Worldwide Averages Research Articles

Geological controls on the mineralogy and geochemistry of the Beypazari lignite, central Anatolia, Turkey

The raw coal from the Çayirhan mine, Beypazari basin, Turkey contains an average of 28.5% mineral matter, consisting up to 80% zeolites. The coal seam is split by a 1-m-thick tuffaceous siltstone into the upper, first (Tv) and lower, second (Tb) seams, which contain essentially different zeolites. The first seam contains Ca-rich zeolites (clinoptilolite/heulandite) whilst the second seam contains Na-rich zeolites (analcime). Experimental work has shown that a Na-rich activation solution will produce Na-rich zeolites when the original volcanic glass is Na-rich, but will produce Ca-rich zeolites when the volcanic material is Ca-rich. It is thought that a Na-rich activation solution, derived from contemporaneous volcanics in the Beypazari basin, reacted with volcanic tuffs of different chemical composition to produce the vertical variability in the mineral matter of the two seams. Trace element analyses of the raw coal showed that they are enriched in As, B, Cr, Ni and Zr when compared to world-wide averages of coal. They are also enriched in the major elements Na and K. These elements are probably also derived from a volcanic source. Barium and Sr show a clear affinity for analcime, whilst Li, Cr, Ni, Cu, Zn, Co and Ga show a clear affinity for clinoptilolite/heulandite. Trace elements showing a positive correlation with the organic matter are Mn, B, Be, Ge, Y, Zr, Nb, Hf, W and U. Manganese, U, Th, Sc, Ge and HREE (heavy rare earth elements) show correlations with phosphate. Trace elements showing correlation with both Fe and S contents are Co, Mo, Ta, Pb and IREE (intermediate rare earth elements). Arsenic and V seem to have mixed affinities with sulphides and zeolites, and organic matter and zeolites, respectively. Although a proportion of the As, B and S are retained in the ash during coal combustion, due to the sorption mechanism of CaO derived from the clinoptilolite/heulandite decomposition, significant emissions of these elements may arise from the Çayirhan thermal power station due to the anomalously high concentrations of these elements in the Beypazari coal. The high total alkali metal content of these coals exceeds the recommended maximum for steam coal, but it is believed that sodium occurring in a mineralogical form such as analcime is not as likely to contribute to boiler fouling as organically-associated sodium.

The effect of membrane filtration artifacts on dissolved trace element concentrations

Abstract Among environment scientists, the current and almost universally accepted definition of dissolved constituents is an operational one-only those materials which pass through a 0.45-μm membrane filter are considered to be dissolved. Detailed laboratory and field studies on Fe and Al indicate that a number of factors associated with filtration, other than just pore size, can substantially alter “dissolved” trace element concentrations; these include: filter type, filter diameter, filtration method, volume of sample processed, suspended sediment concentration, suspended sediment grain-size distribution, concentration of colloids and colloidally-associated trace elements and concentration of organic matter. As such, reported filtered-water concentrations employing the same pore size filter may not be equal. Filtration artifacts may lead to the production of chemical data that indicate seasonal or annual “dissolved” chemical trends which do not reflect actual environmental conditions. Further, the development of worldwide averages for various dissolved chemical constituents, the quantification of geochemical cycles, and the determination of short- or long-term environmental chemical trends may be subject to substantial errors, due to filtration artifacts, when data from the same or multiple sources are combined. Finally, filtration effects could have a substantial impact on various regulatory requirements.

Changes in publication patterns of biotechnologists: An evaluation of the impact of government stimulation programs in six industrial nations

Abstract The effects of a government stimulation program on the development of Dutch biotechnology have been studied scientometrically in comparison with world-wide averages, and with the effects of programs of five important large Western industrial nations, in the period 1976–1985. In two priority fields of the Dutch programme, fermentation and bio-industrial chemistry, and biochemical genetics, publication rates were below world average before 1980–1981, but reached levels significantly above world average in 1984–1985. Both in 1980 and 1984, Dutch articles were characterized by a relatively high short-term impact. In 1984, the impact of Dutch articles was slightly above the 1980 level. When publications were counted in a core set of 19 biotechnology relevant journals, the share of Dutch biotechnologists did not change between 1979–1982 and 1983–1986, while Canada, Japan, France, and, to some extent, the UK, improved their positions, but the Federal Republic of Germany lost some ground.

Heat flow and heat production in the Namaqua Mobile Belt, South Africa

Results of heat flow and heat production surveys at 13 localities in the Namaqua mobile belt, southern Africa, are presented. Twelve stations traverse the 1200–1100 m.y. old gneissic and metamorphic Bushmanland and Gordonia subprovinces. One station is situated in the Richtersveld subprovince, a 2000–1730 m.y. old volcano‐sedimentary domain mildly affected by the 1200–1100 m.y. old orogeny. Surface heat flow in the mobile belt ranges from 39 to 81 mW m−2 and averages at 61 ± 11 mW m−2. Surface heat production ranges from 0.8 μW m−3 in mafic rocks to extreme values of 6.9–12.3 μW m−3 in the Springbok district, western Namaqualand. High heat production in the Springbok district is associated with a thin, tabular granitic intrusive and is not representative of the basement. The mean heat production of the remaining stations in the mobile belt is 2.3 ± 1.1 μW m−3. Linear regression analysis of the heat flow‐heat production data yields a poor fit (correlation coefficient = 0.62) and imprecise estimates for the intercept (34 ± 6 mW m−2) and slope (11 ± 3 km). The eastern margin of the mobile belt has relatively low heat flow and heat production; geothermal, geological, and gravity data suggest a relative depletion of crustal radiogenic heat production in the region. However, the average Namaqua heat flow is higher than worldwide averages for Proterozoic terrains. There is no geological or geophysical evidence for recent mantle heating below the Namaqua mobile belt, suggesting that an elevated crustal radioactive component is largely responsible for the elevated heat flow. In this respect, the mobile belt is similar to several mid‐late Proterozoic heat flow provinces that are characterized by high average surface heat flow and probably have elevated crustal radiogenic heat input. These observations, and seismic data, suggest that the Namaqua crust consists of an upper layer that contributes 40–50%, on average, to the heat flow and a depleted lower layer; the inferred heat flow at midcrustal levels is 50–60% of the average surface heat flow. The mobile belt's average surface heat flow is 40–85% higher than that from the basement of the adjacent Archaean Kaapvaal craton, and its inferred midcrustal heat flow is similar to the lowest surface values in the craton. Heat production data from the Kaapvaal craton indicate that its upper crust is not depleted of heat sources. While enhanced radiogenic heat input from the Namaqua upper crust may account for part of the higher‐than‐craton heat flow, it cannot account for the full excess. Consequently, a larger equilibrium mantle heat flow, related to a reduced lithospheric thickness below Namaqualand, seems to be required by the new data.

Chemical composition and tectonic setting of the Dokhan Volcanic Formation, Eastern Desert, Egypt

The late Precambrian-Cambrian Dokhan Volcanic Formation represents the youngest component of the basement complex in the Egyptian Eastern Desert. Volcanic and sedimentary rocks predating the Dokhan Formation evolved in an oceanic island arc setting and were metamorphosed during the Pan-African event. The Dokhan rocks were subjected to low grade alteration during the waning stages of the Pan-African event. Post-dating the Dokhan Formation are terrestrial sediments and post-tectonic alkali-rich granites. Chemical analyses of the Dokhan volcanic rocks reveal a range of compositions from basaltic andesite to rhyolite (SiO 2 contents from 53 to 79 wt. %). Abundances of most other oxides and trace elements follow patterns similar to those seen in volcanic rocks in orogenic belts. However, certain elements diagnostic of tectonic setting for volcanic rocks (notably alkalis, Ti, Zr and Nb) are elevated in the Dokhan Formation with respect to worldwide averages of igneous rocks from active continental margins. These chemical characteristics are interpreted as reflecting genesis of the Dokhan lavas in a setting that was transitional toward a stable continental craton.

Observational study of terrestrial eigenvibrations

A comprehensive analysis has been made of analog and digital recordings of eigenvibration ground motion obtained following four great earthquakes; August 1976 (Philippines), August 1977 (Indonesia), September 1979 (West Irian), and December 1979 (Colombia). The time series (ranging in length from ∼28 to ∼140 h) are assumed to be linear combinations of damped harmonics in the presence of noise. Tables are calculated from values of the four parameters: Θ, used in describing eigenvibrations, period of oscillation, amplitude, damping factor Q, and phase together with their statistical uncertainties (53 spheroidal modes, 0S 4 to 0S 48 , and 13 torsional modes, 0T 8 to 0T 45 ). The estimation procedures are by the methods of complex demodulation and non-linear regression that specifically incorporate into the basic model the decaying aspect of the oscillations. These methods, extended to simultaneous estimations of groups of modes, help to eliminate measurement error and measurement bias from estimations of Θ. The result is that overtone modes very near in frequency to fundamental modes can, under certain conditions, be resolved through a non-linear regression technique, although parameter uncertainties are underestimated in general. Of the time series analyzed, 17 were from a northern California regional network of ultra-long period seismographs at Berkeley (three components), Jamestown (vertical component), and Whiskeytown (vertical component) following the four listed earthquakes. The other 7 time series were recorded digitally by the worldwide IDA network following the 1977 Indonesian earthquake. Weighted regional and worldwide averages were made for period and Q of each eigenvibration mode. From the theoretical viewpoint, comparisons of measured period, Q, amplitude, and phase for all modes analyzed led to five conclusions. First, there are no detectable systematic shifts in period, Q, or phase of eigenvibrations within a region whose dimensions are less than a wavelength. Second, though not conclusive, there may be slight systematic shifts in period (<0.65 s) and relative amplitudes within the California regional network due to different source positions and mechanisms. Differences in Q values are not statistically significant. Third, even though differences in period obtained worldwide were as great as 1.33 s (≈0.33%), differences between Q values (as great as 20%) for the same mode were not significant. The conclusion is that the damping characteristics of singlet eigenfunctions are not observed to be significantly different. Fourth, the assumption that a multiplet nS l behaves as a single oscillation is valid from at least 0S 7 through 0S 30 . Fifth, no systematic pattern emerged for the shift of eigenperiod as a function of order / or posit on the Earth.

Origin and fate of hydrocarbons in Sullom Voe

SynopsisThe results of chemical analyses for hydrocarbon components in the surface water film, water, sediment traps and sediments are presented for samples collected during the period 1973–78. The n-alkane profiles of these samples are used to characterise the hydrocarbons and to help in determining their origin. The amounts of hydrocarbon present are compared to the estimated inputs of petroleum hydrocarbons from operational losses and accidents based upon analogies with worldwide averages and with data taken from other similar oil terminals. Some conclusions are drawn as to the likely fate of this oil in Sullom Voe.

Heat-flow measurements in the ririwai ring complex, Nigeria

The result of some temperature gradient measurements in available boreholes, located in the centre of the Nigerian Ririwai complex gave a heat flow of 0.92 ± 0.04 hfu. This result agrees with that of the worldwide averages for Precambrian shield areas but compared with the mean for post orogenic provinces elsewhere, this result is perhaps anomalously low. An attempt to explain this result indicates that detailed heat-flow observations over ring complexes might lead to interesting conclusions concerning the origin and emplacement of such complexes.

GEOPHYSICAL ACTIVITY IN 1977

This report provides worldwide statistical data on geophysical activity in 1977. The primary source of information was a survey questionnaire that was mailed to more than 500 companies, contractors, government agencies, and universities. We have attempted to gather data from all users of geophysical methods in the areas of petroleum, minerals, geothermal, and groundwater exploration; and from those who employ geophysical techniques in engineering, oceanography, and research. In general, response to the survey was good. Detailed information was collected on airborne, drill hole, land, and marine surveys. Statistics were compiled on miles of coverage and acquisition cost. Data not supplied on the questionnaires for cost and line miles were estimated on the basis of worldwide averages to minimize distortion of individual statistical items.

GEOPHYSICAL ACTIVITY IN 1976

This report provides statistics on worldwide use of geophysical methods in 1976. Data were obtained primarily through a survey questionnaire which was mailed out to more than 500 companies, government agencies, and universities that use geophysical techniques for petroleum exploration, oceanography, engineering, mining, geothermal exploration, and groundwater exploration. Response to the survey was excellent, providing detailed information on all types of airborne, land, and marine surveys. Computer processing was utilized in tabulating the statistics to provide detailed information on methods used, line‐miles covered, and average costs. Data not supplied on the questionnaire for costs or line‐mileage were estimated on the basis of worldwide averages to produce a more comprehensive report.

GEOPHYSICAL ACTIVITY IN 1975

This report provides statistics on worldwide use of geophysical methods in 1975. Data were obtained primarily through a survey questionnaire which was mailed out to more than 1500 companies, government agencies, and universities that use geophysical techniques for petroleum exploration, oceanography, engineering, mining, geothermal exploration, and groundwater exploration. Response to the survey was excellent and provided detailed information on more than 2100 geophysical surveys. Data on unit costs, methods used, and line‐miles covered are believed to be more accurate this year as a result of better cooperation from industry in filling out the questionnaires. Computer processing was utilized in tabulating the statistics to provide increased accuracy and detail. Data not supplied on the questionnaire for costs or line mileage were estimated on the basis of worldwide averages to produce a more comprehensive report.

Upper mantle models from ‘pure-path’ dispersion data

‘Pure-path’ phase and group velocities of mantle Rayleigh waves in combination with mantle Love wave velocities and worldwide averages of free oscillation data are used to derive upper mantle models with the smallest possible number of parameters. The shear-velocity solutions between the crust-mantle boundary and 400 km appear to be unique for an assumed set of averaging lengths, despite the fact that the density solutions are nonunique over the same depth interval. Oceanic models are characterized by a well-developed low-velocity zone. For the set of data used in this study, the thickness of the oceanic lithosphere proves to be a critical parameter that influences the density solutions. If the thickness of the lithosphere is 80 km or less, a reversal in density distribution is necessary to explain the data. If the thickness is 100 km or greater, the densities between 10 and 400 km can be represented by a single average value. The shield data do not require a low-velocity channel when the velocity in the lid is 4.60 km/sec or less, but they do require a low-velocity channel for higher Sn velocities. The characteristic feature of tectonic models is high shear velocity between 200 and 400 km (>4.80 km/sec). This feature could be explained by the thrust of oceanic lithosphere under tectonic regions.

On Regional Differences in Dispersion of Mantle Rayleigh Waves

Summary Rayleigh waves generated by the Peru-Bolivian border earthquake of 1963 August 15 have been analysed at 35 WWSSN stations in the period range between 150 and 300 seconds. Thirty-one of these stations were grouped into six narrow azimuth windows as a result of an analysis of observed phase velocities. In each of these windows the phase velocity dispersion shows similar characteristics, and the composition along the paths (in terms of the shield, oceanic and tectonic fractions of a path) was approximately the same. An error analysis indicates that differences in phase velocities obtained for individual windows are statistically meaningful, thus proving that the Rayleigh wave dispersion measured on world-circling paths shows regional variations. These six areal windows cover a third of the Earth's surface. Group velocities were measured for the six azimuthal windows by summing the auto-correlograms of individual seismograms for stations within each azimuth range. A statistical test has shown that the measurements of phase and group velocities are mutually consistent proving for the first time that the lateral inhomogeneities in crust and mantle can also be detected by measurements of group velocities for world-circling paths. The simultaneous least-squares condition for both phase and group velocity observations for each window was used to derive a polynomial approximation for the frequency of free oscillations as a function of order number measured as the excess over a reference model. ‘Pure path‘ phase and group velocities derived according to the approach of Toksoz and Anderson indicate substantial differences in dispersion for each basic type of mantle. Pure path phase velocities derived in this report differ considerably from the corresponding results of an analysis by Kanamori, whereas world-wide averages are very similar for both reports. Group velocities can be separated much more effectively than phase velocities, especially at the longest periods. This effect may be explained by world-wide variations of depths to the so-called 400 km and 650 km discontinuities. These variations appear to be unrelated to the regionalization adapted in this paper.