Properties of the solar nebula and the origin of the moon

The basic geochemical model of the structure of the Moon proposed by Anderson, in which the Moon is formed by differentiation of the calcium, aluminium, titanium-rich inclusions in the Allende meteorite, is accepted, and the conditions for formation of this Moon within the solar nebula models of Cameron and Pine are discussed. The basic material condenses while iron remains in the gaseous phase, which places the formation of the Moon slightly inside the orbit of Mercury. Some condensed metallic iron is likely to enter the Moon in this position, and since the Moon is assembled at a very high temperature, it is likely to have been fully molten, so that the iron can remove the iridium from the silicate material and carry it down to form a small core. Interactions between the Moon and Mercury lead to the present rather eccentric Mercury orbit and to a much more eccentric orbit for the Moon, reaching past the orbit of the Earth, establishing conditions which are necessary for capture of the Moon by the Earth. In this orbit the Moon, no longer fully molten, will sweep up additional material containing iron oxide. This history accounts in principle for the two major ways in which the bulk composition of the Moon differs from that of the Allende inclusions.Paper dedicated to Professor Harold C. Urey on the occasion of his 80th birthday on 29 April 1973.     

Hypogene Zn carbonate ores in the Angouran deposit,NW Iran

The world-class Angouran nonsulfide Zn–Pb deposit is one of the major Zn producers in Iran, with resources estimated at about 18 Mt at 28% Zn, mainly in the form of the Zn carbonate smithsonite. This study aims to characterize these carbonate ores by means of their mineralogy and geochemistry, which has also been extended to the host rocks of mineralization and other local carbonate rock types, including the prominent travertines in the Angouran district, as well as to the local spring waters. Petrographical, chemical, and stable isotope (O, H, C, Sr) data indicate that the genesis of the Zn carbonate ores at Angouran is fairly distinct from that of other “classical” nonsulfide Zn deposits that formed entirely by supergene processes. Mineralization occurred during two successive stages, with the zinc being derived from a preexisting sulfide ore body. A first, main stage of Zn carbonates (stage I carbonate ore) is associated with both preexisting and subordinate newly formed sulfides, whereas a second stage is characterized by supergene carbonates (Zn and minor Pb) coexisting with oxides and hydroxides (stage II carbonate ore). The coprecipitation of smithsonite with galena, pyrite and arsenopyrite, as well as the absence of Fe- and Mn-oxides/hydroxides and of any discernible oxidation or dissolution of the sphalerite-rich primary sulfide ore, shows that the fluids responsible for the main, stage I carbonate ores were relatively reduced and close to neutral to slightly basic pH with high fCO₂. Smithsonite δ¹⁸O_VSMOW values from stage I carbonate ore range from 18.3 to 23.6‰, while those of stage II carbonate ore show a much smaller range between 24.3 and 24.9‰. The δ¹³C values are fairly constant in smithsonite of stage I carbonate ore (3.2–6.0‰) but show a considerable spread towards lower δ¹³C_VPDB values (4.6 to −11.2‰) in stage II carbonate ore. This suggests a hypogene formation of stage I carbonate ore at Angouran from low-temperature hydrothermal fluids, probably mobilized during the waning stages of Tertiary–Quaternary volcanic activity in an environment characterized by abundant travertine systems throughout the whole region. Conversely, stage II carbonate ore is unambiguously related to supergene weathering, as evidenced by the absence of sulfides, the presence of Fe-Mn-oxides and arsenates, and by high δ¹⁸O values found in smithsonite II. The variable, but still relatively heavy carbon isotope values of supergene smithsonite II, suggests only a very minor contribution by organic soil carbon, as is generally the case in supergene nonsulfide deposits.     

First steps in the enclosure of the oceans: The origins of Truman's proclamation on the resources of the continental shelf, 28 September 1945

The movement to establish coastalstate jurisdiction over a distance of 200 miles has its origins in President Truman's proclamation of September 1945 on the resources of the continental shelf and ‘certain high seas fisheries’. The author analyses the processes and motives which led to the proclamation, the US justification of its revolutionary policy statements, the reactions of other nations (in particular the warning of the UK and the parallel declaration of Mexico), and the subsequent assessment of the consequences of the action in the USA.     

THE INVESTIGATIVE GENRE: PROBLEMS AND PROSPECTS

This paper argues that investigative journalists have developed successful strategies for illuminating issues characterized by sensitive information and obscure decision-making processes. Many issues in geography, particularly those involving the examination of policies, of both public and private bodies, are amenable to the investigative approach, which requires interviewing key decision-makers and others, assessment of publicly available documents, and discovery of nonpublic and other sensitive information. An empirical examination of some elements of recent regional-development policy in the Province of Ontario illustrates the investigative approach. History by and large is quite inaccurate but you see in the effluxion of time those who might correct it disappear. And so it's just there and taken to be deadly accurate, which of course it isn't. The other thing is that all the humanity of the events is generally washed out by the historians. The fact that guys do get drunk and that men do do crazy things. Men have lapses of judgment. And men make horrible mistakes. And it's the human condition. And much of that unfortunately gets sort of washed out of the whole story [14].     

High-resolution analyses of recent sediments from a Norwegian mountain lake and comparison with instrumental records of climate

The purpose of the palaeolimnological research project carried out at Øvre Neådalsvatn was to apply a number of physical and biological proxy-climate analyses to recent sediments and to compare the results of these analyses with instrumental records of climate. Using a radiometric chronology to match the sediment core with the calendar ages of the reconstructed instrumental record, and by time-averaging the instrumental record, the statistical significance of the relationships between each of the sediment-climate proxies and the reconstructed instrumental-climate measurements were evaluated.Acid deposition at Øvre Neådalsvatn has been low and its impact limited. Whilst there has been an overall rise in mean annual temperature of about 1 °C since 1900, the physical and biological sediment records studied appear to be insensitive to climate warming of this magnitude. On the one hand, this may be a result of the loss in temporal resolution caused by time-averaging the instrumental data; on the other hand, the lake may be insensitive to the impact of this climate change.     

10 μm imaging of the nucleus of NGC 1068: The bell tolls for parsec-scale tori?

The potential of mid-infrared imaging, at a resolution of 0.5 or better, as a powerful tool in unravelling the complex environments in the vicinity of active galactic nuclei is discussed in the light of new data on the Seyfert nucleus in NGC 1068. In particular, we examine the growing body of evidence that the extinction of the broad-line region in NGC 1068 has its origins in an extended molecular disk and is the result of obscuration at 100 pc from the AGN.     

Book reviews

BURNING BUSH: a fire history of Australia by S.J. Pyne. 15 × 23 cm, xix + 520 pp. Allen & Unwin, Sydney 1992. (ISBN 1–86373–194–6) $19–95 (soft).

ADVANCES IN RESOURCE MANAGEMENT: tributes to W.R. Derrick Sewell edited by H.D. Foster. 15 × 23 cm, viii + 366 pp. Belhaven Press, London 1992 (ISBN 1–85293–292‐ 9) £39.50 (hard).

FEMINISM AND GEOGRAPHY: the limits to geographical knowledge by G. Rose. 15 × 23 cm, 205 pp. Polity Press, Cambridge 1993. (ISBN 0–7456–1156–7) $34.95 (soft).

EVERYDAY LIFE: women's adaptive strategies in time and space (Lund Studies in Geography, Ser.B Human Geography 55) by T. Friberg (translated by M. Gray). 16 × 24 cm, 217 pp. Lund University Press, Lund, and Chartwell‐Bratt, Bromley 1993. (ISBN 0‐ 86238–345–5)

NATURAL DISASTERS by D. Alexander. 16 × 23 cm, xix + 632 pp. University College London Press, London 1993 (ISBN 1–85728–094–6) $55.00 (soft).