Lithological controls on structural evolution of mineralised schist, Macraes gold mine, Otago, New Zealand

Petrie, B. S.; Craw, D.

doi:10.1080/00288306.2005.9515124

Cited by 17 publications

(2 citation statements)

References 20 publications

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“…It dips 20-35°northeast (subparallel to foliation in the hanging wall and footwall blocks), and hosts important gold mineralisation (Teagle et al 1990;Forsyth 2001;Craw and Mackenzie 2016;Mortimer, Craw, et al 2016;Allibone et al 2017). In this paper we follow recent usage (Petrie and Craw 2005;Mortimer, Craw, et al 2016) and distinguish between the thrust-type Hyde-Macraes Shear Zone and the Footwall Fault directly beneath the Hyde-Macraes Shear Zone (e.g. figure 3 in Mortimer, Craw, et al 2016).…”

Section: Footwall Fault and Hyde-macraes Shear Zonementioning

confidence: 95%

“…More widely separated foliationsubparallel faults and shears, some mineralised, occur at higher structural levels in the hanging wall block ( Figure 3). Deformation within the sheared and mineralised Hyde-Macraes Shear Zone schist package has been reported as being thrust related (McKeag et al 1989;Teagle et al 1990;Winsor 1991;Petrie and Craw 2005;Begbie and Craw 2006). To a large degree, the horizontal shortening interpretation relies on shallow-dipping veins interpreted to have formed by nearvertical extension during horizontal shortening deformation.…”

Section: Footwall Fault and Hyde-macraes Shear Zonementioning

confidence: 99%

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Extensional deformation along the Footwall Fault below the Hyde-Macraes Shear Zone, Otago Schist, New Zealand

Ring

Mortimer

Butz³

et al. 2018

New Zealand Journal of Geology and Geophysics

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We describe ductile-to-brittle structures across the Footwall Fault directly below the Hyde-Macraes Shear Zone in the Otago Schist. These indicate that pervasive deformation along the Footwall Fault was due to northeast-southwest crustal extension. Structures below the Footwall Fault are ductile top-to-the-northeast extensional shear bands that formed in a penetrative lower greenschist facies foliation. With progressive deformation, shear bands formed at higher angles to the foliation, culminating in the shear bands being cut by lowand high-angle normal faults. In the hanging wall, extensional structures are much less pervasive and comprise a few high-angle normal faults. This sharp contrast in structural evolution of footwall and hanging wall resembles the tectonic evolution of major extensional shear zones worldwide. We propose that mid Cretaceous normal movement on the lowangle Footwall Fault accompanied the formation of the steeper Waihemo Fault further north. On a regional scale, much of the boundary between the Otago Schist core and its northern flank is cut by mid Cretaceous normal faults. Zircon fission-track ages from the footwall range from 79 ± 13.7 to 46.1 ± 6.2 Ma (2σ uncertainties) and young in the direction of hanging wall transport. One sample from the hanging wall yielded a zircon fission-track age of 76 ± 12.9 Ma. The fission-track ages are hard to interpret as zircon across the fault zone was affected by partial or full annealing. In part, the ages confirm mid Cretaceous movement but may also be interpreted to suggest additional reactivation of the Footwall Fault at slow inferred slip rates. ARTICLE HISTORY

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