Abstract

The crust of the Pilbara Craton is 28-33 km thick, and its boundary with the upper mantle dips south at slightly less than one degree. The southern edge of the craton is marked by a sharp increase in crustal thickness about 40 km south of the Sylvania Dome in the east and along the northern boundary of the Ashburton Trough in the west. Seismically, the crust has two layers, an upper one with P-wave velocity 6.0-6.1 km s^-1, and a lower of 6.4-6.6 km s^-1. The boundary between them is depressed beneath the deepest part of the Hamersley Basin, and rises along the southern part of the basin and craton, beneath a topographic ridge of higher grade metamorphic rocks. The velocities in the lower crustal layer are highest along the southern part of the Hamersley Basin, an area known to have been depressed during the formation and filling of the basin, and then uplifted. The crust of the northern Yilgarn Craton is at least 50 km thick and, seismically, has three layers. The uppermost layer has P-wave velocities of 6.1-6.2 km s^-1, the middle layer, at 10-16 km depth, 6.4 km s^-1, and the lowest, at 32 km depth, 6.7-7.0 km s^-1. A zone of crust, about 50 km wide, along the northern margin of the craton was extensively reworked during Proterozoic orogenesis, and is now characterised by thinner crust than the rest of the Yilgarn Craton, extensive granitoid emplacement, intense deformation and folding of the upper crustal rocks, and low gravity values. The Capricorn Orogen between the cratons is marked by high velocities in the lower crust, probably caused by dense mafic intrusions or a higher metamorphic grade. The seismic layering within the crust is most likely caused by increasing metamorphic grade with depth. The crust is probably of average acid to intermediate chemical composition, and has a low metamorphic grade at the surface. The velocities are attributed to metamorphic grade increasing to felsic granulite at 9-16 km depth, and garnet granulite at 32 km depth in the Yilgarn Craton.
Google map showing geographic bounding box with values North bound -19.0 East bound 121.0 West bound 115.0 South bound -27.0
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Product Type/Sub Type

nonGeographicDataset

Constraints

Creative Commons Attribution 4.0 International Licence

IP Owner

Commonwealth of Australia (Geoscience Australia)

Author(s)

Date (publication)

1981-01-01T00:00:00

Product Type

nonGeographicDataset

Topic Category

geoscientificInformation

GA Catalogue Number

81068 Product http://www.ga.gov.au/metadata-gateway/metadata/record/81068/

Keywords

GA Publication
Journal
WA
Earth Sciences

Resource Language

English

Resource Character Set

utf8

Resource Security Classification

unclassified

Geographic Extent

North bound
-19.0
East bound
121.0
West bound
115.0
South bound
-27.0

Lineage

Unknown

Digital Transfer Options

onLine

Distributor

Role
distributor
Organisation Name
Commonwealth of Australia (Geoscience Australia)
City
Canberra
Administrative Area
ACT
Postal Code
2601
Country
Australia
Email Address

Source Description

Source data not available.

Metadata File Identifier

fae9173a-7009-71e4-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 SECURITY CLASSIFICATION

unclassified

Metadata Contact

Role
pointOfContact
Organisation Name
Commonwealth of Australia (Geoscience Australia)
City
Canberra
Administrative Area
ACT
Postal Code
2601
Country
Australia
Email Address
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