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| Registros recuperados: 20 | |
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| Bellaiche, G.; Cheminee, J.l.; Francheteau, Jean; Hekinian, Roger; Le Pichon, Xavier; Needham, H.d.; Ballard, R.d.. |
| THE Rift Valley of the Mid-Atlantic Ridge, within which lies a segment of the accreting plate boundary between Africa and North America, is well defined between 36°40'N and 36°55' N. It is about 30 km wide and 1.5 km deep in that area (Fig. 1). This small portion of the rift, WSW of the Azores, was chosen as the primary target of the French-American Mid-Oceanic Undersea Survey (FAMOUS) programme, and many surface ship studies have heen conducted already. We report here preliminary results of seven dives into the deepest part of the Rift Valley that were made by the bathyscaphe Archimède during the summer of 1973. [NOT CONTROLLED OCR] |
| Tipo: Text |
Palavras-chave: Histoire Ifremer. |
| Ano: 1974 |
URL: http://archimer.ifremer.fr/doc/1974/publication-5443.pdf |
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| Patriat, Martin; Klingelhoefer, Frauke; Aslanian, Daniel; Contrucci, Isabelle; Gutscher, Marc-andré; Talandier, Jacques; Avedik, Felix; Francheteau, Jean; Weigel, Wilfried. |
| [1] In French Polynesia, the young (< 5Ma) Society Islands appear to result from intraplate volcanism, while the old (>50 Ma) Tuamotu plateau was likely created at or near the ridge axis. The structure of the crust between those two archipelagoes is constrained by a 300 km long refraction seismic profile. Crustal and upper mantle arrivals recorded by 6 OBHs and 3 land stations were used to provide a 2D model of the crust. Results of our study, combined with that of Grevemeyer et al. [2001] show a slight flexure below the Tahiti apron, while a deep crustal root (21 km) underlies the Tuamotu plateau. These structures reflect the different modes of load emplacement and compensation mechanisms between these two volcanic edifices, consistent with an... |
| Tipo: Text |
Palavras-chave: Volcanic Islands; Flexure; Hotspot; Refraction methods; French Polynesia. |
| Ano: 2002 |
URL: http://archimer.ifremer.fr/doc/2002/publication-621.pdf |
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| Francheteau, Jean; Needham, H.d.; Choukroune, P.; Juteau, T.; Seguret, M.; Ballard, R.d.; Fox, J.p.; Normark, W.r.; Carranza, A.; Cordoba, D.; Guerrero, J.; Rangin, C.. |
| A submersible study has been conducted in February - March 1978 at the axis of the East Pacfic Rise near 21°N. The expedition CYAMEX, the first submersible program to be conducted on the East Pacific Rise, is part of the French-American-Mexican project RiTA (Rivera-Tamayo), a 3-year study devoted to detailed geological and geophysical investigations of the East Pacific Rise Crest. On the basis of the 15 dives made by CYANA in the axial area of the Rise, a morphological and tectonic zonation can be established for this moderately-fast spreading center. A narrow, 0.6 to 1.2 km wide zone of extrusion (zone 1), dominated by young lava flows, is flanked by a highly fissured and faulted zone of extension (zone 2) with a width of 1 to 2 km. Further out, zone... |
| Tipo: Text |
Palavras-chave: Histoire Ifremer. |
| Ano: 1980 |
URL: http://archimer.ifremer.fr/doc/1980/publication-5332.pdf |
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| Francheteau, Jean; Le Pichon, Xavier. |
| A plate tectonic model of the early opening of the south atlantic is used to des cibe the structural framework of the continental margins and adjacent oceanic and coastal areas on both sides of the ocean. It is proposed that major offsets of the continental margins necessarily induce the subsidence of coastal basins where fracture zones intersect the continents. The configuration of the accreting plate-margin boundary gradually developed throughout the opening of the ocean after Late Jurassic time. [NOT CONTROLLED OCR] |
| Tipo: Text |
Palavras-chave: Histoire Ifremer. |
| Ano: 1972 |
URL: http://archimer.ifremer.fr/doc/1972/publication-5033.pdf |
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| Needham, H.d.; Francheteau, Jean. |
| The Rift Valley between 36° 42'N and 36° 55'N in the Atlantic Ocean is 31 km wide, with half-widths of 12 and 19 km for the western and eastern sides respectively. Both outer edges of the Rift Valley stand about 1500 m above an Inner Floor where very fresh pillow lavas occur. The Inner Floor probably includes the locus of new crust ; and its bordering slopes, which are particularly well-defined on the western side, limit to less than about 2.5 km the width of the zone over which new crust may have evolved with little or no vertical displacement. The width of the locus of new crust may be less than 0.5 km between 36° 45'N and 36° 47'N, where the deepest slopes of the Rift Valley walls nearly merge. Near 36° 50'N, the Inner Floor accommodates an... |
| Tipo: Text |
Palavras-chave: Histoire Ifremer. |
| Ano: 1974 |
URL: http://archimer.ifremer.fr/doc/1974/publication-5159.pdf |
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| Le Pichon, Xavier; Hekinian, Roger; Francheteau, Jean; Carre, Daniel. |
| IN OCTOBER 1972, the bathyscaphe Archimède made a series of training dives-to a 2600-m water-depth off northwest Corsica in order to test new equipment.Two of these dives (72-5 and 72-7) were made at the limit of the lower continental slope and the abyssal plain near an acoustic transponder (X'4 in Fig. 1) with respect to which the submersible could position itself with an accuracy of 10 to 200 m within a radius of 1450 m. The position of X'4 with respect to the geographic grid is not known to better than 200 to 300 m. We feel, however, that the position of the transponder shown on Fig. 1 leads to a good agreement with the relief revealed by the bathymetric map. These dives, in spite of technical shortcomings, gave some unexpected information about the... |
| Tipo: Text |
Palavras-chave: Histoire Ifremer. |
| Ano: 1975 |
URL: http://archimer.ifremer.fr/doc/1975/publication-5452.pdf |
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| Hekinian, Roger; Bideau, Daniel; Francheteau, Jean; Cheminee, Jean-louis; Armijo, Rolando; Lonsdale, Peter; Blum, Norbert. |
| The Hess Deep, a rifted oval-shaped depression located east of the Galapagos Triple Junction at the tip of the Cocos-Nazca ridge (about 101-degrees-W, 2-degrees-N), was explored in 1988 during 21 submersible dives. A total of 11 dives were devoted to the exploration of the E-W trending Intrarift ridge (15 km in length, 3000-5400 m in depth) north of the Hess Deep depression. The Intrarift ridge represents, an outcrop of recent (1 m.y.) crustal and subcrustal material created at the axis of the East Pacific Rise (EPR), and emplaced during the lithospheric extention responsible for the westward propagation of the Cocos-Nazca rift (Francheteau et al., 1990). The lithospheric block has undergone cataclastic deformation and was dislocated by tectonic activity... |
| Tipo: Text |
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| Ano: 1993 |
URL: http://archimer.ifremer.fr/doc/00193/30391/29225.pdf |
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| Francheteau, Jean; Juteau, T.; Rangin, C.. |
| Observations of peculiar volcanic objects, made by a submersible on the deep sea floor at a depth of about 2.600 m at and near the axis of the East Pacific Rise during the CYAMEX expedition as part of the RITA Project are presented here. Two basic types of flow forms were observed within the crestal area of the East Pacitic Rise : pillow flows and fluid lavas, the latter sometimes overlying massive flows. The East Pacific Rise at 21°N comprises an axial, unfaulted extrusion zone bordered by an extension zone chararterised by faulting. Pillow flows occupy the innermost or extrusion zone and constitute small elongated volcanic highs. [NOT CONTROLLED OCR] |
| Tipo: Text |
Palavras-chave: Histoire Ifremer. |
| Ano: 1979 |
URL: http://archimer.ifremer.fr/doc/1979/publication-5395.pdf |
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| Cheminee, J-l; Hekinian, Roger; Talandier, J; Albarede, F; Devey, C W; Francheteau, Jean; Lancelot, Y. |
| The Teahitia-Mehetia hot spot region located in the southeastern extension of the Society Islands chain, near 18 degree S-148 degree W, consists of several active volcanoes. The distribution of recent volcanic activity correlates with seismic epicenters, and covers an area of more than 1,000 km super(2). Intermittent volcanic activity has given rise to large (> 1,000 m high) and small (< 500 m high) edifices composed of various types of flows. Several recent volcanic events have produced a suite of alkalic rocks ranging from ankaramites, through alkali basalts to trachy-phonolites. The presence of altered MORB-like tholeiites on one small seamount suggests that a different mantle source material was involved in forming some of the crust in this hot... |
| Tipo: Text |
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| Ano: 1990 |
URL: http://archimer.ifremer.fr/doc/00268/37896/35977.pdf |
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| Francheteau, Jean; Choukroune, P.; Hekinian, Roger; Le Pichon, Xavier; Needman, H.d.. |
| Data from rock-dredging have often been used to infer that oceanic fracture zones provide a 'window' into layers of the oceanic crust lying at a depth below the surface that is approximately equivalent to the vertical offset of the fracture zone, and thus permit the reconstruction of a crustal stratigraphy for the whole of acoustic layer 2 (commonly considered to have an average thickness of ~2 km) and in some interpretations for the upper part of layer 3. Alternatively, it has been suggested that fracture zones are preferential sites of serpentinite mega-dykes differing in composition from layer 3 but containing inclusions of the third layer. The published data indicate that basalts and basaltic rubble are abundant in fracture zones and on analysis do not... |
| Tipo: Text |
Palavras-chave: Histoire Ifremer. |
| Ano: 1976 |
URL: http://archimer.ifremer.fr/doc/1976/publication-5109.pdf |
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| Francheteau, Jean; Needham, H.d.; Choukroune, P.; Juteau, T.; Seguret, M.; Ballard, R.d.; Fox, P.j.; Normark, W.; Carranza, X; Cordoba, D.; Guerrero, J.; Rangin, C.; Bougault, Henri; Cambon, Pierre; Hekinian, Roger. |
| Massive ore-grade zinc, copper and iron sulphide deposits have been found at the axis of the East Pacific Rise.Although their presence on the deep ocean-floor had been predicted there was no supporting observational evidence. The East Pacific Rise deposits represent a modern analogue of Cyprus-type sulphide ores associated with ophiolitic rocks on land.They contain at least 29% zinc metal and 6% metallic copper.Their discovery will provide a new focus for deep-sea exploration, leading to new assessments of the concentration of metals in the upper layers of the oceanic crust. [NOT CONTROLLED OCR] |
| Tipo: Text |
Palavras-chave: Histoire Ifremer. |
| Ano: 1979 |
URL: http://archimer.ifremer.fr/doc/1979/publication-5278.pdf |
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| Molnar, Peter; Francheteau, Jean. |
| IF reconstructions of plate tectonic movement based on magnetic anomaly data are found to be inconsistent with reconstructions based on palaeomagnetic data (see refs 1-3) it may indicate that one or more of the basic assumptions of the plate tectonic model is erroneous : the age or identification of a particular anomaly may be incorrect, the pole positions or sample ages may be unreliable or there may be an error in assessing plate rigidity. We present an example of inconsistency between the two types of data and explore its implications for the chronology of magnetic reversals during the late Cretaceous and early Tertiary and for the age of the Deccan Traps. [NOT CONTROLLED OCR] |
| Tipo: Text |
Palavras-chave: Histoire Ifremer. |
| Ano: 1975 |
URL: http://archimer.ifremer.fr/doc/1975/publication-4985.pdf |
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| Chenet, P. Y.; Francheteau, Jean. |
| It is well known that a general relationship exists between the age of the earth's crust at mid-ocean ridges and its depth (Menard, 1969; Sclater and Francheteau, 1970; Sclater et al., 1971). Depths increase from 2500 300 meters at a spreading center, to 5800 5300 meters in oceanic crust of Early Cretaceous to Late Jurassic age (Figure 1; Sclater et al., 1971). The 3 km deepening of the oceanic crust can be satisfactorily explained by simple models involving the thermal structure of the oceanic lithosphere during its spreading from the axis of ridges to the adjacent oceanic basins (Sclater and Francheteau, 1970; Davis and Lister, 1974). It has also been suggested that structural highs like aseismic ridges, which have not come about by accretion,... |
| Tipo: Text |
Palavras-chave: Histoire Ifremer. |
| Ano: 1980 |
URL: http://archimer.ifremer.fr/doc/1980/publication-5393.pdf |
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| Francheteau, Jean; Needman, David; Choukroune, Pierre; Juteau, Thierry; Seguret, Michel; Ballard, Robert D.; Fox, Jeffery; Normark, William; Carranza, Arturo; Cordoba, Diego; Guerrero, José; Rangin, Claude; Bougault, Henri; Cambon, Pierre; Hekinian, Roger. |
| Massive zinc, copper and iron sulfide ore deposits have been found at the axis of the East Pacific Rise. Although several investigators had predicted their presence on the deep-ocean floor, there was no supporting observational evidence. The East Pacific Rise deposits represent an appealing modern analogue of Cyprustype ores associated with ophiolitic rocks on land. They contain up to about 29% zinc metal and up to at least nearly 3% metallic copper. Their discovery will provide a new focus for deep-sea exploration, leading to new assessments of the concentration of noble metals in the upper layers of the oceanic crust. [NOT CONTROLLED OCR] |
| Tipo: Text |
Palavras-chave: Histoire Ifremer. |
| Ano: 1978 |
URL: http://archimer.ifremer.fr/doc/1978/publication-5388.pdf |
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| Rangin, C.; Francheteau, Jean. |
| Manned submersible observations on a transect from the axis of the East Pacific Rise (21°N) to the area of the Brunhes-Matuyama magnetic inversion were made during the Cyamex and Rise diving phases of the Rita project. In the northern part of the study area, axial, linear. 400 to 600 m-wide topographic highs are formed by relatively unfaulted fresh pillow-lava-flows (zone 1). Flanking the axis of recent volcanism is a 1,200 to 1.500 m-wide zone of highly fractured volcanic hilly terrain that represents the main region of extension as expressed on the surface (zone 2). In the southern part of the study area, the volcanic highs of zones 1 and 2 are flooded by fluid lava flows forming a gentle topography. In both areas, this central part of the Rise is... |
| Tipo: Text |
Palavras-chave: Histoire Ifremer. |
| Ano: 1981 |
URL: http://archimer.ifremer.fr/doc/1981/publication-5330.pdf |
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| Registros recuperados: 20 | |
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