ALBERT

Notes: Abstract The upper Jurassic Nikoro greenstone complex of eastern Hokkaido suffered high-pressure intermediate type metamorphism. Characteristic minerals include lawsonite, aragonite, sodic pyroxene of the aegirinejadeite series, winchite. sodic amphibole of the glaucophane-riebeckite series, pumpellyite, epidote and actinolite.High-pressure metamorphism of the Nikoro greenstone complex is related to subduction of the Kula plate toward the Palaeo-Okhotsk Land during Cretaceous time.

Notes: Abstract The Berzosa fault is a major ductile shear zone, the Berzosa Shear Zone (BSZ), which separates the ‘Ollo de Sapo’anticline from the inner higher-grade crystalline axis of the Iberian Hercynian Belt. This shear zone is the site of abundant early kinematic quartz (± Al-silicates) segregations, rich in fluid inclusions. Host rocks are medium-grade staurolite schists and sillimanite gneisses.Fluid inclusions in selected quartz segregations across the Berzosa shear zone have been studied by microthermometric methods as well as, in some instances, by Raman analysis. The recorded fluid inclusion history begins at the end of an intense secondary recrystallization period during late-peak metamorphic conditions and lasts until late in the uplift history of the zone.Three types of inclusions have been found, which in a time sequence are: CO2± H2O; H2O+salt (B-type); and, N2+CH4. Three types of B inclusion may be distinguished in turn, depending on whether they were trapped during an earlier dynamic-recovery phase (B1-type), formed later as intergranular trails (B2-type), or were trapped apparently along with N2+CH4 in clusions from a heterogeneous fluid (B3-type).Considerations from isochores confirm that CO2± H2O inclusions were trapped during late-peak and high-T retrograde metamorphic conditions (in the range 650–500°C and 5–2 kbar), whilst N2+CH4 inclusions, along with the B3-type of inclusions, formed at low-pressures (〈1 kbar) and temperatures (± 300°C). B2-type inclusions were trapped chronologically between these two in a period in which strong inverse lateral thermal gradients developed in the zone. Inferred P-T paths for the area are convex to the T-axis.

Notes: Abstract The orthopyroxene-clinopyroxene, garnet-orthopyroxene and garnet-clinopyroxene geothermometers, and the garnet-orthopyroxene-plagioclase, garnet-clinopyroxene-plagioclase and anorthite-ferrosilite-grossular-almandine-quartz geobarometers are applied to metabasites and the garnetplagioclase-sillimanite-quartz geobarometer is applied to a metapelite from the Proterozoic Arendal granulite terrain, Bamble sector, Norway. P–T conditions of metamorphism were 7.3 ± 0.5 kbar and 800 ± 60°C.This terrain shows a regional gradation from the amphibolite facies, into normal LILE content granulite facies rocks and finally strongly LILE deficient granulite facies gneisses. Neither P nor T vary significantly across the entire transition zone. The change in ‘grade’parallels the increasing dominance of CO2 over H2O in the fluid phase.LILE-depletion is not a pre-condition of granulite facies metamorphism: granulites may have either ‘depleted’or ‘normal’chemistries. The results presented herein show that LILE-deficiency in granulite facies orthogneisses is not necessarily related to variations in either P or T. The important mechanisms in the Arendal terrain were (a) direct synmetamorphic crystallization from magma, with primary LILE-poor mineralogies imposed by the prevailing fluid regime, and (b) metamorphic depletion, involving scavenging of LILEs during flushing by mantle-derived CO2-rich fluids. The latter process is constrained by U–Pb and Rb–Sr isotopic work to have occurred no later than 50 Ma after intrusion of the acid-intermediate gneisses, and was probably associated with contemporary basic magmatism in a tectonic environment similar to a present day cordilleran continental margin.

Notes: Abstract Peridotite and infolded marble of the Seiad ultramafic complex were recrystallized in the upper amphibolite facies as part of the regional progressive metamorphism of the Rattlesnake Creek terrane. Field relations, including the occurrence of metarodingites, and metasomatic zones between dissimilar rock types, demonstrate that the metasediments and serpentinized ultramafic rocks were juxtaposed prior to regional, barrovian metamorphism. Temperatures are estimated to have reached 760–800°C at pressures of 7–8 kbar during the peak of metamorphism. Four low-variance parageneses have been identified within a small (3 km2) area of the complex, which may reasonably be assumed to have formed under the same P and T conditions. Isobaric T-Xco2 diagrams of appropriate equilibria are presented for three different internally consistent sets of thermodynamic data. Despite the seemingly small numerical differences between the standard state thermodynamic properties of the data sets, only one diagram allows the four observed assemblages to coexist within a reasonable temperature range. All three phase diagrams require differences in fluid composition on the scale of a thin section; strong evidence for effective control of pore fluid composition by local mineral reactions during metamorphism.

Notes: Abstract Chromian omphacite which contains up to 4 wt % Cr2O3 has been identified from low-grade metamorphic rocks in Nishisonogi, Kyushu, Japan. It occurs as aggregates, forming a thin horizon ([20 mm thick) in alayered metagabbro within a serpentinite melange zone, together with Cr-free omphacite, actino-lite, epidote and sphene. It may have been formed by the metasomatic introduction of Cr into the metagabbro from the serpentinite rather than by reaction with chromite. The structural formula, based on EPMA analyses, and the optical absorption spectrum of the chromian omphacite show that the Cr is positioned in the octahedral site.

Notes: Abstract A diagenctic through anchizone to epizone transition is demonstrated in pelitic rocks of the Lower Palaeozoic marginal basin of Wales by examination of variations in phyllo-silicate mineralogy, illite crystallinity and bo parameter of white micas. This transition represents a temperature range from ∼ 150°C to ∼ 400°C and the metamorphism is of a low-pressure facies series type, with a geothermal gradient of ∼ 40°Ckm-1. Variations in grade can be correlated largely with the original basin and shelf form, suggesting a depth-related metamorphism. However, in areas closer to the site of Caledonian plate collision an increasingly syn-tectonic metamorphic event is apparent.Correlation of pelite data with metabasite assemblages is variable, the most consistent relationship being between epizone crystallinity values andepidote-actinolite (greenschist facies) assemblages. Diagenetic clay mineral assemblages are found associated with prehnite-pumpellyite assemblages in metabasites and it is suggested that the latter represent non-buffered, and therefore non-diagnostic, assemblages.

Notes: Abstract The magnitudes of plastic strains of 104 metacherts were determined from the deformed shape of initially spherical radiolarians in the Sambagawa high-P type metamorphic belt of Western Shikoku, Japan. The strain magnitude increases with increasing metamorphic temperature from several per cent to 250%. The a2/a3 ratio of strain ellipsoids in the higher metamorphic grades decreases with increasing metamorphic grade while the a1/a2 ratio increases rapidly. The long axis of the strain ellipsoid for every grade is nearly parallel to the length of the metamorphic belt, suggesting that the flow direction of the synmetamorphic deformation was uniform along the belt. A map of strain zones within the Sambagawa high-P type metamorphic belt reveals that the metamorphic belt underwent a progressive bulk inhomogeneous shear deformation and that the high-grade zones represent a deep-seated boundary shear zone on the accretionary wedge between a subducting oceanic plate and the immobile rigid continental plate.

Notes: Abstract Compositions of actinolite, hornblende and cummingtonite, together with pyroxene and plagioclase, are studied in basic intrusions in the Dalradian of north-east Scotland, and the Glen Scaddle complex in the West Moine. Amphibolitization is due to influx of water from the country rocks. Pyroxene compositions are found to have adjusted to the regional metamorphic environment. Owing to the difficulty of diffusion of Al and Si, calcic amphiboles are zoned and commonly contain quartz blebs. Discontinuities in zoning give rise to actinolite-hornblende pairs. Compared with north-east Scotland, disequilibrium is less strong in the Glen Scaddle area: in the latter, plagioclase compositions have been greatly changed, Na partition between hornblende and plagioclase is close to equilibrium, the maximum Al content of hornblende is lower and zoning patterns are more consistent. The Fe/Mg ratio in calcic amphiboles varies with Al content, while approaching equilibrium partition with other minerals. Both zoning patterns and Fe/Mg partition with cummingtonite suggest that Fe/Mg of the calcic amphiboles increases more strongly with increasing (Alvi+Fe3+) than can be explained simply by substitution of Al,Fe3+ for Mg on M2. Model reactions for amphibole formation are constructed. Cummingtonite formed at lower chemical potential of CaO than actinolite: Ca was exchanged for Mg,Fe between orthopyroxene-derived and clinopyroxene-derived local systems. Both cummingtonite and actinolite were formed because of kinetic constraints, as intermediate reaction products: actinolite-hornblende pairs represent disequilibrium. This work suggests that many occurrences of actinolite with hornblende, where the minerals are zoned, may also be due to diffusion kinetics.

Notes: Abstract Lewisian grey gneisses from Gruinard Bay, North-west Scotland retain mineralogical and geochemical evidence for Scourian horn-blende-granulite facies metamorphism, and they may be used to assess current models of elemental depletion at granulite grade. Their ‘immobile’major and trace element geochemistry is indistinguishable from that of Lewisian amphibolite and pyroxene-granulite facies counterparts. The K, Rb, Th and U contents of the Gruinard Bay gneisses are depleted relative to amphibolite facies gneisses, but generally the abundances of these elements are above those of comparable pyroxene granulites. U and Th have reached an advanced stage of depletion, but allanite appears to be crucial in maintaining significantly higher U and Th abundances at Gruinard Bay than in pyroxene granulites. K and Rb loss is less extreme, and depends on the stability of the rock-forming minerals: K-feldspar; biotite; and, amphibole. Early removal of K and Rb has resulted in a small rise in K/Rb, but further preferential Rb loss would have been required to generate the characteristically high K/Rb ratios of Lewisian pyroxene granulites.The residence of U and Th in the accessory minerals of granulite facies gneisses, which are often correlated with the residua of intracrustal partial melting, renders unlikely their extreme incompatibility required by such models. Even if such phases are ignored, high mineral-melt partition coefficients for silicic melts argue against partial fusion as an efficient depletion mechanism. On the other hand, the advanced stage of U and Th depletion reached in Gruinard Bay gneisses, which were still partly hydrous, severely restricts the role played by CO2-dominated fluids and a hydrous medium is preferred.

Notes: Abstract Oxygen and hydrogen isotope analyses have been made of coexisting quartz, ilmenite, muscovite, and biotite from Late Precambrian metapelitic rocks, staurolite-kyanite to K-feldspar-muscovite-sillimanite zones, from Mica Creek, British Columbia. The δ18O and †D values of these minerals are generally uniform and do not decrease significantly with increasing metamorphic grade. This implies that there has not been significant infiltration of deep crustal, possibly magmatic, fluids into the metapelites that has been suggested for other high-grade metamorphic terranes. The uniformity of oxygen isotope compositions of the Mica Creek metapelite rocks may reflect isotopic uniformity in the sedimentary protolith rather than widespread exchange with an isotopically homogeneous metamorphic pore fluid.Temperature estimates based upon 18O exchange thermometry for samples below the sillimanite zone are in reasonable agreement with the results of garnet-biotite Fe–Mg exchange thermometry. In the higher grade rocks, the oxygen isotope and garnet-biotite thermometry yield results which disagree by about 100°C. The highest temperatures recorded by oxygen isotope thermometry, 595°C, are at least 60°C below the minimum temperatures required by phase equilibria. These discrepancies appear to result from pervasive equilibrium retrograde exchange of oxygen isotopes between coexisting minerals. In addition, there are problems with calibration of garnet-biotite thermometry at higher temperatures. Retrograde oxygen isotope exchange may be a general characteristic of high-grade metamorphic rocks and oxygen isotope thermometry may not usually record peak metamorphic temperatures if they significantly exceed 600°C.

Notes: Abstract Mctamorphic rocks of the St Anthony Complex of north-western Newfoundland are best interpreted in terms of a high-temperature shear zone formed between down-going continental margin rocks and overriding oceanic lithosphere in a subduction zone. High-grade rocks, immediately beneath the oceanic lithosphere peridotite, display retrograde meta-morphism in high-strain zones, whereas lower grade rocks, near the base of the metamorphic complex, display prograde metamorphism in high-strain zones. Mylonite zones in meta-basitcs at all levels in the complex contain the assemblage epidote-hornblende-albite-sodic oligoclase. These observations suggest that the ‘inverted metamorphic gradient’within the St Anthony Complex results from the fortuitous preservation of residual metamorphic assemblages from different crustal levels within an epidote amphibolite facies shear zone. The degree of re-equilibration is strongly dependent on the degree of strain, and is best achieved in synmetamorphic mylonite zones. This interpretation of the St Anthony Complex can be extended to other sub-ophiolite metamorphic sheets, which show very similar relationships. It is proposed that most metamorphic sheets beneath ophiolites are high temperature shear zones, the P-T paths of which preserve records of burial and exhumation in subduction zones.

Notes: Abstract Layer-parallel (i.e. parallel to foliation or bedding) vein formation in the graywackes and pelites of the Quetico Metasedimentary Belt occurred during synchronous prograde metamorphism and regional (D2) compression. In a traverse across metasediments which change in metamorphic grade from greenschist to upper amphibolite (migmatite) facies, layer-parallel veins show the following trends: (1) an increase in thickness and internal complexity, the latter due to successive boudinage; (2) low-grade veins are parallel to planes of anisotropy due to the original sedimentary fabric of the host rocks, but at higher grades other sites are also used and (3) a systematic increase in plagioclase/quartz ratio in the veins towards higher grade, adjacent mafic selvedges first exhibit quartz depletion then, in the amphibolite facies, plagioclase depletion. Mineralogical zoning is often preserved in a single vein, older parts are more quartz-rich than younger.Mass balance calculations and whole-rock geochemistry based on veins, mafic selvedges and country rock are consistent with a closedsystem subsolidus segregation origin. The layerparallel veins are syntectonic, and migration of the mobile components required to form their mineralogy is a stress-induced mass transfer. The source of these components appears to be dominantly pressure solution of the same minerals in the host rocks, although metamorphic reactions may also have contributed. Veins nucleated first at those sites where initial sedimentary heterogeneites, such as fine-scale graded bedding, provided gradients of normal stress across grain boundaries, and hence of chemical potential, necessary to drive the subsolidus segregation process. The earliest veins are thus parallel to bedding. Later, nucleation of the veins could also occur along more randomly distributed sites within the metasediments, and these veins grew parallel to the schistosity rather than bedding, if the two were distinct. Once formed, the veins themselves, which are more competent than the surrounding rock, provide the stress heterogeneity required for their further growth. The increasing plagioclase/quartz ratio in the veins may be due to a temperature dependent increase in plagioclase component mobility relative to quartz. Alternatively, the increasing transfer distances for silica, resulting from prior quartz depletion in the inner parts of the mafic selvedge, may increase the relative mobility of plagioclase component.

Notes: Abstract Gneisses from the southern part of the Bunte Series have been studied in order to determine their metamorphic evolution. They all belong to the paragenetic facies type Bt+Sil+ Kfs+Qtz+Grt. The garnets of these rocks generally exhibit typical features of garnets from this high-temperature facies type: diffusional homogenization throughout the bulk of the garnet and retrograde zoning patterns at the outer rim. Ca- and Mn-richer relict cores in some garnets are evidence of the early metamorphism. These cores are enveloped by the high-temperature homogenized garnet. The element distribution curves of the relict cores show evidence of partial element-specific modification by volume diffusion.Paragenetic and textural relations as well as temperature and pressure calculations suggest the following conditions of the main metamorphism: 700–770°C at 7-9 kbar and PH2O PtotDespite the uncertainty due to the incomplete equilibration among garnet rims and other matrix minerals, an attempt is made to model the cooling and uplift history of the rocks using textural, paragenetic, chemical and literature data.〈section xml:id="abs1-1"〉〈title type="main"〉ZusammenfassungGneise aus dem südlichen Teil der Bunten Serie wurden im Hinblick auf ihre Metamorphoseentwicklung untersucht. Sie gehören allgemein dem Faziestyp Bt+Sil+Kfs+Qtz+Grt an. Die Granate weisen alle für diesen Faziestyp charakteristischen Merkmale auf: weitgeheride Homogenisierung durch Diffusion und Abkühlungserscheinungen am äuβeren Rand. Ca- und Mn- reiche reliktische Kerne mancher Granate weisen auf ein älteres Ereignis hin. Diese Relikte werden im homogenisierten Granat höherer Bildungstem-peratur eingeschlossen. Ihre Element- Verteilungskurven sind teilweise durch die intrakristalline Diffusion dem Kationenradius entsprechend abgeflacht.Paragenetische Beziehungen und T- und P-Berechnungen ergeben folgende Bedingungen für die Hauptmetamorphose: 700–770°C bei 7-9 kbar und PH2OPtot.Trotz der Unsicherheit, die auf eine unvoll-ständige Einstellung des Gleichgewichtes zwischen Granaträndern und den übrigen Matrixmineralen zurückzuführen ist, wurde ver-sucht, ein Modell über die Abkühlungs- und Hebungsgeschichte der untersuchten Gesteine zu erstelleu.

Notes: Abstract A study has been made of the high-pressure early-Alpine re-equilibration in the eclogites and metasedimentary cover of the Val d'Ala di Lanzo ophiolite. All of the main high-pressure minerals have been analysed and their compositions used to determine re-equilibration temperatures. The minimum conditions proposed (P= 1.3 GPa, T= 450–460°C) are also indicated by the presence of a jadeite+quartz-bearing metagranite.The temperatures are compared with those reported for similar eclogites from the Voltri Group, the Aosta Valley and the Valais. Comparison of recalculated temperatures shows that the temperature (and probably the pressure) of the eclogitic re-equilibration increased in the Aosta Valley and the Valais, in keeping with what has been observed in the internal Penninic basement of the Gran Paradiso and Monte Rosa crystalline massifs.

Notes: MIGMATITES

Notes: Abstract This work uses a simplified model of equilibrium to predict the assemblage sequence and compositional zoning in garnet that should result from prograde metamorphism of common bulk compositions of pelitic rocks. An internally-consistent set of model thermodynamic data are derived for natural mineral compositions from natural assemblages. Equilibrium assemblages can be calculated for pelitic compositions with excess quartz and either muscovite or K-feldspar at any pressure and water pressure. The compositions and abundances of phases in equilibrium assemblages can be calculated where the elements Mg, Fe and Mn are exchanged among phases. The prograde metamorphic assemblage sequences and the effects of pressure on assemblages, predicted by the simulation method presented here, are similar enough to natural observations to suggest that the simulations can be used to analyse natural equilibrium and growth processes.The calculated phase diagrams at moderate and high crustal pressures explain the mineral assemblage sequence produced by prograde metamorphism in common pelitic compositions. Garnet appears by continuous reaction of biotite and chlorite as the garnet-biotite-chlorite divariant field migrates toward higher Mg/Fe ratios over the bulk composition. Staurolite appears in common bulk compositions when garnet and chlorite become incompatible. An aluminum silicate phase can appear when staurolite and chlorite react. Staurolite breaks down at an extremum point to produce garnet. Continuous reaction of biotite and sillimanite causes growth of abundant garnet.The reaction sequence involving garnet, staurolite and aluminum silicates is probably different at low pressure, but the main reason that staurolite and garnet are rare is the restricted compositional range over which their assemblages exist. Andalusite appears by the divariant reaction of chlorite and cordierite appears at low temperature in low pressure assemblages for common bulk compositions by the extremumpoint breakdown reaction of chlorite.Compositional zoning of garnet and the systematic variation of biotite composition in metamorphic sequences indicate that garnet is probably fractionated during growth. Fractionation of garnet causes garnet-consuming, univariant reactions to become multivariant. The metastable persistence of garnet should reduce the abundance and stability range of staurolite. Fractionation of even small quantities of garnet should deplete the equilibrating bulk composition of Mn, but have little effect otherwise. The simulations show that the prograde assemblage sequence in pelitic rocks can be complex in detail, with some assemblages lasting over temperature intervals of only a few degrees.The major prograde reactions that release water are the breakdown of chlorite to form garnet at low grade and the breakdown of muscovite at high grade. The volume of water released by formation of garnet at high grade is also important. These reactions have the capacity to buffer water pressure.The density of anhydrous pelitic rock increases markedly when chlorite breaks down and by the continuous reaction forming garnet at high grade. The heat content is controlled principally by heat capacity and continuous reactions. Discontinuous reactions have little thermal buffering capacity.Simulations of garnet fractionation show that commonly-observed garnet zoning profiles can be formed by garnet growth in the assemblage garnet-biotite-chlorite in common bulk compositions. A reversal of Fe-zoning in garnet can occur when garnet resumes growth above staurolite grade in the assemblage garnetbiotite-sillimanite. Discontinuities in zoning profiles can be caused only by disequilibrium. The disequilibrium can be due to either metastable persistence during a hiatus in growth or to growth by irreversible reaction.Because the appearance of garnet is controlled by a continuous rather than a discontinuous reaction, the appearance of garnet is very sensitive to bulk composition. The early development of garnet is also sensitive to the pressure and water pressure of metamorphism. As a consequence the first garnet isograd is of limited thermometric value.Metastable persistence of kyanite and manite at high grades could reduce the abundance of garnet and allow biotite to persist. Metastable persistence would also limit the of cordierite formation.

Notes: Abstract The paragenetic relations of epidote-glaucophane schists are described in terms of the system Al2O3-Fe2O3-Fe2O3-MgO-CaO with excess of quartz, albite and epidote. If alkali-amphibole is free from Ca and AlIV, its composition when associated with epidote is invariant, univariant or divariant at a given pressure and temperature on Miyashiro's (1957) diagram of alkali-amphibole solid solution if it is also associated, respectively, with three, two or one additional minerals in the system.Using a group of epidote-glaucophane schists from the Kotu area of the Sanbagawa metamor-phic belt in Shlkoku, Japan (isophysical compositional),univariant boundary lines were determined for the assemblages that, in addition to the ubiquitous quartz + albite + phengitic mica, contain hematite + chlorite, garnet + chlorite and actinolite + chlorite, respectively. The slopes of the univariant boundary lines obtained from petrographical data are in good agreement with those calculated in a model system.The positions of isophysical univariant boundary lines on the amphibole compositional diagram serve to distinguish the grade of metamorphism among the rocks of the same mineral facies. The hematite-chlorite univariant boundary line can be used to divide the zone of epidote-glaucophane schists of the Sanbagawa metamorphic belt into three, and the garnet-chlorite-paragonite invariant equilibrium can be used to divide the epidote zone of New Caledonia into three.

Notes: Abstract In regional metamorphic rocks, the partitioning of deformation into progressive shearing and progressive shortening components results in strain and strain-rate gradients across the boundaries between the partitioned zones. These generate dislocation density gradients and hence chemical potential gradients that drive dissolution and solution transfer. Phyllosilicates and graphite are well adapted to accommodating progressive shearing without necessarily building up large dislocation density gradients within a grain, because of their uniquely layered crystal structure. However, most silicates and oxides cannot accommodate strain transitions within grains without associated dislocation density gradients, and hence are susceptible to dissolution and solution transfer.As a consequence, zones of progressive shearing become zones of dissolution of most minerals, and of concentration of phyllosilicates and graphite. Exceptions are mylonites, where strain-rates are commonly high enough for plastic deformation to dominate over diffusion rates and therefore over dissolution and solution transfer. Porphyroblastic minerals cannot nucleate and grow in zones of active progressive shearing, as they would be dissolved by the effects of shearing strain on their boundaries. However, they can nucleate and grow in zones of progressive shortening and this is aided by the propensity for microfracturing in these zones, which allows rapid access of fluids carrying the material presumed to be necessary for nucleation and growth. Zones of progessive shortening also have a number of characteristics that help to lower the activation energy barrier for nucleation, this includes a build up of stored strain-energy relative to zones of progressive shearing, in which dissolution is occuring.Porphyroblast growth is generally syndeformational, and previously accepted criteria for static growth are not valid when the role of deformation partitioning is taken into account.Porphyroblasts in a contact aureole do not grow statically either, as microfracturing, associated with emplacement, allows access of fluids in a fashion that is similar to microfracturing in zones of progressive shortening.The criteria used for porphyroblast timing can be readily accommodated in terms of deformation partitioning, reactivation of deforming foliations, and a general lack of rotation of porphyroblasts, with the spectacular exception of genuinely spiralling garnet porphyroblasts.

Notes: Abstract A deerite-bearing rock occurs at the boundary between quartzite and metabasites within the ‘schistes lustrés’of eastern Corsica. It contains the typomorphic assemblage pyroxene, blue amphibole, hematite and magnetite. Pyroxene shows homogeneous composition close to the aegirine end-member and blue amphibole is zoned from crossite core to riebeckite rim. The bulk chemical analysis of the rock is remarkable by its very high iron content and the presence of an unusually large amount of Zn which is concentrated in both deerite and amphibole. Electron microprobe analyses of the Corsican deerite are compared with those published in the literature; as shown by deerite from the Fransciscan iron formation, the principal substitution for Fe2+ is Mn whereas the amount of substitution for Fe3+ is low. In the system SiO2-FeO-Fe2O3-Al2O3-Na2O-MgO-H2O the typomorphic paragenesis can be described by an univariant reaction interpreted as the result of a pressure decrease. P-T conditions of metamorphism, previously estimated to be 8 kbar and 300°C, are in good agreement with present knowledge of the deerite stability field. The occurrence of hematite and magnetite in equilibrium permits an estimation of the oxygen fugacity (log fo2= -29.41 bar). Oxidation conditions are higher than those previously mentioned in the literature for similar assemblages.

Notes: Abstract Reactivation of early foliations accounts for much of the progressive strain at more advanced stages of deformation. Its role has generally been insufficiently emphasized because evidence is best preserved where porphyroblasts which contain inclusion trails are present. Reactivation occurs when progressive shearing, operating in a synthetic anastomosing fashion parallel to the axial planes of folds, changes to a combination of coarse- and finescale zones of progressive shearing, some of which operate antithetically relative to the bulk shear on a fold limb. Reactivation of earlier foliations occurs in these latter zones.Reactivation decrenulates pre-existing or just-formed crenulations, generating shearing along the decrenulated or rotated pre-existing foliation planes. Partitioning of deformation within these foliation planes, such that phyllosilicates and/or graphite take up progressive shearing strain and other minerals accommodate progressive shortening strain, causes dissolution of these other minerals. This results in concentration of the phyllosilicates in a similar, but more penetrative manner to the formation of a differentiated crenulation cleavage, except that the foliation can form or intensify on a fold limb at a considerable angle to the axial plane of synchronous macroscopic folds.Reactivation can generate bedding-parallel schistosity in multideformed and metamorphosed terrains without associated folds. Heterogeneous reactivation of bedding generates rootless intrafolial folds with sigmoidal axial planes from formerly through-going structures. Reactivation causes rotation or ‘refraction’of axial-plane foliations (forming in the same deformation event causing reactivation) in those beds or zones in which an earlier foliation has been reactivated, and results in destruction of the originally axial-plane foliation at high strains. Reactivation also provides a simple explanation for the apparently ‘wrong sense’, but normally observed ‘rotation’of garnet porphyroblasts, whereby the external foliation has undergone rotation due to antithetic shear on the reactivated foliation. Alternatively, the rotation of the external foliation can be due to its reactivation in a subsequent deformation event.Porphyroblasts with inclusion trails commonly preserve evidence of reactivation of earlier foliations and therefore can be used to identify the presence of a deformation that has not been recognized by normal geometric methods, because of penetrative reactivation. Reactivation often reverses the asymmetry between pre-existing foliations and bedding on one limb of a later fold, leading to problems in the geometric analysis of an area when the location of early fold hinges is essential. The stretching lineation in a reactivated foliation can be radically reoriented, potentially causing major errors in determining movement directions in mylonitic schistosities in folded thrusts.Geometric relationships which result from reactivation of foliations around porphyroblasts can be used to aid determination of the timing of the growth of porphyroblasts relative to deformation events. Other aspects of reactivation, however, can lead to complications in timing of porphyroblast growth if the presence of this phenomenon is not recognized; for example, D2-grown porphyroblasts may be dissolved against reactivated S1 and hence appear to have grown syn-D1.

Notes: Abstract Fluid inclusions in ore skarn minerals reflect the physiochemical nature of the solutions present during the skarn-forming process. Because of the dense nature of skarn minerals and the dynamic processes operative during skarn genesis, sufficient primary fluid inclusions are usually present. Ore skarn solutions, as opposed to metamorphic skarn or ore vein solutions, have much higher CaCl2 contents and usually very high formation temperatures (〉500°C) and salinities (〉40 wt % T.D.S.). Temperatures and salinities generally decrease away from the solution source, both in time and space. The gradients found at greater distances from the source in distal (far from contact) skarns tend to be less (e.g. 210–350°C) for a particular skarn stage to that in proximal (near contact) skarns (e.g. 400–650°C). This information is useful for delineating the parts of such a hydrothermal system. Temperatures also tend to decrease with time, which is reflected by the superimposition of various overprinting, retrograde mineral stages. In a few areas (e.g. Naica, Mexico) intermittent boiling of ore solutions occurs, periodically elevating both temperatures and salinities, but commonly boiling only occurs early in skarn genesis just after an early, commonly lower temperature, phase.Most fluid inclusions represent a mix of‘exhaust’or reacted solutions with minor unreacted or new (pre-) ore solution components. Limited data on the distribution of elements present in fluid inclusions that do not normally take part in skarn genesis (Na, K and Cl) indicate that their proportions reflect the nature of the associated pluton. High KC1 contents are found in skarns adjacent to high K granitoids, whereas high NaCl contents are found in skarns adjacent to calcic granitoids.In many examples, daughter minerals present in minor proportions in opened fluid inclusion cavities reflect the metal characteristics of the ore solution. Small rare-earth metal, tungsten, zinc and copper daughter(?) minerals have been identified. The temperature and (or) salinity data for skarns of different metal or geological type is not particularly useful to delineate whether a skarn locality is part of a more complex, as yet unexplored system. Solutions in Pb–Zn skarns tend to be lower-temperature (150–400°C) and more dilute (〈30 wt % T.D.S.) than in other skarn types, but exceptions occur.

Notes: Abstract In the Kamuikotan zone, jadeite occurs in pelitic rocks, in metaplagiogranites, in veins in amphibolites and mafic sedimentary rocks, and in jadeite-albite rocks. In the first and second types, jadeite is associated with quartz, and is often in direct contact with it. However, such rock-types never occur as part of the coherent metamorphic sequence, but are found only as exotic blocks enclosed in serpentinite. Thus, jadeite + quartz-bearing assemblages are not regarded as representative of the Kamuikotan metamorphism. Lawsonite and aragonite, however, commonly do occur in the Kamuikotan metamorphic rocks, and this metamorphism belongs to a subfacies of the lawsonite-albite facies, in which aragonite is stable. The serpentinite matrix which carried jadeite + quartz-bearing pelites and metaplagiogranites into the metamorphic sequence is interpreted as a tectonic rather than a sedimentary melange.

Notes: Abstract Contact aureoles of plutons emplaced into regionally metamorphosed terranes can provide indicators of physical conditions along a portion of regional metamorphic P-T trajectories, thereby allowing reconstruction of more complete P-T loops than would be otherwise possible. In the Northern Alabama Piedmont of the southern Appalachians, Wedowee Group metapelites preserve evidence for two regional metamorphic phases overprinted by contact metamorphism adjacent to the Blakes Ferry Trondhjemite. Textural evidence indicates that an early bt+st+grt assemblage was replaced by bt+chl+grt during the latter stages of regional metamorphism. Changes in AKFM topology, complex Fe-Mg-Ca garnet zoning, and the latestage appearance of epidote indicate that a sequence of continuous reactions (bt+st = grt+ ms followed by chl+ms+Ca-grt+Ca-pl=bt+ (Fe+Mg)-grt+ep) occurred in response to increasing pressure and resulted in the observed changes in mineral assemblage. Pl-ms-bt-grt thermobarometry indicates conditions of 580° 65°C, 8.5±0.8 kbar for equilibration of grt+ bt+chl. Pluton emplacement, subsequent to penetrative deformation, caused textural annealing and mineral re-equilibration by the continuous reaction bt+(Fe+Mg)-grt+ep = chl+ms+Ca-grt+Ca-pl within 50 m of the pluton. Conditions of 510±65°C, 5-7 kbar are inferred. A reconstructed P-T trajectory for this area is characterized by (1) early moderate-T, moderate-P metamorphism; (2) an increase in P to approximately 8.5 kbar; and (3) decompression and slight cooling prior to pluton emplacement. The compressional phase of this path is interpreted to result from underthrusting of the Wedowee metasediments to mid-crustal levels during Palaeozoic crustal thickening. Late-stage decompression prior to intrusion records uplift of these rocks in response to movement on structurally lower thrusts.

Notes: Abstract Mineralogical and petrological studies of Triassic Verrucano metasediments of the Northern Apennines are reported. The widespread occurrence of Al-silicates allows the delineation of four metamorphic zones with increasing metamorphic grade: (1) kaolinite zone (well Perugia 2, Umbria); (2) kaolinite-pyro-phyllite zone (Monte Argentario and part of the Verrucano of the Monticiano-Roccastrada area and Monti Leoni); (3) pyrophyllite zone (Monti Pisani, Iano, Monti Leoni, the Monticiano-Roccastrada area and some wells in the Larderello region); (4) kyanite zone (Massa area and some wells in the Larderello area).The four metamorphic zones correspond to temperatures ranging from 300°C to about 450°C. On the basis of the Si content of muscovite and geological arguments, pressures of between 3 and 5 kbar are estimated. The metamorphic zones are located more or less parallel to the bent north-west-south-east trending structural zonation of the Northern Apennines, with the concave side towards the Tyhrrenian Sea.During the Alpine orogeny, the Verrucano metasediments underwent three folding phases each of which has produced an axial plane schistosity (S1, S2, S3). During the first folding phase the Verrucano sediments were buried increasingly deeply within the crust from east to west. The climax of Alpine metamorphism was attained prior to the second folding phase with crystallization of porphyroblasts of kyanite and chloritoid in a central area located between Massa and Larderello. The inferred paleo-temperature distribution pattern resembles an asymmetric thermal high defined by the kyanite zone, and surrounded by the pyrophyllite zone. A similar pattern is still present in the Tuscan crust, as indicated by a series of geothermal anomalies passing through the Northern Apennines.

Notes: Abstract Rare layers of an aluminous, muscovite-rich rock from the Lewisian Complex at Stoer, North-West Scotland, display evidence which suggests that the rock has undergone local partial melting to form quartz-bearing veins and a corundum-bearing restite. The assemblages observed in these rocks match those predicted by modelling in the system KAlO2-NaAlO2-Al2O3-SiO2-H2O (KNASH) where certain bulk compositions melt peritectically to give corundum-bearing restites and quartz-normative melts. Study of the model system shows that the observed parageneses could have formed from a range of bulk compositions with a variety of possible values of aH2O which could have been internally or externally buffered. The KNASH petrogenetic grid, together with another in the system CaO-Na2O-FeO-Al2O3-SiO2-H2O (CNFASH), allows the P–T path of the rocks to be delineated and an estimate to be made of the conditions at the peak of metamorphism as 〉 11 kbar and 900-925°C. This estimate is in agreement with P–T estimates using thermobarometric methods on adjacent lithologies: The activity of H2O in the system throughout metamorphism is calculated to have been 〉0.3.

Notes: Abstract. In the European Community (EC) a change towards more market-oriented land use planning is required because of surplus stocks of cereals and dairy products, while at the same time other agricultural goods have to be imported. The implementation of such a policy has to be based on a scientifically sound and objective inventory of the physical potential of the EC as a whole.Principles of such a physical land assessment are explained, using the concepts of the FAO-Framework for Land Evaluation and the Agro-ecological Zone Approach, but adapted to European conditions. The conclusions arrived at through this procedure lead to different alternatives and scenarios, and hence provide valuable background information for future land use planning.

Notes: Abstract. Modern land use problems in the Netherlands are now focused on striking a balance between agricultural production, environmental protection, and nature and landscape conservation by means of new laws on soil protection. Quantitative expressions for crucial land qualities for different land management scenarios are needed to obtain adequate input for the decision making process emphasizing not only actual, but particularly potential conditions. Computer simulation techniques are being applied in this context. Three case studies are reviewed, covering: (i) adsorption of excess phosphate from animal manure; (ii) effects of lowering of water deficits for crops, and (iii) effects of soil tillage and compaction on crucial land qualities for agricultural production. Lack of representative basic data for simulation models inhibits their widespread practical application. Derivation of such basic data from existing soil-survey databases is therefore being discussed in terms of using various types of transfer functions, which allow more effective use of available data. In addition, geographical information systems are needed to allow rapid output for areas of land as represented on soil maps.

Notes: Abstract. A nationwide soil database system has been established containing soil maps, analytical data, and soil classification. The system has been widely used in agricultural planning at county and national level. This paper describes the basic data used for the soil database system, and the exploitation of this system in agricultural water planning. The principles for calculating the irrigation need at county level are given and also those for nationwide mapping of the potential need for drainage. Mapping of potentially acid sulphate soils, which has given rise to legislation on drainage of wetlands, is described, and the future use of the soil database system in agricultural water planning is discussed.

Notes: Abstract. Results of recent research on moisture regimes of surface water soils and on soil credibility are summarized, and proposals are made for the use of results in soil evaluation for selected crops.Measurements of water table depth show high variability from year to year and during the same season. Soil moisture regimes seem to affect soil management more than crop yield. A probabilistic calendar is needed for the occurrence of topsoil moisture content near the lower plastic limit in periods corresponding to the most important management practices. This is required in order to assess important soil qualities like workability and trafficability.Soil erosion is greatest when superficial run-off can create rills. This happens when run-off shear stresses exceed a threshold proportional to soil shear strength. Consequently, soil shear strength can be used as a measure of soil resistance to erosion. Probabilistic calendars are needed on the occurrence of heavy rainstorms able to create rills when the soil is most at risk.Entries for ratings of workability, trafficability and erosion risk are outlined.

Notes: Abstract. A system is described using data processed to combine maps from different sources in order to meet specific needs. The system, known as the KALEIDOS-INRA system, has many advantages over traditional map making and provides the user with better information. Its value is illustrated by a map showing the risk of drought to crops growing in central France.

Notes: Abstract. The purpose of this study was to try to estimate from soil and climate data both absolute and temporal individual soil hydraulic loading limits under Irish conditions. The two concepts cumulative soil moisture deficit (CSMD) and winter rain acceptance potential were used.Cumulative soil moisture deficit (1956–75) ranged from 116 mm in the southeast to 2 mm in the northwest. Four regions were delineated with mean cumulative maximum deficits (mm) of 105.3, 57.7, 20.0, and 2.0 respectively. Consequently, except for Region 4, hydraulic overloading is unlikely to occur under normal farm practices during soil moisture deficit period. Soil moisture deficit was present in Region 1 from early April through October, in Region 2 from early May through September, in Region 3 from early May through August and in Region 4, only in July.The concept of winter rain acceptance potential (WRAP) has been used to assess the possibilities for farm effluent disposal outside of the SMD period. Some 49% of Irish soils have a very high to moderate WRAP, 36% have a low to very low WRAP. These latter categories are likely to exhibit problems if effluents are applied outside of the SMD period.Regional farm slurry storage duration requirements have been estimated from SMD and WRAP data. These are 11.3, 14.0, 16.7 and 20.0 weeks respectively for regions 1, 2, 3 and 4.

Notes: Abstract. Soils mainly in alluvial marine sediments around the coast of England and Wales, occupy about 6% of the agricultural land. The extent of salt-affected soils within these parent materials is unknown, but is believed to be significant from the evidence of existing soil surveys.The principal salt is sodium chloride, and the degree of salinity depends on depth to saline groundwater, the intensity of leaching, and the frequency and severity of past marine flooding. Evidence suggests that while the effects of the flooding are obvious and immediate, long-term salinity owes more to groundwater behaviour and chemistry.The amount of sodium in these soils, particularly the heavier-textured ones, makes them structurally unstable, especially when wet. The instability in turn makes them difficult to drain. Ameliorative treatments are possible, but are expensive and slow to take effect.In their natural or semi-natural state these soils form large areas of wetland or unimproved grassland, often of interest to conservationists. In spite of this, and their generally unfavourable properties for cultivation, extensive areas have become arable in recent years.Structural stability, salt content, and exchangeable sodium percentage are intimately linked and can be measured during soil survey, which then aids rational decisions about land use. Such a survey of the North Kent Marshes is presented as a case study.

Notes: Abstract. The effect of various cultivation sequences on the performance of field drainage systems was investigated in a number of case studies carried out on former opencast coal mining land. Comparisons of drain flow patterns before and after cultivation indicated marked deteriorations in performance following preparation of the final seedbed. Neither mouldboard ploughing nor discing alone affected drain flow.Soil moisture, hydraulic conductivity and drain flow data suggested that drainage performance may have deteriorated as a result, initially, of secondary drainage channels being blocked with fine materials translocated from the seedbed. A subsequent collapse of tilth to form a surface pan reinforced this adverse effect. It was not clear to what extent the failure of secondary drainage channels contributed to this collapse.Implications for the management of former opencast land and the advantages of various cultivation techniques are discussed.

Notes: Abstract. Evidence based on observations of colour, growth and measurements of stem nitrate on carrots and sugar beet, colour and yield of grass, and of yield of wheat in different areas of Britain showed that growth and yield may have been substantially reduced in the wet summer of 1985 due to deficiency of nitrogen following large losses by denitrification. An account of die processes involved is given, together with observations and tests on affected soils. These were compared with field measurements of denitrification also made in 1985, under barley.Examination of climatic data suggests that there were several periods in May, June, July and August when the soils close to the surface would have been saturated for days on end, and in the presence of many tine roots typical of crops at that time of year, the onset of an anaerobic state and accompanying denitrification would have been highly likely. The field evidence in 1985 suggests that nitrogen losses may have been much higher than those reported previously from research station investigations.

Notes: Abstract. The effect of a short-term freeze/thaw cycle (15°C to -8°C to 15°C) on gaseous N-loss (denitrification and NH3-volatilization) from intact blocks of an upland soil is described. Rates of both denitrification and NH3-volatilization were increased by the freeze/thaw cycle, particularly when the blocks had previously been fertilized with urea. Increased gaseous N-loss due to freeze/thaw is reported for soils under heather and under improved grass pasture.

Notes: Abstract. Avalon winter wheat was grown on deep silty clay loam soil (Hook series) under a fixed shelter at Rothamsted with either full drought or irrigation from the end of March to July, 1982. During this time the irrigated crop used 295 mm of irrigation water plus 45 mm of stored soil water, while the droughted crop extracted 223 mm of water from the soil. The roots penetrated to at least 1.8m and water was extracted from 2 m depth.Even with a fully developed root system the crops could transpire at the full rate of atmospheric demand only when the near-surface soil was well supplied with water. However, the draughted crop extracted enough water from the loamy sub-soil to maintain a reduced transpiration flow for a further nine weeks after the near-surface water was depleted. Thus crop growth was maintained with a loss at final harvest of only 10% in total dry weight and even less in grain yield.A summary of other results confirm that yield losses due to drought have been reported only for light soils, except in the exceptional year of 1976, and that drought is not normally an important factor affecting yields of winter wheat in the UK.

Notes: Abstract. Manurial treatments and cropping history have remained unchanged for many years in classical and long-term experiments at Rothamsted and Woburn, in some cases for more than 100 years. Soil samples taken periodically have been analysed to follow changes in organic carbon content with time and treatment. Data presented here clearly show effects of carbon input and soil texture on equilibrium organic matter content.Until recently increasing amounts of soil organic matter had little effect on yields of arable crops especially if fertilizer nitrogen dressings were chosen correctly. However the yield potential of many crops has increased and various agronomic inputs have become available to achieve that potential. Yields of many crops are now larger on soils with extra organic matter both on the sandy loam at Woburn and the silty clay loam at Rothamsted. Some of the effect appears to be related to extra water holding capacity, some to availability of nitrogen in ways which cannot be mimicked by dressings of fertilizer N, and some to improved soil physical properties. Responses to fertilizer N have been larger on soils with more organic matter.

Notes: Abstract. Guidelines are proposed to indicate the range of drainage problems encountered under Scottish conditions, along with some of the main factors to be considered for the treatment of these problems. The identified categories are briefly discussed, together with the potential application of the guidelines.

Notes: Abstract. High rates of erosion are reported from three sites on brickearth (loess) soils in east Kent. Problems are acute where soils are used for intensive production of vegetables and salad crops. Erosion appears to be the result of structural instability, lack of crop cover for much of the year, and certain managment practices, such as ridging the soil for the crop. In the autumn of 1984, about 120 tonnes of soil was lost from rills in a field of onions: an erosion rate of about 15 t ha−1. A large field under winter cereals also eroded and this resulted in damage to property. Conservation techniques are recommended.

Notes: Abstract. Previous studies have shown marked increases in wheat yields on a swelling clay soil due to gypsumslotting compared to no-gypsum and surface gypsum applications, largely through improved aeration in the surface layers. In the present study, steady infiltration rates indicated 2-fold increases due to surface gypsum applications and 4- to 6-fold increases due to slotted gypsum. This should provide increased moisture storage and reduced soil erosion hazards during prolonged heavy rainfall periods, provided that a crust does not form under the impact of raindrops. However, gypsum-slotted lands should not be used in crop rotations which include ponded rice, due to increased potential water use and risk of rising watertables and salinization.The effect of the ‘throttle’ in the upper B horizon which restricts moisture storage in the lower soil layers during short-term and prolonged ponding was reduced, but not eliminated, by surface and slotted gypsum applications. Thus the moisture contents of the lower depths in both the non-ameliorated and ameliorated soils were less than the moisture content at saturation or at -10 kPa potential even after flooding for 11 days.

Notes: Abstract. Reductions in hydraulic conductivity and specific yield (drainable porosity) of large cores of Evesham clay soil were observed for periods up to 40 days under continuous ponding. A strong linear relationship (r2= 0.94) found between these two variables was used as parameter input to a layered drainage model for mole drained soils. Model results indicated that soils of lower drainable porosity and hydraulic conductivity produced higher peaked hydrographs widi faster recessions. These results are discussed in relation to the effects of soil loosening on drain response in heavy clay soils.

Notes: Abstract. The use of sportsfields in winter results in drastic changes in the physical properties of most soils. In consequence adequate sportsfield drainage demands much greater attention to the transmission of incident rainfall to the underdrain system than is normally necessary in agricultural drainage. Solutions to the problem differ in concept and cost, and range from complete profile construction to bypass drainage systems, causing minimal soil disturbance. Specific requirements are examined and practical solutions illustrated and discussed.

Notes: Abstract. The prediction of water-table levels from groundwater theory for a drainage system in a uniform homogeneous soil was tested in an existing field system. Specially designed meters recorded water-table heights and drain discharge with time. A comprehensive hydraulic conductivity survey was made below the water table.The results agreed with theory for water-table heights up to about 300 mm above the mean drain level. The drainage above that level was larger than predicted, either because of an increased hydraulic conductivity (which could have been produced by subsoiling the previous year and would not have been picked up by die hydraulic conductivity measurements), or because of the presence of an older shallower lateral drainage system, broken and blocked, that was discovered during the work.Attention is drawn to the inadequacies of dip-wells for monitoring rapid changes in water-table levels and to the problem of sample size in hydraulic conductivity measurements, which if too small can lead to apparent variability.

Notes: Abstract. Mole drainage of the Hallsworth Series was compared to a traditional treatment of drains alone at 12 m spacing. It is demonstrated that mole drainage offers superior control of water tables and reduces surface run-off. Some management implications of these results are discussed.

Notes: Abstract. Afforestation in the British uplands can lead to changes in the hydrology, sediment load and chemistry of streams. These changes may affect water resource management costs, stream biota and the health of fisheries. Some of the changes can be related to specific phases of the forest management cycle, e.g. site preparation, fertilization, felling; modifications in management practice can limit their impact. Other changes in water yield and chemistry seem to have complex origins in forest-atmosphere and forest-soil interactions; these are more difficult to counteract.

Notes: Abstract. Much field drainage work in Great Britain includes costly permeable backfill material as a connector between mole drains, subsoiler fissures, or permeable subsoil layers and the pipe. This paper reviews the role of the Ministry of Agriculture in sponsoring research and advice on drainage design, as well as providing grant-aid to farmers for the installation of field drainage. As a result of this involvement permeable backfill is now regarded as an essential element in the drainage of clayey soils and springs. The cost is fully justified by the establishment and maintenance of highly efficient and flexible farming systems. These techniques are applicable to many countries where clayey, slowly permeable soils predominate.

Notes: Abstract. Losses of nitrogen in the tile drainflow from a clay soil (Evesham series) under grazed grassland were monitored during the 1982/83 and 1983/84 drainflow seasons. In 1982/83, 40% of the discharge had a NO3− concentration 〉 11.3 mgNl−1, while in 1983/84 concentrations were always 〉 20 mgNl−1. Total N lost by leaching was 17.5 and 48.7 kg ha−1 in 1982/83 and 1983/84 respectively, which was equivalent to 9 and 43% of the fertilizer applied. The marked difference in N losses for the two seasons was attributed to differences in the quantity and timing of N fertilizer applications, the dryness of the preceding summer and the duration and density of stocking.

Notes: Abstract. The literature indicates that cane yield-tonnes cane per hectare (tc ha−1)-is directly related to actual evapotranspiration (Et) and that a ratio 1 tc ha−1 cm−1 Et should be a reasonable objective; this is frequently not attained in commercial practice. Analysis of extensive data from non-irrigated cane in upland Kenya demonstrated water use efficiencies of 0.5 to 0.6 tc ha−1 cm−1 Et in relationships which were remarkably precise; some of the reasons for the failure to achieve higher efficiencies at this location are discussed. The practice of irrigation is likely to introduce additional complications and so reduce water use efficiencies even further; thus responses to irrigation should be measured experimentally before capital expenditure is approved. The main additional complications are the interactions between irrigation and soil type on rooting and growth, in particular the influence of soil type on yield responses; and the fact that advective energy interferes with the convenient, direct relationships between radiation and evaporation and yield.

Notes: Abstract. An interview survey of farmers' assessment of the overall capacity of land, as well as its suitability for specific uses is compared with the judgement of the Soil Survey of England and Wales. The results are interpreted as showing that in a general evaluation the farmers are accurately aware of the quality of their land, but they are less well informed as to its true suitability for specific uses. The comparison shows the potential importance of land suitability analysis to the farmers, especially at a time of changing economic pressures.

Notes: Abstract The effect of incorporating straw of Vigna radiata L. (moong) into the soil at 3.2 t ha-1 on the grain yields of mustard and wheat was investigated with and without 0, 50 and 100% of optimum levels of fertilizers (100 kg N + 50 kg P2O3 ha-1 for mustard and 125 kg N + 62.5 kg P2O3+ 30 kg k2O ha-1 for wheat). In the two-year field experiment, the incorporation of moong residue reduced the grain yield of mustard by 24 to 31% and wheat by 13 to 17%. This adverse effect was, however, diminished with the application of fertilizers. It was concluded that management of crop residues is possible without any adverse effect on the subsequent crop yield when incorporated with adequate levels of N and P fertilizers.

Notes: Abstract Soil samples have been taken periodically from unlimed plots of the 130-year-old Park Grass Experiment and from the 100-year-old Geescroft Wilderness at Rothamsted. Changes in the pH of the samples show how acidification has progressed. The soils are now at, or are approaching, equilibrium pH values which depend on the acidifying inputs and on the buffering capacities of the soils. We have calculated the contributions to soil acidification of natural sources of acidity in the soil, atmospheric deposition, crop growth and nutrient removal, and, where applicable, additions of fertilizers. The relative importance of each source of acidification has changed as the soils have become more acid. Acid rain (wet deposited acidity) is a negligible source, but total atmospheric deposition may comprise up to 30% of acidifying inputs at near neutral soil pH values and more as soil pH decreases. Excepting fertilizers, the greatest causes of soil acidification at or near neutral pH values are the natural inputs of H+ from the dissolution of CO2 and subsequent dissociation of carbonic acid, and the mineralization of organic matter.Under grassland, single superphosphate and small amounts of sodium and magnesium sulphates have had no effect on soil pH, whilst potassium sulphate increased soil acidity slightly. All of these effects are greatly outweighed under grassland, however, by those of nitrogen fertilizers. Against a background of acidification from atmospheric, crop and natural inputs, nitrogen applied as ammonium sulphate decreased soil pH up to a maximum of 1.2 units at a rate in direct proportion to the amount added, and nitrogen applied as sodium nitrate increased soil pH by between 0.5 and 1 unit.

Notes: Abstract. The principles and practice of bulk soil handling for mine reclamation are reviewed, with special reference to the agricultural restoration of sand and gravel quarries in the UK. The principal forms of damage to soils when moved are due to trafficking, and include compaction in cohesive soils and loss of structure in granular soils. Of the wide range of soil moving equipment available, earthscrapers are often responsible for severe compaction. New soil handling techniques have been developed to minimize such damage. On chalky boulder clay soils earthscrapers can be combined with excavators for topsoil placement. On more granular soils all soil handling can be carried out by excavators and dumptrucks, with virtually immediate restoration to full agricultural productivity.

Notes: Abstract. A computer simulation model was used to estimate the effects of season, site, sowing date, residual-N after harvest, autumn-N and field drains on winter losses of nitrate from soils growing winter wheat. The simulations were based on weather data between 1970–71 and 1983–84 and soil data from Rothamsted and Woburn. The residual-N after harvest was predicted to have most effect on nitrate losses, followed by season and site. For the values of residual-N and autumn-applied fertilizer-N tested, the predicted average nitrate-N losses differed between seasons by up to 100 kg N ha-1, and the nitrate-N concentrations varied between 30 and 80 mg N l-1.

Notes: Abstract. The impact of three methods of pasture improvement on soil water chemistry were studied: ploughing plus 15 t ha-1 lime c. 40 years ago, 5 t ha-1 surface spread lime c. 20 years ago and surface cultivation with 7 t ha-1 lime plus compound fertilizer 10 years ago. Soil solution was sampled using tensionless lysimeters and porous ceramic cups. Concentrations of several solutes were higher in the treated soils than a control, including solutes not added in lime or fertilizers. Calcium, magnesium and bicarbonate concentrations showed the largest increases; these were apparent in all horizons, and all treatments. Bicarbonate had become the dominant anion. Solute concentrations varied between treatments and were related to the amount of an element added rather than time since treatment. Highest mean calcium concentrations, 6.25 mg l-1 were still low compared with drainage from lowland arable soils but could have a significant impact on the calcium-poor surface waters of the uplands.

Notes: Seismic reflection data always exhibit a progressive loss of high-frequency energy with time. This effect is partly attributable to irreversible processes such as the conversion of elastic energy into heat (commonly known as absorption), and partly to reversible processes associated with interference between reflected waves arriving at different times. This paper looks only at reversible linear elastic effects at normal incidence and asks the following question: if there were no such absorption, would there still be a progressive loss of high-frequency energy?Using normal incidence and a layered elastic earth model we prove the following results.1. The normal incidence response of a sequence of plane parallel elastic layers is non-white.2. The pressure wave reflected by a layer that is thin compared with a wavelength is differentiated with respect to the incident wave.3. The transmission response of a thin layer is consequently low-pass and the transmission response of a sequence containing many thin layers is very low-pass.4. The well-known effect of the transport of acoustic energy by peg-leg multiples within thin layers is identical with this low-pass transmission response.5. It follows that the high frequency energy is reflected back early in the seismogram.6. By comparison, very low-frequencies are transmitted through the layered sequence easily and are reflected with difficulty. There is probably a lack of low-frequency energy in the reflection seismogram, by comparison with the spectrum of the incident plane wave.It follows that any meaningful evaluation of frequency-dependent absorption in seismic data cannot take place unless the frequency-dependent linear elastic effects are taken into account first.

Notes: A new integral-equation program for calculation of the E-polarization response allows modeling of VLF for plane wave or line source input, e.g., magnetotellurics and Turam responses. The anomalous conducting body is modeled by a number of square cells, each of individual size and resistivity, and with arbitrary position in the host medium. This provides a high degree of flexibility and allows for simulation of rather complex conductivity structures. The computation time has been drastically reduced by using techniques such as digital filtering and fast Fourier transformation.The interpretation of a measured Turam profile and the influence of galvanically channelled currents in the conducting body is discussed.

Notes: Examples show that the sampling operation–i.e., the change from the continuous time domain to the discrete time domain–does not necessarily preserve the minimum-phase property. Further examples can be constructed to show that the resampling operation on the discrete time domain does not necessarily preserve the minimum-phase property. Finally it can be shown that the minimum-phase property can be either created or destroyed by sampling or resampling.

Notes: An integral equation method is described for solving the potential problem of a stationary electric current in a medium that is linear, isotropic and piecewise homogeneous in terms of electrical conductivity. The integral equations are Fredholm's equations of the ‘second kind’ developed for the potential of the electric field. In this method the discontinuity-surfaces of electrical conductivity are divided into ‘sub-areas’ that are so small that the value of their potential can be regarded as constant.The equations are applied to 3-D galvanic modeling. In the numerical examples the convergence is examined. The results are also compared with solutions derived with other integral equations. Examples are given of anomalies of apparent resistivity and mise-a-la-masse methods, assuming finite conductivity contrast. We show that the numerical solutions converge more rapidly than compared to solutions published earlier for the electric field. This results from the fact that the potential (as a function of the location coordinate) behaves more regularly than the electric field. The equations are applicable to all cases where conductivity contrast is finite.

Notes: The propagation of Love seam-waves across washouts of coal seams was studied by calculating synthetic seismograms with a finite-difference method. Seam interruption, seam end and seam thinning models were investigated. The horizontal offset, the dip of the discontinuities and the degree of erosion served as variable parameters. Maximum displacement amplitudes, relative spectral amplitudes and phase and group slowness curves were extracted from the synthetic seismograms.Both seam interruption and seam thinning reduce the maximum displacement amplitudes of the transmitted Love seam-waves. The degree of amplitude reduction depends on the horizontal offset and the degree of erosion. It is four times greater for a total seam interruption than for an equivalent seam thinning with a horizontal offset of four times the seam thickness. In a seam cut vertically, the impedance contrast between the coal and the washout filling determines the maximum displacement amplitudes of the reflected Love seam-waves. They diminish by a maximum factor of four in oblique interruption zone discontinuities with a dip of maximum 27°, and by a maximum factor of ten in a seam thinning with a degree of erosion of at least 22%.The analysis of the relative spectral amplitudes indicates a preferential transmission of those phases with frequencies below, and a preferential reflection of those phases with frequencies above the first mode Airy-phase. The relative spectral amplitudes of the reflected Love seam-waves show a distinct interference pattern of the waves reflected at both interruption zone discontinuities.The dispersion analysis reveals a flattening of the phase and group slowness curves with increasing frequencies, horizontal offset and degrees of erosion.These results imply that a detection of washouts in-mine will be possible in a frequency range including at least the first mode Airy-phase. An interference pattern and a flattening of the dispersion curve indicate a washout rather than other seam obstructions and leads to an estimate of the washout dimension.

Notes: Investigations show that the depth range of the gravity method for detecting cavities is considerably greater than expected on the basis of theoretical calculations that consider only the depth and shape of the cavity.The cavity generates its own gravity field that is the sum of the activity of the cavity itself and the density changes caused in the surrounding rocks by the process of their destruction as a result of the cavity's expansion. The latter factor is decisive for the cavity's detection by the gravity method in several cases.The extent of the zones of change density in the surrounding rocks and their actual shape depend on many parameters. Thus, the determination of the depth of the cavity cannot be made by comparing measured and theoretical curves of gravity anomalies. The location of the center of gravity of the area disturbed by the cavity or upper boundary of its development towards the ground surface can be determined by denoting the singular point of gravity as a result of the downward analytical continuation of Ag.The Strakhov-Grigorieva-Lapina (1977) method fulfils the necessary conditions in the field.

Notes: Short filters for calculating Hankel-transformations, with special attention to the d.c.-sounding problem, have been published in recent years. These filters, with a typical length of less than 25 coefficients, have made it possible to implement, e.g., VES-interpretation programs on microcomputers and 3-D electric and electromagnetic modeling programs on minicomputers. Initially the performance of the short filters was rather poor, but with the introduction of short optimized filters there has been a considerable improvement in the accuracy.An optimization procedure is applied to design a 20-point filter for the Fourier sine-transformation. This filter may be useful in electromagnetic prospecting theory, e.g., in the calculation of the electric and magnetic field from a line source.

Notes: This paper reviews computer techniques used in the automatic zoning and correlation of well-logs. Prior to correlating, well-logs are to be segmented–or ‘zoned’–so as to delineate sections that have similar properties. Techniques discussed include statistical methods such as variance tests and Student's t-test, linguistic analysis, the use of Walsh functions and spectral analysis.Well-log correlation, which may be between traces from different wells or between traces from the same hole (as in dip logs), is used in basin studies and the determination of structural dip. A variety of methods are reviewed including conventional time and frequency correlation, sequence slotting, pattern recognition and frequency analysis. Future directions for investigation are proposed.

Notes: A portable low-power Very Low Frequency (VLF) transmitter using a large square loop antenna has been designed, assembled and tested by the Geological Survey of Canada (GSC) for geological studies of fracture patterns in igneous rock masses. Standard laboratory equipment, consisting of a signal generator, a 1100-W power amplifier and several high-power tuning capacitors, was used for the purpose.Field tests at the Chalk River facilities of Atomic Energy of Canada Limited have demonstrated a remarkable similarity between survey results obtained using the VLF signals from the local loop transmitter and from distant US Navy VLF transmitters. The local loop was used to simulate the fields from navy stations NAA in Cutler, Maine and NSS in Annapolis, Maryland. Conductor axes, mapped by using these navy stations, and by using the loop antenna yielded almost identical results. A survey was also done in the same area with the local loop placed in such a manner that the direction of the VLF field was at 45° to the field directions from NAA and NSS. In this case, the same conductor axes were located with only minor shifts in position, indicating that conductors whose axes lie within 45° of the direction of the primary horizontal magnetic field are mapped. Thus, it is probably sufficient to have two sources with orthogonal VLF fields to map all VLF conductors in an area. Since in most areas at least one navy VLF station can be used, the local loop transmitter can be used to generate a signal at right angles to the direction from the navy transmitter to allow a more complete VLF survey coverage.

Notes: The article provides a theoretical basis for the extension of the method of scaling law deconvolution to three dimensions using airgun arrays as a sound source.Earlier papers by the author required the dimensions of the scaled sources to be different while the depths and firing pressures were maintained the same in order to preserve the same dynamics of the scaled sources at scaled time. However, this forces the source ghost to be considered as part of the impulse response of the earth rather than as part of the downgoing source wave. And, in fact, the dynamics of the scaled sources are not the same at the same depth because the ghost reflection modulates the behaviour of the oscillating bubbles generated by the airguns, and this modulation does not scale.To force the sources to scale properly, including the ghost interaction, the larger source must be put at greater depth, where hydrostatic pressure is greater, and the initial firing pressure must be adjusted accordingly. Thus, the depth, initial firing pressure and gun volume are all variables. The interaction among guns in scaled airgun arrays also scales exactly if the geometry of an array and the depth of its deployment are scaled by the same factor.

Notes: Wave field extrapolation including critical angle events in modeling, migration and inversion can be handled with algorithms based on both the one-way wave equations and the two-way wave equation. It is shown that for 1-D inhomogeneous media, critical angle events as well as multiple reflections may elegantly be included in pre-stack modeling, pre-stack migration and velocity inversion. For 2-D and 3-D inhomogeneous media a powerful pre-stack migration scheme can be developed which includes critical angle events as well as multiple reflections. Finally, suggestions for practical applications are given.

Notes: Bayesian statistics are applied to the problem of signal-to-noise ratio enhancement from a common-midpoint gather. By maximizing the a posteriori probability distribution of the gather with respect to the minimum-offset trace and suppressing multiples via a semblance criterion, a statistically biased stack is formed with signal-to-noise ratio comparable to that of the usual stack while preserving the resolution and registration of the original noisy trace.Application of the algorithm to real data reveals geologically significant features which are indistinct in the standard stacked section.

Notes: Specific electrical resistivity of natural waters contains information on their genesis. The authors propose to conduct mass and regime observations of this parameter in river and stream beds.The electrical resistivities in streams flowing from under a glacier reveal details formed at the same time as the glacier. Observations in the beds of big rivers show a gradual increase in water salinity overlain by reductions by inflowing glacial waters.The diurnal and annual trend of changes in the electrical conductivity of water associated with the change in the balance of glacial and ground waters has been established near to glaciers.Resistivity observations help to locate discharge sites of sub-permafrost waters, for water.

Notes: The VLF response of laterally inhomogeneous and anisotropic models is calculated numerically using the finite element method.Some results are presented for a slab model in terms both of the polarization parameters, i.e., the tilt angle and ellipticity of the magnetic polarization ellipse, and the amplitude ratio |Hz/Hx|.On the basis of both the ellipticity and the tilt angle, it is possible to discriminate between a poor conductor and a good one. The direction of the dip can be determined from the anomaly profiles of all diagnostic parameters. The effect of the conductive overburden is most noticeable on the ellipticity profile: one observes attenuation for a poor conductor and “negative attenuation” for a good conductor. The anomaly profiles for anisotropic cases are consistent with the ones of the isotropic cases.

Notes: Master curves are presented for three-layer earth-sections, the electrical resistivity in the intermediate layer of which has a linear variation with depth. A new approach is proposed to interpret the sounding data with the help of RMS difference in apparent resistivity values.

Notes: Basic Laterolog devices employ a measure-current focusing technique to provide well logs of formation resistivity that feature sharp vertical definition combined with a depth of investigation much improved over those of normals of comparable spacings.To develop the concept of measure-current focusing, a disk-electrode arrangement analogous to a guard-ring capacitor is considered first, leading finally to consideration of a real sonde in a cylindrical borehole. In the latter, auxiliary currents are adjusted to maintain substantially at zero the vertical potential gradients above and below the central measure-current electrode; this has the effect of focusing the measure-current beam.However, prediction of sonde responses on the basis of current patterns can in some cases be misleading. Indeed, for a given Laterolog array, one may use a (reciprocalmode) current pattern radically different from the one defined by the basic (direct-mode) measure-current focusing scheme and still obtain the same resistivity measurement. This feature is illustrated for Laterolog 3 by use of transfer impedances, and demonstrated for certain more general cases using the reciprocity theorem.Comparisons of Laterolog responses across typical thin beds, both non-invaded and invaded, with those of normal devices of a comparable range of spacings illustrate the improved vertical resolution obtained with Laterolog devices. The examples also show the different magnitudes of the auxiliary currents (thenceforth designated “bucking”- or “focusing” currents) used in the direct and reciprocal modes and illustrate how these currents must continuously vary in order to maintain the focused condition as the sonde moves through the bed.Finally, briefly considering possible applications of Laterolog-type arrays in surface prospecting, it is shown that a one-dimensional array laid out on the surface does not provide the same degree of measure-current focusing as is obtained in a borehole. Some improvement is obtained with a combination of two crossed linear arrays. Much more is obtained using a circular array.

Notes: Inferior reflection quality in the Gulf of Suez at the target depth interval is attributable in part to surficial multiple reflections. An excellent example of the latter is observed on a typical seismic line in the northern portion of the Gulf. An increase in prominence of the multiple reflections appears associated with decreasing depth to a dipping highvelocity layer.Inversion of a second-order polynomial time-distance function, fitted to the observed refraction onset time-distance values, gives the velocity-depth function for sediments between the water bottom and a high-velocity layer. Velocities thus determined increase non-linearly with depth from a value near water velocity at the water bottom. Depths to the high-velocity layer are obtained from the associated head-wave linear time-distance function and by ray tracing in the overlying sediments.As the high-velocity layer approaches the water bottom from sub-water depths exceeding 0.6 km to a depth of 56 m, intensity of the multiple reflections increases to the extent of completely dominating individual records to a time of at least 3 s. The estimated plane-wave normal-incident reflection coefficient at the top of the high-velocity layer increases with decreasing depth to this layer, approaching 0.5 at the shallowest depth. This strong reflection coefficient further substantiates the existence of multiple reflections between the high-velocity layer and water layer. However, existence of water-layer multiples cannot be ruled out. The estimated water-bottom reflection coefficient is approximately 0.3, a substantial value. Multiple reflections of considerably less intensity are apparent where the high-velocity layer is deepest, and it is likely that such are waterlayer multiple reflections. Unfortunately, water-layer multiple reflections and multiple reflections between the water surface and high-velocity layer cannot be separated by their coincidence with time-distance (normal moveout) curves, the configuration of each visibly matching the curves equally well.

Notes: Seismic exploration techniques which have been developed for oil prospecting contribute a valuable means for surveying coal measures. Since the object is to detect minor faults within the first 1500 m, rather than structural features at great depth, the new technique requires much higher resolution in the early part of the traditional seismic cross-section.Higher resolution means broader bandwidth, which must be obtained by extending the high frequency end of the spectrum. This is achieved (a) by scaling down the explosive charge size and using single geophones instead of groups, and (b) by reducing the sampling interval in space and time. Noise which does not scale down includes static anomalies and ground-roll. The consideration of statics, ground-roll, and the high-cut filtering effect of the near surface layers forces the use of deep shot holes and, where possible, deep detectors. This approach is confirmed by experiments and has been implemented on a regular basis in production.It is demonstrated that the present technique will clearly resolve faults with a vertical throw of about 5 m at 800 m depth.

Notes: Correlations between longitudinal velocities and rock mechanic parameters such as fracture frequencies and “Rock Quality Designation” (RQD) values have been studied, based upon velocity data from various rock types and different geographical locations.The dispersion of values at different sites studied is on average ± 0.8 cracks per meter and for the RQD values ± 3.5%. Within sites the dispersion of individual values relative to the average for the site is ± 1.0 – 2.0 cracks per meter and ± 2 – 6% for the RQD values.The deviations are rather moderate, especially when considering the variation of rock type involved in the studies: amphibolite, granite, gneiss, meta-anorthosite, pegmatite, porphyry, quartzite, and mylonite. The studies thus confirmed earlier assumptions that there is a strong correlation between longitudinal velocity and fracturing and that the velocities can be used to give rather accurate predictions of the quality of rock masses for construction purposes. The accuracy of the predictions increases if the velocity level of the more competent rock is taken into account.The correlation between velocity and fracturing is related to jointed but unweathered igneous and metamorphic rock and cannot be applied without introducing serious errors to a site where the rocks present a higher degree of alteration and weathering.Comparisons between rock permeability and longitudinal velocity proved that a more reliable general correlation is not likely to be found.By comparing the elastic moduli Edyn, μ, and k with ø, Vp/V8, and k/μ, indications have been obtained where the optimum rock conditions for a certain site are to be encountered. This has been verified by a similar comparison where the elastic moduli have been replaced by fracturing values.The value of the longitudinal velocity as a means to evaluate rock quality increases if the position of the velocity in the range of the Poisson's ratio has been established.The average relationships between longitudinal velocities and the corresponding elastic moduli proved to be:The values from each site differ from the average values with about ± 2 GPa for Edyn and about ± 1 GPa for μ and k.It was confirmed that in igneous and metamorphic rocks longitudinal velocities ≤ 4000 m/s generally indicate rock masses where heavier tunnel support will be needed. This velocity limit corresponds to an average fracture frequency of about 10 cracks per meter and a RQD value of about 65 %. The prediction of the tunnel reinforcements needed at a particular site will, however, be improved if the general velocity level of the more competent rock is considered.

Notes: The Minimum Entropy Deconvolution (MED) technique of Wiggins (1977) represents a breakthrough in deconvolution and will undoubtedly find wide application in many fields. MED does not require any phase assumptions about the disturbing function and seeks a deconvolved output which consists of the smallest number of large spikes consistent with the input data.The efficiency of MED is much improved when an exponential transformation is incorporated into the algorithm. This is particularly true when the input traces contain additive noise. In this case the noise suppression characteristics of MED are considerably enhanced by the transformation and the identification of smaller spikes is improved. This paper also presents a kurtosis criterion of simplicity rather than the varimax norm introduced by Wiggins. It appears that for a multiple trace input the kurtosis measure leads to improved results.

Notes: Long leg multiples can be suppressed by a method which provides an alternative to weighted common-depth-point stacking and multichannel stacking filtering. The suppression is achieved by coherency weighting whereby the time-dependent weighting factor decreases as the semblance of the multiple reflections increases.The algorithm of the method is described. Its efficiency is discussed in relation to the input data and results of its application to marine seismic data are presented.For practical application, the stacking velocity of the multiples has to be known. As the process is based on stacking velocities, different types of multiples can be handled, for instance water-bottom multiples or internal multiples. The parameter analysis shows that the degree of multiple suppression can easily be controlled by adapting the parameters of the procedure to the field conditions.During the suppression of multiples, the primaries are saved according to the moveout differences between the two. The non-linear behaviour of the process causes signal suppression and distortion effects, which have to be corrected by AGC normalization and low-pass filtering.Among the various applications available, only the suppression of long leg water-bottom multiples is treated here. The results show that their suppression on the basis of moveout differences is efficient even when standard length streamers are used in regions with water depth of up to 1500 m and more, if the stacking velocity of the primaries is about 10 to 20% higher than that of the multiples. Even if those parts of the primaries which are masked by the multiples are suppressed in the individual common-depth-point gathers by the procedure, the remaining primaries in the AGV stacked section are largely uncovered by the multiple suppression.

Notes: Investigation of fluctuating earth-currents has led to a simple method of eliminating the noise superimposed on the signal in geoelectrical resistivity surveys. The similarity of the potential fluctuations, simultaneously measured at different locations, is used to calculate the direction and magnitude of the potential gradient. Contour maps of equipotential lines were made, both from disjointed gradient measurements using a numerical approximation method and from a network of measured potential differences. These contour maps were compared with potential fields calculated for simple homogeneous models. A good fit was obtained with the field of a conducting plate. When this is subtracted from the measured field, the result is a map that shows anomalies that can be correlated with geological structures.

Notes: The calculation of potential field anomalies on different levels below the measuring level permits to localize the singular points related to the sources of anomalies.It is possible to achieve considerable improvement of the resolution of this method〈list xml:id="l1" style="custom"〉1) filtering of analytical downward continuation,2) the use of the magnitude of the gravitational vector,3) calculation of physe changes.The numerical examples confirm these assumptions.

Notes: Results are presented of a series of cross-hole acoustic measurements made between four horizontal boreholes drilled from a near-surface underground opening situated in a basaltic rock mass. The objectives of the program were to assess the extent of blast damage around the opening, and to evaluate the rock mass characteristics and their spatial variation around the opening. The acoustic velocity and attenuation data are indicative of an anisotropic, jointed rock mass, with a greater intensity of jointing along travel paths in the horizontal than the vertical direction. Low acoustic P- and S-velocities are indicative of blast damage and of zones of intense jointing or fracturing. In this case blast damage extends to approximately 1.5 m from the face. Attenuation data appear to be less sensitive in distinguishing between the blast-damaged zone and intense vertical jointing and fracturing in the virgin rock mass. Taken together with field data, laboratory measurements of P- and S-wave velocities on intact core samples suggest that the rock mass is probably water saturated.

Notes: Analysis of the phase spectra from the signatures, impulse responses and other wavelets observed in seismic data leads to the construction of equivalent minimum-phase functions. The accuracy of such computations using digitally sampled data is questioned with special reference to Texas Instruments DFS IV and DFS V recording filters. Results vary with the lengths and sample rates of the time functions, and further errors may be introduced when implementing the Hilbert transform. Such problems are related to poor resolution in the low amplitude areas of the spectrum. Techniques for correction are described. With appropriate shaping a reasonably accurate phase spectrum may be computed for the minimum-phase function. The generation of minimum-phase wavelets within the processing sequence is briefly discussed.

Notes: The electrochemical transfer characteristics of nickel sulphides from six West Australian localities are examined by the nonlinear complex resistivity (nlcr) method. Ores are classified on the basis of their state of oxidation (supergene, transition zone and primary ores) in an equivalent mine water electrolyte; evidence is found for a systematic change of electrical response with oxidation that is symptomatic of electrochemical reactions varying from diffusion to charge-transfer controlled processes. The analysis is based on the assumption that the Randies’ circuit is an effective model of a rock's electrical response in its natural electrolyte. Both complex impedance plane graphs and computer inversion are used to study the model. Harmonic distortion is a useful aid in this interpretation.