The history of tritium fallout in Southern Australia as inferred from rainfall and wine samples

Rainfall and wine samples have been analysed for tritium in order to obtain a record of tritium fallout since 1950 for use in hydrologic studies in southern Australia.The tritium concentrations of rainfall have been estimated for years when no samples are available by using measured values of the tritium concentration of wine samples together with Roether's (1967) exchange model and and a simple model for predicting the age of soil water used by vines.As expected, the tritium fallout pattern is similar to that obtained for Kaitoke in New Zealand and Pretoria in southern Africa.     

Geology,geomorphology, hydrology,groundwater and physical resources of the desertified Badia environment in Jordan

This paper summarizes the information on the geomorphology and physical resources component of the Jordan Badia Research and Development Programme. The research focuses on the issue of the environment in arid lands and aims to provide practical options for sustainable development, for the benefit not only of the Hashemite Kingdom of Jordan but for other arid regions of the world. The research is significantly development driven because there is a need to identify useable natural resources and establish a framework for their effective exploitation and management in a marginal, fragile environment, which is sensitive to change.Pressure for development of the Badia stems from the fact that the great majority of the population in Jordan is compressed into less than 10% of the country by environmental constraits. It is hoped that the Jordan Badia Research and Development Programme will provide the required framework to ease current environmental pressures, encourage migration to the Badia, a sparsely populated region, and establish economically and ecologically self-supporting communities.This paper discusses the following areas that are related to the sustainable development of the Jordan Badia with special emphasis on the Safawi area in the Northern Jordan Badia; geomorphology including landform, processes and hazards, geology and physical resources, hydrology, surface water and water engineering, groundwater, soils and vegetation, sediment erosion and mobility and environmental management.     

Alteration zoning and primary geochemical dispersion at the Bronzewing lode-gold deposit, Western Australia

The Late Archaean Bronzewing lode-gold deposit is in the Yandal greenstone belt, Western Australia. It is located in a 500-m-wide, N–S trending, structural corridor consisting of an anastomosing set of brittle–ductile shear zones and is chiefly hosted by tholeiitic basalts, which are metamorphosed at mid- to upper-greenschist facies. Syn-peak metamorphic alteration surround all ore bodies, and alteration extends laterally for ≤80 m from individual mineralised structures. Individual alteration haloes partially overlap and form a >1.5-km-long and ≤300-m-wide domain. The alteration sequence, studied here at 140 m below the present undisturbed surface, comprises distal calcite–chlorite–albite–quartz, intermediate calcite–dolomite–chlorite–muscovite–albite–quartz and proximal ankerite–dolomite–muscovite–albite–quartz–pyrite zones. Mass transfer calculations indicate that chemical changes during alteration include enrichment of Ag, Au, Ba, Bi, CO₂, K, Rb, S, Sb, Te and W, and depletion of Na, Sr and Y. The elements Al, Ca, Cr, Cu, Fe, Mg, Mn, Ni, P, Ti, V, Zn and Zr are immobile. The degree of chemical change increases with proximity to gold ore zones. In addition, abundant quartz veins indicate substantial silica mobility during the hydrothermal event, although there is no large relative silica loss or gain in the host rock. The broadest anomaly surrounding the Bronzewing gold deposit is defined by tellurium (>10 ppb) which, if it is a hydrothermal anomaly, extends beyond the 400 × 600 m study area. Anomalous values for CO₂, K, Rb and Sb also define wider zones than does anomalous gold (>4 ppb), although even the lithogeochemical gold anomaly extends across strike for as much as 80 m away from ore and >600 m along the N–S strike of the shear zone corridor. Also carbonation and sericitisation indices outline large exploration targets at the Bronzewing deposit. Sericitisation indices define anomalies that extend for tens of metres beyond visible potassic alteration, whereas the anomalies defined by the carbonation indices do not extend beyond visible carbonation. None of the individual alteration indices or pathfinder elements are able to define consistent gradients towards ore. However, the respective dimensions of individual geochemical anomalies can be used as an extensive, although stepwise, vector towards ore. This sequence is, from species with broadest dispersion first, as follows: Te > CO₂/Ca ≥ Sb, 3K/Al, Rb/Ti ≥ Au, W > Y/Ti (depletion) > Ag ≥ Bronzewing ore. Received: 25 October 1999 / Accepted: 11 May 2000     

Carbonate spots: understanding the relationship to gold mineralization in Central Victoria,southeastern Australia

Historically, carbonate spots have been identified as an indicator of gold mineralization throughout central Victoria, Australia. However, the exact timing relationships between the growth of carbonates, development of deformation fabrics, and the introduction of gold has only been determined in more recent times through isolated studies on individual gold deposits. Detailed examination of the evolution of hydrothermal alteration associated with the Magdala gold deposit at Stawell recognized the fact that there were at least two generations of carbonate growth, an early rounded ankerite phase that predated gold mineralization and a later euhedral siderite phase coincident with gold mineralization. This pattern of carbonate growth is repeated in the majority of significant gold deposits, including Bendigo and Ballarat, throughout central Victoria. Timing relationships within the carbonates suggest that a fluid was introduced along bedding planes and early deformation fabrics prior to the main upright folding events that significantly modified the original sedimentary basin. It is suggested that the early rounded carbonates may have formed as a result of anaerobic oxidation of methane, derived from the sediments and advected along normal growth faults within the sedimentary basin, through interaction with downward diffusing seawater sulfate. Although the growth of the early carbonates is not related to gold mineralization, the change in the speciation of the carbonate during the later carbonate event is critical and can be tracked using a simple geochemical index that can be used not only in areas of outcrop but also in conjunction with exploration undercover.     

Exploration potential of Cu isotope fractionation in porphyry copper deposits

We examined the copper isotope ratio of primary high temperature Cu-sulfides, secondary low temperature Cu-sulfides (and Cu-oxides) as well as Fe-oxides in the leach cap, which represent the weathered remains of a spectrum of Cu mineralization, from nine porphyry copper deposits. Copper isotope ratios are reported as δ⁶⁵Cu‰ = ((⁶⁵Cu/⁶³Cu_sample/⁶⁵Cu/⁶³Cu_{NIST 976 standard}) − 1) ? 10³. Errors for all the analyses are ± 0.14‰ (determined by multiple analyses of the samples) and mass bias was corrected through standard-sample-standard bracketing. The overall isotopic variability measured in these samples range from − 16.96‰ to 9.98‰.     

Seasonal Production and Biomass of the Seagrass, <Emphasis Type="Italic">Halodule wrightii</Emphasis> Aschers. (Shoal Grass), in a Subtropical Texas Lagoon

A study of Halodule wrightii in a shallow subtropical Texas lagoon was performed to obtain seasonal data on its physiological ecology. Leaf production and biomass dynamics of H. wrightii were intensively monitored along with the underwater light environment at a 1.2-m depth study site over a 21-month period from June 1995 to February 1997. The annual photosynthetically active radiation (PAR) flux of 6,764 mol m⁻² year⁻¹ was more than twice as high as 2,400 mol m⁻² year⁻¹, the minimum annual PAR required for maintenance of growth. As light intensity declined, blade chlorophyll a/b ratios increased suggesting that the plants were photo-adapting. Seasonal trends were evident in shoot growth and biomass. Compared to other Halodule populations in Texas, H. wrightii in LLM displayed slow growth and low biomass, high leaf tissue N content, and low C/N ratio but high N/P ratio of 38 suggesting that the plants were phosphorus-limited.     

Characterization of a mud deposit offshore of the Patos Lagoon,southern Brazil

Rapid deposition of mud on the beach along the shoreface of Rio Grande do Sul, Brazil dramatically influences the normal operations in the littoral zone. In the surf zone, fluid and suspended mud opposes water-wave movement and dissipates water-wave energy; on the beach, mud limits trafficability. As part of a multinational, multidisciplinary program to evaluate the influence of mud strength, density and viscosity on water-wave attenuation, sediments were evaluated in situ or collected for evaluation from an area offshore of Cassino Beach, slightly south of the Patos Lagoon mouth. Shear strength of deposited sediments ranged from 0.6 kPa at the seafloor to 3.4 kPa at ∼1 m below the seafloor. Mud sediments were also collected to simulate the in situ response of fluid mud to shear stresses. For this determination, rheological evaluations were made using a strain-controlled Couette viscometer on numerous remixed samples that ranged in density from 1.05 to 1.30 g/cm³. It was determined that this mud is a non-ideal Bingham material in that it has a true initial yield stress as well as a upper Bingham yield stress. Initial yield stress ranged from 0.59 to 2.62 Pa, upper Bingham yield stress ranged from 1.05 to 7.6 Pa. Apparent viscosity ranged from 0.02 to 4.7 Pa s with the highest viscosities occurring between the two yield stresses. Sediment strength in the remixed samples is 2 to 3 orders of magnitude lower than the horizontal shear strength of the sediment bed as determined by shear vane or predicted from penetrometer measurements. This difference is partially due to the fact that rheological evaluations are made on fully remixed sediments, whereas horizontal shear strength is determined within relatively undisturbed sediments. Similar values of viscosity and shear strength are comparable to those determined for mud in other coastal areas where fluid mud deposits occur.     

Transforming management of tropical coastal seas to cope with challenges of the 21st century

Over 1.3 billion people live on tropical coasts, primarily in developing countries. Many depend on adjacent coastal seas for food, and livelihoods. We show how trends in demography and in several local and global anthropogenic stressors are progressively degrading capacity of coastal waters to sustain these people. Far more effective approaches to environmental management are needed if the loss in provision of ecosystem goods and services is to be stemmed. We propose expanded use of marine spatial planning as a framework for more effective, pragmatic management based on ocean zones to accommodate conflicting uses. This would force the holistic, regional-scale reconciliation of food security, livelihoods, and conservation that is needed. Transforming how countries manage coastal resources will require major change in policy and politics, implemented with sufficient flexibility to accommodate societal variations. Achieving this change is a major challenge – one that affects the lives of one fifth of humanity.     

Does use of tropical beaches by tourists and island residents result in damage to fringing coral reefs? A case study in Moorea French Polynesia

Although coral reefs worldwide are subject to increasing global threats, humans also impact coral reefs directly through localized activities such as snorkeling, kayaking and fishing. We investigated five sites on the northern shore of Moorea, French Polynesia, and quantified the number of visitors on the beach and in shallow water. In field surveys, we measured total coral cover and colony sizes of two common genera, Porites and Acropora, a massive and branching morphology, respectively. One site, which hosted over an order of magnitude more people than the other four, had significantly less total coral cover and supported very little branching Acropora. In addition, size frequency distributions of both the branching and massive genera were skewed toward smaller colony sizes at the high use site. Our results demonstrated that the use of tropical beaches may result in less coral cover, with branching colonies rare and small.