A geochronological framework for orogenic gold mineralisation in central Victoria, Australia

New ⁴⁰Ar/³⁹Ar geochronological data support, and significantly expand upon, preliminary age data that were interpreted to suggest an episodic and diachronous emplacement of gold across the western Lachlan fold belt, Australia. These geochronological data indicate that mineralisation in the central Victorian gold province occurred in response to episodic, eastward progressing deformation, metamorphism and exhumation associated with the formation of the western Lachlan fold belt. Initial gold formation throughout the Stawell and the Bendigo structural zones can be constrained to a broad interval of time between 455 and 435 Ma, with remobilisation of metals into new structures and/or new pulses of mineralisation occurring between 420 and 400 Ma, and again between 380 and 370 Ma, linked to episodic variations in the regional stress-field and during intrusion of felsic dykes and plutons. This separation of ages is incompatible with the view that gold emplacement in the western Lachlan fold belt was the result of a single, orogen-wide event during the Devonian. A distinct phase of gold mineralisation, characterised by elevated Cu, Mo, Sb or W, is associated with both Late Silurian to Early Devonian (~420 to 400 Ma) and Middle to Late Devonian (~380 to 370 Ma) magmatism, when crustal thickening and shortening during the ongoing consolidation of the western Lachlan Fold Belt led to extensive melt development in the lower crust and resulted in widespread magmatism throughout central Victoria. These ~420 to 400 Ma and ~380 to 370 Ma occurrences, best exemplified by the Wonga deposit in the Stawell structural zone and many of the Woods Point deposits in the Melbourne structural zone, but also evidenced by occurrences at Fosterville and Maldon in the Bendigo structural zone, clearly formed synchronous with, or post-date, the emplacement of plutons and dykes, and thus are spatially (if not genetically) related to melt generation at depth. This later, magmatic-associated and polymetallic type of gold mineralisation is economically subordinate to the earlier, metamorphic-associated type of gold deposition in the Stawell and Bendigo structural zones, but tends to be the dominant style in the Melbourne Zone. These new geochronological constraints, together with zircon U-Pb data from felsic intrusive rocks of known relationship to gold mineralisation, demonstrate that initial hydrothermal alteration associated with gold emplacement in the western Lachlan fold belt was metamorphic-related, predating the emplacement of granite plutons by as much as 80 million years. This timing differs from other important orogenic gold districts where gold deposition is closely associated spatially with felsic magmatism. The early introduction of metamorphically derived fluids well before magmatism may reflect variations in the timing of peak metamorphic conditions at different crustal levels in an accretionary prism undergoing simultaneous deformation and erosion. Consequently, no genetic link exists between the main phase(s) of gold mineralisation and magmatism in the central Victorian gold province. With the exception of formation of a minor magmatism-related and geochemically-distinct mineralisation style at about 420 to 400 Ma, and again at about 380 to 370 Ma, the apparent spatial relationship between gold mineralisation and felsic intrusions is merely the result of melts and fluids being channelised along the same structures.     

An assessment of Portland cement,cement kiln dust and Class C fly ash for the immobilization of Zn in contaminated soils

Zn-contaminated soils obtained from a steel company in the Republic of Korea were stabilized using Portland cement (PC), cement kiln dust (CKD) and Class C fly ash (FA). The effectiveness of the treatment was evaluated by the United States Environmental Protection Agency toxicity characteristic leaching procedure (TCLP) and the Universal Treatment Standard (UTS) of 4.3 mg/L. X-ray powder diffraction (XRPD) analyses were performed to investigate the crystalline phases associated with Zn immobilization. Scanning electron microscopy (SEM)–energy dispersive X-ray (EDX) analyses were utilized to support the XRPD results. The treatment results showed that the TCLP-Zn concentrations obtained from the 10 wt% PC and 15 wt% CKD treated samples were less than the UTS, after 7 days curing. However, the FA treatment (up to 30 wt%) was not effective in meeting the UTS even after 28 days curing. All PC–CKD treatment combinations were effective in reducing the TCLP-Zn concentrations below the UTS criteria. Moreover, a 20 wt% dose of a PC-FA treatment combination (75/25 PC-FA) was successful in reducing the TCLP-Zn concentrations below 4.3 mg/L after 1 day. The XRPD results showed that ettringite and Zn₆Al₂(OH)₁₆CO₃·4H₂O were the possible phases associated with Zn immobilization upon PC and CKD treatment. The SEM–EDX results confirmed the presence of ettringite, while Zn₆Al₂(OH)₁₆CO₃·4H₂O was not identified.     

Aeolian activity at a giant sandstone weathering pit in arid south‐central Utah

Aeolian abrasional, depositional and deflational features indicate exceptionally strong southwesterly winds in a giant sandstone weathering pit in Grand Staircase Escalante Monument, about 22 km southeast of Escalante, Utah. The 60 m wide, 5–20 m deep pit has developed near the summit of a broad, barren 160‐m‐high dome on the Lower Jurassic Navajo Sandstone. Unlike other giant weathering pits (10–30 m diameter) in the region, the bedrock floor of this pit is undulatory, and there is a cylindrical, 10‐m‐high rock pedestal in the centre of the pit. An active dune surrounds the central pedestal and at times has as much as 8 m of local relief. The dune shifts considerably over brief (<1 year) periods of time. Fine‐grained (<250 µm) dunal sand on the pit floor is periodically removed by deflation, leaving coarser sand (>250 µm) trapped in the pit. Dunal sand is typically derived from external sources (other than the pit walls and floor). Centimetre to metre‐scale abrasional features such as grooves, flutes and dedos occur on the bedrock walls and floor of the pit. These dedos and other streamlined aeolian sculpted host‐rock features occur in clusters and typically form in the lee of iron concretions. The dedos are similar to the controversial stalked blueberries on Mars. Above the western rim of the pit there is a 29‐m‐long, 5‐m‐wide aeolian groove with a fluted bedrock floor. A 1·2‐km‐long bedrock valley descends to the southwest from the pit and groove, amplifying southwesterly winds. Data from hand‐held anemometers suggest that southwesterly winds can be accelerated 200–300 per cent or more by local topography. Copyright © 2008 John Wiley and Sons, Ltd.     

Balloon observations of solar ultraviolet irradiance at solar minimum

Balloon observations of solar irradiance between 200 and 240 nm have been performed in 1976 and 1977 corresponding to minimum conditions of solar activity. Ultraviolet spectra have been recorded for different zenith angles at an altitude of 41 km by means of a spectrometer with a spectral bandpass of 0.4 nm. Solar irradiances at 1 a.u. confirm previous values obtained by balloon. They are compared with other measurements and discussed in term of possible long-term variability.     

Nekton Use of Flooded Salt Marsh and an Assessment of Intertidal Creek Pools as Low-Tide Refuges

Patterns of nekton occurrence on the salt marsh surface at high tide and in an adjacent intertidal creek pool at low tide were used to investigate movements of nekton in an intertidal basin. Paired collections were made in North Inlet estuary, SC on 67 dates over 9 years. Comparisons of high- and low-tide total abundance indicated that what remained in the creek pool at low tide was representative of the nekton on the flooded marsh. Of the 64 taxa collected, the same 8 species ranked in the top 10 in both the high- and low-tide collections. Abundances of most resident species were positively correlated with the area of marsh flooded, but mummichog (Fundulus heteroclitus), the most abundant resident, was not. Abundances of young-of-the-year transient species were not related to the extent of tidal flooding. Some transient species used the flooded marsh but did not occupy the pool at low tide, and others found in the pool did not use the marsh. Differences in abundance, biomass, and length between the marsh and pool collections indicated differences in the tendency of species and life stages to retreat downstream of the pool to the subtidal channel. Proportionately more of the nekton that were present on the flooded marsh left the intertidal basin when large changes in temperature and salinity occurred between high and low tides. More transients left the basin following higher tides, but more residents did not. The results demonstrate a wide range of taxonomic and ontogenetic patterns among nekton using intertidal salt marsh basins and the underappreciated importance of intertidal creek pools as alternative low-tide refuges.     

Adventive occurrence of the fouling serpulid Ficopomatus enigmaticus (Polychaeta) in New Zealand

The exotic marine‐fouling polychaete Ficopomatus enigmaticus (Fauvel) is recorded and described from New Zealand. Its sudden occurrence in New Zealand around 1967 was marked by its ecological prominence in estuaries of Whangarei and Auckland Harbours, as a nuisance species on submerged artificial structures including pleasure craft and power station intake pipes.     

Turbulence structure in a deciduous forest

Three-dimensional wind velocity components were measured at two levels above and at six levels within a fully-leafed deciduous forest. Greatest shear occurs in the upper 20% of the canopy, where over 70% of the foliage is concentrated. The turbulence structure inside the canopy is characterized as non-Gaussian, intermittant and highly turbulent. This feature is supported by large turbulence intensities, skewness and kurtosis values and by the large infrequent sweeps and ejections that dominate tangential momentum transfer. Considerable day/night differences were observed in the vertical profiles of the mean streamwise wind velocity and turbulence intensities since the stability of the nocturnal boundary layer dampens turbulence above and within the canopy.     

Urban heat island and its effect on the cooling and heating demands in urban and suburban areas of Hong Kong

This study investigates the urban heat island characteristics of four major areas of Hong Kong. The areas of study include a densely populated and well-developed commercial area (i.e., Tsim Sha Tsui) and three suburban areas (i.e., Cheung Chau, Lau Fau Shan and Sha Tin) with differing degrees of development. The weather station data of respective areas were acquired from the Hong Kong Observatory. The urban heat island intensity, determined as the air-temperature difference between the selected urban/suburban area and the reference rural area (i.e., Ta Kuw Ling) with thin population and lush vegetation, was used for the analysis. Results showed stronger heat island effect during winter and nighttime than during summer and daytime. An investigation of the cooling and heating degree days indicate that all areas have observed higher number of cooling degree days. However, the cooling degree days were the maximum while heating degree days were the minimum in the urban area (i.e., Tsim Sha Tsui). Clearly, the minimum heating degree days and the maximum cooling degree days in the urban area were a direct consequence of urban heat island. The 10-year (i.e., from 1995 to 2005) average shows that Cheung Chau experienced the least number of cooling degree days while Lau Fau Shan experienced the highest number of heating degree days. Seemingly, the area of Cheung Chau offers better thermal comfort conditions with the minimum number of cooling and heating degree days.     

Effects of nitrate and phosphate on growth and C2 toxin productivity of Alexandrium tamarense CI01 in culture

Growth and C2 toxin productivity of a marine dinoflagellate, Alexandrium tamarense CI01 (ATCI01) which predominantly produces C2 toxin, were studied in unialgal batch cultures to optimize the concentrations of nitrate and phosphate for a maximal toxin yield. A range of start concentrations of the two major nutrients was determined in which algal growth was proportional to the nutrient concentrations used. The highest concentrations of nitrate and phosphate in this growth-enhancing range were 264 and 20 μM, respectively. In this concentration range, the C2 toxin yield (μg/l) and cellular toxin content (Qt, fmole per cell) reached a maximum at the lowest end of phosphate (5 μM) and the highest end of nitrate (264 μM). Further increase in the supply of nitrate continued to enhance the toxin yield. Our results indicated that the growth and toxin productivity of this algal strain in batch cultures had distinctly different optimal ranges of nitrate and phosphate concentrations. For a maximum toxin yield, a judicious use of phosphate under a nitrate-replete condition is called for.     

Preparing for Climatic Change: The Water, Salmon, and Forests of the Pacific Northwest

The impacts of year-to-year and decade-to-decade climatic variations on some of the Pacific Northwest's key natural resources can be quantified to estimate sensitivity to regional climatic changes expected as part of anthropogenic global climatic change. Warmer, drier years, often associated with El Niño events and/or the warm phase of the Pacific Decadal Oscillation, tend to be associated with below-average snowpack, streamflow, and flood risk, below-average salmon survival, below-average forest growth, and above-average risk of forest fire. During the 20th century, the region experienced a warming of 0.8 °C. Using output from eight climate models, we project a further warming of 0.5–2.5 °C (central estimate 1.5 °C) by the 2020s, 1.5–3.2°C (2.3 °C) by the 2040s, and an increase in precipitation except in summer. The foremost impact of a warming climate will be the reduction of regional snowpack, which presently supplies water for ecosystems and human uses during the dry summers. Our understanding of past climate also illustrates the responses of human management systems to climatic stresses, and suggests that a warming of the rate projected would pose significant challenges to the management of natural resources. Resource managers and planners currently have few plans for adapting to or mitigating the ecological and economic effects of climatic change.