ALBERT

Notes: We present, as a progress report, a revised and much enlarged version of the thermodynamic dataset given earlier (Holland & Powell, 1985). This new set includes data for 123 mineral and fluid end-members made consistent with over 200 P–T–XCO2–fO2 phase equilibrium experiments. Several improvements and advances have been made, in addition to the increased coverage of mineral phases: the data are now presented in three groups ranked according to reliability; a large number of iron-bearing phases has been included through experimental and, in some cases, natural Fe:Mg partitioning data; H2O and CO2 contents of cordierites are accounted for with the solution model of Kurepin (1985); simple Landau theory is used to model lambda anomalies in heat capacity and the Al/Si order–disorder behaviour in some silicates, and Tschermak-substituted end-members have been derived for iron and magnesium end-members of chlorite, talc, muscovite, biotite, pyroxene and amphibole.For the subset of data which overlap those of Berman (1988), it is encouraging to find both (1) very substantial agreement between the two sets of thermodynamic data and (2) that the two sets reproduce the phase equilibrium experimental brackets to a very similar degree of accuracy. The main differences in the two datasets involve size (123 as compared to 67 end-members), the methods used in data reduction (least squares as compared to linear programming), and the provision for estimation of uncertainties with this dataset. For calculations on mineral assemblages in rocks, we aim to maximize the information available from the dataset, by combining the equilibria from all the reactions which can be written between the end-members in the minerals. For phase diagram calculations, we calculate the compositions of complex solid solutions (together with P and T) involved in invariant, univariant and divariant assemblages. Moreover we strongly believe in attempting to assess the probable uncertainties in calculated equilibria and hence provide a framework for performing simple error propagation in all calculations in thermocalc, the computer program we offer for an effective use of the dataset and the calculation methods we advocate.

Notes: A combination of fluid inclusion, stable isotope and geochemical techniques has been used to study the nature of fluids present and their behaviour during Caledonian low-grade metamorphism of the Harlech Dome, north Wales. Fluid inclusion studies show that in most of the metasedimentary sequence the peak metamorphic fluid was an aqueous Na–K–Cl brine but in the graphitic Clogau Formation and in parts of the overlying Maentwrog Formation immiscible H2O-rich and CH4-rich fluids coexisted.Late-stage inclusions are of calcium-rich brine and a dilute aqueous fluid. The chemical composition of chlorite in metamorphic veins and rocks varies between different formations and quartz-oxygen isotopic compositions show considerable variation between different units. Both of these features are taken to indicate that there was little or no pervasive movement of fluid between different units at the peak of metamorphism. After the metamorphic peak there was focused flow of fluid upward through the sequence along fractures, in response to end-Caledonian uplift and unloading. Where the migrating fluid crossed the graphitic shales, interaction between the fluid and the shales gave rise to the formation of the auriferous veins of the Dolgellau Gold Belt. Subsequent to this mineralizing event there was widespread development of 18O-enriched calcites and micas.In the case of vein minerals it is possible that these crystallized directly from late-stage fluids at lower temperature than the quartz in the same veins. Alternatively, the original vein minerals may have re-equilibrated with later 18O-enriched or cooler fluid. In the case of muscovites in the rock matrix it is proposed that the isotopically heavy compositions are the result of re-equilibration of initially light grains with an introduced fluid, requiring considerable influx of fluid. This event may relate to either of two late-stage fluids observed as inclusions.

Notes: DPX-A7881, methyl 2-[(4-ethoxy-6-methyl-amino-1, 3, 5-triazin-2-yl)carbamoylsulphanoyl] benzoate, is a sulfonylurea herbicide being developed in Canada and Europe for post-emergence broadleaf weed control in spring and winter rapeseed. Growth room studies were conducted to determine the environmental factors affecting the herbicidal activity of DPX-A7881 applied post-emergence on winter rapeseed (Brassica napusu L. ‘Tandem’) and on a closely related weed species, Sinapis arvensis L. (wild mustard).Laboratory tests were carried out at tempera tures ranging from 2–26°C, at relative humidities from near 40% to 〉95%, with rain-free periods from 0.25–8 h after herbicide application, at soil moisture contents from 50–200% of field capacity, and with irradiances from 23–450 μEm−2s−1 Significant control of S. arvensis was demonstrated for all treatments except under poor growing conditions at the lowest temperatures and irradiances tested. After two weeks' exposure to each of the tem perature treatments, the herbicide maintained control of S. arvensis during a subsequent week of favourable growing conditions. Relative humidity, soil moisture or simulated rainfall did not significantly alter the herbicidal activity of DPX-A7881 on S. arvensis. DPX-A7881 showed a high degree of crop safety on B. napus. The herbicide did not significantly reduce the dry weights of B. napus grown under any of the environmental conditions tested.

Notes: In order to produce electrical conductivity-temperature plots suitable for interpreting mantle conductivity profiles, we have used several spatial averaging schemes to reduce the orthorhombic conductivity tensor of olivine to that appropriate for an isotropic material. The starting data were new measurements of electrical conductivity σ in the three orthogonal principal directions of a San Carlos olivine (fayalite 9 per cent) to 1500°C at 1 atmosphere total pressure. These measurements were made in a CO2/CO atmosphere that provided an oxygen partial pressure of 10-4Pa (10-9 atmosphere) at 1200°C; this is slightly more reducing than the quartzfayalite-magnetite (QFM) buffer curve. The highest [001] and lowest [010] conducting directions differ by a factor of 2.3. The next step was to obtain series and parallel bounds from the three principal directions; these absolute upper and lower bounds differ by 15 per cent. A standard conductivity curve comes from applying to the series and parallel curves various averaging schemes such as the Hashin-Shtrikman and Maxwell-Waff bounds or the effective medium, geometric mean, or (a new technique) self-similar methods; these all agree to within 3 per cent. The self-similar calculation demonstrates that the VRH method is a form of parallel average that is biased toward high values. The standard curve SO1 is given by σ= 46.9 exp (-1.38/kT) + 5.22 times 108 exp(-3.90/kT) where T is absolute temperature, k is the Boltzmann constant, and the activation energy is in eV. It is valid for the measurement interval of 1200°-1500°C and can be used for extrapolation on either side of this range. Uncertainties associated with applying SO1 to inferring mantle temperatures are discussed.

Notes: In the southern sector of the Scandinavian Caledonides a metamorphic gneiss complex (the Basal Gneiss Region or BGR) underthrusts a nappe complex of Precambrian granulites (the Jotun Nappe) in an assemblage collectively recording orogenic events culminating in the Scandian (Upper Silurian and Lower Devonian) episode. Palaeomagnetic study of a large regional sample spanning the combined outcrop identifies properties strongly controlled by metamorphic retrogression to amphibolite and greenschist facies. Low blocking temperature (Ibt) components in the BGR have E+ directions with a mean of D = 69° 1 = 60° (N = 19 sites,α95= 7.0°); sporadic higher blocking temperature components define a dual polarity northeast negative/southwest positive (NE - /SW+) axis with a mean of D = 42°, 1 = -24° (20 sites, α95= 8.1°). Granulite facies rocks in the Jotun Nappe yield a high-quality palaeomagnetic record reflected in high $LQn values and dominated by medium and high blocking temperature (hbt) components. A dual polarity (‘A’) axis defines a palaeofield migration from NE+ to E+ during uplift and cooling of this terrane with a predominance of normal polarities. A smaller population of Ibt (‘B’) components show E+ directions distributed along the Mesozoic palaeofield migration path for Eurasia, and probably acquired during brittle tectonic events of this age. ‘A’ magnetizations from 86 sites define mean south pole positions between 301°E, 2°N and 325°E, 10°S linked to uplift-related cooling following the climactic Scandian orogenic episode and dated at 420–400 Ma from the collective geological and radiometric evidence. Both the outward and return segments of an APW loop may be represented. The polar swathe correlates with (i) a higher blocking temperature component from the BGR, (ii) the uplift magnetization record in the western orthotectonic Caledonides of Scotland, and (iii) primary magnetizations from the Siluro-Devonian molasse facies in Britain. This study shows that the westerly extension of the APW path identified by British Siluro-Devonian data is not peculiar to that crustal segment but applies to continental Europe, and presumably to Laurentia, as well. The pattern of remanence acquisition within the Caledonides suggests contrasting zones of thermal and thermochemical remanence, with the latter probably linked to fluid migration consequent upon orogenic loading.

Notes: Abstract. First feeding fry of Atlantic salmon, Salmo salar L., were reared under four experimental light regimes from mid-June until mid-September. One group was reared under a simulated natural photoperiod 4 months out of phase, with initial daylength in mid-June corresponding to natural daylength in mid-February. Two groups were reared under continuous light of either low (27 lux) or high (1400 lux) intensity. The fourth group received a dual photoperiod combining a continuous, low intensity (27 lux) background illumination and a superimposed simulated natural photoperiod phase adjusted according to the natural photoperiod group.Growth rate and survival was higher during the first 3 weeks under continuous light or dual photoperiod than under the phase adjusted simulated natural photoperiod. This could partly be due to the restricted feeding time during the initial short daylength of the simulated natural photoperiod, and partly to a photostimulation of growth in groups reared under the continuous light regimes.Fish reared under a simulated natural photoperiod migrated vertically during the 24-hour cycle. The same behaviour was seen, though not as ctearly, in the fish reared under a dual photoperiod. Changes in light intensity appeared to be the primary releasing factor for the vertical migration observed. The fish reared under continuous light showed no diurnal vertical migration.〈section xml:id="abs1-1"〉〈title type="main"〉AcknowledgmentsThe authors would like to thank Dr Gunnar Nævdal and Dr Lars Petter Hansen for helpful suggestions and criticism of the manuscript. We also thank the staff at Matre Aquaculture Station for skilled assistance during the experiment. This study was financed by the Norwegian Fisheries Research Council (NFFR V.701.146).

Notes: Abstract. Triploidy was induced in the zebrafish, Brachydanio rerio (Hamilton), by varying all possible combinations of the time after fertilization (AF) (1-3min after insemination), temperature (36-42°C) and shock duration (1-7min). A thermal shock of 41°C for 4min, 2.5min AF ensured 100% triploidy and maximum (51%) survival. Induction of triploidy was confirmed by measurement of erythrocyte nuclear volume and chromosome counting. There was no significant difference in the growth rate of triploid and diploid fishes. All surviving triploids developed into males, and produced a few spermatozoa unable to fertilize normal eggs. A study on thermal and other characteristics required to ensure 100% triploidy rate in fish indicates that these characteristics are species specific.