East Pacific Rise: Hot Springs and Geophysical Experiments

Hydrothermal vents jetting out water at 380� � 30�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 Gal�pagos 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.

[1]  W. Bryan.  Regional Variation and Petrogenesis of Basalt Glasses from the FAMOUS Area, Mid-Atlantic Ridge , 1979 .

[2]  David L. Williams,et al.  Submarine Thermal Springs on the Gal�pagos Rift , 1979, Science.

[3]  R. Ballard,et al.  Massive deep-sea sulphide ore deposits discovered on the East Pacific Rise , 1979, Nature.

[4]  M. Mottl,et al.  Chemical exchange during hydrothermal alteration of basalt by seawater—I. Experimental results for major and minor components of seawater , 1978 .

[5]  Mitchell W Lyle,et al.  The chemistry of hydrothermal mounds near the Galapagos Rift , 1978 .

[6]  P. Lonsdale.  Deep-tow observations at the mounds abyssal hydrothermal field, Galapagos Rift , 1977 .

[7]  J. Lupton,et al.  Hydrothermal plumes in the Galapagos Rift , 1977, Nature.

[8]  Ken C. Macdonald,et al.  Deep-tow studies of the structure of the Mid-Atlantic Ridge crest near lat 37°N , 1977 .

[9]  T. H. Andel,et al.  Project FAMOUS: Its origin, programs, and setting , 1977 .

[10]  P. J. Fox,et al.  Density and P-wave velocity of rocks from the FAMOUS region and their implication to the structure of the oceanic crust , 1977 .

[11]  W. Bryan,et al.  Compositional variations of young basalts in the Mid-Atlantic Ridge rift valley near lat 36°49′N , 1977 .

[12]  W. Seyfried,et al.  Hydrothermal transport of heavy metals by seawater: The role of seawater/basalt ratio , 1977 .

[13]  L. L. Nettleton.  Gravity and magnetics in oil prospecting , 1976 .

[14]  Arcyana.  Transform Fault and Rift Valley from Bathyscaph and Diving Saucer , 1975, Science.

[15]  Robert D. Ballard,et al.  Manned Submersible Observations in the FAMOUS Area: Mid-Atlantic Ridge , 1975, Science.

[16]  J. Mudie,et al.  The Galapagos Spreading Centre: A Near-Bottom Geophysical Survey , 1974 .

[17]  R. Parker,et al.  The inversion of magnetic anomalies in the presence of topography , 1974 .

[18]  N. Christensen,et al.  Velocities, elastic moduli and weathering-age relations for pacific layer 2 basalts , 1973 .

[19]  R. Yeats,et al.  Iron-Rich Basal Sediments from the Eastern Equatorial Pacific: Leg 16, Deep Sea Drilling Project , 1972, Science.

[20]  J. D. Hays.  Initial Reports of the Deep Sea Drilling Project, 9 , 1972 .

[21]  R. Larson.  Near-Bottom Geologic Studies of the East Pacific Rise Crest , 1971 .

[22]  P. Roeder,et al.  Olivine-liquid equilibrium , 1970 .

[23]  T. L. Wright,et al.  A Linear Programming and Least Squares Computer Method for Solving Petrologic Mixing Problems , 1970 .

[24]  F. Spiess,et al.  East Pacific Rise Crest: A Near-Bottom Geophysical Profile , 1969, Science.

[25]  C. G. Engel,et al.  Chemical Characteristics of Oceanic Basalts and the Upper Mantle , 1965 .

[26]  S. Hammer.  Terrain corrections for gravimeter stations , 1939 .