National Geochemical Survey of Australia: the geochemical atlas of Australia

Caritat, Patrice de; Cooper, Michelle

doi:10.11636/record.2011.020

Cited by 67 publications

(83 citation statements)

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“…The average sampling density for the area sampled is~1 sample/5500 km 2 (5.5 Â10 9 m 2 ). Sample collection and preparation were carried out as per the Field Manual (Lech et al 2007) and Sample Preparation Manual (de Caritat et al 2009) developed for the NGSA project. The preliminary soil pH map of Australia constitutes the first data release of the NGSA project , and the field pH data, the subject of the present contribution, can be downloaded from Geoscience Australia's website (www.ga.…”

Section: Background Methodologymentioning

confidence: 99%

The pH of Australian soils: field results from a national survey

2011

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Abstract. The pH is one of the fundamental soil properties governing nutrient availability, metal mobility, elemental toxicity, microbial activity, and plant growth. The field pH of topsoil (0-0.10 m depth) and subsoil (~0.60-0.80 m depth) was measured on floodplain soils collected near the outlet of 1186 catchments covering >6 Mkm 2 (6 Â10 12 m 2 ) or~80% of Australia. Field pH duplicate data, obtained at 124 randomly selected sites, indicate a precision of 0.5 pH unit (or 7%), and mapped pH patterns are consistent and meaningful. The median topsoil pH is 6.5, while the subsoil pH has a median of 7 but is strongly bimodal (6-6.5 and 8-8.5). In most cases (64%) the topsoil and subsoil pH values are similar; among the sites exhibiting a pH contrast, those with more acidic topsoils are more common (28%) than those with more alkaline topsoils (7%). The distribution of soil pH at the national scale indicates the strong controls exerted by precipitation and ensuing leaching (e.g. low pH along the coastal fringe, high pH in the dry centre), aridity (e.g. high pH where calcrete is common in the regolith), vegetation (e.g. low pH reflecting abundant soil organic matter), and subsurface lithology (e.g. high pH over limestone bedrock). The new data, together with existing soil pH datasets, can support regional-scale decision-making relating to agricultural, environmental, infrastructural, and mineral exploration decisions.

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Section: Background Methodologymentioning

confidence: 99%

The pH of Australian soils: field results from a national survey

2011

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“…The proposed spectral clustering is applied to a real-world dataset from the National Geochemical Survey of Australia (NGSA) database [10]. The dataset of interest comprises six variables which are concentration elements (heavy metals) for 1314 collection sites from topsoil (0-10 cm depth) and coarse grain-size fraction (<2 mm).…”

Section: Applicationmentioning

confidence: 99%

A spectral clustering approach for multivariate geostatistical data

Fouedjio

2017

Int J Data Sci Anal

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Spectral clustering has recently become one of the most popular modern clustering methods for conventional data. However, applied to geostatistical data, the general spectral clustering method produces clusters that are spatially non-contiguous which is certainly undesirable for many geoscience applications. In this paper, a spectral clustering approach is proposed, allowing to discover spatially contiguous and meaningful clusters in multivariate geostatistical data, in which spatial dependence plays an important role. The proposed spectral clustering approach relies on a similarity measure built from a nonparametric kernel estimator of the multivariate spatial dependence structure of the data, emphasizing the spatial correlation among data locations. It integrates existing methods to find the relevant number of clusters and to assess the contribution of variables in the formation of the clusters. The results from both synthetic and real-world datasets demonstrate that the proposed spectral clustering approach can effectively provide spatially contiguous and meaningful clusters.

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“…Recently, Geoscience Australia with its State/NT partners embarked on a systematic continental-scale geochemical sampling program, the National Geochemical Survey of Australia (NGSA;Caritat & Cooper 2011a). The aim of the NGSA project was to provide ultra-low (spatial) density compositional data and information regarding the near-surface regolith to advance exploration for energy and mineral resources.…”

Section: The National Geochemical Survey Of Australiamentioning

confidence: 99%

“…point locations, to that represented by catchment outlet sediments, which are transported sediments derived from upstream sources. Thus, NGSA data provide a representative indication of the overall geochemical characteristics of rocks and soils within a catchment (Caritat & Cooper 2011a) and potentially a catchment's entire upstream watershed.…”

Section: Spatial Supportmentioning

confidence: 99%

Catchment-based gold prospectivity analysis combining geochemical, geophysical and geological data across northern Australia

Cracknell

Caritat

2017

GEEA

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Abstract:The results of a pilot study into the application of an unsupervised clustering approach to the analysis of catchmentbased National Geochemical Survey of Australia (NGSA) geochemical data combined with geophysical and geological data across northern Australia are documented. NGSA Mobile Metal Ion® (MMI) element concentrations and first and second order statistical summaries across catchments of geophysical data and geological data are integrated and analysed using Self-Organizing Maps (SOM). Input features that contribute significantly to the separation of catchment clusters are objectively identified and assessed.A case study of the application of SOM for assessing the spatial relationships between Au mines and mineral occurrences in catchment clusters is presented. Catchments with high mean Au code-vector concentrations are found downstream of areas known to host Au mineralization. This knowledge is used to identify upstream catchments exhibiting geophysical and geological features that indicate likely Au mineralization. The approach documented here suggests that catchment-based geochemical data and summaries of geophysical and geological data can be combined to highlight areas that potentially host previously unrecognised Au mineralization.

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National Geochemical Survey of Australia: the geochemical atlas of Australia

Cited by 67 publications

References 0 publications

The pH of Australian soils: field results from a national survey

The pH of Australian soils: field results from a national survey

A spectral clustering approach for multivariate geostatistical data

Catchment-based gold prospectivity analysis combining geochemical, geophysical and geological data across northern Australia

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