, dominated by a large boundary fault zone to the north. It is partially filled up by the 1-3 Myr old Gulf Basalts which onlapped the older Somali Basalts along its shallower southern flexural margin. The major and trace element analysis of 78 young onshore lavas allows us to distinguish and map four distinct basaltic types, namely the Gulf, Somali, Goumarre, and Hayyabley Basalts. These results, together with radiometric age data, lead us to propose a revised... |
| Tipo: Text |
|
| Ano: 2011 |
URL: http://archimer.ifremer.fr/doc/00200/31103/29502.pdf |
| |
|
| |
|
| |
|
|
| Le Gall, Bernard; Authemayou, Christine; Ehrhold, Axel; Paquette, Jean-louis; Bussien, Denise; Chazot, Gilles; Aouizerat, Arthur; Pastol, Yves. |
| An exceptional structural picture of the immerged Variscan basement, offshore the Leon metamorphic domain, is supplied by high-resolution LiDAR and echosounder data recorded in the Molene archipelago, western Brittany (France). Various types of fabrics are identified and, from in situ rock sample analyses further combined with field structural data, are interpreted on a lineament trajectory map as the trace of magmatic and tectonic structures. Our onshore/offshore study leads us to propose a two-phase kinematic model that emphasizes the role of a strike-slip duplex in an EW-trending relay zone linking the North Armorican and Pierres Noires ductile shear zones (NASZ, PNSZ). Dextral shearing occurred within a transtensional setting, synchronously with... |
| Tipo: Text |
Palavras-chave: Armorican massif; Leon metamorphic domain; Offshore structural mapping; LiDAR records; Dextral ductile shearing; U/Pb zircon/monazite dating. |
| Ano: 2014 |
URL: http://archimer.ifremer.fr/doc/00194/30490/28895.pdf |
| |
|
|
| Caroff, Martial; Le Gall, Bernard; Authemayou, Christine; Grosjean, Denise Bussien; Labry, Cyrill; Guillong, Marcel. |
| The metasedimentary and magmatic terranes in the southern part of the Ouessant Island (Western Brittany, France) are the offshore prolongation of the Leon Variscan metamorphic domain. They mainly consist of micaschists and subordinate amphibolitic lenses (meta-pillow lavas and volcaniclastic successions) cut by a swarm of trondhjemite sills, together with a large porphyritic monzogranite body, newly dated at 336 Ma, and later syeno-leucogranitic intrusions. A large spectrum of fluidal peperites, including spectacular "fiamme"-bearing breccias, is observable at the contact between metasediments and most of the intrusives. The coexistence of amphibolitized basalts, adakitic trondhjemites, and peraluminous granites in the inferred South Ouessant basin is... |
| Tipo: Text |
|
| Ano: 2016 |
URL: https://archimer.ifremer.fr/doc/00639/75091/75557.pdf |
| |
|
|
| Gernigon, Laurent; Lucazeau, Francis; Brigaud, Frederic; Ringenbach, Jean-claude; Planke, Sverre; Le Gall, Bernard. |
| High P-wave velocities (7.1-7.8 km/s) lower crustal bodies (LCBs) imaged along volcanic margins are commonly interpreted as plume and break-up-related thick mafic underplating. This interpretation is partly challenged in this paper based on new seismic observations and modelling of the outer Voring Basin (Norway). An exceptional strong amplitude reflection, the T Reflection, is particularly well defined below the North Gjallar Ridge (NGR) between 7 and 8 s TWT. The T Reflection is located near the volcanic lava flows emplaced during the NE Atlantic breakup (similar to 55-54 Ma ago) and coincides with the top of the LCB, forming a mid-crustal dome. Based on structural and temporal relationships, we show that the dome clearly influences the structural... |
| Tipo: Text |
Palavras-chave: Mantle plume; Norwegian margin; Underplating; Breakup; Modelling; Rifting; Volcanic margins. |
| Ano: 2006 |
URL: http://archimer.ifremer.fr/doc/2006/publication-1042.pdf |
| |
| Registros recuperados: 10 | |
|
|
|
