The geology and magnetic characteristics of precious opal deposits, southwest Queenslands

Precious opal in southwest Queensland is found within a weathered profile developed in sedimentary rocks of the Cretaceous Winton Formation. This kaolinitic profile is the product of two periods of deep chemical weathering. The first weathering event is Maastrichtian to Early Eocene, and formed a tri-Iayered profile (Morney profile) in excess of 90 m in thickness. At this time ironstone was chemically precipitated within the basal layer. A period of sedimentation along river systems, with fragmentation and minor erosion of this profile along interfluves, was followed by a second weathering event about the Late Oligocene. A morphologically distinct profile formed (Canaway profile), consisting of an indurated crust and mottled zone, which grades down into a varying thickness of the residual older profile. During the second weathering event silica migrated as an aqueous sol, and was precipitated within voids in ironstone host rocks. The gemmological properties of Queensland boulder opal are described in relation to the weathering history and bedding characteristics of the opal deposits. Rocks which contain scattered opal deposits are poorly exposed in scarp-bounded mesas and flat-topped landforms, or are concealed below a pedimented land surface. Ironstone host rocks are remanently magnetised, and an exploration method based on ground magnetic surveying, using portable and vehicle-borne magnetometers, is discussed.

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Identification info

Date (Publication)
1977-01-01T00:00:00
Citation identifier
Geoscience Australia Persistent Identifier/https://pid.geoscience.gov.au/dataset/ga/80933

Cited responsible party
Role Organisation / Individual Name Details
Publisher

Bureau of Mineral Resources, Geology and Geophysics

 Canberra
Author

Senior, B.R.

 1
Author

McColl, D.H.

 2
Author

Long, B.E.

 3
Author

Whiteley, R.J.

 4
Name

BMR Journal of Australian Geology and Geophysics

Issue identification

2:4:241-251

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Role Organisation / Individual Name Details
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Corp
Owner

Commonwealth of Australia (Geoscience Australia)
Custodian

Commonwealth of Australia (Geoscience Australia)

 Voice
Topic category
  • Geoscientific information

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N
S
E
W


Maintenance and update frequency
Unknown

Resource format

Title

Product data repository: Various Formats

Website

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

Keywords

  • GA Publication

  • Journal

Keywords

  • QLD

Australian and New Zealand Standard Research Classification (ANZSRC)

  • Earth Sciences

Keywords

  • Published_External

Resource constraints

Title

Creative Commons Attribution 4.0 International Licence

Alternate title

CC-BY

Edition

4.0

Website

http://creativecommons.org/licenses/

Access constraints
License
Use constraints
License

Resource constraints

Title

Australian Government Security ClassificationSystem

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

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

Classification
Unclassified
Language
English
Character encoding
UTF8

Distribution Information

Distributor contact
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Distributor

Commonwealth of Australia (Geoscience Australia)

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OnLine resource

Journal article (pdf)

Journal article (pdf)

Distribution format

  • pdf

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Unknown

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Non geographic dataset
Other

GA Publication

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Source data not available.

Metadata constraints

Title

Australian Government Security ClassificationSystem

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

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

Classification
Unclassified

Metadata

Metadata identifier
urn:uuid/fae9173a-6f82-71e4-e044-00144fdd4fa6

Title

GeoNetwork UUID

Language
English
Character encoding
UTF8
Contact
Role Organisation / Individual Name Details
Point of contact

Commonwealth of Australia (Geoscience Australia)

 Voice

Type of resource

Resource scope
Document
Name

AGSO BMR Journal

Alternative metadata reference

Title

Geoscience Australia - short identifier for metadata record with

uuid

Citation identifier
eCatId/80933

Metadata linkage

https://ecat.ga.gov.au/geonetwork/srv/eng/catalog.search#/metadata/fae9173a-6f82-71e4-e044-00144fdd4fa6

Date info (Revision)
2018-04-20T06:10:20
Date info (Creation)
2014-06-03T00:00:00

Metadata standard

Title

AU/NZS ISO 19115-1:2014

Metadata standard

Title

ISO 19115-1:2014

Metadata standard

Title

ISO 19115-3

Title

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

Edition

Version 2.0, September 2018

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

 
 

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N
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W



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