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Hydrothermal plumes, hot springs, and conductive heat flow in the Southern Trough of Guaymas Basin
OLR (1985)32 (12)
D. SubmarineGeologyand Geophysics
D140. Submarine hydrology (springs, hydrothermal deposits, etc.) 85:7113 Brault, M., J.C. Marty and A. Saliot, 1984. Fatty acids from particulate matter and sediment in hydrothermal environments from the East Pacific Rise, near 13°N. Ors. Geochem., 6:217-222. The fatty acid content of particulates from vent waters is compared to that of surrounding bottom waters. The production of organic matter in vent waters is confirmed by the examination of biological and microbiological markers in the fatty acid series. An additional contribution to the organic matter content of particulates by advection and resuspension of sedimented material is discussed. The fatty acid distribution pattern of the hydrothermal sediment is very different from that of sediments collected off the ridge axis. The large abundance of microbiological markers in the hydrothermal sediment indicates a high microbiotic activity near the vents. Lab. de Phys. et Chim. Mar., Univ. P.et M.C., LA CNRS 353, Tour 24, 4 Place Jussieu, 75230 Paris Cedex 05, France. 85:7114 Lonsdale, Peter and Keir Becket, 1985. Hydrothermal plumes, hot springs, and conductive heat flow in the Southern Trough of Guaymas Basin. Earth planet. Sci. Letts, 73(2-4):211-225. A number of thermal plumes, most of which overlie mineral deposits, were examined on ten Alvin dives and a 9-km segment of the axial rift valley was mapped by Deep Tow. Plumes, anhydrite and sulfide deposits, chimneys, and fluid discharge are described here. The pattern of deposits and the measured heat flow suggest that 'shallow sills...act as cap rocks for intense, shallow hydrothermal circulations above a magma chamber.' Discharge occurs mainly through tectonic fractures in and around the sills; recharge probably is from regional sources. Scripps Inst. of Oceanogr., La Jolla, CA 92093, USA. (msg) 85:7115 Rona, P.A., 1985. Hydrothermal mineralization at slow-spreading centers: Red Sea, Atlantic Ocean, and Indian Ocean. Mar. Min., 5(2):117-145. A review of field evidence and thermal considerations supports the potential for the presence of a variety of hydrothermal mineral deposits at slowspreading centers. Complete series of hydrothermal mineral phases ranging from sulfides to oxides in various forms are known to occur at slow-spreading centers, although the proportion, frequency of
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occurrence and mineral distribution may differ significantly from deposits found at intermediate and fast-spreading centers. A composite model of hydrothermal mineralization at slow-spreading ridges is included. NOAA, AOML, 4301 Rickenbacker Causeway, Miami, FL 33149, USA. (hbf)
85:7116 Simoneit, B.R.T., 1984. Hydrothermal effects on organic matter--high vs low temperature components. Ors. Geochem., 6:857-864. Samples from the Guaymas Basin, Central Gulf of California, showed significant accumulations of petroliferous exudate. The hydrothermal petroleums were derived from immature organic matter at depth by thermal alteration, rapid quenching by hydrothermal removal, and condensation at the sea bed. Under the proper geological setting, 'a hydrothermally altered sediment province could become a significant petroleum source.' Coll. of Oceanogr., Oregon State Univ., Corvallis, OR 97331, USA. (mwf)
D170. Historical geology, stratigraphy 85:7117 Boulton, G.S., G.D. Smith, A.S. Jones and J. Newsome, 1985. Glacial geology and glaciology of the last mid-latitude ice sheets. J. geol. Soc., Lond., 142(3):447-474. Sch. of Environ. Sci., Univ. of East Anglia, Norwich, UK. 85:7118 Dinter, D.A., 1985. Quaternary sedimentation of the Alaskan Beaufort shelf: influence of regional tectonics, fluctuating sea levels, and glacial sediment sources. Tectonophysics, 114(!-4): 133161. High-resolution reflection seismic records of the top 100-m of shelf sediments detail the offshore extension of the Quaternary Gubik Formation and provide information on glacioeustatic lowstands and marine transgressions situated below present-day sea level. In general, the deposits consist of wedgeshaped transgressive units, which thicken to the shelf break, then diminish as a result of landslides and slumps. The youngest wedge, locally >40-m thick, is thought to be Late Wisconsinian or younger. The presence of exotic relict gravels is attributed to rafting by icebergs which became grounded on the Alaskan shelf. USGS, 345 Middlefield Rd., Menlo Park, CA 94025, USA. (hbf)
D. SubmarineGeologyand Geophysics
D140. Submarine hydrology (springs, hydrothermal deposits, etc.) 85:7113 Brault, M., J.C. Marty and A. Saliot, 1984. Fatty acids from particulate matter and sediment in hydrothermal environments from the East Pacific Rise, near 13°N. Ors. Geochem., 6:217-222. The fatty acid content of particulates from vent waters is compared to that of surrounding bottom waters. The production of organic matter in vent waters is confirmed by the examination of biological and microbiological markers in the fatty acid series. An additional contribution to the organic matter content of particulates by advection and resuspension of sedimented material is discussed. The fatty acid distribution pattern of the hydrothermal sediment is very different from that of sediments collected off the ridge axis. The large abundance of microbiological markers in the hydrothermal sediment indicates a high microbiotic activity near the vents. Lab. de Phys. et Chim. Mar., Univ. P.et M.C., LA CNRS 353, Tour 24, 4 Place Jussieu, 75230 Paris Cedex 05, France. 85:7114 Lonsdale, Peter and Keir Becket, 1985. Hydrothermal plumes, hot springs, and conductive heat flow in the Southern Trough of Guaymas Basin. Earth planet. Sci. Letts, 73(2-4):211-225. A number of thermal plumes, most of which overlie mineral deposits, were examined on ten Alvin dives and a 9-km segment of the axial rift valley was mapped by Deep Tow. Plumes, anhydrite and sulfide deposits, chimneys, and fluid discharge are described here. The pattern of deposits and the measured heat flow suggest that 'shallow sills...act as cap rocks for intense, shallow hydrothermal circulations above a magma chamber.' Discharge occurs mainly through tectonic fractures in and around the sills; recharge probably is from regional sources. Scripps Inst. of Oceanogr., La Jolla, CA 92093, USA. (msg) 85:7115 Rona, P.A., 1985. Hydrothermal mineralization at slow-spreading centers: Red Sea, Atlantic Ocean, and Indian Ocean. Mar. Min., 5(2):117-145. A review of field evidence and thermal considerations supports the potential for the presence of a variety of hydrothermal mineral deposits at slowspreading centers. Complete series of hydrothermal mineral phases ranging from sulfides to oxides in various forms are known to occur at slow-spreading centers, although the proportion, frequency of
1023
occurrence and mineral distribution may differ significantly from deposits found at intermediate and fast-spreading centers. A composite model of hydrothermal mineralization at slow-spreading ridges is included. NOAA, AOML, 4301 Rickenbacker Causeway, Miami, FL 33149, USA. (hbf)
85:7116 Simoneit, B.R.T., 1984. Hydrothermal effects on organic matter--high vs low temperature components. Ors. Geochem., 6:857-864. Samples from the Guaymas Basin, Central Gulf of California, showed significant accumulations of petroliferous exudate. The hydrothermal petroleums were derived from immature organic matter at depth by thermal alteration, rapid quenching by hydrothermal removal, and condensation at the sea bed. Under the proper geological setting, 'a hydrothermally altered sediment province could become a significant petroleum source.' Coll. of Oceanogr., Oregon State Univ., Corvallis, OR 97331, USA. (mwf)
D170. Historical geology, stratigraphy 85:7117 Boulton, G.S., G.D. Smith, A.S. Jones and J. Newsome, 1985. Glacial geology and glaciology of the last mid-latitude ice sheets. J. geol. Soc., Lond., 142(3):447-474. Sch. of Environ. Sci., Univ. of East Anglia, Norwich, UK. 85:7118 Dinter, D.A., 1985. Quaternary sedimentation of the Alaskan Beaufort shelf: influence of regional tectonics, fluctuating sea levels, and glacial sediment sources. Tectonophysics, 114(!-4): 133161. High-resolution reflection seismic records of the top 100-m of shelf sediments detail the offshore extension of the Quaternary Gubik Formation and provide information on glacioeustatic lowstands and marine transgressions situated below present-day sea level. In general, the deposits consist of wedgeshaped transgressive units, which thicken to the shelf break, then diminish as a result of landslides and slumps. The youngest wedge, locally >40-m thick, is thought to be Late Wisconsinian or younger. The presence of exotic relict gravels is attributed to rafting by icebergs which became grounded on the Alaskan shelf. USGS, 345 Middlefield Rd., Menlo Park, CA 94025, USA. (hbf)