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| Registros recuperados: 30 | |
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| Hoffert, M; Perseil, A; Hekinian, Roger; Choukroune, P; Needham, Hd; Francheteau, J; Le Pichon, X. |
| Deep-sea hydrothermal deposits were observed, mapped and sampled in situ with the submersible "Cyana" in the Famous area of the Mid-Atlantic Ridge.Two neighbouring fields, each covering an area of about 600 m2, are associated with low, E-W trending sediment-covered ridges that lie at a depth of about 2 700 m close to the axis of Transform Fault "A".In each field the deposits are thicker (up to about 1 m) close to the small, fissure-like vents through which they were evidently delivered. Despite their heterogeneous composition, their mineralogical and chemical variations have an orderly pattern.The principal constituents are a green clay-rich material, and Fe-Mn oxides in the form of black concretions. The relative abundances of these products vary with... |
| Tipo: Text |
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| Ano: 1978 |
URL: http://archimer.ifremer.fr/doc/1978/publication-5216.pdf |
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| Hekinian, Roger; Rosendahl, Bruce R.; Natland, James H.. |
| Two distinct sedimentary facies produced by sea-floor hydrothermal activity were cored during Deep Sea Drilling Project Leg 54. The first is equivalent to the typical basal iron- and manganese-rich, clayey mud recovered at many DSDP sites. It was sampled as a dispersed component throughout the cores taken in small sediment ponds in several sites within 120 km of the East Pacific Rise at 9°N. We infer that this component was originally deposited as iron hydroxides dispersed from high-temperature vents over the axial magma chamber of the East Pacific Rise. In the sediments, the iron hydroxides have reacted diagenetically with siliceous microfossil tests and detrital clays to form K- and Fe-rich clays with variable SiO(2)/Fe(2)O(3) and... |
| Tipo: Text |
Palavras-chave: Histoire Ifremer. |
| Ano: 1980 |
URL: http://archimer.ifremer.fr/doc/1980/publication-5328.pdf |
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| Bideau, Daniel; Hekinian, Roger. |
| Small-scale distribution of basaltic compositions along the mid-ocean ridge crests suggests that the magmatic processes are sensitive to spatial and temporal fluctuations related to proximity of ridge hot spots, changes in spreading rate, thermal boundary effects associated with ridge offsets, off-axis volcanoes and ridge propagators, and variations in magma supply through time. A detailed sampling of the East Pacific Rise (EPR) axis, near 13 degrees N, revealed that complex basalt compositional variations unrelated to morphology and structure occur both on the ridge axis and on nearby off-axis seamounts. This small-scale heterogeneity is attributed to successive magmatic cycles separated by periods of quiescence (amagmatic phases) where each cycle... |
| Tipo: Text |
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| Ano: 1995 |
URL: http://archimer.ifremer.fr/doc/00258/36974/35516.pdf |
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| Boucault, H.; Hekinian, Roger. |
| Dredged rocks from an area of about 15 km² within the inner floor and on the adjacent walls of the Rift Valley were collected. Based on petrographic and chemical data, four types of basaltic rocks were recognized: (1) picritic basalts with olivine xenocrysts, Ti02 inf 0.6%, K20 inf 0.l%, (2) olivine basalts with olivine megacrysts, Ti02=0.8-1.5%, K20=0.1-0.2%, (3) highly phyric and moderately phyric plagioclase basalts with megacrystic plagioclase, Ti02 inf 1.3%, K20 inf 0.3%, and (4) pyroxene basalts with pyroxene > plagioclase, Ti02=0.8-1%, K20=0.2-0.4%. The Cr and Ni having high partition coefficients show different variation trends for each type of rock and their values decrease continuously as crystallization proceeds within each type of basalt. It... |
| Tipo: Text |
Palavras-chave: Histoire Ifremer. |
| Ano: 1974 |
URL: http://archimer.ifremer.fr/doc/1974/publication-5460.pdf |
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| Hekinian, Roger; Bideau, Daniel; Hebert, Réjean; Niu, Yaoling. |
| The Garrett transform is characterized by recent (zero age) volcanic activity located within the active tectonic domain of the transform valley at depths greater than the 3500 m. This intratransform volcanic activity contributed to the formation of constructional edifices forming ridges (>300 m in height) and small mounds (<20 m in height) built near slivers of serpentinized peridotites. The erupted lavas are depleted mid ocean ridge basalts (MORBs) with low ratios of K/Ti (0.02-0.11), Zr (30-100 ppm), Y (18-50 ppm), and (La/Sm)(N) (0.25-0.60). Their more depleted nature and smaller range of variability for the compatible elements (Ni=70-180 ppm, Mg#=0.58-0.71, where Mg# is the magnesium number (=Mg+2/Mg+2+Fe+2)) are the main points of difference... |
| Tipo: Text |
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| Ano: 1995 |
URL: http://archimer.ifremer.fr/doc/00259/36975/35515.pdf |
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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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| Hekinian, Roger; Thompson, Geoffrey. |
| New chemical analyses and a review of published data show that there is a compositional diversity between volcanics of basaltic composition found in the M.A.R. rift valley, M.A.R. transform faults and aseismic ridges. The basaltic rocks from, the M.A.R. transform faults are less mafic (depleted in olivine content) than those from the M.A.R. rift valley. The transform fault basalts have a higher range of TiO2 content (1-4%), of Fe2O3 + FeO content (8-14%) and a lower range of Cr content (50-500 ppm) and Ni content (50-300 ppm). The volcanics from aseismic ridges around the world are considered to be the more felsic types of the two provinces. They have a higher range of variation for their TiO2, and Fe203 + Fe0 (1.6-5% ; 9-15% ; respectively) and a lower... |
| Tipo: Text |
Palavras-chave: Histoire Ifremer. |
| Ano: 1976 |
URL: http://archimer.ifremer.fr/doc/1976/publication-5011.pdf |
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| Hekinian, Roger; Cheminee, J; Dubois, J; Stoffers, P; Scott, S; Guivel, C; Garbe Schonberg, D; Devey, C; Bourdon, B; Lackschewitz, K; Mcmmurtry, G; Le Drezen, Eliane. |
| Multibeam bathymetry and bottom imaging (Simrad EM12D) studies on an area of about 9500 km(2) were conducted over the Pitcairn hotspot near 25degrees10'S, 129degrees 20'W In addition, 15 dives with the Nautile submersible enabled us to obtain ground-true observations and to sample volcanic structures on the ancient ocean crust of the Farallon Plate at 3500-4300 in depths. More than 100 submarine volcanoes overprint the ancient crust and are divided according to their size into large ( > 2000 in in height), intermediate (500-2000 in high) and small ( < 500 in high) edifices. The interpretation of seafloor backscatter imagery accompanied by submersible observations and sampling enabled us to infer that the total volume of submarine lava erupted during... |
| Tipo: Text |
Palavras-chave: Petrology; Volcanic sequences; Morphology; Volcanism; Hotspot. |
| Ano: 2003 |
URL: https://archimer.ifremer.fr/doc/2003/publication-784.pdf |
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| Hekinian, Roger. |
| THE Walvis Ridge is a non-continuous aseismic feature in the south-eastern Atlantic Ocean with a general trend north-east/ south-west. Close to the principal interruptions of the ridge is a north-south topographiç lineation shown on Simpson's map (Fig. 1). The ridge appears to be attached at its northeast end to the shelf of Angola and South-west Africa and at its south-west end to the east flank of the Mid-Atlantic Ridge through two volcanic islands, Tristan da Cunha and Gough (Fig. 1). These two islands are made up of recent alkalibasalt-trachyte suite². . The geology of the Walvis Ridge has remained relatively unknown. [NOT CONTROLLED OCR] |
| Tipo: Text |
Palavras-chave: Histoire Ifremer. |
| Ano: 1972 |
URL: http://archimer.ifremer.fr/doc/1972/publication-5124.pdf |
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| Rosendahl, Bruce R.; Hekinian, Roger; Natland, James H.; Warren, Nick; Petersen, Nikolai; Roggenthen, William; Briqueu, Louis. |
| The Pacific phase of IPOD ocean crust drilling was initiated with Leg 54, the region targeted for study by the Ocean Crust Panel being survey area PT-4 (Figure 1) (and Plate 1 [in back pocket]) north of the Siqueiros fracture zone on the western flank of the East Pacific Rise (EPR). The original purpose of this leg was to establish a type section for fast-spreading, nonrifted crust by direct sampling with stratigraphic control. We anticipated that this section would serve, in part, as a standard of comparison for other type sections, such as the Mid-Atlantic Ridge (MAR). [NOT CONTROLLED OCR] |
| Tipo: Text |
Palavras-chave: Histoire Ifremer. |
| Ano: 1980 |
URL: http://archimer.ifremer.fr/doc/1980/publication-5325.pdf |
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| Hekinian, Roger; Fevrier, M.. |
| Deep-sea hydrothermal deposits from the accreting plate boundaries of the Rift valley in the gulf of Aden of the Galapagos spreading center of the Rift valley on the Mid-Atlantic Ridge near 26° North and from Transform fault "A" on the Mid-Atlantic Ridge near 37° North are studied and compared. Two main types of products are found occurring in all these areas.1 ) Dark-brown Fe-Mn concretions made up essentially of todorokite and birnessite and 2) A variegated clay-rich material composed mainly ol Fe-Si-rich smectite.In general the textural appearance, the mineralogy and the chemistry of the hydrothermal maicrial from the various localities are similar. Secondary alteration products found in basaltic rocks are compared with the clay-rich material from the... |
| Tipo: Text |
Palavras-chave: Histoire Ifremer. |
| Ano: 1979 |
URL: http://archimer.ifremer.fr/doc/1979/publication-5265.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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| 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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| Hekinian, Roger; Rosendahl, Br; Cronan, Ds; Dmitriev, Y; Fodor, Rv; Goll, Rm; Hoffert, M; Humphris, Se; Mattey, Dp; Natland, J; Petersen, N; Roggenthen, W; Schrader, El; Srivastava, Rk; Warren, N. |
| Relatively thick (up to 15 m) hydrothermal deposits from the southern flank of the Galapagos spreading center were drilled on a crust of about 0.62 myr old (magnetic age), during Leg 54 of the "Glomar Challenger" in the central Eastern Pacific Ocean. A stratigraphic sequence of ferrobasalt, pelagic oozes, and hydrothermal deposits of green clay-rich material and Fe-Mn concretions were recovered. The green clay-rich material (Fe-Si type of smectite) is also found interlayered between the pelagic ooze and filling veins, veinlets and vesicles in the drilled basement rocks. The low transitional metal content (Cu < 150 ppm). Ni < 100 ppm and Co < 200 ppm) and the nature of the green clay-rich material from the Galapagos deposits make them comparable to... |
| Tipo: Text |
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| Ano: 1978 |
URL: http://archimer.ifremer.fr/doc/1978/publication-5254.pdf |
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| Hekinian, Roger; Chaigneau, M.; Cheminee, J.l.. |
| During the 1972 Midlante* cruise of the RV Jean Charcot to survey a limited area of the rift valley south of the Azores, a dredge (CH-DR11) was taken at a depth of 1,360 fathoms in a depression near the foot of the eastern wall at latitude 36° 49.3' N and longitude 33° 15' W. Two types of rocks were recognized from their structure and their degree of weathering. One type is "slab-like" rock, 2 to 13 cm in diameter and 1 to 2 cm thick (Fig. la and b). The other type of rock consists of oval glassy pebbles (1 to 5 cm in diameter, Fig. 1c) which were observed to jump and explode, one or two at a time, for 3 d after the dredge haul was emptied on to the deck of the ship. [NOT CONTROLLED OCR] |
| Tipo: Text |
Palavras-chave: Histoire Ifremer. |
| Ano: 1973 |
URL: http://archimer.ifremer.fr/doc/1973/publication-5155.pdf |
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| Natland, James H.; Rosendhal, Bruce; Hekinian, Roger; Dmitriev, Yuri; Fodor, Ronald V.; Goll, Robert M.; Hoffert, Michel; Humphris, Susan E.; Mattey, David P.; Peterson, Nikolai; Roggenthen, William; Schrader, Edward L.; Srivasiava, Ramesh K.; Warren, Nick. |
| The Galapagos mounds sea-floor hydrothermal system is at least 300,000 years old and once produced manganese-poor sediments, which nearly blanketed the area of the present mounds field. Present-day mound deposits are limited manganese-rich exposures, suggesting that the system has changed from rock- to water-dominated and has diminished in intensity with time. [NOT CONTROLLED OCR] |
| Tipo: Text |
Palavras-chave: Histoire Ifremer. |
| Ano: 1979 |
URL: http://archimer.ifremer.fr/doc/1979/publication-5382.pdf |
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| Registros recuperados: 30 | |
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