The nature and origin of brecdation and mineralization at the White Crystal ore deposit,Ardlethan tin mine,New South Wales

The White Crystal ore zone consists of an ovoid mass of fine grained quartz‐tourmaline topaz rock containing disseminated cassiterite together with prominent vughs of quartz and/or tourmaline, cassiterite, and sulphides. Toward the margins of the ore zone the decreasing intensity of alteration illustrates formation via a process of brecciation, infill, and alteration. The rectangular slab‐like fragments are commonly aligned and their plunge indicates a dip towards a common epicentre. The tourmalinized ore zone is surrounded by successive zones of sericitization and argillization. The brecciation is of large scale tensional origin which is suggestive of collapse. Beneath the ore zone mineralization/alteration continues at subeconomic grades and limited data suggests an intrusive hydrothermal style of brecciation. The entire system is a form of breccia pipe and has yielded some 1.5 Mt of ore at around 0.64% Sn.     

Plankton copper requirements and uptake in the subarctic Northeast Pacific Ocean

We undertook the first measurements of metabolic Cu requirements (net Cu:C assimilation ratios) and steady-state Cu uptake rates (ρCu_ss) of natural plankton assemblages in the northeast subarctic Pacific using the short-lived radioisotope ⁶⁷Cu. Size-fractionated net Cu:C assimilation ratios varied ～3 fold (1.35–4.21 μmol Cu mol C^?1) among the stations along Line P, from high Fe coastal waters to the Fe-limited open ocean. The variability in Cu:C was comparable to biogenic Fe:C ratios in this region. As previously observed for Fe uptake, the bacterial size class accounted for half of the total particulate ρCu_ss. Interestingly, carbon biomass-normalized rates of Fe uptake from the siderophore desferrioxamine B (DFB) (ρFe_DFB; a physiological proxy for Fe-limitation) by the >20 μm size class were positively correlated with the intracellular net Cu:C assimilation ratios in this size class, suggesting that intracellular Cu requirements for large phytoplankton respond to increased Fe-limitation. At Fe-limited Ocean Station Papa (OSP), we performed short-term Cu uptake (ρCu_L) assays to determine the relative bioavailability of Cu bound to natural and synthetic ligands. Like the volumetric ρCu_ss measured along Line P, the bacterial size class was responsible for at least 50% of the total ρCu_L. Uptake rates of Cu from the various organic complexes suggest that Cu uptake was controlled by the oxidation state of the metal and by the metal:ligand concentration ratio, rather than the concentration of inorganic species of Cu in solution. Collectively, these data suggest that Cu likely plays an important role in the physiology of natural plankton communities beyond the toxicological effects studied previously.     

Hydrolytic ectoenzyme activity associated with suspended and sinking organic particles within the anoxic Cariaco Basin

Ectohydrolase activities of suspended microbiota were compared to those associated with sinking particles (sed-POM) retrieved from sediment traps deployed in the permanently anoxic Cariaco Basin. In shore-based assays, activities of aminopeptidase, β-glucosidase, chitinase and alkaline phosphatase were measured in samples obtained from oxic and anoxic depths using MUF- and MCA-labeled fluorogenic substrate analogs. Hydrolysis potentials for these enzymes in the seston varied widely over the nine cruises sampled (8 Nov 1996–3 May 2000) and among depths (15–1265 m); from <10 to over 1600 nM d^?1 hydrolysate released, generally co-varying with one another and with suspended particulate organic carbon (POC) and particulate nitrogen (PN). Hydrolytic potentials, prokaryotic abundances and POC/PN concentrations in sinking debris were 400–1.3×10⁷ times higher than in comparable volumes of seawater. However when normalized to PN, hydrolytic potentials in sediment trap samples were not demonstrably higher than in Niskin bottle samples. We estimate that PN pools in sediment trap samples were turned over 2–1400 times (medians=7–26x) slower by hydrolysis than were suspended PN pools. Median prokaryotic growth rates (divisions d^?1) in sinking debris were also ～150 times slower than for bacterioplankton. Hydrolytic potentials in surface oxic waters were generally faster than in underlying anoxic waters on a volumetric basis (nM hydrolysate d^?1), but were not significantly (p>0.05) different when normalized to PN or prokaryote abundances. Alkaline phosphatase was consistently the most active ectohydrolase in both sample types, suggesting that Cariaco Basin assemblages were adapted to decomposing phosphate esters in organic polymers. However, phosphorus limitation was not evident from nutrient inventories in the water column. Results support the hypothesis that efficiencies of polymer hydrolysis in anoxic waters are not inherently lower than in oxic waters.     

Regionalism as resistance: Governance and identity in Western Australia’s Wheatbelt

Extensive rural regions are facing major socio-economic, political and environmental change from the dual effects of agricultural restructuring and environmental degradation. While central governments often rely on regional level policy responses, local actors, such as rural local governments may resist these ‘top-down’ initiatives. This paper examines the oppositional response of 34 rural local governments to state-led regionalisation for economic development and natural resource management in the extensive and sparely populated Wheatbelt region of Western Australia. The analysis explores how state threats of amalgamation; shifting national policy empathies in rural development; and, local preferences for horizontal rather than vertical forms of cooperation are influential in catalysing a brand of defensive regionalism amongst local government actors. Adopting this defensive posture allowed local actors to both buffer state intervention and improve the effectiveness of their own cooperative planning and management activities for sustainable development. These observations are interpreted through concepts of collective identity formation, providing an analytical perspective that is sensitive to the inter-scalar politics in rural governance.     

Constraining groundwater flow,residence times,inter-aquifer mixing,and aquifer properties using environmental isotopes in the southeast Murray Basin,Australia

Environmental isotopes (particularly δ¹⁸O, δ²H, and δ¹³C values, ⁸⁷Sr/⁸⁶Sr ratios, and a¹⁴C) constrain geochemical processes, recharge distribution and rates, and inter-aquifer mixing in the Riverine Province of the southern Murray Basin. Due to methanogenesis and the variable δ¹³C values of matrix calcite, δ¹³C values are highly variable and it is difficult to correct ¹⁴C ages using δ¹³C values alone. In catchments where δ¹³C values, ⁸⁷Sr/⁸⁶Sr ratios, and major ion geochemistry yield similar a¹⁴C corrections, ∼15% of the C is derived from the aquifer matrix in the silicate-dominated aquifers, and this value may be used to correct ages in other catchments. Most groundwater has a¹⁴C above background (∼2 pMC) implying that residence times are <30 ka. Catchments containing saline groundwater generally record older ¹⁴C ages compared to catchments that contain lower salinity groundwater, which is consistent with evapotranspiration being the major hydrogeochemical process. However, some low salinity groundwater in the west of the Riverine Province has residence times of >30 ka probably resulting from episodic recharge during infrequent high rainfall episodes. Mixing between shallower and deeper groundwater results in ¹⁴C ages being poorly correlated with distance from the basin margins in many catchments; however, groundwater flow in palaeovalleys where the deeper Calivil–Renmark Formation is coarser grained and has high hydraulic conductivities is considerably more simple with little inter-aquifer mixing. Despite the range of ages, δ¹⁸O and δ²H values of groundwater in the Riverine Province do not preserve a record of changing climate; this is probably due to the absence of extreme climatic variations, such as glaciations, and the fact that the area is not significantly impacted by monsoonal systems.     

On the initialization of tropical cyclones with a three dimensional variational analysis

A method of initializing tropical cyclones in high-resolution numerical models is developed by modifying a data assimilation system, the NRL atmospheric variational data assimilation system (NAVDAS), which was designed for general mesoscale weather prediction using a three-dimensional variational (3DVAR) analysis with intermittent updates. The method includes the following three upgrades to overcome difficulties resulting from tropical cyclone initialization with the NAVDAS analysis. First, synthetic observation soundings are generated on 9 vertical levels at 49 points for strong storms (v _max?>?23.1?m?s^?1) and 41 points for weak storms around each cyclone center to supplement the observations used by the analysis. Secondly, a vortex relocation method for nested grids is developed to correct the cyclone position in the background fields of the analysis for each nested mesh. Lastly, the 3DVAR analysis is modified to gradually reduce the horizontal length scale and geostrophic coupling constraint near the center of a tropical cyclone for minimizing the problems introduced by improper covariances and coupling constraint used in the analysis. The synthetic observations significantly improve the intensity and structure of the analysis and the track forecast. The vortex relocation significantly improves the first guess background, avoiding the large analysis corrections that would be needed to correct cyclone position, and reducing the imbalance introduced by such large analysis increments. The modifications to the analysis length scale and geostrophic coupling constraint successfully improve the inner core analysis, providing a tighter circulation, and reducing the underestimate of the mass field gradient. Among the three upgrades, the vortex relocation provides the largest improvement to the tropical cyclone initialization and forecast.     

Post-equinox observations of Uranus: Berg’s evolution, vertical structure, and track towards the equator

We present observations of Uranus taken with the near-infrared camera NIRC2 on the 10-m W.M. Keck II telescope, the Wide Field Planetary Camera 2 (WFPC2) and the Wide Field Camera 3 (WFC3) on the Hubble Space Telescope (HST) from July 2007 through November 2009. In this paper we focus on a bright southern feature, referred to as the “Berg.” In Sromovsky et al. (Sromovsky, L.A., Fry, P.M., Hammel, H.B., Ahue, A.W., de Pater, I., Rages, K.A., Showalter, M.R., van Dam, M. [2009]. Icarus 203, 265-286), we reported that this feature, which oscillated between latitudes of −32° and −36° for several decades, suddenly started on a northward track in 2005. In this paper we show the complete record of observations of this feature’s track towards the equator, including its demise. After an initially slow linear drift, the feature’s drift rate accelerated at latitudes ∣θ∣ < 25°. By late 2009 the feature, very faint by then, was spotted at a latitude of −5° before disappearing from view. During its northward track, the feature’s morphology changed dramatically, and several small bright unresolved features were occasionally visible poleward of the main “streak.” These small features were sometimes visible at a wavelength of 2.2 μm, indicative that the clouds reached altitudes of ∼0.6 bar. The main part of the Berg, which is generally a long sometimes multipart streak, is estimated to be much deeper in the atmosphere, near 3.5 bars in 2004, but rising to 1.8-2.5 bars in 2007 after it began its northward drift. Through comparisons with Neptune’s Great Dark Spot and simulations of the latter, we discuss why the Berg may be tied to a vortex, an anticyclone deeper in the atmosphere that is visible only through orographic companion clouds.