Página 1 dos resultados de 392 itens digitais encontrados em 0.002 segundos

Influence of Martian regolith analogs on the activity and growth of methanogenic archaea, with special regard to long-term desiccation

Schirmack, Janosch; Alawi, Mashal; Wagner, Dirk
Fonte: Frontiers Media S.A. Publicador: Frontiers Media S.A.
Tipo: Artigo de Revista Científica
Publicado em 20/03/2015 Português
Relevância na Pesquisa
27.51%
Methanogenic archaea have been studied as model organisms for possible life on Mars for several reasons: they can grow lithoautotrophically by using hydrogen and carbon dioxide as energy and carbon sources, respectively; they are anaerobes; and they evolved at a time when conditions on early Earth are believed to have looked similar to those of early Mars. As Mars is currently dry and cold and as water might be available only at certain time intervals, any organism living on this planet would need to cope with desiccation. On Earth there are several regions with low water availability as well, e.g., permafrost environments, desert soils, and salt pans. Here, we present the results of a set of experiments investigating the influence of different Martian regolith analogs (MRAs) on the metabolic activity and growth of three methanogenic strains exposed to culture conditions as well as long-term desiccation. In most cases, concentrations below 1 wt% of regolith in the media resulted in an increase of methane production rates, whereas higher concentrations decreased the rates, thus prolonging the lag phase. Further experiments showed that methanogenic archaea are capable of producing methane when incubated on a water-saturated sedimentary matrix of regolith lacking nutrients. Survival of methanogens under these conditions was analyzed with a 400 day desiccation experiment in the presence of regolith analogs. All tested strains of methanogens survived the desiccation period as it was determined through reincubation on fresh medium and via qPCR following propidium monoazide treatment to identify viable cells. The survival of long-term desiccation and the ability of active metabolism on water-saturated MRAs strengthens the possibility of methanogenic archaea or physiologically similar organisms to exist in environmental niches on Mars. The best results were achieved in presence of a phyllosilicate...

Inferring the Spatial Distribution of Regolith Properties Using Surface Measurable Features

Laffan, Shawn William
Fonte: Universidade Nacional da Austrália Publicador: Universidade Nacional da Austrália
Tipo: Thesis (PhD); Doctor of Philosophy (PhD)
Português
Relevância na Pesquisa
37.71%
The aim of this research is to determine to what extent properties of the regolith may be inferred using only features easily measured from the surface. To address this research question, a set of regolith properties from Weipa, Queensland, Australia, are analysed. The set contains five variables, oxides of Aluminium, Iron, Silica and Titanium, as well as Depth to Ironstone. This last represents the depth of the layer from which the oxides are sampled.¶ The research question is addressed in two ways. First, locations where the properties are related to modern surface hydrology are assessed using spatially explicit analyses. This is done by comparing the results of spatial association statistics using geometric and watershed-based spatial samples. Second, correlations are sought for between the regolith properties and geomorphometric indices of land surface morphology and Landsat Thematic Mapper spectral response. This is done using spatially implicit Artificial Neural Networks (ANN) and spatially explicit Geographically Weighted Regression (GWR). The results indicate that the degree to which regolith properties are related to surface measurable features is limited and spatially variable.¶ ... ¶ The implications of these results are significant for anyone intending to generate spatial datasets of regolith properties. If there is a low spatial density of sample data...

Neotectonic disruption of silicified palaeovalley systems in an intraplate, cratonic landscape: regolith and landscape evolution of the Mulculca range-front, Broken Hill Domain, New South Wales

Hill, S.; Eggleton, R.; Taylor, G.
Fonte: Blackwell Science Asia Publicador: Blackwell Science Asia
Tipo: Artigo de Revista Científica
Publicado em //2003 Português
Relevância na Pesquisa
37.66%
The landscape expression of a wide range of ancient and contemporary regolith materials in the vicinity of the Mulculca Fault demonstrates two important points: (i) tectonism can be a significant factor in the evolution of landscapes in some parts of the Australian craton; and (ii) ancient and young regolith-landform features can coexist within a tectonically active landscape. Tectonic activity along the Mulculca Fault has created a range-front near the Broken Hill Domain - Murray Basin margins. This tectonism defeated a now silicified palaeodrainage system that flowed from the area now occupied by the Barrier Ranges towards the present area of the Murray Basin. Stream defeat led to the development of lacustrine-overbank conditions within the area of the fault-angle depression, which was later breached by stream incision across the range-front. The area of lacustrine-overbank deposition is now dominated by alluvial (channel and overbank) deposits with minor colluvial and aeolian deposition. Silicification of palaeovalley sediments and adjacent saprolite has been occurring over a broad range of times during landscape development, including several stages of palaeovalley evolution and as minor red-brown hardpan development in the contemporary landscape. Ferruginised regolith has been developing at many different times during the evolution of the landscape...

Regolith-landform and mineralogical mapping of the White Dam Prospect, eastern Olary Domain, South Australia, using integrated remote sensing and spectral techniques.

Lau, Ian Christopher
Fonte: Universidade de Adelaide Publicador: Universidade de Adelaide
Tipo: Tese de Doutorado Formato: 3637006 bytes; 999251 bytes; 170283 bytes; 2051855 bytes; 7734545 bytes; 6985505 bytes; 3073591 bytes; 2562218 bytes; 718600 bytes; 4116886 bytes; application/pdf; application/pdf; application/pdf; application/pdf; application/pdf; application/pdf; applic
Publicado em //2004 Português
Relevância na Pesquisa
37.89%
The research contained within this thesis was directed at examining the spectral properties of regolith-dominated terrains using airborne and proximal hyperspectral instruments. The focus of the investigation was to identify the mineralogy of the regolith and determine if surficial materials were indicative of the underlying bedrock in the regolithdominated terrain of the eastern Olary Domain, South Australia. The research area was constrained to a 250 km2 area around the Cu-Au mineralisation of the White Dam Prosect. Integrated remote sensing, using airborne hyperspectral datasets (HyMap), Landsat imagery and gamma-ray spectroscopy data, was performed to map regolith-landforms and extract information on surficial materials. Detailed calibration of the HyMap dataset, using a modified model-based/empirical line calibration technique, was required prior to information extraction. The White Dam area was able to be divided into: alluvial regolith-dominated; in situ regolith-dominated; and bedrock-dominated terrains, based on mineralogical interpretations of the regolith, using the remotely sensed hyperspectral data. Alluvial regions were characterised by large abundances of vegetation and soils with a hematite-rich mineralogy. Highly weathered areas of in situ material were discriminated by the presence of goethite and kaolinite of various crystallinities...

Calcium in regolith carbonates of central and southern Australia: Its source and implications for the global carbon cycle

Dart, R.; Hatch, K.; Chittleborough, D.; Hill, S.
Fonte: Elsevier Science BV Publicador: Elsevier Science BV
Tipo: Artigo de Revista Científica
Publicado em //2007 Português
Relevância na Pesquisa
27.6%
The widespread regolith carbonates of the Australian continent are a potential sink for CO2. We have used Sr isotopes to investigate the source of the Ca in regolith carbonates that cover approximately 1.6 × 106 km2 of inland Australia. 87Sr/86Sr ratios for nearly all the carbonates were in the range 0.7094 to 0.7211. The results show that only about 10% of the Ca in regolith carbonates is derived from weathered bedrock, with the remaining component being derived from an external marine source. The exceptions are the most northerly samples with a range of 0.7270 to 0.7374, in which bedrock content may be as high as 30%. The likely Ca source areas are sedimentary carbonates located on the continental shelf and calcareous aeolianites that surround much of the southern and western Australian coastline. Winds passing over these carbonates continually rework and transport the material over the Australian continent where it has settled and formed the regolith carbonates we see today. The impact of this process is that, despite the immense area covered, Australian regolith carbonates do not capture any additional CO2; instead the carbonate is simply being remobilised from one pool (marine) to another (terrestrial).; http://www.elsevier.com/wps/find/journaldescription.cws_home/503355/description#description; Robert C. Dart...

Termitaria as regolith landscape attributes and sampling media in northern Australia.

Petts, Anna E.
Fonte: Universidade de Adelaide Publicador: Universidade de Adelaide
Tipo: Tese de Doutorado
Publicado em //2009 Português
Relevância na Pesquisa
37.66%
This study provides one of the first accounts of the relationships between termites, termitaria and the pedolith, towards developing their application as a biogeochemical sampling medium for mineral exploration. Mapping regolith–landforms, termitaria, and the associated termitaria biogeochemistry show that termites are an integral control on the organisation of trace metals in the landscapes of northern Australia. In particular, termites are important for transporting geochemical signatures from depth, through the pedolith and to the ground surface. This occurs by way of bioturbative and constructional activities of the mound-building termites, which in this study included Nasutitermes triodiae, Amitermes vitiosus, Drepanotermes rubriceps, Tumulitermes hastilis and T. pastinator. Termitaria from these species are mappable regolith– landform attributes at the local scale; this highlights their specific preferences for colony sites, such as access to vegetation, drainage, and the availability of construction materials. The mound-building termites featured in this study are also soil modifiers, altering the pedolith terms of both structure and chemistry. Developing an understanding of these processes has helped to refine a model for pedolith development through biotic processes...

Gold-in-calcrete: a continental to profile scale study of regolith carbonates and their association with gold mineralisation.

Dart, Robert C.
Fonte: Universidade de Adelaide Publicador: Universidade de Adelaide
Tipo: Tese de Doutorado
Publicado em //2009 Português
Relevância na Pesquisa
37.89%
Regolith carbonate, especially when indurated (calcrete), has been widely adopted as a sampling medium by many Australian Au exploration companies. Rapid uptake of the medium in geochemical exploration programs, following its reported success in the South Australia Challenger Au deposit discovery, has resulted in poorly constrained sampling methodology with many inconsistencies. Results have therefore been equivocal. This study of regolith carbonates and their association with Au will improve this situation. Three aspects of regolith carbonate development and association with Au are investigated. These are based on variable spatial scales, ranging from the southern Australian continent, to local area, to individual profile. On a continental scale, regolith carbonates cover extensive areas of southern Australia. The primary component, Ca, is sourced from mineral weathering or atmospheric sources. Through the use of Sr isotopes to provide a surrogate expression for Ca sources, the source was identified as > 90% atmospheric or marine derived. A uniform inland signature is identified, which is due to the continual recycling and mixing of marine derived Ca with minimal bedrock input. An external Ca source means that Ca does not have a direct relationship with Au...

Sr-isotopes as a tracer of Ca sources and mobility in profiles hosting regolith carbonates from southern Australia

Dart, R.; Hatch, K.; Hill, S.; Chittleborough, D.
Fonte: Taylor & Francis Ltd. Publicador: Taylor & Francis Ltd.
Tipo: Artigo de Revista Científica
Publicado em //2012 Português
Relevância na Pesquisa
37.23%
Regolith carbonates are common in soil profiles in the arid to semiarid areas of southern and central Australia. Extrinsic sources are now inferred to be the dominant source of Ca even as far inland as Alice Springs in central Australia. This study of Ca sources in a near coastal 2 m deep profile at Clarendon, South Australia, and two inland 4- and 3 m-deep profiles near Olary, South Australia uses Sr isotopes as a proxy for Ca. Our results show that up to 90% of Sr (and by association Ca) in both labile fractions and in soil carbonate is sourced from atmospheric input. The silicate weathering input is minor (510%) and independent of the influence of different bedrock types. The Sr isotope composition throughout the profiles is relatively homogeneous with most values between 0.714 and 0.717, increasing only when in the saprolith, indicating that a process of continual reworking and mixing of the Sr (and Ca) goes beyond the near surface and continues throughout the profile.; R.C. Dart, K.M. Barovich, S.M. Hill and D.J. Chittleborough

New regolith mapping approaches for old Australian landscapes.

Wilford, John Richard
Fonte: Universidade de Adelaide Publicador: Universidade de Adelaide
Tipo: Tese de Doutorado
Publicado em //2014 Português
Relevância na Pesquisa
37.96%
The regolith, or ‘critical zone’, forms a discontinuous layer that covers large areas of Earth’s terrestrial surface. It is a dynamic zone that forms and changes through time in response to interactions between air, rocks (minerals), water and biota. Knowledge of regolith is critical because of its key role in supporting terrestrial life, through physical, chemical and biological processes that operate at mineral-water interaction scales up to the regional scale through geological and tectonic activity. There are many disciplines or areas of applied integrated research that rely on an improved understanding of regolith formation and information on surface and sub-surface regolith properties at appropriate spatial scales. These areas of study include; agriculture, land use sustainability, hydrology, salinity management, ecology, mineral exploration, natural hazard risk assessment and civil engineering. Furthermore, mapping regolith is critical in understanding the origin and evolution of regolith through space and time. Mapping the regolith and formulation of associated robust process models are in their infancy compared with geological and soil mapping, which have had a long history of development and refinement. Regolith mapping can be seen as a hybrid approach combining elements from the existing mapping disciplines of geology...

Conceptual soil-regolith toposequence models to support soil survey and land evaluation

Grealish, G.; Fitzpatrick, R.; King, P.; Shahid, S.
Fonte: Springer; Netherlands Publicador: Springer; Netherlands
Tipo: Parte de Livro
Publicado em //2013 Português
Relevância na Pesquisa
37.23%
Soil maps and the accompanying soil survey report are used to portray the spatial variation of soils in landscapes by indicating what soils, their proportion and their soil properties are likely to occur at a particular location or within a soil map unit. Soil surveyors intuitively understand this soil variation and how it may occur by reading the landscape. However, soil maps and soil survey reports are often too technical and not easily understood by land managers and decision-makers who are not specialist soil scientists. This chapter demonstrates how conceptual soil-regolith toposequence models can be used to describe (supporting soil survey map data and reports), explain (providing an understanding of the processes) and predict (supporting land evaluation) soil spatial variability in a range of complex landscapes. Case studies from Australia and Brunei are provided to illustrate how soil toposequence models are critical to explain, predict and solve practical land use problems, especially in complex soil-landscape environments. These conceptual models provide the following critical data to support land evaluation and ­management decisions by illustrating soil properties that are changing in time and space, which is especially important in salt-affected and acid sulphate soils (e.g. seasonal and climatic changes in occurrences of salt efflorescences)...

Regolith and associated mineral systems of the Eucla Basin, South Australia.

Johnson, Ashlyn Kate
Fonte: Universidade de Adelaide Publicador: Universidade de Adelaide
Tipo: Tese de Doutorado
Publicado em //2015 Português
Relevância na Pesquisa
37.23%
This thesis documents previous research into the heavy mineral sands (HMS) of the Eucla Basin. It presents new research designed to incorporate previous work, and to then encourage a broadening of research into the future. Specifically, this thesis is dedicated to demonstrating the importance of encompassing all aspects of research within a mineral system rather than isolating system components. In order to understand the complex regolith geology expressed within the Eucla Basin and its contained HMS deposits, a multi-faceted approach is applied, targeting two broad research areas. The first research area addresses processes acting prior to deposition of the Eucla Basin sediments, including providing constraints on the source of the sediments using U-Pb zircon analysis. The conclusions of this area of the research are that the dominant U-Pb zircon population lies between 1100 and 1250 Ma. Further, that these zircon populations match with the ages of zircon growth events in two of the most proximal potential source regions, the Musgrave Province and the Albany-Fraser Province. This research has also shown that due to the similar magmatic and metamorphic history of the Musgrave Province and Albany-Fraser Province it is difficult to distinguish between the possible sources regions using the U-Pb zircon data alone...

The stratification of regolith on celestial objects

Schräpler, Rainer; Blum, Jürgen; von Borstel, Ingo; Güttler, Carsten
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 12/05/2015 Português
Relevância na Pesquisa
27.6%
All atmosphere-less planetary bodies are covered with a dust layer, the so-called regolith, which determines the optical, mechanical and thermal properties of their surface. These properties depend on the regolith material, the size distribution of the particles it consists of, and the porosity to which these particles are packed. We performed experiments in parabolic flights to determine the gravity dependency of the packing density of regolith for solid-particle sizes of 60 $\mu$m and 1 mm as well as for 100-250 $\mu$m-sized agglomerates of 1.5 $\mu$m-sized solid grains. We utilized g-levels between 0.7 m s$^{-2}$ and 18 m s$^{-2}$ and completed our measurements with experiments under normal gravity conditions. Based on previous experimental and theoretical literature and supported by our new experiments, we developed an analytical model to calculate the regolith stratification of celestial rocky and icy bodies and estimated the mechanical yields of the regolith under the weight of an astronaut and a spacecraft resting on these objects.; Comment: 15 pages, 12 figures

Timescale of asteroid resurfacing by regolith convection resulting from the impact-induced global seismic shaking

Yamada, Tomoya M.; Ando, Kousuke; Morota, Tomokatsu; Katsuragi, Hiroaki
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 26/08/2015 Português
Relevância na Pesquisa
27.66%
A model for the asteroid resurfacing by regolith convection is built to estimate its timescale. In the model, regolith convection is driven by the impact-induced global seismic shaking. The model consists of three steps: (i) intermittent impact of meteors, (ii) impact-induced global vibration (seismic shaking), and (iii) vibration-induced regolith convection. In order to assess the feasibility of the resurfacing process driven by the regolith convection, we estimate the resurfacing timescale as a function of the size of a target asteroid. According to the estimated result, the regolith-convection-based resurfacing timescale is sufficiently shorter than the mean collisional lifetime for the main belt asteroids. This means that the regolith convection is a possible mechanism for the asteroid resurfacing process. However, the timescale depends on various uncertain parameters such as seismic efficiency and convective roll size. To clarify the parameter dependences, we develop an approximated scaling form for the resurfacing timescale.; Comment: 11pages, 7figures

Lunar Outgassing, Transient Phenomena and The Return to The Moon, II: Predictions for Interactions between Outgassing and Regolith

Crotts, Arlin P. S.; Hummels, Cameron
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 26/06/2007 Português
Relevância na Pesquisa
27.71%
We consider the implications from Paper I on how gas leaking through the lunar surface might interact with the regolith, and in what respects this might affect or cause the appearance of optical Transient Lunar Phenomena (TLPs). We consider briefly a range of phenomena, but concentrate at the extremes of high and low gas flow rate, which might represent the more likely behaviors. Extremely fast i.e., explosive, expulsion of gas from the surface is investigated by examining the minimal amount of gas needed to displace a plug of regolith above a site of gaseous overpressure at the regolith's base. The area and timescale of this disturbance, it is consistent with observed TLPs. Furthermore there are several ways in which such an explosion might be expected to change the lunar surface appearance in a way consistent with many TLPs, including production of obscuration, brightening and color changes. At the slow end of the volatile flow range, gas seeping from the interior is retained below the surface for extensive times due to the low diffusivity of regolith material. A special circumstance arises if the volatile flow contains water vapor, because water is uniquely capable of freezing as it passes from the base to the surface of the regolith. For a large TLP site...

Lunar Outgassing, Transient Phenomena & the Return to the Moon, II: Predictions and Tests for Outgassing/Regolith Interactions

Crotts, Arlin P. S.; Hummels, Cameron
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Português
Relevância na Pesquisa
27.71%
We follow Paper I with predictions of how gas leaking through the lunar surface could influence the regolith, as might be observed via optical Transient Lunar Phenomena (TLPs) and related effects. We touch on several processes, but concentrate on low and high flow rate extremes, perhaps the most likely. We model explosive outgassing for the smallest gas overpressure at the regolith base that releases the regolith plug above it. This disturbance's timescale and affected area are consistent with observed TLPs; we also discuss other effects. For slow flow, escape through the regolith is prolonged by low diffusivity. Water, found recently in deep magma samples, is unique among candidate volatiles, capable of freezing between the regolith base and surface, especially near the lunar poles. For major outgassing sites, we consider the possible accumulation of water ice. Over geological time ice accumulation can evolve downward through the regolith. Depending on gases additional to water, regolith diffusivity might be suppressed chemically, blocking seepage and forcing the ice zone to expand to larger areas, up to square km scales, again, particularly at high latitudes. We propose an empirical path forward, wherein current and forthcoming technologies provide controlled...

A new method to determine the grain size of planetary regolith

Gundlach, Bastian; Blum, Jürgen
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 13/12/2012 Português
Relevância na Pesquisa
27.66%
Airless planetary bodies are covered by a dusty layer called regolith. The grain size of the regolith determines the temperature and the mechanical strength of the surface layers. Thus, knowledge of the grain size of planetary regolith helps to prepare future landing and/or sample-return missions. In this work, we present a method to determine the grain size of planetary regolith by using remote measurements of the thermal inertia. We found that small bodies in the Solar System (diameter less than ~100 km) are covered by relatively coarse regolith grains with typical particle sizes in the millimeter to centimeter regime, whereas large objects possess very fine regolith with grain sizes between 10 and 100 micrometer.; Comment: Accepted by Icarus

Micro-meteoroid seismic uplift and regolith concentration on kilometric scale asteroids

Garcia, Raphael F.; Murdoch, Naomi; Mimoun, David
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 06/03/2015 Português
Relevância na Pesquisa
27.66%
Seismic shaking is an attractive mechanism to explain the destabilisation of regolith slopes and the regolith migration found on the surfaces of asteroids (Richardson et al. 2004; Miyamoto et al. 2007). Here, we use a continuum mechanics method to simulate the seismic wave propagation in an asteroid. Assuming that asteroids can be described by a cohesive core surrounded by a thin non-cohesive regolith layer, our numerical simulations of vibrations induced by micro-meteoroids suggest that the surface peak ground accelerations induced by micro-meteoroid impacts may have been previously under-estimated. Our lower bound estimate of vertical accelerations induced by seismic waves is about 50 times larger than previous estimates. It suggests that impact events triggering seismic activity are more frequent than previously assumed for asteroids in the kilometric and sub-kilometric size range. The regolith lofting is also estimated by a first order ballistic approximation. Vertical displacements are small, but lofting times are long compared to the duration of the seismic signals. The regolith movement has a non-linear dependence on the distance to the impact source which is induced by the type of seismic wave generating the first movement. The implications of regolith concentration in lows of surface acceleration potential are also discussed. We suggest that the resulting surface thermal inertia variations of small fast rotators may induce an increased sensitivity of these objects to the Yarkovsky effect.; Comment: Accepted for publication in Icarus

Regolith Thickness of the Delaware Piedmont

Christopher, M.J.; Woodruff, K.D.
Fonte: Newark, DE: Delaware Geological Survey, University of Delaware Publicador: Newark, DE: Delaware Geological Survey, University of Delaware
Tipo: Map
Português
Relevância na Pesquisa
37.4%
This map shows the total thickness (regolith) of both the loose, transported material and the weathered rock that overlies crystalline rocks of the Delaware Piedmont. Transported material is generally thin and the weathered rock in place (saprolite) usually makes up the bulk of the regolith. Saprolite may vary gradationally from a weathered rock that has retained much of the characteristics of the parent rock to a product mineralogically and texturally different from its source rock.

Predicting regolith properties using environmental correlation: a comparison of spatially global and spatially local approaches

Laffan, Shawn; Lees, Brian G
Fonte: Elsevier Publicador: Elsevier
Tipo: Artigo de Revista Científica
Português
Relevância na Pesquisa
37.51%
In this paper we assess the utility of mapping regolith properties as continuously varying fields using environmental correlation over large spatial areas. The assessment is based on a comparison of results from spatially global and local analysis methods. The two methods used are a feed-forward, back propagation neural network, applied globally, and moving window regression, applied locally. These methods are applied to five regolith properties from a field site at Weipa, Queensland, Australia. The properties considered are the proportions of oxides of aluminum, iron, silica and titanium present in samples, as well as depth to the base of the bauxite layer. These are inferred using a set of surface measurable features, consisting of Landsat data, geomorphometric indices, and distances from streams and swamps. The moving window regression results show a much stronger relationship than do those from the spatially global neural networks. The implication is that the scale of the analysis required for environmental correlation is of the order of hundreds of metres, and that spatially global analyses may incur an automatic reduction in accuracy by not modelling geographically local relationships. In this case, this effect is up to 45% error at a tolerance near half of a standard deviation.

Bacillus cereus, gold and associated elements in soil and other regolith samples from Tomakin Park Gold Mine in southeastern New South Wales, Australia

Reith, Frank; McPhail, Derry; Christy, Andrew
Fonte: Elsevier Publicador: Elsevier
Tipo: Artigo de Revista Científica
Português
Relevância na Pesquisa
37.51%
Efficient exploration for new Au deposits is increasingly important as existing deposits become depleted. This is particularly relevant in Australia, where exploration can be difficult because of a thick regolith cover. New and effective methods of exploration need to be developed, and possibilities lie in geomicrobiological methods. For instance, Bacillus cereus, a common soil bacterium, has been shown to act as a biogeochemical indicator for concealed mineralisations, including vein-type Au deposits. We report the results of the first Australian case study of the association of B. cereus and Au at the Tomakin Park Gold Mine in southeastern New South Wales. Soil samples from the Ah horizon were analysed for B. cereus spores and 56 major and trace elements. The results show enrichment of Au, As, B. cereus spores and, to a lesser extent, Sb, Bi and Pb over the top of the Au deposit. Gold concentrations over the mineralisation range from 100 ppb to 1.1 ppm compared to a background of 2 ppb and As concentrations are enriched to 100 ppm from a background of 5 ppm. B. cereus spore counts were up to 10 times higher in soils with elevated concentrations of Au. Factor analysis indicates four main associations: TiO2 +lanthanides+actinides; CaO+MgO+Cs+Be+Ba(+Ga+Pb+Rb); B. cereus+Au+As+Sb+Bi(+Pb); Fe2O3+MnO+Co+Ni+Cu+Mo. Selective sequential leaching was used to study the fractionation of Au and As in soils...