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Geochemistry and tectonic settings of meta-igneous rocks in the Arthur Lineament and surrounding area, northwest Tasmania


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Holm, OH, Crawford, AJ and Berry, RF 2003 , 'Geochemistry and tectonic settings of meta-igneous rocks in the Arthur Lineament and surrounding area, northwest Tasmania' , Australian Journal of Earth Sciences, vol. 50, no. 6 , pp. 903-918 , doi: 10.1111/j.1400-0952.2003.01033.x.

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The Arthur Lineament is a Cambrian age high-strain metamorphic belt that transects northwestern
Tasmania and forms the eastern margin of the Mesoproterozoic and Neoproterozoic Rocky Cape
Block. It formed as a result of Middle Cambrian arc–continent collision, and is composed of both
allochthonous slices (Bowry Formation and Reece amphibolite), the para-autochthonous ‘eastern’
Ahrberg Group and the autochthonous ‘western’ Ahrberg Group. Amphibolites and mafic schists of
the ‘eastern’ Ahrberg Group rocks show a temporal change in composition from transitional alkaline
basalt to dominant E-MORB-type rift tholeiites, whereas the ‘western’ Ahrberg Group metabasic rocks
are typical E-MORB rift tholeiites. The lithostratigraphy of the Ahrberg Group matches very well that of
the Upper Neoproterozoic (650–580 Ma) Togari Group of the Smithton Trough and King Island. In
contrast, amphibolites of the allochthonous Bowry Formation, which also show E-MORB-type patterns
typical of rift-type tholeiites, are intruded by granitoid sheets dated at 777
7 Ma, similar to the
Precambrian granites exposed on King Island (760
12 Ma). The Bowry Formation granitoids have
distinctive high Ti, Zr, Nb compositions best matched by granites produced by extended fractionation
of rift basalts with significant crustal assimilation. This suggests that the Bowry Formation metabasic
rocks may correlate with the Willouran flood basalts in South Australia, and together record the
780 Ma breakup event hypothesised to mark the breakup of the Rodinian supercontinent.

Item Type: Article
Authors/Creators:Holm, OH and Crawford, AJ and Berry, RF
Keywords: Arthur Lineament, Cambrian, geochemistry, igneous rocks, Neoproterozoic, rifts, Rodinia, Tasmania
Journal or Publication Title: Australian Journal of Earth Sciences
ISSN: 0812-0099
DOI / ID Number: 10.1111/j.1400-0952.2003.01033.x
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