Rum Jungle Research Articles

GROUNDWATER FLOW AND MULTI-COMPONENT REACTIVE TRANSPORT SIMULATION OF ACID MINE DRAINAGE AT A FORMER MINE SITE

Contamination of groundwater resources due to Acid Mine Drainage (AMD) is one of the severest environmental problems. Understanding complex geochemical processes responsible for the generation of AMD within the mine waste deposits is imperative for effective management and remediation of contaminated mine sites. A multi-component reactive transport simulation is developed based on PHT3D to simulate the geochemical evolution of AMD at the Rum Jungle Mine site that has undergone a long history of groundwater contamination. The reactive transport simulation utilized hydraulic head distribution obtained from MODFLOW based calibrated flow model. Geochemical processes considered for the reactive simulation were conceptualized based on previous geochemical characterization and the contaminant of concerns were limited to copper, iron, manganese, aluminum, zinc, and pyrite minerals considering their environmental significance. The simulation results showed that the simulated plume followed mobility pattern dominated by oxidation of sulfide minerals resulting in AMD and subsequent escalation in the concentration of dissolved metals. Simulated and observed concentration for different reactive species appeared to be in a similar range implying reasonable approximation of the physical system. The detailed calibration of reactive transport simulation is restrained by uncertainties associated with aquifer heterogeneity, sparsity in available information, and inaccurate understanding of the geochemical processes.

Woodcutters 55 Years Later: A New Look at an Old Discovery

Abstract The Woodcutters Zn-Pb-Ag deposit in the Rum Jungle district of the Pine Creek orogen in northern Australia was discovered in 1964 and produced 4.6 Mt of ore grading 12.3% Zn, 5.6% Pb, and 83 g/t Ag between 1985 and 1999. Woodcutters, together with several other polymetallic, uranium, and phosphate deposits, is within a Paleoproterozoic sequence of fluviatile and shallow marine sediments deposited in a deepening basin between ~2100 and 2025 Ma around the margins of an Archean granitic and gneissic dome. These sediments were overlain by turbidites and volcaniclastic rocks until the basin was inverted and the sediments and mineral deposits were deformed and metamorphosed at 1860 Ma. Whereas the polymetallic and uranium bodies at Rum Jungle are considered to be syngenetic or syndiagenetic, sulfides in the Woodcutters orebody replace dolomitic horizons in an otherwise carbonaceous unit. This suggests that Woodcutters is similar to Mississippi Valley-type mineralization and rules out affinities with younger sedimentary exhalative-style deposits elsewhere in the Pine Creek orogen. A model is proposed whereby metals were eroded from Archean basement rocks into Paleoproterozoic sandstone aquifers following the Great Oxidation Event, which also liberated sulfur by oxidation of pyrite. Evaporative conditions, as suggested by the widespread occurrence of dolomite and magnesite, may have increased the chloride content of seawater and enhanced its capacity to transport metals. Subsequently, deeply circulating seawater leached metals from the aquifers and ascended up a deep, basin-penetrating fault until it intersected carbonaceous sediments. In this environment, Zn and Pb sulfides were deposited under reducing conditions, while sulfur may have been provided by H2S from organic material. The Woodcutters and other deposits at Rum Jungle show how metals formerly locked up in Archean cratons were delivered by erosion under an oxygenated atmosphere to Paleoproterozoic shorelines, where they were further mobilized and concentrated by a variety of processes.

Water hardness determines 226Ra uptake in the tropical freshwater mussel

Chemical data for freshwater mussels (Velesunio spp.) and water from 15 sampling sites in the Alligator Rivers Region and Rum Jungle uranium provinces in tropical Northern Australia were analysed to develop a predictive model of radium-226 (226Ra) bioaccumulation for variable water calcium (Ca) and magnesium (Mg) concentrations. Application of the model as a 226Ra screening approach for freshwater mussels in tropical waterbodies potentially impacted by operational or remediated uranium mine sites is discussed in relation to Mudginberri Billabong, located approximately 12 km downstream of Ranger uranium mine in the Alligator Rivers Region.

Diminished Metal Accumulation in Riverine Fishes Exposed to Acid Mine Drainage over Five Decades

Bony bream (Nematalosa erebi) and black catfish (Neosilurus ater) were sampled from the fresh surface waters of the Finniss River in tropical northern Australia, along a metal pollution gradient draining the Rum Jungle copper/uranium mine, a contaminant source for over five decades. Paradoxically, populations of both fish species exposed to the highest concentrations of mine-related metals (cobalt, copper, lead, manganese, nickel, uranium and zinc) in surface water and sediment had the lowest tissue (bone, liver and muscle) concentrations of these metals. The degree of reduction in tissue concentrations of exposed populations was also specific to each metal and inversely related to its degree of environmental increase above background. Several explanations for diminished metal bioaccumulation in fishes from the contaminated region were evaluated. Geochemical speciation modeling of metal bioavailability in surface water showed no differences between the contaminated region and the control sites. Also, the macro-nutrient (calcium, magnesium and sodium) water concentrations, that may competitively inhibit metal uptake, were not elevated with trace metal contamination. Reduced exposure to contaminants due to avoidance behavior was unlikely due to the absence of refugial water bodies with the requisite metal concentrations lower than the control sites and very reduced connectivity at time of sampling. The most plausible interpretation of these results is that populations of both fish species have modified kinetics within their metal bioaccumulation physiology, via adaptation or tolerance responses, to reduce their body burdens of metals. This hypothesis is consistent with (i) reduced tissue concentrations of calcium, magnesium and sodium (macro-nutrients), in exposed populations of both species, (ii) experimental findings for other fish species from the Finniss River and other contaminated regions, and (iii) the number of generations exposed to likely selection pressure over 50 years.

Low δ18O zircon grains in the Neoarchean Rum Jungle Complex, northern Australia: An indicator of emergent continental crust

The timing of widespread continental emergence is generally considered to have had a dramatic effect on the hydrological cycle, atmospheric conditions, and climate. New secondary ion mass spectrometry (SIMS) oxygen and laser-ablation–multicollector–inductively coupled plasma–mass spectrometry (LA-MC-ICP-MS) Lu-Hf isotopic results from dated zircon grains in the granitic Neoarchean Rum Jungle Complex provide a minimum time constraint on the emergence of continental crust above sea level for the North Australian craton. A 2535 ± 7 Ma monzogranite is characterized by magmatic zircon with slightly elevated δ18O (6.0‰–7.5‰ relative to Vienna standard mean ocean water [VSMOW]), consistent with some contribution to the magma from reworked supracrustal material. A supracrustal contribution to magma genesis is supported by the presence of metasedimentary rock enclaves, a large population of inherited zircon grains, and subchondritic zircon Hf (eHf = −6.6 to −4.1). A separate, distinct crustal source to the same magma is indicated by inherited zircon grains that are dominated by low δ18O values (2.5‰–4.8‰, n = 9 of 15) across a range of ages (3536–2598 Ma; eHf = −18.2 to +0.4). The low δ18O grains may be the product of one of two processes: (1) grain-scale diffusion of oxygen in zircon by exchange with a low δ18O magma or (2) several episodes of magmatic reworking of a Mesoarchean or older low δ18O source. Both scenarios require shallow crustal magmatism in emergent crust, to allow interaction with rocks altered by hydrothermal meteoric water in order to generate the low δ18O zircon. In the first scenario, assimilation of these altered rocks during Neoarchean magmatism generated low δ18O magma with which residual detrital zircons were able to exchange oxygen, while preserving their U-Pb systematics. In the second scenario, wholesale melting of the altered rocks occurred in several distinct events through the Mesoarchean, generating low δ18O magma from which zircon crystallized. Ultimately, in either scenario, the low δ18O zircons were entrained as inherited grains in a Neoarchean granite. The data suggest operation of a modern hydrological cycle by the Neoarchean and add to evidence for the increased emergence of continents by this time.

The chemical composition and bacteria communities in acid and metalliferous drainage from the wet–dry tropics are dependent on season

Acid and metalliferous drainage (AMD) occurs when sulphidic minerals, such as arsenopyrite, chalcopyrite and pyrite, are exposed to oxygen and water. Climate, geology and mine site practices can have a significant impact on AMD composition. The elemental composition of the AMD can also affect the bacterial community. Our hypothesis was that in the dry season the AMD at two mine sites, Rum Jungle and Mt Todd, in the Northern Territory, Australia, has a higher concentration of dissolved metals because standing water evaporates during the extended dry period. Our second hypothesis was that the wet and dry season bacteria community in AMD at Rum Jungle and Mt Todd are different, and this difference is correlated to seasonally specific changes in physicochemistry. The first hypothesis was tested by measuring elemental concentrations in AMD during the wet and dry seasons at Mt Todd and Rum Jungle mine sites. The physicochemical properties such as temperature, pH and dissolved oxygen were also measured. To test the second hypothesis, we extracted DNA from AMD samples collected at Rum Jungle and Mt Todd during the wet and dry seasons. The hypervariable V6 region of the bacterial 16S rRNA gene was sequenced by 454 pyrosequencing. The bacterial community composition was examined and related to physiochemical variables. The elemental concentrations in Rum Jungle AMD were higher in the dry season compared to the wet season, but at Mt Todd the elemental composition of AMD changed with year, rather than season. The bacteria community in AMD at Rum Jungle changed between the wet and dry season while in Mt Todd AMD the bacteria community from year 1 was significantly different from year 2. The data showed that the elemental composition and bacteria communities of AMD at Rum Jungle and Mt Todd are influenced by season, mine site practices and geological characteristics of the ore body. In addition, the iron oxidising bacteria Leptospirillum and Acidithiobacillus typically associated with AMD in temperate regions were not prevalent at out tropical study sites.

Kombolgie AEM Survey Images to 2 km

Airborne electromagnetic (AEM) data are being acquired by Geoscience Australia (GA) under the Australian Government’s Onshore Energy Security Program (OESP) in areas considered to have potential for uranium or thorium mineralisation. The surveys are managed and interpreted by members of GA’s AEM Acquisition and Interpretation Project. In contrast to deposit-scale investigations carried out by industry these surveys are designed to reveal new geological information at a regional scale. The Pine Creek AEM survey shown in Figure 1 is comprised of three survey areas: Woolner Granite, Rum Jungle and Kombolgie. The TEMPESTTM AEM system was used for the Woolner Granite and Rum Jungle surveys and the VTEMTM system was used for the Kombolgie survey.

Continuing pollution from the Rum Jungle U–Cu project: A critical evaluation of environmental monitoring and rehabilitation

The former Rum Jungle uranium–copper project, Australia, is an internationally important case study on environmental pollution from and rehabilitation of mining. The Rum Jungle mining project is briefly reviewed, followed by a critical evaluation of monitoring data and pollution loads prior to and after rehabilitation – leading to the conclusion that rehabilitation has clearly failed the test of time after just two decades. The most critical findings are the need to understand pollution cycles holistically, and designing monitoring regimes to match, explicit inclusion of radiological criteria (lacking in original planning), and finally the need to set targets based on environmental criteria. Two examples include polluted groundwater which was excluded from rehabilitation and the poor design, construction and/or performance of engineered soil covers – both leading to increasing acid drainage impacts on the Finniss River. The critical review therefore presents a valuable case study of the environmental performance of uranium mine site rehabilitation.

High-K granites of the Rum Jungle Complex, N-Australia: Insights into the Late Archean crustal evolution of the North Australian Craton

The Late Archean (c. 2.54–2.52 Ga) high-K granitoids of the Rum Jungle Complex, Northern Australia, display the igneous mineral assemblage of K-feldspar, quartz, plagioclase, biotite, and magnetite, and accessories such as zircon, monazite, titanite, allanite, apatite, and ilmenite. The granites underwent a variably severe greenschist facies alteration and associated deformation during the Barramundi Orogeny (1.88–1.85 Ga). The K-rich granitoids have variable compositions, mainly comprising syenogranite and quartz-monzonite. They can be subdivided into two major groups, (1) felsic granites and (2) intermediate to felsic granites, quartz-monzonites, and diorite. The felsic group (69–76 wt.% SiO 2) shares many features with typical Late Archean potassic granites. They are K- and LILE-rich and show marked depletion in Sr and Eu and the high field strength elements (HFSE), particularly Nb and Ti, relative to LILE and LREE. Compared to the average upper crust they have anomalously high Th (up to 123 ppm) and U (up to 40 ppm). The intermediate to felsic group (56–69 wt.% SiO 2) differs from the felsic group in having weakly lower Th and U but higher Mg#, Ti, Ba, Sr, Ni, Cr and REE, with a less pronounced negative Eu anomaly. This group displays well-defined trends in Harker diagrams, involving a negative correlation of Si with Sr, Ca, Na, and P whereas K, Rb, and Ba increase in the same direction, suggesting fractional crystallization of feldspar was more prominent than in the felsic suite. The mineralogical and geochemical characteristics of the felsic group are consistent with granite formation by intracrustal melting of plagioclase-rich igneous protoliths, probably of tonaltic to granodioritic composition, at moderate crustal levels. The intermediate to felsic granites, on the other hand, appear to be the products of mantle–crust interaction, possibly by melting of or mixing with more mafic igneous rocks. As evidenced by the presence of older inherited zircons crustal recycling of a pre-greenstone crust of the North Australian Craton of > 3.5 Ga played an important role in the formation of the Late Archean granites of the Rum Jungle Complex.

Distribution and storage of sediment-associated heavy metals downstream of the remediated Rum Jungle Mine on the East Branch of the Finniss River, Northern Territory, Australia

Instream, overbank and cut riverbank exposures along the East Branch of the Finniss River downstream of Rum Jungle Mine, Northern Territory have been analysed for their total metal concentrations using instrumental neutron activation analysis (INAA). Concentration values for the < 62.5 μm and bulk sample fractions are compared to Australian sediment quality guidelines values ( ANZECC/ARMCANZ, 2000). The results reveal that channel and overbank environments are contaminated with heavy metals, with many samples exceeding the low and high sediment guidelines values. The < 62.5 μm fraction is consistently more contaminated than bulk samples as are instream environments compared to adjacent overbank environments. Metal concentrations are strongly correlated to sediment pH and Fe values, suggesting that these variables are significant in controlling the spatial distribution of sediment-associated metals. The strong positive correlation between sediment-associated metals and Fe is probably related to the process of metal sequestration by Fe (and Mn) oxyhydroxides. The spatial distribution of sediment-associated metals downstream of the Rum Jungle Mine site does not display a simple distance–metal concentration decay pattern. It is suggested that the non-uniform spatial distribution of sediment-associated metals is a function of local, reach-scale variations in channel geometry and geomorphology, which control sediment storage and transfer patterns. In cut riverbank exposures the vertical of metals distribution is non-uniform and probably reflects differential metal mobility. Despite rehabilitation of the mine site in the 1980s, the elevated sediment-associated metal concentrations that remain within the East Branch of the Finniss River system are likely to render the system contaminated for the foreseeable future and limit the potential for the full recovery of aquatic and terrestrial flora and fauna.

Polymetallic Mineralization at the Browns Deposit, Rum Jungle Mineral Field, Northern Territory, Australia

The Rum Jungle mineral field, Northern Territory, Australia, forms part of the Paleoproterozoic Pine Creek orogen. The geology of the area comprises two Archean granitic basement domes, overlain by a Paleoproterozoic sequence of metasedimentary and subordinate metavolcanic rocks. The rocks have been deformed and metamorphosed to greenschist facies during the 1880 Ma Barramundi orogeny, but the original stratigraphic succession has been preserved. The Browns deposit (Browns and its extension Browns East), hosted within black carbonaceous pelites of the Paleoproterozoic Whites Formation, is the largest base metal deposit found to date in the Pine Creek orogen. Present resource estimates are 39 million metric tons (Mt) at 0.44 percent Cu, 3.61 percent Pb, 0.11 percent Co, and 0.09 percent Ni (Browns), and 31 Mt at 1.29 percent Cu, 1.28 percent Pb, 0.13 percent Co, and 0.13 percent Ni (Browns East). Major sulfide minerals in the ore zone are galena, sphalerite, chalcopyrite, pyrite, and the main carrier of Ni and Co, siegenite (Ni,Co) 3 S 4 . Digenite group minerals and bornite, Ca-bearing plumbogummite (PbAl 3 (PO 4 ) 2 (OH) 5 .H 2 O), arsenopyrite, and gersdorffite are present in minor quantities. Ore minerals occur as fine-grained wisps parallel to the main bedding-parallel foliation and as coarse-grained mono- and polyminerallic aggregates that crosscut the foliation. Total noncarbonate carbon contents of unaltered rocks range from 1.07 to 7.51 wt percent. Total sulfur contents range from 2.13 to 6.14 wt percent. Petrographic studies and Raman spectroscopy identify three varieties of carbonaceous matter: primary syngenetic; premetamorphic, epigenetic grain coating; and postmetamorphic, epigenetic, uraniferous migrated. Altered rocks are rarely encountered. Values of δ 34 S for sulfides range from –5 to +15 per mil and are interpreted to reflect a combination of inorganic thermochemical reduction of seawater and bacterial activity. No specific sulfur isotope patterns for individual minerals can be established indicating nonequilibrium conditions. Homogeneous lead isotope signatures of galena ( 206 Pb/ 204 Pb = 16.20–16.22, 207 Pb/ 206 Pb = 15.48–15.51, 208 Pb/ 207 Pb = 35.86–35.92) suggest that all Pb was derived from a single crustal source, and paragenetically late crosscutting galena appears to have been remobilized from bedding-parallel galena. Despite the occurrence of uranium in similar rocks nearby, uranium is quantitatively insignificant in the Browns deposit and is not genetically related to base metal mineralization. Instead, it is linked to brittle deformation in the waning stages of orogenesis. The Browns deposit differs from other well-known sediment-hosted stratiform ore deposits. Both the Zambian Copperbelt and the Polish Kupferschiefer deposits are copper dominant and hosted in sedimentary sequences with significant psammitic components. The Pb-Zn-Ag deposits of the Proterozoic Australian zinc province also have significant carbonate in their host rocks (e.g., carbonaceous dolomitic and siltstone at McArthur River) and lack economically interesting Cu, Co, and Ni. The nearby Woodcutters Pb-Zn-Ag deposit, in rocks of similar age, also differs in structural setting (veins), dominant metals, and Pb isotopes from the Browns deposit.

U/Th‐rich bitumen in Archean granites and Palaeoproterozoic metasediments, Rum Jungle Mineral Field, Australia: implications for mineralizing fluids

AbstractUranium/thorium (U/Th)‐rich bitumen has been discovered within both Palaeoproterozoic black pelites and the Archean granitic basement of the Rum Jungle Mineral Field, Northern Territory, Australia. Granite‐hosted bitumen occurs as small (up to 400‐µm diameter) discrete individual nodules, which exhibit many morphological similarities to those observed in Phanerozoic siliciclastic rocks. Thorium, the dominant radioelement, occurs primarily as a hydrated Th–Y–Si–P phase. Uranium‐rich inclusions are rare, and correspond to a hydrated U–Th–Y–Si–P phase, identified as coffinite–thorogummite. Metasediment‐hosted bitumen is more variable in morphology, occurring as massive (&lt;2 cm in width) veins that cross‐cut all foliations, as discrete individual nodules or as elongate seams (up to 500 µm in length), interpreted to represent a series of coalesced individual nodules. In all examples, uranium, the dominant radioelement in the metasediment‐hosted bitumen, is present as Th‐poor uraninite, with variable Y2O3 contents (up to 3.21 wt.%).Raman investigation of all types of bitumen indicates that it is a poorly organized carbonaceous matter, which has not been subjected to metamorphism. Consequently, a post‐metamorphic timing for hydrocarbon emplacement can be inferred and a magmatic origin can be precluded.Potential source rocks for the bitumen are black shales of the Whites Formation (up to 8 wt.% total organic carbon (TOC)) and the Koolpin Formation (approximately 13 wt.% TOC). Post‐metamorphic sericitization of rocks within the Whites Formation is accompanied by a near‐complete removal of organic matter. Alteration was possibly the catalyst for hydrocarbon generation.The Th–Y–Si–P phase within the granite‐hosted nodules is interpreted to be the result of the alteration of antecedent monazite. During this alteration, U, LREE and P were fractionated and removed, while Th, Y and Si remained immobile, and recombined to form a hydrated Th–Y–Si phase. This pervasive alteration within the basement U/Th‐rich granites is proposed as a genetic model for the formation of uranium deposits in the Rum Jungle Mineral Field and possibly unconformity associated uranium deposits on a global scale.

The Use of Lead Isotopes in Monitoring Environmental Impacts of Uranium and Lead Mining in Northern Australia

Lead isotope ratios, determined by inductively coupled plasma quadropole mass spectrometry (ICPMS), have been used to assess environmental impacts from uranium and lead mining in northern Australia. The lead isotope composition of most environmental samples contained evidence of mixing of two or more end-member components; their characteristic lead isotope ratios allowed lead sources to be unambiguously identified. The isotopic characteristics and sources identified include highly radiogenic lead (low 207Pb/206Pb and 208Pb/206Pb ratios) in sediments from the Finniss River derived from the former Rum Jungle uranium mine; relatively non-radiogenic lead (high 207Pb/206Pb and 208Pb/206Pb ratios) in the livers of magpie geese from the Finniss River floodplains, originating from lead ores via ingested lead shot; and relatively non-radiogenic lead in seagrass leaves and oyster soft tissue from the Gulf of Carpentaria resulting from dispersion of small amounts of lead–zinc concentrate from a coastal loading facility.

Insights into the mechanisms of copper tolerance of a population of black-banded rainbowfish ( Melanotaenia nigrans) (Richardson) exposed to mine leachate, using 64/67Cu

This study investigates the mechanisms of copper tolerance of a population of black-banded rainbowfish ( Melanotaenia nigrans) (Richardson). The population has been exposed to elevated copper concentrations for over 40 years, due to leachate from the Rum Jungle uranium/copper mine. At the time of collection the 96 h EC 50 of exposed [E] fish was 8.3 times higher than that of reference [R] fish. The bioconcentration of 64/67Cu in fish was used to investigate the mechanism of copper tolerance in E fish. Both E and R fish were exposed to low (L Cu, 30 μg Cu l −1) and elevated (E Cu, 300 μg Cu l −1) copper concentrations for 24 and 48 h, respectively. Radioactivity was measured at seven or eight time points in four tissue sections: head (including gills, heart and brain), internal organs (including gastrointestinal tract, liver, kidneys and gonads), muscle and whole body. One-compartment bioconcentration models were fit to data and compared using an F-test. Copper concentrations in all tissue sections were significantly ( P<0.05) less (up to 50%) in E fish compared with the respective tissue sections of R fish when exposed to both L Cu and E Cu. The exception was copper accumulation in the internal organs, which was not significantly different between E and R fish exposed to E Cu. The mechanism of copper tolerance was concluded to be reduced copper uptake in the gills, rather than increased binding or elimination. Allozyme electrophoresis was performed to determine if genetic selection had occurred in the E fish population. Allozyme frequencies at the AAT-1 and GPI-1 loci were significantly ( P<0.05) different between E and R fish. Heterozygosity was reduced in E fish compared with that of R fish. Collectively these results suggest that genetic selection may have occurred in the E fish population. Consequently, the selection of allozymes less sensitive to copper may be another mechanism of copper tolerance of E fish. This is the first study on the mechanisms of copper tolerance in a wild fish population that has been exposed to elevated copper concentrations. These findings aid the understanding of metal tolerance in fish and emphasise the importance of sample selection and its implication for toxicity testing.

Freshwater bivalve shells as archival indicators of metal pollution from a copper-uranium mine in tropical northern Australia.

Freshwater bivalves (Velesunio angasi) were sampled in 1996 from the Finniss River in tropical northern Australia at 10 sites a priori exposed and nonexposed to acid rock drainage (ARD), containing elevated metal concentrations, from the rehabilitated Rum Jungle copper-uranium mine. Secondary ion mass spectrometry (SIMS) was used to measure Cu, Mn, Zn, U, Ni, Co, Pb, and Fe/Ca ratios across the annual shell laminations of the longest-lived bivalves found at each site, with the aim of evaluating the ability of the shells to archive measured annual metal inputs and their temporal patterns. At sites not contaminated by ARD, relatively constant and similar (baseline) SIMS signals were found for all metals in the shell laminations of V. angasi, dating as far back as 1965. At sites contaminated by ARD, relatively constant, but variably elevated, SIMS signals were evident for Cu, Mn, Zn, Ni, and Co in the shell, which extended back to the end of rehabilitation (1986) only. Since rehabilitation, the temporal patterns of Cu, Zn, and Mn observed in the shells at the most contaminated sites reflected those of the measured annual dissolved loads in the surface waters. The average concentrations of Cu, Mn, Zn, Ni, and Co in the shells decreased (3-13-fold) with increasing distance downstream of the mine site, until concentrations characteristic of the noncontaminated sites were reached. This geographic pattern of decline in pollution signal in the shell with increasing distance downstream of the pollution input is consistent with the pattern established for water and sediment chemistry. Overall, the SIMS results support the proposition that the shells of V. angasi can be used as archival indicators of metal pollution in surface waters of the Finniss River over their lifetime.

Recovery of fish communities in the Finniss River, northern Australia, following remediation of the Rum Jungle uranium/copper mine site.

The Finniss River in the wet-dry tropics of northern Australia has received acid rock drainage (ARD) contaminants from the Rum Jungle uranium/copper mine site over more than four decades. Annual-cycle loads of Cu, Zn, Mn, and sulfate, calculated from daily water and flow measurements, have been determined both prior to and following mine-site remediation, that began in the early 1980s. The effects of varying contaminant loads on the relative abundances of seven fish species, sampled by enmeshing nets during dry seasons, were determined by nonmetric multidimensional scaling (nMDS), in combination with cluster-analysis and other nonparametric statistical techniques. These analyses showed that (i) prior to remediation, the impacted region of the Finniss River in 1974 had significantly dissimilar (P < 0.001) and more heterogeneous fish communities, generally characterized by reduced diversity and abundance, compared to sites unexposed to elevated contaminant water concentrations and (ii) postremediation, recovery in fish communities from the impacted region was indicated because they were not significantly dissimilar from those sampled at contemporary (P = 0.16) unimpacted sites, that were also similar to preremedial unimpacted sites. Even though considerable contaminant loads are still being delivered to the impacted region of the Finniss River over the annual cycle, the recovery in fish diversity and abundances is consistent with (a) reductions of in situ contaminant water concentrations at the time of fish sampling, (b) reductions in annual-cycle contaminant loads of sulfate, Cu, Zn, and Mn by factors of 3-7, (c) greatly reduced frequencies of occurrence and magnitude of elevated contaminant water concentrations over the annual cycle, that was most pronounced for Cu, and (d) the absence of extensive fish-kills during the first-flushes of contaminants into the Finniss river proper at the beginning of the wet season, that were observed prior to remediation. As such, the results indicate that there has been ecological benefit to the Finniss River attributable to remedial works undertaken at the Rum Jungle mine site. Recovery in abundances of these fishes may also be due to their time-dependent evolution of tolerance to mine-waste contaminants over their long period of exposure.

Vegetation Dieback on Clay‐Capped Pyritic Mine Waste

AbstractWaste rock dumps at the abandoned Rum Jungle uranium mine were capped with clay covers in order to limit entrance of water and oxygen into the dump, and hence to reduce generation of acid drainage. The soil covers consisted of a clay seal layer overlain by moisture retention and erosion resistant layers and stabilized with vegetation. An investigation of this cover system, primarily at one of the dumps, was undertaken in response to the concern that the vegetation dieback apparent on some areas was spreading. Reduced vegetative cover could potentially threaten the integrity and effectiveness of the rehabilitation. Areas of vegetation dieback on soil covers were shown to be the result of Cu toxicity. The soil covers had been acidified and contaminated with Cu by capillary rise of water from pyritic waste immediately underlying the soil capping. Over time, the surface soil on areas with progressively deeper capping is being contaminated, resulting in a gradual expansion of the bare area. The activity of Al3+ in the soil solution appears to be controlled in these contaminated soils by the solubility of an Al‐SO4 mineral, resulting in nonphytotoxic Al levels in the surface soil, despite the low pH. The lower portion of the clay seal layer was sufficiently acid that Al toxicity would restrict root growth.

Management of waste from uranium mining and milling in Australia

Australia has a long history of uranium mining. Most of the early production came from Rum Jungle in the Northern Territory and Mary Kathleen in Queensland. The second generation of uranium mines (Ranger, Nabarlek and Olympic Dam) came on line in the 1970s and 1980s at a time of increased environmental awareness and public scrutiny. The waste management practices at these mines are in accordance with best practicable technology for the uranium mining industry. This paper describes Australia's experience in managing the front end of the fuel cycle; uranium mining and ore processing.

Organic tissues, graphite, and hydrocarbons in host rocks of the Rum Jungle Uranium Field, northern Australia

The Rum Jungle Uranium field consists of at least six early Proterozoic deposits that have been mined either for uranium and/or the associated base and precious metals. Organic matter in the host rocks of the Whites Formation and Coomalie Dolomite is now predominantly graphite, consistent with the metamorphic history of these rocks. For nine samples, the mean total organic carbon content is high (3.9 wt%) and ranged from 0.33 to 10.44 wt%. Palynological extracts from the host rocks include black, filamentous, stellate ( Eoastrion-like), and spherical morphotypes, which are typical of early Proterozoic microbiota. The colour, abundance, and shapes of these morphotypes reflect the thermal history, organic richness, and probable lacustrine biofacies of the host rocks. Routine analysis of rock thin sections and of palynological residues shows that mineral grains in some of the host rocks are coated with graphitized organic matter. The grain coating is presumed to result from ultimate thermal degradation of a petroleum phase that existed prior to metamorphism. Hydrocarbons are, however, still present in fluid inclusions within carbonates of the Coomalie Dolomite and lower Whites Formation. The fluid inclusions fluoresce dull orange in blue-light excitation and their hydrocarbon content is confirmed by gas chromatography of whole-rock extracts. Preliminary analysis of the oil suggests that it is migrated, and because it has escaped graphitization through metamorphism it is probably not of early Proterozoic age. The presence of live oil is consistent with fluid inclusion data that suggest subsequent, low-temperature brine migration through the rocks. The present observations support earlier suggestions that organic matter in the host formations trapped uranium to form protore. Subsequent fluid migrations probably brought additional uranium and other metals to these formations, and the organic matter provided a reducing environment for entrapment.

Rehabilitation of the Rum Jungle Mine Site

Rehabilitation of the Rum Jungle Mine Site