Citation

Blake, D.H., 1987. Geology of the Mount Isa Inlier and environs, Queensland and Northern Territory. Scale 1:500000. Bulletin  225. Bureau of Mineral Resources, Geology and Geophysics, Canberra.

Abstract

Geological mapping of the Mount Isa Inlier and environs by the Bureau of Mineral Resources and Geological Survey of Queensland from 1969 to 1980 resulted in the production of the 1:100 000 maps which form the basis for the accompanying 1:500 000 geological map. Three broad tectonic divisions are distinguished within the Mount Isa Inlier: the Western Fold Belt, Kalkadoon-Leichhardt Belt, and Eastern Fold Belt. These are formed of early and middle Proterozoic sedimentary and volcanic rocks many thousands of metres thick, which are assigned to four major sequences, and numerous igneous intrusions. Correlatives to the northwest are exposed within and around the younger Proterozoic South Nicholson Basin and along the Murphy Tectonic Ridge. The oldest sequence in the region, designated basement, was deformed and regionally metamorphosed, in places forming migmatite, before about 1875 Ma. The three younger sequences are cover sequence 1 (1875-1850 Ma), consisting mainly of subaerial felsic volcanics, and cover sequences 2 (mostly 1790 1760 Ma) and 3 (mostly 1680-1670 Ma), comprising felsic, and mafic volcanics and predominantly shallow-water sediments. These sequences are intruded by I-type granites isotopically dated (U-Pb zircon) at around 1860 Ma, 1840 Ma, 1820 Ma, 1800 Ma, 1720-1740 Ma, 1700 Ma, 1670 Ma, and 1500 Ma. Mafic intrusions, ranging in age from pre-1860 Ma to about 1100 Ma, form dykes, sills, and pod-like bodies, and also netveined complexes with granite. The cover sequences were mildly to strongly deformed and regionally metamorphosed up to upper amphibolite facies between about 1620 and 1550 Ma. The deformation included thrusting, faulting, and open to tight upright folding. Major displacements have taken place subsequently along faults trending between northwest and northeast. The igneous rocks are markedly bimodal in composition. Four major chemically distinctive suites of felsic volcanics are identified, the oldest of which (cover sequence 1) is cogenetic with extensive granites. Most of the mafic igneous rocks are similar in chemistry to continental tholeiites. The Mount Isa Inlier contains major deposits of copper, lead, zinc and silver, and significant deposits of gold, uranium and cobalt; it has also produced minor amounts of manganese, cadmium, bismuth, tungsten, beryl, and mica. Most copper occurs in brecciated sediment-hosted deposits within the Western Fold Belt, but there are also numerous small shear and fault-controlled vein copper deposits to the east; most of the gold production has come as a by-product from these veins. Large stratiform lead-zinc-silver ores are hosted in shales, such as at Mount Isa mine. Geochemical, geographical, sedimentological and geophysical evidence favours an intracratonic tectonic setting for the Mount Isa Inlier and environs during the early and middle Proterozoic. Since about 1500 Ma, the region has been part of an essentially stable tectonic unit.
Google map showing geographic bounding box with values North bound -17.0 East bound 141.0 West bound 130.5 South bound -23.0
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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)

1987

Product Type

dataset

Topic Category

geoscientificInformation

Keywords

GA Publication
Bulletin
geology
Earth Sciences

Resource Language

English

Resource Character Set

utf8

Resource Security Classification

unclassified

Geographic Extent

North bound
-17.0
East bound
141.0
West bound
130.5
South bound
-23.0

Lineage

Unknown

Digital Transfer Options

onLine

DISTRIBUTION Format

pdf

Distributor

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

Metadata File Identifier

a05f7892-7f95-7506-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

1996-10-29

METADATA SECURITY CLASSIFICATION

unclassified

Metadata Contact

Role
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