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1.
Fossil worm tubes of Cretaceous age preserved in the Bayda massive sulfide deposit of the Samail ophiolite, Oman, are apparently the first documented examples of fossils embedded in massive sulfide deposits from the geologic record. The geologic setting of the Bayda deposit and the distinctive mineralogic and textural features of the fossiliferous samples suggest that the Bayda sulfide deposit and fossil fauna are remnants of a Cretaceous sea-floor hydrothermal vent similar to modern hot springs on the East Pacific Rise and the Juan de Fuca Ridge. 相似文献
2.
Spiess FN Macdonald KC Atwater T Ballard R Carranza A Cordoba D Cox C Garcia VM Francheteau J Guerrero J Hawkins J Haymon R Hessler R Juteau T Kastner M Larson R Luyendyk B Macdougall JD Miller S Normark W Orcutt J Rangin C 《Science (New York, N.Y.)》1980,207(4438):1421-1433
Hydrothermal vents jetting out water at 380 degrees +/- 30 degrees C have been discovered on the axis of the East Pacific Rise. The hottest waters issue from mineralized chimneys and are blackened by sulfide precipitates. These hydrothermal springs are the sites of actively forming massive sulfide mineral deposits. Cooler springs are clear to milky and support exotic benthic communities of giant tube worms, clams, and crabs similar to those found at the Galápagos spreading center. Four prototype geophysical experiments were successfully conducted in and near the vent area: seismic refraction measurements with both source (thumper) and receivers on the sea floor, on-bottom gravity measurements, in situ magnetic gradiometer measurements from the submersible Alvin over a sea-floor magnetic reversal boundary, and an active electrical sounding experiment. These high-resolution determinations of crustal properties along the spreading center were made to gain knowledge of the source of new oceanic crust and marine magnetic anomalies, the nature of the axial magma chamber, and the depth of hydrothermal circulation. 相似文献
3.
A heterodont bivalve mollusk Calyptogena magnifica, from the East Pacific Rise and the Galápagos Rift hydrothermal vent areas, contains abundant hemoglobin in circulating erythrocytes. No other known heterodont clam contains a circulating intracellular hemoglobin. The hemoglobin is tetrameric and has a relatively high oxygen affinity, which varies only slightly between 2 degrees and 10 degrees C. The presence of hemoglobin in the clam may facilitate the transport of oxygen to be used in chemoautotrophic hydrogen sulfide metabolism. 相似文献
4.
An extensive plume of water enriched with helium-3 has been discovered in the deep Pacific Ocean at latitude 15 degrees S on the East Pacific Rise. In the core of the plume, at a depth of 2500 meters over the ridge crest, the helium-3/helium-4 ratio is 50 percent higher than the ratio in atmospheric helium, indicating a strong injection of mantle or primordial helium at the spreading center axis through local hydrothermal systems. The helium-3 plume is completely absent east of the rise, but it can be traced over 2000 kilometers to the west above a newly observed physical feature: a density discontinuity here caled the "ridge-crest front." The injected plume provides a unique deep-sea tracer with an asymmetric distribution which shows that the deep circulation across the rise is from east to west. The striking intensity and lateral extent of this helium-3 anomaly, compared to observations at known oceanic hydrohrmal sites, suggest that the largest hydrothermal fields in the ocean are yet to be discovered and that they will be found near 15 degrees S on the East Pacific Rise. 相似文献
5.
Germanium enrichment in the oceanic water column above the southern axis of the East Pacific Rise results from hydrothermal solutions emanating from hot springs along the rise crest. This plume signature provides a new oceanic tracer of reactions between seawater and sea floor basalts during hydrothermal alteration. In contrast to the sharp plumes of (3)He and manganese, the germanium plume is broad and diffuse, suggesting the existence of pervasive venting of low-temperature solutions off the ridge axis. 相似文献
6.
East Pacific Rise Study Group 《Science (New York, N.Y.)》1981,213(4503):31-40
Independent geological and geophysical investigations of the Mid-Ocean Ridge system have begun to focus on the nature of the magma chamber system underlying its central axis. Thermal models predict the existence of a steady-state chamber beneath a thin crustal lid ranging in thickness from 2 to 13 kilometers. The only aspect of the system that these models fail to account for is the extremely slow spreading rates. Seismological studies reveal the existence of a low-velocity zone beneath segments of the East Pacific Rise, which is thought to correspond to a chamber system having a half-width of approximately 5 to 10 kilometers. These estimates compare favorably with those derived separately through petrological investigations of deep-sea drilling results, various sampling programs, and field and laboratory studies of ophiolites. The chamber is thought to be wing-shaped and to remain continuously open; it is thought to be fed from the center while simultaneously solidifying at the sides as spreading carries the two halves apart. Progressive fractionation occurs by crystal settling coupled with repeated replenishment and magma mixing in an open steady-state system. Near-bottom studies reveal that the zone of extrusion above the chamber is narrow, but its eruptive history is cyclic in nature, in conflict with the predictions of a steady-state model. On-bottom gravity data at 21 degrees N on the East Pacific Rise reveal a negative gravity anomaly that may be related to the uppermost part of the chamber. The anomaly is only 2 kilometers wide and 1 kilometer below the sea floor. This feature may be associated with a short-term upper magma reservoir. The cyclic volcanic activity is directly related to the active phase of hydrothermal circulation responsible for the observed negative thermal anomaly. The volume of water associated with this circulation is equal to the entire ocean volume passing through the accretion zone approximately every 8 million years. This is about 0.5 percent of the world's rivers, but the effective transport rates of elements are comparable to those of rivers in that anomalies for individual elements are frequently between 100 and 1000 times the average river composition. The degree of subsurface dilution determines the final exit temperature and composition of the hydrothermal fluids, ranging from manganese domination at extreme dilution to iron at intermediate levels to sulfide deposition when low dilution occurs. The discovery of massive sulfide deposits on the East Pacific Rise is destined to have a profound impact on our understanding of ore-forming processes. Whether it will have any economic significance remains to be seen. 相似文献
7.
本文根据作者多年的调查研究，对所得栖息水深２００￣１１００ｍ的鱼类３５０种（包括５０余种我国新记录），结合有关文献资料增录１８２种，共整理出中国深海鱼类５３２种，就这些种类对中国深海鱼类的区系组成作出初步的研究，并对这些种类的优势种、地理分布、水深分布作了初步分析。 相似文献
8.
Along with specimens of manganese oxides and basalt, rocks containing more than 30 percent iron by weight and consisting mainly of poorly crystallized goethite have been dredged from the flanks of a seamount located on the East Pacific Rise. The Fe-Mn ratio varies widely among the various oxide rocks deposited at this locality and at another seamount in the same area. The deposit was probably formed by fractional precipitation of iron and manganese which had been introduced locally into the bottom water by hydrothermal solutions of volcanic origin, and by leaching from deep-sea basaltic lavas. 相似文献
9.
Hekinian R Fevrier M Avedik F Cambon P Charlou JL Needham HD Raillard J Boulegue J Merlivat L Moinet A Manganini S Lange J 《Science (New York, N.Y.)》1983,219(4590):1321-1324
Abundant massive sulfide deposits are present at the crest of the East Pacific Rise near 13 degrees North, where the opening rate is about 12 centimeters per year. Large manganese and helium-3 anomalies in seawater samples, evidence of intense present-day activity of hydrothermal springs, indicate that sulfides are still being produced along this segment of the rise. Massive sulfides also occur on adjacent off-axis seamounts. 相似文献
10.
《Science (New York, N.Y.)》1985,230(4726):687
The "turritid gastropod" referred to on page 713 (column 2, line 22) of the article "Hydrothermal vent animals: Distribution and biology" by J. Frederick Grassle (23 Aug.) should have been a "turrid gastropod." The first reference 26 on page 716 (column 2, line 14) should have been to R. A. Lutz and D. C. Rhoads, Eos 64, 1017 (1983). The statement at the end of page 716 that vent animals have metabolic rates that are orders of magnitude higher than relatives in other parts of the deep sea cannot be substantiated because, although many deep-sea organisms have low metabolic rates, benthic decapod crustacea and echinoderms from areas away from hydrothermal vents in the deep sea have metabolic rates similar to those of vent species when measured at the same temperature. This is further discussed in a forthcoming issue of the Bulletin of the Biological Society of Washington. 相似文献
11.
Johnson TC 《Science (New York, N.Y.)》1976,192(4242):887-890
A map of the preservation pattern of siliceous microfossils was constructed from an examination of 125 piston and gravity cores of Quaternary sediments from throughout the eastern tropical Pacific. Preservation is enhanced where high surface water productivity supplies a high input rate of siliceous tests to the sea floor, except in a large area north of 5 degrees N, east of the East Pacific Rise. Here a high input rate of terrigenous silicates may adversely affect preservation of biogenic opal in the sea-floor sediments. 相似文献
12.
Riedel WR 《Science (New York, N.Y.)》1967,157(3788):540-542
In sediments west of the East Pacific Rise between the equator and 20 degrees N, Eocene microfossils are recorded no farther east than 134 degrees W; Oligocene, no farther east than 125 degrees W; while Miocene and Pliocene occurrences extend closer to the crest of the rise. This distribution may result from post-Eocene spreading of the sea floor here averaging about 8 centimeters per year. 相似文献
13.
The clam Calyptogena magnifica lives at abyssal depths in association with hydrothermal venting on midocean ridges. Analysis of strontium/calcium ratios in C. magnifica shells provides a temperature proxy with submonthly time resolution. A 21-year strontium/calcium record of two clams from 9 degrees50'N on the East Pacific Rise captures the known 1991 and 1992 eruptive events, documents several additional events between 1992 and 1996, and demonstrates the absence of major hydrothermal episodes during the period 1974 to 1991. These clam archives can increase our understanding of the thermal and chemical history of midocean ridge hydrothermal and volcanic activity on decadal time scales. 相似文献
14.
Van Dover CL Humphris SE Fornari D Cavanaugh CM Collier R Goffredi SK Hashimoto J Lilley MD Reysenbach AL Shank TM Von Damm KL Banta A Gallant RM Gotz D Green D Hall J Harmer TL Hurtado LA Johnson P McKiness ZP Meredith C Olson E Pan IL Turnipseed M Won Y Young CR Vrijenhoek RC 《Science (New York, N.Y.)》2001,294(5543):818-823
Within the endemic invertebrate faunas of hydrothermal vents, five biogeographic provinces are recognized. Invertebrates at two Indian Ocean vent fields (Kairei and Edmond) belong to a sixth province, despite ecological settings and invertebrate-bacterial symbioses similar to those of both western Pacific and Atlantic vents. Most organisms found at these Indian Ocean vent fields have evolutionary affinities with western Pacific vent faunas, but a shrimp that ecologically dominates Indian Ocean vents closely resembles its Mid-Atlantic counterpart. These findings contribute to a global assessment of the biogeography of chemosynthetic faunas and indicate that the Indian Ocean vent community follows asymmetric assembly rules biased toward Pacific evolutionary alliances. 相似文献
15.
Urabe T Baker ET Ishibashi J Feely RA Marumo K Massoth GJ Maruyama A Shitashima K Okamura K Lupton JE Sonoda A Yamazaki T Aoki M Gendron J Greene R Kaiho Y Kisimoto K Lebon G Matsumoto T Nakamura K Nishizawa A Okano O Paradis G Roe K Shibata T Tennant D Vance T Walker SL Yabuki T Ytow N 《Science (New York, N.Y.)》1995,269(5227):1092-1095
A survey of hydrothermal activity along the superfast-spreading (approximately 150 millimeters per year) East Pacific Rise shows that hydrothermal plumes overlay approximately 60 percent of the ridge crest between 13 degrees 50' and 18 degrees 40'S, a plume abundance nearly twice that known from any other rige portion of comparable length. Plumes were most abundant where the axial cross section is inflated and an axial magma chamber is present. Plumes with high ratios of volatile ((3)He, CH(4), and H(2)S) to nonvolatile (Mn and Fe) species marked where hydrothermal circulation has been perturbed by recent magmatic activity. The high proportion of volatile-rich plumes observed implies that such episodes are more frequent here than on slower spreading ridges. 相似文献
16.
Mantle discontinuity structure beneath the southern east pacific rise from P-to-S converted phases 总被引：4，自引：0，他引：4
Y Shen AF Sheehan KG Dueker de Groot-Hedlin C H Gilbert 《Science (New York, N.Y.)》1998,280(5367):1232-1235
Receiver functions derived from teleseismic body waves recorded by ocean-bottom seismometers on the southern East Pacific Rise reveal shear waves converted from compressional waves at the mantle discontinuities near 410- and 660-kilometer depth. The thickness of the mantle transition zone between the two discontinuities is normal relative to the global average and indicates that upwelling beneath the southern East Pacific Rise is not associated with an excess temperature in the mantle transition zone. 相似文献
17.
Paull CK Hecker B Commeau R Freeman-Lynde RP Neumann C Corso WP Golubic S Hook JE Sikes E Curray J 《Science (New York, N.Y.)》1984,226(4677):965-967
Dense biological communities of large epifaunal taxa similar to those found along ridge crest vents at the East Pacific Rise were discovered in the abyssal Gulf of Mexico. These assemblages occur on a passive continental margin at the base of the Florida Escarpment, the interface between the relatively impermeable hemipelagic clays of the distal Mississippi Fan and the jointed Cretaceous limestone of the Florida Platform. The fauna apparently is nourished by sulfide rich hypersaline waters seeping out at near ambient temperatures onto the sea floor. 相似文献
18.
Menard HW 《Science (New York, N.Y.)》1967,155(3758):72-74
The great fracture zones of the northeastern Pacific extend into the central Pacific. At a relatively constant distance of 4500 to 4900 kilometers west of the crest of the East Pacific Rise and of its projection through North America, the typically straight and simple fracture zones branch and become more complex. However, the Clipperton fracture zone, including one branch, follows a great circle for almost 10,000 kilometers, a quarter of Earth's circumference. 相似文献
19.
Bischoff JL 《Science (New York, N.Y.)》1980,207(4438):1465-1469
Pressure-volume-temperature relations for water at the depth of the magma chamber at 21 degrees N on the East Pacific Rise suggest that the maximum subsurface temperature of the geothermal fluid is about 420 degrees C. Both the chemistry of the discharging fluid and thermal balance considerations indicate that the effective water/rock ratios in the geothermal system are between 7 and 16. Such low ratios preclude effective metal transport at temperatures below 350 degrees C, but metal solubilization at 400 degrees C and above is effective even at such low ratios. It is proposed that the 420 degrees C fluid ascends essentially adiabatically and in the process expands, cools, and precipitates metal sulfides within the upper few hundred meters of the sea floor and on the sea floor itself. 相似文献
20.
Hekinian R Fevrier M Bischoff JL Picot P Shanks WC 《Science (New York, N.Y.)》1980,207(4438):1433-1444
Massive sulfide deposits were discovered from the diving saucer Cyana on the accreting plate boundary region of the East Pacific Rise near 21 degrees N. The deposits form conical and tubular structures lying on a basaltic basement. Mineralogical and geochemical analyses showed two main types of intimately associated products: a polymetallic sulfide-rich material composed of pyrite and marcasite in association, zinc-rich phases, and copper-rich compounds, and an iron-rich oxide and hydroxide material (also called gossan) composed largely of goethite and limonite. Silicate phases such as opaline, silica, iron-silicon clay, and trace amounts of mica and zeolite are encountered in both types of material. Possible mechanisms for the formation of the sulfide deposits on the East Pacific Rise are discussed. 相似文献