Mercury in Stratabound copper mineralization in the Mammoth area,northwest Queensland

Copper mineralization along the Mount Gordon Fault Zone in northwest Queensland contains sufficient mercury to permit mercury pathfinder techniques to be used for exploration for further deposits in the area. At the Mammoth mine, the No. 1 orebody contains 310–14000 ppb Hg, with the highest contents in “sooty chalcocite” which may be of supergene origin. The B orebody contains 100–4300 ppb Hg, with highest concentrations at the top of the deposit. Other deposits in the Mammoth area contain 10–1600 ppb Hg, with mean mercury contents > 200 ppb in fault-related mineralization.There is a strong positive correlation between mercury and copper, sulfur, silver, arsenic, bismuth, lead, antimony and thallium contents in the deposits which suggests mercury was introduced during the mineralizing process. However, most of the mercury occurs on the surfaces of sulfide minerals, indicating its introduction at a late stage of mineralization.Mercury in the No. 1 orebody is partly of supergene origin whereas primary mineralogy may control mercury distribution in the B orebody. The presence near the Mammoth Fault of a lens of pyrite containing high concentrations of mercury (geometric mean 820 ppb) suggests that the mercury content of pyrite encountered in future exploration programmes in the region might be used to indicate proximity to mineralized fault zones.Gossans derived from copper deposits contain more than five times the amount of mercury in ironstones developed over unmineralized or poorly mineralized fault zones. The mercury contents of iron-rich rocks may be used to discriminate gossans from the numerous fault ironstones in the Mammoth area.     

Macrofaunal involvement in the sublittoral decay of kelp debris: The sea urchin Psammechinus miliaris (Gmelin) (Echinodermata: Echinoidea)

Psammechinus miliaris occurs in the Clyde Sea area in large numbers (<18 individuals per 100 g^?1 weed dry wt) on sublittoral beds of detached Laminaria saccharina. Its rôle in weed decomposition has been examined by comparing its responses (behavioural choice, growth rate, absorption efficiencies of both carbon and protein, gut retention times and rate of faecal output) to fresh and rotting weed.Younger urchins grew faster than older individuals on a diet of rotting weed but not on fresh weed. Large seasonal variation existed, however, with fast growth occurring in June–August and little, or no, growth in December–February, irrespective of diet. Starved controls did not grow. Correcting for seasonality, rotting kelp still promoted faster growth of young urchins than did fresh weed. Larger (older) individuals showed no difference. Urchins fed fresh weed had significantly longer gut retention times. Protein absorption efficiency was higher on fresh than rotting weed, varying with weed protein content and size of urchin. Very young individuals can only digest high protein weed efficiently, eg. material derived from near the frond meristem. Organic carbon content of rotting weed was significantly lower than fresh weed. Carbon absorption efficiencies were significantly higher on fresh weed which related to organic carbon content. Standard-sized urchins fed rotting weed produced larger dry weights of faeces per day, reflecting increased ingestion rate. In closed-system choice experiments urchins preferred rotting weed kinetically. Size-frequency analysis of field populations suggested that weed beds are principally colonized by larval settlement from the plankton.Mature Psammechinus have evolved different ‘strategies’ for exploiting fresh and rotting weed. Fresh weed is relatively difficult to digest and long gut retention times allow high protein absorption efficiencies to be attained. Rotting weed has microbial protein in quantities and a lower organic carbon fraction. Some bacterial protein is seemingly unavailable though and lower protein absorption efficiencies result. Thus gut retention time is shortened and more food passed through the gut. Growth remains equivalent. Substratum digestion is of paramount importance for Psammechinus feeding on either fresh or rotting weed, cf. the ‘classical’ microbe-stripping detritivore of Fenchel.     

Rainfall interception by trees of Pinus radiata and Eucalyptus viminalis in a 1300 mm rainfall area of southeastern New South Wales: II. Influence of wind-borne precipitation

Analyses were made of the concurrent canopy precipitation balances of a seed orchard pine and a mature forest eucalypt during protracted rainfalls selected for their representativeness of the range of variation encountered in the two canopy types at Tallanganda State Forest (ca. 990 m a.s.l.) in the Upper Shoalhaven Valley of southeastern New South Wales. Although their canopy storage capacities were widely different there was consistent interception behaviour in the pine and the eucalypt in all events. Detailed weather data and the time courses of interception loss provided circumstantial evidence for a varying and, at times, substantial influence of cloud or mist deposition on the canopy precipitation balances during rainfall that made a significant contribution to the variation in rainfall interception data. Mean evaporation rates from the saturated canopies during rainfall varied from ?0·02 mm hr^?1 up to 0·68 mm hr^?1 in the pine; and from ?0·04 mm hr^?1 up to 0·13 mm hr^?1 in the eucalypt. The implications of cloud-capture during rainfall for studies of rainfall interception in forests of southeastern Australia are discussed.     

REPEATED SHOCK AND THERMAL METAMORPHISM OF THE ABERNATHY METEORITE

Based on the example of Abernathy (L6 chondrite), this study shows how petrographic investigation can be used to unravel the nature, chronology and conditions of superposed metamorphic events in chondrites. Features considered include the texture of the rock, optical characteristics of olivine, pyroxene and plagioclase, refractive index of plagioclase, metallographical characteristics and microhardness of Fe-Ni alloys. From these data it is deduced that Abernathy has been involved in at least six metamorphic events since the formation of the chondrite. Four distinct shock events and two separate reheating events have been identified. The chronology of these events is established. The conditions for the last four events are reasonably well constrained. These include successively, i) severe reheating (T > 1200°C), ii) severe shock causing complete melting of plagioclase and local melting of the rock (90 < P < 110 GPa, 1250°GC < T < 1350°C), iii) mild shock (10 < P < 25 GPa, T<500°C), and iv) reheating below 800°C.     

The Icelandic Laki volcanic tephra layer in the Lomonosovfonna ice core, Svalbard

The largest sulphuric acid event revealed in an ice core from the Lomonosovfonna ice cap, Svalbard, is associated with the densest concentration of microparticles in the ice core at 66.99 m depth. Electron microscope analysis of a volcanic ash particle shows it has the same chemical composition as reported for debris from the eruption of Iceland's Laki fissure in 1783 and confirms the identification of the tephra. Most of the particles in the deposit are not ash, but are common sand particles carried aloft during the eruption event and deposited relatively nearby and downwind of the long-lasting eruption. The tephra layer was found 10–20 cm deeper than high sulphate concentrations, so it can be inferred that tephra arrived to Lomonosovfonna about 6–12 months earlier than gaseous sulphuric acid precipitation. The sulphuric acid spike has a significant cooling impact recorded in the oxygen isotope profile from the core, which corresponds to a sudden drop in temperature of about 2°C which took several years to recover to previous levels. These data are the first particle analyses of Laki tephra from Svalbard and confirm the identification of the large acidic signal seen in other ice cores from the region. They also confirm the very large impact that this Icelandic eruption, specifically the sulphuric acid rather than ash, had on regional temperatures.     

Managing the Future

Prediction of the future is implicit in most management decisions. This paper examines how far it is necessary to make this prediction explicit in deciding management strategy, what technical changes are likely to affect survey and photogrammetry in the near and medium term future, and the balance between the disciplines. The question is posed as to what extent management should invest effort and money in attempting to stay ahead of the game.     

A Photo-elicitation Approach to Exploring the Place Meanings Ascribed by Campers to the Ningaloo Coastline,North-western Australia

Although there have been numerous studies of the meanings ascribed to terrestrial places, their applicability or otherwise to coastal and marine places has received limited attention. Through the process of photo-elicitation, the meanings ascribed to a remote coastal camping environment are examined, with the coastline of Ningaloo Marine Park in north-western Australia the focus for this study. Thirty participants were provided with digital cameras and the ascribed place meanings were explored when their photographs were discussed in subsequent in-depth interviews. Key meanings related to the physical environment providing opportunities for escape, participating in multiple marine-based activities, bonding with family and like-minded people, and offering a rewarding experience that makes everybody happy. This emergent meaning of ‘everybody's happy’ progresses the understanding of the affective elements of place, especially those realised by families and groups of friends. The paper traces important implications of this meaning, and provides a paradoxical perspective on isolation evident from the interviews, for managing coast-based recreation.     

Tower-based backscatter measurements of the sea

In September 1979, the radar scattering coefficient (sigmadeg) was measured at platform Noordwijk in the North Sea 10 km off the Dutch coast. This was done in conjunction with similar measurements by Dutch and French investigators as part of Project MARSEN (Marine Remote Sensing). Our measurements were made with vertical and horizontal polarizations, in the frequency baud 9-17 GHz, at incidence angles0deg - 70deg, with wind speeds from 2-22 m/s, and look directions upwind, downwind, and crosswind. This paper presents the scattering-coefficient variation with these radar and ocean parameters. In particular, the exponents for the windspeed response are compared with those from other investigators. Some of the exponents reported here are higher than reported previously, possibly because orthogonal regression was used rather than regression ofsigmadegversus windspeed.