Hydrothermal mineralization at slow-spreading center: Red Sea, Atlantic Ocean, and Indian Ocean

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  • OLR (1985) 32 (12) D. Submarine Geology and Geophysics 1023

    D140. Submarine hydrology (springs, hy- drothermal 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 13N. 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 resuspen- sion of sedimented material is discussed. The fatty acid distribution pattern of the hydrothermal sed- iment is very different from that of sediments collected off the ridge axis. The large abundance of microbiological markers in the hydrothermal sed- iment 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. Hydro-

    thermal 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 circu- lations 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 consider- ations supports the potential for the presence of a variety of hydrothermal mineral deposits at slow- spreading 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

    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 Ricken- backer Causeway, Miami, FL 33149, USA. (hbf)

    85:7116 Simoneit, B.R.T., 1984. Hydrothermal effects on

    organic matter--high vs low temperature com- ponents. 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 hydro- thermal removal, and condensation at the sea bed. Under the proper geological setting, 'a hydro- thermally 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): 133- 161.

    High-resolution reflection seismic records of the top 100-m of shelf sediments detail the offshore exten- sion 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 wedge- shaped 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)


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