Multiple deformations with successive subvertical and subhorizontal axial planes in the Mount Isa region; their impact on geometric development and significance for mineralization and exploration

Bell, T. H.; Hickey, Kenneth A.

doi:10.2113/gsecongeo.93.8.1369

Cited by 57 publications

(24 citation statements)

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“…Initial attempts to correlate deformation and metamorphic events between the Eastern and Western Fold Belts assumed an early episode of north -south shortening, followed by a major period of east -west shortening that resulted in the dominant north -south structural grain of the inlier (Bell 1983;Winsor 1986;Loosveld & Schreurs 1987;Reinhardt 1987Reinhardt , 1992Loosveld 1989aLoosveld , 1992Reinhardt & Rubenach 1989;Hill et al 1992;Adshead-Bell 1998). In some areas (Connors & Lister 1995;Bell & Hickey 1998), detailed overprinting studies of structural fabrics have led to proposals of more complex deformation schemes, and recent structural and seismic studies show significant differences in the styles of crustal shortening, regional tectonic transport directions, and the overall crustal architecture between the Western and Eastern Fold Belts . Processes responsible for crustal shortening may have been different in different parts of the inlier, thus making regional correlation of foliations more complicated than previously assumed (Giles et al 2006).…”

Section: Isan Orogenymentioning

confidence: 99%

Synthesis of the proterozoic evolution of the Mt Isa Inlier

Betts

Giles

Mark

et al. 2006

Australian Journal of Earth Sciences

124

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Section: Isan Orogenymentioning

confidence: 99%

Synthesis of the proterozoic evolution of the Mt Isa Inlier

Betts

Giles

Mark

et al. 2006

Australian Journal of Earth Sciences

124

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“…The (Figure 2), and subjected to multiple regional deformation and metamorphic events during the ca 1595 to 1500 Ma Isan orogeny (Bell & Hickey 1998). The Mt Isa Group is a 4.5-6.0 km thick sequence of carbonaceous and dolomitic siltstones, mudstones and shales that include the Urquhart interbedded siltstones and shales (Gregory 2006 …”

Section: Regional Geologymentioning

confidence: 99%

Paleomagnetism of the Mt Isa Zn–Pb–Cu–Ag and George Fisher Zn–Pb–Ag deposits, Australia

Kawasaki

Symons

2011

Australian Journal of Earth Sciences

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Paleomagnetic results are reported for the Mt Isa Zn-Pb-Cu-Ag and George Fisher Zn-Pb-Ag blackshale-hosted deposits in northwestern Queensland, Australia. Both deposits are hosted in greenschist facies carbonaceous and dolomitic siltstones, mudstones and shales of the ca 1655 Ma Urquhart Shale Formation of the Mt Isa Group. Lead model ages for both deposits are ca 1655 Ma, and an Ar-Ar biotite age for Cu mineralisation at Mt Isa is ca 1523 Ma. Paleomagnetic and rock magnetic analyses of 333 specimens (28 sites) isolate, excluding modern hematite, a stable characteristic remanent magnetisation (ChRM) carried mainly by single-or pseudosingle-domain pyrrhotite for Zn-Pb-Ag ore specimens and pyrrhotite and/or titanomagnetite for Cu ore specimens. A paleomagnetic fold test shows that the ChRM postdates D 3 deformation of the ca 1595 to 1500 Ma Isan orogeny, yielding a Mesoproterozoic paleopole at ca 1505 Ma on the northern Australian apparent polar wander path, thereby providing a minimum age for the ores and an age for greenschist metamorphism during the last major metamorphic peak of the Isan orogeny in the Mt Isa inlier.

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“…Sketches showing the progressive development of foliations due to 3 deformations (respectively a, b, c) with the 3 rd foliation re-using the first in portions of rock unaffected by the 2 nd event (modified from Bell and Hickey, 1998). of that operating on the newly developing foliation. Any foliation oblique to sub-horizontal and sub-vertical bulk forces operating in the earth's crust can be reactivated and care needs to be taken at a macroscopic scale to determine whether reactivation produced the observed shear sense.…”

Section: Fig14mentioning

confidence: 99%

Foliations and shear sense: A modern approach to an old problem

Bell

Hobbs

2010

J Geol Soc India

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Argument about shear on foliations began in the mid 19 th century and continues to the present day. It results from varying interpretations of what takes place during the development of different types of foliations ranging from slaty cleavages through differentiated crenulation cleavages, schistosity and gneissosity to mylonites. Computer modelling, quantitative microstructural work and monazite dating have provided a unique solution through access to the history of foliation development preserved by porphyroblasts. All foliations involve shear in their development and most can be used to derive a shear sense. The shear sense obtained is consistent between foliation types and accords with recent computer modelling of these structures preserved within porphyroblasts relative to those in the matrix. The asymmetry of curving foliation into a locally developing new one allows determination of the shear sense along the latter foliation in most rocks. The problem of shear on fold limbs and parallelism of foliation and the flattening plane of the strain ellipse is resolved through the partitioning of shearing and shortening components of deformation into zones that anastomose around ellipsoidal domains lying parallel to the XY plane. Conflicts in shear sense occur if multiple reuse or reactivation of foliations is not recognized and allowed for but are readily resolved if taken into account.

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Multiple deformations with successive subvertical and subhorizontal axial planes in the Mount Isa region; their impact on geometric development and significance for mineralization and exploration

Cited by 57 publications

References 0 publications

Synthesis of the proterozoic evolution of the Mt Isa Inlier

Synthesis of the proterozoic evolution of the Mt Isa Inlier

Paleomagnetism of the Mt Isa Zn–Pb–Cu–Ag and George Fisher Zn–Pb–Ag deposits, Australia

Foliations and shear sense: A modern approach to an old problem

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