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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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| Le Suave, R; Hoffert, M; Pautot, G. |
| During the world tour of R/V Jean Charcot , 2 types of polymetalic deposits have been investigated: the cobalt-rich crusts in the Tuamotu Archipelago (French Polynesia) and the manganese nodules in the Clarion-Clipperton Fracture Zone. In the South Pacific Ocean, a genetic model of site bearing cobalt-rich crusts has been identified: the polymetallic deposits are located at a 1,000 m water depth on a subsident fossil atoll built on a volcanic substrate. In the North Pacific Ocean, a 2 months cruise has been conducted on the basis of preexisting data (seabeam, bottom photographs, nodules and sediment sampling). Three types of geological environment have been characterized: a sedimentary plateau, an area particularly representative of the abyssals hills... |
| Tipo: Text |
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| Ano: 1990 |
URL: http://archimer.ifremer.fr/doc/00268/37941/36022.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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