Petrology and platinum-group-element geochemistry of Archaean layered mafic-ultramafic intrusions, west Pilbara Block, Western Australia

In a group of Archaean, layered, mafic-ultramafic

intrusions in the west Pilbara Block, Western Australia, the Munni Munni Complex (2925 Ma)

contains a substantial resource of PGEs (20-30 Mt @ 2.9 ppm Pt + Pd + Au) and other intrusions

contain subeconomic resources of Ni and Cu. Contrasting PGE distribution patterns within the group

indicate that the timing and mechanism of S-saturation were critical for the formation of PGE-enriched

sulphide units. Generally, overlying mafic units are thicker than the rhythmically layered ultramafic

components. Olivine and clinopyroxene were usually the first minerals to crystallise and cumulus

orthopyroxene is restricted to the upper parts of the ultramafic zones. Chromium partitioned into early

crystallising clinopyroxene, thus downgrading the potential for PGE-chromite associations. The parent

magmas were probably siliceous, high-Mg basalts of Aldepleted komatiitic affinity. In this study,

the variations of PGEs and incompatible trace elements were documented up the entire stratigraphic

successions. In the Munni Munni Complex (the intrusion studied in most detail) the PGEsulphide

mineralisation is directly below the ultramafic/gabbroic contact and is thought to have resulted

from crystal fractionation and mixing of S-undersaturated and S-saturated magmas; as in the Great

Dyke of Zimbabwe, it does not occur at or near the base of clearly defined cyclic units. The other

(smaller,mainly sheet-like) intrusions studied typically contain basal segregations of PGE-poor

Ni-Cu sulphides; the magmas were generally S-saturated early in their evolution and there was no

PGE enrichment at higher levels. In exploration, variations in the ratios of precious metals and

the trends of the incompatible lithophile and chalcophile elements should be used in association

with field and mineralogical evidence to indicate potential PGE-enrichment processes, such as

S-saturation, crustal contamination, crystal fractionation, magma mixing, and/or hydrothermal

remobilisation.

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Date (Publication)
1992-01-01T00:00:00
Citation identifier
Geoscience Australia Persistent Identifier/https://pid.geoscience.gov.au/dataset/ga/5

Citation identifier
Digital Object Identifier/http://dx.doi.org/10.26186/5c636aeb084aa

Cited responsible party
Role Organisation / Individual Name Details
Publisher

Australian Geological Survey Organisation

 Canberra
Author

Hoatson, D.M.

 1
Author

Wallace, D.A.

 2
Author

Sun, S.S.

 3
Author

Simpson, C.J.

 4
Author

Keays, R.R.

 5
Name

Bulletin

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242

ISBN

0644249072

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MNHD
Owner

Commonwealth of Australia (Geoscience Australia)
Custodian

Commonwealth of Australia (Geoscience Australia)

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  • Geoscientific information

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  • GA Publication

  • Bulletin

Theme

  • petrology

Theme

  • geochemistry

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  • AU-WA

Australian and New Zealand Standard Research Classification (ANZSRC)

  • Earth Sciences

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  • Published_External

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Creative Commons Attribution 4.0 International Licence

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4.0

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Australian Government Security ClassificationSystem

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2018-11-01T00:00:00
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Unclassified
Language
English
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UTF8

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Commonwealth of Australia (Geoscience Australia)

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OnLine resource

Bulletin (pdf)

Bulletin (pdf)

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  • pdf

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Non geographic dataset
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GA Publication

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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

Classification
Unclassified

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Metadata identifier
urn:uuid/a05f7892-7f8d-7506-e044-00144fdd4fa6

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GeoNetwork UUID

Language
English
Character encoding
UTF8
Contact
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Point of contact

Commonwealth of Australia (Geoscience Australia)

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Resource scope
Document
Name

Legacy AGSO BMR Bulletins

Alternative metadata reference

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Geoscience Australia - short identifier for metadata record with

uuid

Citation identifier
eCatId/5

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https://ecat.ga.gov.au/geonetwork/srv/eng/catalog.search#/metadata/a05f7892-7f8d-7506-e044-00144fdd4fa6

Date info (Revision)
2018-04-20T06:00:31
Date info (Creation)
1999-08-03T00:00:00

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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Keywords

geochemistry petrology

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