Product catalogue
An unmixing approach to geochemical mapping using alluvial sediments - An example from northern Australia
<div>Alluvial sediments have long been used in geochemical surveys as their compositions are assumed to be representative of areas upstream. Overbank and floodplain sediments, in particular, are increasingly used for regional to continental-scale geochemical mapping. However, during downstream transport, sediments from heterogeneous source regions are carried away from their source regions and mixed. Consequently, using alluvial sedimentary geochemical data to generate continuous geochemical maps remains challenging. In this study we demonstrate a technique that numerically unmixes alluvial sediments to make a geochemical map of their upstream catchments. The unmixing approach uses a model that predicts the concentration of elements in downstream sediments, given a map of the drainage network and element concentrations in the source region. To unmix sedimentary chemistry, we seek the upstream geochemical map that, when mixed downstream, best fits geochemical observations downstream. To prevent overfitting we penalise the roughness of the geochemical model. To demonstrate our approach we apply it to alluvial samples gathered as part of the Northern Australia Geochemical Survey. This survey gathered samples collected over a ∼ 500,000 km2 area in northern Australia. We first validate our approach for this sample distribution with synthetic tests, which indicate that we can resolve geochemical variability at scales greater than 0.5 – 1◦ in size. We proceed to invert real geochemical data from the total digestion of fine-grained fraction of alluvial sediments. The resulting geochemical maps for two elements of potential economic interest, Cu and Nd, are evaluated in detail. We find that in both cases, our predicted downstream concentrations match well against a held-out, unseen subset of the data, as well as against data from an independent geochemical survey. By performing principal component analysis on maps generated for all 46 available elements we produce a synthesis map showing the significant geochemical domains of this part of northern Australia. This map shows strong spatial similarities to the underlying lithological map of the area. Finally, we compare the results from our approach to a geochemical map produced by kriging. We find that, unlike the method presented here, kriging generates geochemical maps that are both dampened relative to expected magnitude, as well as being spatially distorted. We argue that the unmixing approach is the most appropriate method for generating geochemical maps from regional-scale alluvial surveys. </div>
<b>Citation:</b>
Alex G. Lipp, Patrice de Caritat, Gareth G. Roberts, Geochemical mapping by unmixing alluvial sediments: An example from northern Australia, <i>Journal of Geochemical Exploration,</i> Volume 248, <b>2023</b>, 107174, ISSN 0375-6742, https://doi.org/10.1016/j.gexplo.2023.107174.
( https://www.sciencedirect.com/science/article/pii/S0375674223000213)
Simple
Identification info
- Date (Creation)
- 2022-09-28T16:00:00
- Date (Publication)
- 2023-05-26T00:56:26
- Citation identifier
- Geoscience Australia Persistent Identifier/https://pid.geoscience.gov.au/dataset/ga/147261
- Cited responsible party
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Role Organisation / Individual Name Details Author Lipp, A.G.
External Contact Author de Caritat, P.
Internal Contact Author Roberts, G.G.
External Contact Publisher Elsevier B.V.
External Contact
- Name
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Journal of Geochemical Exploration
- Issue identification
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Volume 248 (2023) 107174
- Purpose
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Publication in peer reviewed scientific journal (prepared for submission to Journal of Geochemical Exploration)
- Status
- Completed
- Point of contact
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Role Organisation / Individual Name Details Resource provider Minerals, Energy and Groundwater Division
External Contact Point of contact Commonwealth of Australia (Geoscience Australia)
Voice Point of contact Main, P.
MEG Internal Contact
- Spatial representation type
- Topic category
-
- Geoscientific information
Extent
))
- Maintenance and update frequency
- As needed
Resource format
- Title
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Product data repository: Various Formats
- Website
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Data Store directory containing the digital product files
Data Store directory containing one or more files, possibly in a variety of formats, accessible to Geoscience Australia staff only for internal purposes
- Project
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National Geochemical Survey of Australia
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- Project
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EFTF – Exploring for the Future
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- Project
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Northern Australia Geochemical Survey
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- Keywords
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Geochemical Mapping
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- Keywords
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Catchment sediments
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- Keywords
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Inverse Modelling
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- Keywords
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Unmixing
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- theme.ANZRC Fields of Research.rdf
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Inorganic geochemistry
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Soil chemistry and soil carbon sequestration (excl. carbon sequestration science)
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- Keywords
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Published_External
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Resource constraints
- Title
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Creative Commons Attribution 4.0 International Licence
- Alternate title
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CC-BY
- Edition
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4.0
- Addressee
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Role Organisation / Individual Name Details User Any
- Use constraints
- License
- Use constraints
- Other restrictions
- Other constraints
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Crown Copyright © 2023
Resource constraints
- Title
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Australian Government Security Classification System
- Edition date
- 2018-11-01T00:00:00
- Classification
- Unclassified
- Classification system
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Australian Government Security Classification System
Associated resource
- Association Type
- Had derivation
- Title
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National Geochemical Survey of Australia: The Geochemical Atlas of Australia
- Citation identifier
- 71973
- Citation identifier
- a4a1ac2e-0a2c-653b-e044-00144fdd4fa6
Associated resource
- Association Type
- Had derivation
- Title
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Northern Australia Geochemical Survey Data release 1 – Total (fine fraction) and MMI™ element contents
- Citation identifier
- 120116
- Citation identifier
- 581b14c3-17a0-4ff4-a5ce-a28f5bc44721
- Language
- English
- Character encoding
- UTF8
Distribution Information
- Distributor contact
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Role Organisation / Individual Name Details Distributor Commonwealth of Australia (Geoscience Australia)
Voice facsimile
- OnLine resource
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Link to Journal
Link to Journal
- Distribution format
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Resource lineage
- Statement
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<div>Using data from the Northern Australia Geochemical Survey http://dx.doi.org/10.11636/Record.2018.006 </div><div>Using data from the National Geochemical Survey of Australia http://dx.doi.org/10.11636/Record.2011.020 </div>
Metadata constraints
- Title
-
Australian Government Security Classification System
- Edition date
- 2018-11-01T00:00:00
- Classification
- Unclassified
Metadata
- Metadata identifier
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urn:uuid/afd1dc01-2ba5-4f6d-9021-93948727a9dd
- Title
-
GeoNetwork UUID
- Language
- English
- Character encoding
- UTF8
- Contact
-
Role Organisation / Individual Name Details Point of contact Commonwealth of Australia (Geoscience Australia)
Voice Point of contact Main, P.
MEG Internal Contact
Type of resource
- Resource scope
- Document
- Name
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Journal Article / Conference Paper
Alternative metadata reference
- Title
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Geoscience Australia - short identifier for metadata record with
uuid
- Citation identifier
- eCatId/147261
- Date info (Creation)
- 2023-05-25T23:44:38
- Date info (Revision)
- 2023-05-25T23:44:38
Metadata standard
- Title
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AU/NZS ISO 19115-1:2014
Metadata standard
- Title
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ISO 19115-1:2014
Metadata standard
- Title
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ISO 19115-3
- Title
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Geoscience Australia Community Metadata Profile of ISO 19115-1:2014
- Edition
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Version 2.0, September 2018
- Citation identifier
- http://pid.geoscience.gov.au/dataset/ga/122551