Influence of illumination conditions on the sea-bottom visibility

Statistical models of the useful and background signals forming an image of the sea bottom observed through a rough sea surface are constructed. The methods for estimating the signal-to-noise ratio in the image of the bottom with the test distribution of the reflectance are described. The dependence of the signal-to-noise ratio on observational conditions, in particular, on the mutual orientation of the directions of sighting, wind, and solar vertical, is analyzed. Recommendations on the choice of optimal conditions for bottom observations from airborne carriers are given.     

Age and pyrite Pb-isotopic composition of the giant Sukhoi Log sediment-hosted gold deposit, Russia

Sukhoi Log is one of the largest gold deposits in Russia (1100 t Au at 2.45 g/t). Like many other sediment-hosted gold deposits throughout the world, Sukhoi Log preserves textural, structural and geochemical evidence for multiple generations of Au enrichment and pyrite growth.The deposit is located in the Lena gold province of Siberia, on the edge of the Siberian Craton and occurs in the core of a recumbent anticline in a Neoproterozoic black shale and quartz-rich siltstone-sandstone turbidite succession. Temporal constraints on pyrite paragenesis at the deposit have been determined using laser ablation inductively coupled mass spectrometry (LA-ICPMS) measurements of U, Th and Pb isotopes in pyrite, monazite and zircon. LA-ICPMS age determinations on detrital zircons indicate the host rocks were deposited after 600 ± 10 Ma and derived from a mixture of Palaeoproterozoic and Neoproterozoic sources. The U, Th and Pb isotopic systematics indicate the cores of large monazite crystals, which predate obvious tectonic fabric development in the host rocks, began growing at 573 ± 12 Ma. The rims of the same monazite crystals formed at 516 ± 10 Ma, during peak metamorphism and deformation. Small monazite crystals also grew in the sedimentary rocks during the Devonian (374 ± 20 Ma) and the Carboniferous or Early Permian (288 ± 22 Ma), possibly in response to fluid movements triggered by synchronous granite intrusion in the area. Multi-collector and quadrupole LA-ICPMS Pb isotopic determination on pyrite, combined with overprinting criteria, show that the earliest (stratiform) Pb and Au-bearing pyrite formed prior to metamorphism—possibly during sedimentation or early diagenesis (575-600 Ma). Small Au-rich pyrite nodules preserved as cores to folded bedding-parallel pyrite-quartz veins probably grew during late diagenesis or early metamorphism. Large pyrite euhedra, which overgrow the strong axial planar cleavage in the host rocks, have more radiogenic Pb-isotopic compositions and formed either late during or after deformation. Framboidal pyrite that is overgrown by both the late diagenetic-early metamorphic and syn- to post-metamorphic pyrite has the most radiogenic Pb-isotopic composition suggesting exchange with radiogenic Pb in the matrix may have continued until late in the history of the deposit.The dating and Pb isotopes support a multistage origin for the gold deposit with Au first introduced during or prior to growth of the earliest stratiform pyrite and progressively re-concentrated (with or without addition of further gold) during later metamorphic events.     

Social acceptability of a marine protected area: The case of Reunion Island

This paper examines variations in social acceptability of a Marine Protected Area (MPA) prior to implementation. The influence of a number of factors, including socio-economic characteristics, perception of coral resources state of health and attitudes towards non-compliance with regulations are analysed. During May 2006, 640 questionnaires were distributed to school children around Reunion Island, Western Indian Ocean, for completion by their parents, following an informal educational activity made in school. From a 73% (n = 469) response rate, results showed that 78% of participants were in favour of the MPA. Analysis further identified that those supportive of the MPA were generally from higher socio-professional categories, had a negative perception of the coral reef ecosystem's health and were not originally from Reunion. In contrast, locals (born in Reunion) from lower socio-professional categories or with no employment activity and having a positive perception of the health status of coral reefs offered no opinion on the MPA. Attitudes towards enforcement and compliance highlighted that SCUBA divers, fishers and jet skiers attributed a higher value to the protection of the coral reef environment through enforcement of MPA regulations than to their own use of the coral reef resource. When asked about the use of penalties to deter non-compliance, swimmers were awarded the lowest fines, followed by SCUBA divers, fishers then jet skiers being awarded the highest fines. Thus, the more severe the act of non-compliance by a resource user group was perceived to be, the more these users themselves disapproved of non-compliant behaviour and supported use of high penalties. The survey design through focusing on school children's parents, demonstrated a simple and cost-effective method for data collection while providing environmental education, which could be employed in similar case studies elsewhere.     

Reedbed evapotranspiration rates in England

Measurements of evapotranspiration from contrasting stands of Phragmites australis [ET(Reed)] were obtained over several years at three sites within England between 1994 and 1998. A comparison with published ET(Reed) values showed the UK rates to be considerably lower than those measured in continental Europe. From the ET(Reed) data monthly crop coefficients [K_c(Reed)] have been developed, which when used with Reference Crop Evapotranspiration will enable reedbed water use to be determined. Due to the differences in study site characteristics, values for K_c varied widely, and it was not considered appropriate to combine results to produce a single set of monthly mean values. However, suggestions are made regarding the application of the K_c(Reed) values to wetland design. Copyright © 2001 John Wiley & Sons, Ltd.     

Minor and trace elements in bornite and associated Cu-(Fe)-sulfides: A LA-ICP-MS studyBornite mineral chemistry

In situ laser ablation inductively-coupled mass spectroscopy (LA-ICP-MS) has been used to provide a baseline dataset on the minor element contents in hypogene bornite and accompanying Cu-sulfides from 12 deposits with emphasis on syn-metamorphic Cu-vein systems in Norway, and skarn, porphyry and epithermal systems in SE Europe.Bornite contains significant concentrations of both Ag and Bi, especially in the vein and skarn deposits studied and has the potential to be a major Ag-carrier in such ores. Concentrations of up to >1 wt.% of both elements are documented. Measured concentrations appear to be independent of whether discrete Ag- and/or Bi-minerals are present within the analyzed sulfide. Where bornite and chalcocite (or mixtures of Cu-sulfides) coexist, Ag is preferentially partitioned into chalcocite over co-existing bornite and Bi is partitioned into the bornite. Bornite is a relatively poor host for Au, which mimics Ag by being typically richer in coexisting chalcocite. Most anomalous Au concentrations in bornite can be readily tracked to micron- and submicron-scale inclusions, but bornite and chalcocite containing up to 3 and 28 ppm Au in solid solution can be documented. Selenium and Te concentrations in bornite may be as high as several thousand ppm and correlate with the abundance of selenides and tellurides within the sample. Selenium distributions show some promise as a vector in exploration, offering the possibility to track a fluid source. Bornite and chalcocite are poor hosts for a range of other elements such as Co, Ni, Ga and Ge, etc. which have been reported to be commonly substituted within sulfides. Hypogene bornite and chalcocite may have significantly different trace element geochemical signatures from secondary (supergene) bornite.     

Impact of brine acidification on hatchability,survival and reproduction of Artemia parthenogenetica and Artemia franciscana in salt ponds,Bohai Bay,China

We studied the effect of pH(pH 5, 6, 7 and 8) on the hatching percentage, survival and reproduction of Artemia strains in Bohai Bay salt ponds. Strains included parthenogenetic Artemia from Bohai Bay(BHB), Artemia franciscana from San Francisco Bay, and A. franciscana artifi cially produced in salt ponds in Vietnam. The latter was included as a potential inoculum for biological management of salt ponds. The hatching percentage of cysts after 24 h and the survival rate of the tested Artemia strains were signifi cantly reduced when exposed to a culture medium at pH 5 for 18 d( P 0.05). The tolerance of Artemia to 48 h acid exposure varied with developmental stage, increasing in the following order: juvenile, nauplii, pre-adult, with maximum tolerance in adults. All strains of Artemia tested could not reproduce at pH 5. At pH levels from pH 6–8, a higher pH generally resulted in a shorter brood interval and enhanced ovoviviparity. Hence, we suggest that brine acidifi cation has a negative impact on Artemia populations in the Bohai Bay saltworks. Inoculation of Artemia with either local parthenogenetic Artemia or exotic A. franciscana should be feasible at pH 7–8.     

ASSEMBLÉE D'HELSINKI: COMPTES-RENDUS DES TRAVAUX DE LA COMMISSION DES EAUX DE SURFACE. I. COLLOQUE SUR LES SÉCHERESSES ET DÉBITS DE BASES

Abstract

Reserves stand for the gravific or releasable water volume stored up in an aquiferous level. It is possible to distinguish regulative, geological and potential reserves. Their calculation is necessitating the knowledge of hydrogeological structures and the determination of specific yield or coefficient of storage. The use of recession curves allows speedy valuations.