Field determination of air-sea gas exchange by continuous measurement of radon-222

Equipment has been developed for automatic measurement of the radon dissolved in sea water, with the aim of determining gas exchange rates at sea on the basis of the radon-222 deficiency in the mixed layer with respect to its parent nuclide radium-226. The equipment will be employed to obtain, over an extended period at fixed position, repeated measurements of the vertically integrated radon deficiency. The repetition period will be 2 hours, and sampling will be by a winch-operated submersible pumping system which will continuously scan the radon-deficient layer. The repeated measurements will allow to derive gas exchange rates even under transient meteorological conditions. As opposed to this, radon work carried out to date relied on isolated deficiency measurements and stationary conditions were commonly assumed (the deficiency relaxation time is about 5 days), which, under transient conditions, may lead to considerable errors. Equipment tests have been made at sea and the first integrated-deficiency measurements were obtained on the RSSChallenger in July 1977. Field programs are in preparation for JASIn (Joint Air-Sea Interaction, July–September 1978) and FGGE (First GARP Global Experiment, January–July 1979). The ultimate goal is a parameterization of the gas exchange rate in terms of external parameters, primarily wind speed.     

13C Nuclear magnetic resonance studies of kerogen from Cretaceous black shales thermally altered by basaltic intrusions and laboratory simulations

Cretaceous black shales from DSDP Leg 41, Site 368 in the Eastern Atlantic Ocean were thermally altered during the Miocene by an intrusive basalt. The sediments overlying and underlying the intrusive body were subjected to high temperatures (up to ~ 500°C) and, as a result, their kerogen was significantly altered. The extent of this alteration has been determined by examination by means of ¹³C nuclear magnetic resonance, using cross polarization/magic-angle spinning (CP/MAS). Results indicate that the kerogen becomes progressively more aromatic in the vicinity of the intrusive body. Laboratory heating experiments, simulating the thermal effects of the basaltic intrusion, produced similar results on unaltered shale from the drill core. The ¹³C CP/MAS results appear to provide a good measure of thermal alteration.     

Granulite-facies metabasite ejecta in the Laacher See area,Eifel, West Germany

Near the village of Engeln, Laacher See area, garnet-bearing pyriclasite and pyribolite ejecta were recognized as constituents of alkaline basaltic tuffs; they are interpreted as fragments of the lowermost crust. During the first main stage of granulite facies metamorphism, assemblages with garnet (Alm₄₇Pyr₃₄Spess₂Gross + Andr₁₇), clinopyroxene (Wo₃₇En₃₅Fs₁₅Ts_8.5Jd_4.5), orthopyroxene I (En₃₄Fs₃₈Ts₄Jd₂), and plagioclase I (An₄₀-An₆₀) were formed in a temperature range of 730–850°C and rock pressures somewhere between 6.5 and 12 kb, $\text{P}{}_{\mathrm{tot}}\text{>}\text{P}{}_{\mathrm{<mtext>H</mtext>}}{}_2\text{O}\text{> 0}$. The rare sulfate-rich meionite, and at least a part of the ubiquitous brown hornblende were presumably also formed during this stage. A retrograde metamorphic event under slightly lower pressures and temperatures led to the breakdown of the assemblage garnet + clinopyroxene thereby forming coronas of plagioclase II $\text{(}\text{An}{}_{75}\text{) +}\text{orthopyroxene}\text{II +}\text{Ti-magnetite}\text{±}\text{brown hornblende}$.     

New ports as nodes for industrial and urban development: The cases of Richards Bay and Saldanha in South Africa

Richards Bay and Saldanha were officially opened in 1976 as new deep water ports, primarily for the export of coal and iron ore respectively. The heavy investment in both infrastructure and industrial development by the South African government led to considerable urban and industrial growth in Richards Bay, whereas the port of Saldanha was initiated by one big concern and failed to produce a far reaching multiplier effect. The development of ports as growth centres has to be considered in terms of the location relative to the Pretoria-Witwatersrand-Vereeniging complex, which dominates the economy of the subcontinent, and within the context of the official decentralisation-growth point policy.     

Composition and origin of hydrothermal petroleum and associated lipids in the sulfide deposits of the Rainbow field (Mid-Atlantic Ridge at 36°N)

The lipid components in hydrothermal sulfide deposits from the Rainbow vent field (Mid-Atlantic Ridge at 36°N) were studied by gas chromatography/mass spectrometry. The Rainbow vent field is one of two known active hydrothermal systems related to abyssal circulation, where high-temperature fluids are formed during serpentinization of ultrabasic crustal rocks. The major amount of the extractable organic matter from the sulfides consists of normal and branched alkanes, UCM, PAHs, terpenoids, and fatty acids. The branched alkanes are comprised of unique gem-diethylalkane series, possibly from sulfide oxidizing bacteria, and biphytanes from archaea. The characteristic lipid and biomarker compounds found in the hydrothermal samples support a predominantly biological origin of the bitumens from the thermal transformation of the biomass of microorganisms (bacteria and archea) and minor macrofauna of this vent field. A search for molecular evidence for abiogenic thermocatalytic synthesis of organic compounds was negative. However, methane in the hydrothermal fluids and possibly a minor amount of the alkanes in the sulfides may be of an abiogenic origin in the Rainbow vent field.     

Late Pleistocene and Holocene history of Lake Terrasovoje,Amery Oasis,East Antarctica,and its climatic and environmental implications

A 5.52 m long sediment sequence was recovered from Lake Terrasovoje, Amery Oasis, East Antarctica, in order to reconstruct the regional environmental history. The basal sediments, which are dominated by glacial and glaciofluvial clastic sediments, attest to a Late Pleistocene deglaciation of the lake basin. These sediments are overlain by 2.70 m of laminated algal and microbial mats and a few interspersed moss layers. Radiocarbon dating, conducted on bulk organic carbon of 12 samples throughout the organic sequence, provides a reliable chronology since the onset of biogenic accumulation at c. 12,400 cal. year BP. Successful diatom colonization, however, was probably hampered by extensive ice and snow cover on the lake and restricted input of nutrients until 10,200 cal. year BP. A subsequent increase of nutrient supply culminated between 8600 and 8200 cal. year BP and is related to warm summer temperatures and reduced albedo in the catchment. Warm conditions lasted until 6700 cal. year BP, supporting the establishment of a diatom community. Colder temperatures from 6700 cal. year BP culminated in several periods between 6200 and 3700 cal. year BP, when high amounts of sulphur and low abundances of diatoms were deposited due to a perennial ice and snow cover on the lake. During the late Holocene, relatively warm conditions between 3200 and 2300 cal. year BP and between 1500 to 1000 cal. year BP, respectively, indicated by high accumulation of organic matter and reducing bottom water conditions, were interrupted and followed by colder periods.     

Palaeozoic granites of the Umberatana region,South Australia: the role of volatiles in the crystallization of some alkaline-peralkaline granites

Palaeozoic alkaline to peralkaline sodic granites of the Umberatana area of South Australia have high MnO, P₅O₅, Nb, Ta, Be, F and B abundances as is typical of »A-type« or anorogenic granites. Abundant F and B in the magma permitted primary muscovite to crystallize at pressures that may have been as low as 1 Kbar because of the lowered solidus temperatures. These volatile-rich magmas precipitated both albite and two generations of K-rich alkali feldspar. The hydrothermal fluids released during crystallization of these magmas resulted in considerable element redistribution and recrystallization both in the plutons and the adjacent country rocks.

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Zusammenfassung Paläozoische alkaline-peralkaline Sodagranite von Umberatana, Südaustralien, besitzen erhöhte Gehalte an MnO, P₂O₅, Nb, Ta, Be, F and B und zeigen Charakteristika von »A-Typ« Graniten. Erhöhte Gehalte an F und B erlaubte die Kristallisation von primärem Muskovit bei Drucken, die auf Grund der erniedrigten Solidus Temperaturen möglicherweise 1 Kbar betrugen. Diese Gas reichen Magmen schieden Albit und zwei Generationen von K-reichem Alkalifeldspat aus. Die hydrothermalen fluiden Phasen, die sich während der Kristallisation dieser Magmen bildeten, verursachten eine bedeutene Elementumverteilung und Rekristallisation in den Intrusionen und dem unmittelbaren Nebengestein.

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Résumé Les granites sodiques alcalins à peralcalins paléozoïques de la région d'Umberatana (Australie méridionale) présentent des teneurs élevées en MnO, P₂O₅, Nb, Ta, Be, F et B, caractère typique des granites de type A, ou anorogéniques. La grande quantité de F et de B présente dans le magma a permis la cristallisation de muscovite primaire à une pression qui ne devait pas excéder 1 Kbar, en raison de l'abaissement de la température du solidus. Ces magmas, riches en matières volatiles, ont précipité de l'albite et deux générations de feldspath alcalin potassique. Les fluides hydrothermaux libérés au cours de la cristallisation ont permis une redistribution et une recristallisation importante des éléments à la fois dans les plutons et dans les roches encaissantes.

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- ( ) MnO, P₂O₅, Nb, , Be, F B, , «». , , , , 1 . , . , , , , .

     

Alkaline permanganate oxidation of kerogens from Cretaceous black shales thermally altered by diabase intrusions and laboratory simulations

Potassium permanganate oxidative degradations were conducted for kerogens isolated from Cretaceous black shales (DSDP Leg 41, Site 368), thermally altered during the Miocene by diabase intrusions and from unaltered samples heated under laboratory conditions (250–500°C).Degradation products of less altered kerogens are dominated by normal C₄–C₁₅ α,ω-dicarboxylic acids, with lesser amounts of n-C₁₆ and n-C₁₈ monocarboxylic acids, and benzene mono-to-tetracarboxylic acids. On the other hand, thermally altered kerogens show benzene di-to-tetracarboxylic acids as dominant degradation products, with lesser or no amounts (variable depending on the degree of thermal alteration) of α,ω-dicarboxylic acids. Essentially no differences between the oxidative degradation products of naturally- and artificially-altered kerogens are observed.As a result of this study, five indices of aromatization (total aromatic acids/kerogen; apparent aromaticity; benzenetetracarboxylic acids/total aromatic acids; benzene-1,2-dicarboxylic acid/benzenedicarboxylic acids; benzene-1,2,3-tricarboxylic acid/benzenetricarboxylic acids) and two indices of aliphatic character (Total aliphatic acids/kerogen; Aliphaticity) are proposed to characterize the degree of thermal alteration of kerogens.Furthermore, a good correlation is observed between apparent aromaticity estimated by the present KMnO₄ oxidation method and that from the ¹³C NMR method (DENNIS et al., 1982).