Abstract

A coherent set of timing constraints is produced for Tasmania's Proterozoic and Cambrian geology when only mineral ages are considered and whole-rock ages excluded. The oldest recognised event is the formation of sedimentary deposits which contain detrital zircons that indirectly indicate a depositional age younger than 1180 Ma. Partial melts of these sedimentary rocks were incorporated in Neoproterozoic, Devonian and probably Cambrian felsic magmas. Neoproterozoic granite on King Island has an age of 760 ± 12 Ma and is part of a high-level intrusive episode that accompanied the Wickham Orogeny, an event with regionally varied strain that is represented in northwestern Tasmania by a low-angle unconformity, by altered granitoid with a magmatic age of 777 ± 7 Ma, and by the thick turbidite pile of the Burnie and Oonah Formations with its syndepositional intrusions of Cooee Dolerite. The late Neoproterozoic was relatively quiet tectonically but by early in the Middle Cambrian a crustal collision which marked the early phase of the Tyennan Orogeny brought about high-level emplacement of ultramafic-bearing allochthons and deep-seated metamorphism of quartzose sedimentary and basaltic rocks. The ultramafic allochthons carried tonalite that had crystallised only shortly before at 510 ± 6 Ma, while the deep-seated metamorphism produced eclogite at 502 ± 8 Ma. By middle Middle Cambrian times the metamorphic rocks had been uplifted and they experienced repeated uplift during the period of Mt Read volcanism and onward to the close of the Tyennan Orogeny in the Early Ordovician, an overall period of some 20 million years from the early Middle Cambrian. Regionally varied strain was again a feature during the Tyennan Orogeny, with the Smithton area in northwestern Tasmania and King Island occupying relatively undeformed cratonic positions. * Table 3 [indicated by an asterisk (*) in the text and listed at the end of the paper] is a Supplementary Paper lodged with the National Library of Australia (Manuscript Section); copies may be obtained from the Business Manager, Geological Society of Australia.
Google map showing geographic bounding box with values North bound -40.0 East bound 150.0 West bound 144.0 South bound -44.0
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Product Type/Sub Type

dataset - External Publication - Scientific Journal Paper

Constraints

license
Creative Commons Attribution 3.0 Australia Licence

IP Owner

Commonwealth of Australia (Geoscience Australia)

Author(s)

Date (publication)

1998

Product Type

dataset

Topic Category

geoscientificInformation

Keywords

External Publication
Scientific Journal Paper
Earth Sciences

Resource Language

English

Resource Character Set

utf8

Resource Security Classification

unclassified

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North bound
-40.0
East bound
150.0
West bound
144.0
South bound
-44.0

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Unknown

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onLine

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Organisation Name
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Metadata File Identifier

a05f7892-f99d-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

2010-09-22

METADATA SECURITY CLASSIFICATION

unclassified

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pointOfContact
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Canberra
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ACT
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2601
Country
Australia
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Related Links
For information on acquiring this product,
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fax:
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1800 800 173 (within Australia);
 
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Please note that support hours are 9 am to 5 pm weekdays