Chemical evidence for advection of hydrothermal solutions in the sediments of the Galapagos Mounds Hydrothermal Field

Pore water profiles of Ca, Mg, F, PO₄^?3 and Mn in the Galapagos Mounds Hydrothermal Field are believed to reflect, in part, upwelling of hydrothermal solutions through the sediments. Concentration-depth profiles in a low heat flow area just north of the Mounds Field display diagenetic changes typical of those found in pore waters underlying highly productive surface waters, consistent with the inference of no water flow or very slow downwelling ($\text{w < 5}\text{cm/yr}$) of bottom water through these sediments. Rates of upward advection calculated from Mounds Field pore water profiles of Ca, Mg, and F profiles agree well with each other, averaging about 1 cm/yr in the pelagic sediments near the mounds and 15–30 cm/yr within the hydrothermal mounds themselves. The upward advection also modifies the shape of PO₄^?3 and Mn profiles.Advection rates inferred from the pore water data are generally in reasonable agreement with those made from heat flow data.The higher Ca and lower Mg, F, PO₄^?3 and Mn concentrations in Mounds Field pore waters (compared with those of the low heat flow area) suggest chemical exchange between the solution and basalt prior to upwelling. Li⁺, K⁺, Rb⁺, Sr⁺⁺ and SO₄^? concentrations are indistinguishable from bottom water. This suggests very high effective water/rock ratios during the reactions which produced the upwelling solutions, perhaps due to extensive prior alteration of basalt adjacent to the flow path of water through the crust Inferred reaction temperatures are between 70–150°C.     

Instantaneous photochemical rates in the global stratosphere

Starting with the average actual distribution of ozone (Dütsch [15]) and temperature in the stratosphere, we have calculated the solar intensity as a function of wavelength and the instantaneous rates (molecules cm^–3 sec^–1) for each Chapman reaction and for each of several reactions of the oxides of nitrogen. The calculation is similar to that ofBrewer andWilson [5]. These reaction rates were calculated independently in each volume element in spherical polar coordinates defined by R=1 km from zero to 50, =5° latitude, and ø=15° longitude (thus including day and night conditions). Calculations were made for two times: summer-winter (January 15) and spring-fall (March 22). As input data we take observed solar intensities (Ackerman [1]) and observed, critically evaluated. constants for elementary chemical and photochemical reactions; no adjustable parameters are employed. (These are not photochemical equilibrium calculations.) According to the Chapman model, the instantaneous, integrated, world-wide rate of formation of ozone from sunlight is about five times faster than the rate of ozone destruction, and locally (lower tropical stratosphere) the rate of ozone formation exceeds the rate of destruction by a factors as great as 1000. The global rates of increase of ozone are more than 50 times faster thanBrewer andWilson's [5] estimate of the average annual transfer rate of ozone to the troposphere. The rate constants of the Chapman reactions are believed to be well-enough known that it is highly improbable that these discrepancies are, due to erroneous rate constants. It is concluded that something else besides neutral oxygen species is very important in stratospheric ozone photochemistry. The inclusion of a uniform concentration of the oxides of nitrogen (NO_x as, NO and NO₂) averaging 6.6×10^–9 mole fraction gives a balance between global ozone formation and destruction rates. The inclusion of a uniform mole fraction of NO_x at 28×10^–9 also gives a global balance. These calculations support the hypethesis (Crutzen [10],Johnston [24]) that the oxides of nitrogen are the most important factor in the global, natural ozone balance. Several authors have recently evaluated the natural source strength of NO_x in the stratosphere; the projected fleets of supersonic transports would constitute an artificial source of NO_x about equal to the natural value, thus promising more or less to double an active natural stratospheric ingredient.     

Electrical conductivity of molten FeNiSC core mix

The electrical conductivity of liquid (Fe₉₀Ni₁₀)₃S₂ saturated with 2.6 weight percent carbon averages 2.7·10⁵ mho/m at 1000°C and zero pressure. This may imply a slightly lower electrical conductivity for the earth's core than that obtained by extrapolating the properties of pure liquid iron and solid iron alloys to core pressures and temperatures. Although a sulphur-rich core would have a smaller proportion of sulphur, the effect of lowering the sulphur content of the FeNiSC liquid to about 15 weight percent would be unlikely to increase the conductivity above 5·10⁵ mho/m.     

Chronology of the Black Sea over the last 25,000 years

Deep-water sediments of the Black Sea deposited during Late Pleistocene and Holocene time are distinguished by three sedimentary units: (1) a microlaminated coccolith ooze mainly consisting of Emiliania huxleyi; (2) a sapropel; and (3) a banded lutite. The base of the first unit lies at 3,000 years B.P., that of the second at 7,000 years B.P., and that of the third at least at about 25,000 years B.P. Fossils and geochemical criteria are used to decipher the environmental events of this time period. Beginning with the base of the section dated at about 25,000 years B.P. we witness the final stage of metamorphosis from anoxic marine to oxic freshwater conditions. By the time this stage ended, about 22,000 years B.P., the Black Sea had become a truly freshwater habitat. The lake phase lasted about 12,000 to 13,000 years. Sedimentation rates were in the order of 1 m/10³ years, but began to decrease as sea level rose during the last 5,000 years of this phase (9,000–15,000 years B.P.). Starting at about 9,000 years B.P. and continuing to 7,000 years B.P., Mediterranean waters occasionally spilled over the Bosporus as a consequence of ice retreat and sea level rise. This marked the beginning of a gradual shift from freshwater to marine, and from well aerated to stagnant conditions. At about 7,000 years B.P. when deposition of unit 2 started, the H₂S zone was well established. Sedimentation rates dropped to 10 cm/10³ years. Environmental conditions similar to those of today finally became established around 3,000 years B.P., almost exactly the time when Jason and the Argonauts sailed through the Bosporus in search of the Golden Fleece.     

Occurrence and infrared spectra of holmquistite and hornblende from Mt. Marion,near Kalgoorlie,Western Australia

Coexisting holmquistite and hornblende are described from an amphibolite associated with a spodumene pegmatite at Mt. Marion, near Kalgoorlie, Western Australia. Analytical, optical and infrared absorption data are presented. The distribution of cations in the holmquistite structure is readily determined by study of hydroxyl ion vibrations.     

Short‐term temporal variation in gelatinous zooplankton populations over 48 hours in a coral reef at Redang Island,Malaysia

Gelatinous zooplankton abundance and species composition were investigated at 3‐h intervals for a 48‐h period at a fringing reef in Malaysia. A total of 20 gelatinous zooplankton species were observed; the community was dominated by the calycophoran siphonophore Diphyes chamissonis (79.9%), followed by the trachymedusdae Aglaura hemistoma (5.6%) and Liriope tetraphylla (4.8%). The gelatinous zooplankton were not collected in the water column during most of the daytime hours (1200, 1500 and 1800 h) but were common during the night. However, an abrupt peak in abundance was found at 0900 h on the second day. The times of appearance at night were different depending on the species, and the number of species was also different depending on the hour of sampling. Sampling at 3‐h intervals over a 48‐h period revealed that the temporal variation (or sampling availability) was large in this study. Careful consideration should be given to the sampling variability in handling the gelatinous zooplankton samples in coral reef areas.