Massive sulfides with fluid-inclusion-bearing quartz from a young seamount on the East Pacific Rise

One dredge haul from a young East Pacific Rise sqrmount, located approximately 15 km off-axis, recovered exclusively hydrothermal material that included massive sulfide, crusts consisting of euhedral drusy atacamite, and reddish brown iron oxide crusts and mud. The massive sulfide is primarily quartz, pyrite, and sphalerite, with accessory chalcopyrite, covellite, digenite, and galena; the sulfide fraction contains up to 2 ppm Au and 150 ppm Ag. Conditions of formation were estimated from fluid inclusions in quartz. Inclusion trapping temperatures were 240 + 35oC at the ambient seafloor pressure of 26 MPa, and the fluid had 4.0 wt.9o equivalent NaCl. The massive sulfide is atypical because it contains silica as quartz rather than an amorphous variety, suggesting that the usual kinetic barrier to quartz precipitation was overcome. Some of the quartz apparently replaced earlier amorphous silica, but much of it precipitated as primary quartz, entrapping fluid inclusions. Active hot springs on the seafloor that precipitate quartz have not been directly observed; however, these massive sulfides and other quartz-bearing samples from seafloor deposits suggest that subsurface diffuse flow and conductive heatloss may overcome the unfavorable kinetics of quartz precipitation.

[1]  M. Hannington,et al.  Sulfidation equilibria as guides to gold mineralization in volcanogenic massive sulfides; evidence from sulfide mineralogy and the composition of sphalerite , 1989 .

[2]  R. D. Ballard,et al.  Evidence of hydrothermal activity on Marsili Seamount, Tyrrhenian Basin. Technical report , 1989 .

[3]  Michael O. Garcia,et al.  Loihi Seamount, Hawaii: a mid-plate volcano with a distinctive hydrothermal system , 1988, Nature.

[4]  P. Rona Hydrothermal mineralization at oceanic ridges , 1988 .

[5]  Y. Fouquet,et al.  Filamentous iron-silica deposits from modern and ancient hydrothermal sites , 1988 .

[6]  M. Hannington,et al.  Mineralogy and geochemistry of a hydrothermal silica-sulfide-sulfate spire in the caldera of Axial Seamount, Juan De Fuca Ridge , 1988 .

[7]  P. Stoffers,et al.  Hydrothermal silica chimney fields in the Galapagos Spreading Center at 86°W , 1988 .

[8]  J. Alt Hydrothermal oxide and nontronite deposits on seamounts in the eastern Pacific , 1988 .

[9]  S. Varnavas,et al.  A hydrothermal manganese deposit from the Eratosthenes Seamount, Eastern Mediterranean Sea , 1988 .

[10]  M. Hannington,et al.  Gold and native copper in supergene sulphides from the Mid-Atlantic Ridge , 1988, Nature.

[11]  S. Humphris,et al.  ACTIVE VENTS AND MASSIVE SULFIDES AT 26ON (TAG) AND 23ON (SNAKEPITI ON THE MID.ATLANTIC RIDGE , 1988 .

[12]  E. Gibson,et al.  Mineralogical studies of sulfide samples and volatile concentrations of basalt glasses from the southern Juan de Fuca Ridge. , 1987, Journal of geophysical research.

[13]  T. Urabe,et al.  Hydrothermal sulfides from a submarine caldera in the Shichito-Iwojima Ridge, northwestern Pacific , 1987 .

[14]  R. Haymon,et al.  Hydrothermal sulfide and oxide deposits on seamounts near 21°N, East Pacific Rise , 1987 .

[15]  J. Delaney,et al.  Growth of large sulfide structures on the endeavour segment of the Juan de Fuca ridge , 1986 .

[16]  K. V. Damm,et al.  Chemical evolution of mid-ocean ridge hot springs☆ , 1985 .

[17]  Ray F. Weiss,et al.  Chemistry of submarine hydrothermal solutions at 21 °N, East Pacific Rise , 1985 .

[18]  W. Shanks,et al.  Mineralogy and geochemistry of a sediment‐hosted hydrothermal sulfide deposit from the Southern Trough of Guaymas Basin, Gulf of California , 1985 .

[19]  R. Hékinian,et al.  Volcanism and metallogenesis of axial and off-axial structures on the East Pacific Rise near 13 degrees N , 1985 .

[20]  R. Zierenberg,et al.  Massive sulfide deposits at 21°N, East Pacific Rise: Chemical composition, stable isotopes, and phase equilibria , 1984 .

[21]  F. Bonavia,et al.  Copper-ore grade hydrothermal mineralization discovered in a seamount in the Tyrrhenian Sea (Mediterranean): Is the mineralization related to porphyry-coppers or to base metal lodes? , 1984 .

[22]  P. J. Fox,et al.  East Pacific Rise from Siqueiros to Orozco Fracture Zones: Along‐strike continuity of axial neovolcanic zone and structure and evolution of overlapping spreading centers , 1984 .

[23]  R. Batiza,et al.  Volcanic development of small oceanic central volcanoes on the flanks of the East Pacific Rise inferred from narrow-beam echo-sounder surveys , 1983 .

[24]  R. Searle Submarine central volcanoes on the Nazca Plate — High-resolution sonar observations , 1983 .

[25]  D. Cronan,et al.  Hydrothermal iron deposits and associated sediments from submarine volcanoes off Vanuatu, southwest Pacific , 1983 .

[26]  E. Oudin,et al.  Fluid inclusion studies of deep-sea hydrothermal sulphide deposits on the East Pacific Rise near 21°N , 1982 .

[27]  R. Batiza Abundances, distribution and sizes of volcanoes in the Pacific Ocean and implications for the origin of non-hotspot volcanoes , 1982 .

[28]  A. Malahoff,et al.  Geology and chemistry of hydrothermal deposits from active submarine volcano Loihi, Hawaii , 1982, Nature.

[29]  H. Ohmoto,et al.  Stable isotopes and fluid inclusion study of anhydrite from the East Pacific Rise at 21.DEG.N. , 1982 .

[30]  E. Bonatti,et al.  Copper-iron sulfide mineralizations from the equatorial Mid-Atlantic Ridge , 1976 .

[31]  R. C. Weast CRC Handbook of Chemistry and Physics , 1973 .