Citation

Hoatson, D.M., Wallace, D.A., Sun, S.S., Simpson, C.J. & Keays, R.R., 1992. Petrology and platinum-group-element geochemistry of Archaean layered mafic-ultramafic intrusions, west Pilbara Block, Western Australia. Bulletin  242. Australian Geological Survey Organisation, Canberra.

Abstract

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.
Google map showing geographic bounding box with values North bound -20.25 East bound 121.5 West bound 116.0 South bound -22.25
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Product Type/Sub Type

dataset - GA Publication - Bulletin

Constraints

license
Creative Commons Attribution 3.0 Australia Licence

IP Owner

Commonwealth of Australia (Geoscience Australia)

Author(s)

Date (publication)

1992

Product Type

dataset

Topic Category

geoscientificInformation

Keywords

GA Publication
Bulletin
geochemistry
petrology
Earth Sciences

Resource Language

English

Resource Character Set

utf8

Resource Security Classification

unclassified

Geographic Extent

North bound
-20.25
East bound
121.5
West bound
116.0
South bound
-22.25

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Unknown

Digital Transfer Options

onLine

DISTRIBUTION Format

pdf

Distributor

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distributor
Organisation Name
Geoscience Australia
City
Canberra
Administrative Area
ACT
Postal Code
2601
Country
Australia
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Metadata File Identifier

a05f7892-7f8d-7506-e044-00144fdd4fa6

Metadata Standard Name

ANZLIC Metadata Profile: An Australian/New Zealand Profile of AS/NZS ISO 19115:2005, Geographic information - Metadata

Metadata Standard Version

1.1

Metadata Date Stamp

1999-08-03

METADATA SECURITY CLASSIFICATION

unclassified

Metadata Contact

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pointOfContact
Organisation Name
Geoscience Australia
City
Canberra
Administrative Area
ACT
Postal Code
2601
Country
Australia
Email Address
Downloads
For information on acquiring this product,
please contact the Geoscience Australia Sales Centre via:

fax:
+61 2 6249 9960; or
phone:
1800 800 173 (within Australia);
 
+61 2 6249 9966 (outside Australia).

Please note that support hours are 9 am to 5 pm weekdays