Classification, genesis and evolution of ferruginous surface grains

Studies of ferruginous surface grains (FSGs) have shed considerable light on the origin of both these enigmatic grains and on regolith evolution. This paper describes a user-friendly classification scheme, and the genesis and evolution of FSGs. The classification system has four levels. The first is based on initial observations necessary to recognise the class of regolith material to which FSGs belong, namely lags. The second separates FSGs from other lag components, such as rock fragments and resistant mineral grains, and hence requires more detailed observation of the sampled material. The third level of classification requires petrographic and mineragraphic examination- the main textural types are homogeneous, lithorelic, pseudomorphic, vesicular, sandy, and oolitic. The fourth level of classification identifies modifying microfabrics, namely concentric, cutanic, compound, mottled, and syneresis fabrics. FSGs are formed in three main environments: the weathering profile (mottled zone and saprolite); surfical environments (soils and sediments); and subaqueous environments (lakes and rivers). They form by four main processes: ferruginisation of a protolith (mainly in the weathering profile, but also in subaerial and subaqueous sediments); concretion in a solid medium (surficial materials and the weathering profile); accretion in subaqueous environments, (lakes and rivers); and fragmentation of existing ferruginous material. Diagenesis of FSGs causes both textural and mineralogical changes. Dehydration, mineralogical unmixing, dissolution, and precipitation all alter the original fabric. Replacement, dehydration, and recrystallisation change the mineralogy. Hydration of hematite to goethite also occurs in humid climates. Ions of interest to exploration geochemists may be lost during syneresis and unmixing. Application of this classification system requires integration of microfabric studies with geomorphological mapping, regolith stratigraphy, mineralogy, and geochemical data.

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Date (Publication)
1996-01-01T00:00:00
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Geoscience Australia Persistent Identifier/https://pid.geoscience.gov.au/dataset/ga/81432

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Australian Geological Survey Organisation

 Canberra
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Clarke, J.D.A.

 1
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Chenoweth, L.

 2
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AGSO Journal of Australian Geology and Geophysics

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16:3:213-221

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Commonwealth of Australia (Geoscience Australia)
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Commonwealth of Australia (Geoscience Australia)

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Product data repository: Various Formats

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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

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Australian and New Zealand Standard Research Classification (ANZSRC)

  • Earth Sciences

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Creative Commons Attribution 4.0 International Licence

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CC-BY

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4.0

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http://creativecommons.org/licenses/

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Australian Government Security ClassificationSystem

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2018-11-01T00:00:00
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English
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Commonwealth of Australia (Geoscience Australia)

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Journal article (pdf)

Journal article (pdf)

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Title

Australian Government Security ClassificationSystem

Edition date
2018-11-01T00:00:00
Website

https://www.protectivesecurity.gov.au/Pages/default.aspx

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Unclassified

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urn:uuid/fae9173a-7175-71e4-e044-00144fdd4fa6

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English
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UTF8
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Commonwealth of Australia (Geoscience Australia)

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AGSO BMR Journal

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Geoscience Australia - short identifier for metadata record with

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eCatId/81432

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https://ecat.ga.gov.au/geonetwork/srv/eng/catalog.search#/metadata/fae9173a-7175-71e4-e044-00144fdd4fa6

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2018-04-20T06:07:24
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2014-06-03T00:00:00

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AU/NZS ISO 19115-1:2014

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ISO 19115-1:2014

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ISO 19115-3

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Geoscience Australia Community Metadata Profile of ISO 19115-1:2014

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Version 2.0, September 2018

Citation identifier
https://pid.geoscience.gov.au/dataset/ga/122551

 
 

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