An example of structural and metamorphic relationships in the Musgrave orogenic belt, central Australia

Collerson, K. D.; Oliver, R. L.; Rutland, R. W. R.

doi:10.1080/00167617208728776

Cited by 41 publications

(33 citation statements)

References 11 publications

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“…The Fregon Domain between the Woodroffe Thrust and Mann Fault (split into the Tjuni Purlka and Walpa Pulka Zones in the west Musgrave area) is considered the core of the Petermann Orogen. It is characterised by granulite-facies metamorphism and contains several important faults (Collerson et al, 1972). From north to south these are the Woodroffe Thrust, Cockburn Shear Zone, Davenport Shear Zone, Mann Fault, Wingellina Fault, and Hinckley Fault.…”

Section: The C 570-530 Ma Petermann Orogenymentioning

confidence: 99%

The burning heart — The Proterozoic geology and geological evolution of the west Musgrave Region, central Australia

et al. 2015

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Section: The C 570-530 Ma Petermann Orogenymentioning

confidence: 99%

The burning heart — The Proterozoic geology and geological evolution of the west Musgrave Region, central Australia

et al. 2015

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“…The fact that the gneisses and granitoids of the central Musgrave Block are entirely non-carbonaceous (Collerson et al, 1972;Major, 1973;Major and Conor, 1993; argues for an external source of the CO2-dominated brines.…”

Section: Co2-dominated Brinesmentioning

confidence: 99%

Inverted distribution of ductile deformation in the relatively “dry” middle crust across the Woodroffe Thrust, central Australia

Wex¹,

Mancktelow²,

Hawemann³

et al. 2018

Preprint

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Abstract. Thrust fault systems typically distribute shear strain preferentially into the hanging wall rather than the footwall. In this paper, we present a regional-scale example that does not fit this model. The Woodroffe Thrust developed due to intracontinental shortening during the Petermann Orogeny (ca. 560-520 Ma) in central Australia. It is interpreted to be at least 10 600 km long in its general E-W strike direction, with an approximate top-to-north minimum relative displacement of 60-100 km. The associated mylonite zone is most broadly developed in the footwall. The immediate hanging wall was only marginally involved in mylonitization, as can be demonstrated from the contrasting thorium signatures of the upper amphibolite facies footwall and the granulite facies hanging wall protoliths. Thermal weakening cannot account for such an inverse deformation gradient, as syn-deformational P-T estimates for the Petermann Orogeny in the hanging wall and footwall from the same 15 locality are very similar. The distribution of pseudotachylytes, which act as preferred nucleation sites for shear deformation, also cannot provide an explanation, since these are prevalent in the immediate hanging wall. The most likely reason for the inverted deformation gradient across the Woodroffe Thrust is water-assisted weakening due to the increased, but still limited, presence of aqueous fluids in the footwall. On the contrary, the presence or absence of aqueous fluids does not appear to be linked to the regional variation in mylonite thickness, which generally increases with increasing metamorphic grade. 20

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“…The oldest rocks in the Musgrave Block are felsic gneisses (acidic volcanic protolith), which are dated by SHRIMP U-Pb Zircon to be about 1550 Ma (Camacho & Fanning, 1995;Gray, 1978). Emplacement of these dominantly felsic rocks is succeeded in the Musgrave Block by the 1120-1220 Ma Musgravian Orogeny, which reached amphibolite facies conditions in the north (Mulga Park Subdomain) and granulite facies metamorphism in the south (Fregon Subdomain, Camacho and Fanning, 1995;Collerson et al, 1972;Major, 1973). Metamorphism is accompanied by voluminous syn-to post-tectonic granitoid intrusion assigned to the Pitjantjatjara Supersuite (Smithies et al, 2011).…”

Section: Introductionmentioning

confidence: 99%

“…Another dolerite dyke swarm, the ~ 800 Ma Amata suite (Wingate et al, 1998;Zhao & McCulloch, 1993), also occurs in the area but the two suites are not readily distinguishable in the field, although they are chemically and isotopically distinct (Camacho 1997;Zhao et al, 1994;Zhao & McCulloch, 1993). During the intracontinental 560-520 Ma Petermann Orogeny, the Fregon Subdomain was juxtaposed against the Mulga Park Subdomain across the south-dipping Woodroffe Thrust Collerson et al, 1972;Maboko et al, 1992). The Fregon Subdomain in the hanging wall is heterogeneously overprinted by generally strike-slip shear zones, with strain strongly partitioned and localized on all scales.…”

Section: Introductionmentioning

confidence: 99%

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Weak and slow, strong and fast: How shear zones evolve in a dry continental crust (Musgrave Ranges, Central Australia)

Hawemann¹,

Mancktelow²,

Pennacchioni³

et al. 2018

Preprint

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Key Points: Ductile shearing localizes on precursor pseudotachylytes and fractures. Stress fluctuations range from 10 MPa to at least <1 GPa  Earthquakes in the lower crust can be locally triggered by stress concentrations without the transfer of stresses from the upper crust. KeywordsPseudotachylyte, lower crust, localization of deformation, stress, earthquake AbstractThe Davenport Shear Zone in Central Australia is a strike-slip fault zone developed during the Petermann Orogeny (~ 550 Ma) in an intracontinental lower crustal setting, with conditions of shearing estimated at upper amphibolite to eclogite facies (~ 650 °C, 1.2 GPa). This five kilometer thick mylonite zone encloses several large low-strain domains, allowing a thorough study of the initiation of shear zones and their progressive development. Quartzofeldspathic gneisses and granitoids contain rheologically different layers, such as quartz-rich pegmatite dykes, mafic bands and dykes, which should preferentially localize viscous deformation if favourably orientated. This is not observed, except for long, continuous and fine grained dolerite dykes. Instead, many shear zones, typically only a few millimeters to centimeters in width but extending for tens of meters, commonly exploited pseudotachylytes and are sometimes parallel to a network of little overprinted brittle fractures. The recrystallized mineral assemblage in the sheared pseudotachylyte is similar to that in the host gneiss, without associated fluid-rock interaction. Lack of localization in quartz-rich, coarser grained (typically >50 microns) rocks compared to mafic dykes, precursor factures and pseudotachylytes implies that localization in the dry lower crust preferentially occurs along elongate planar layers with a relatively fine grain size. Transient high stress events repeatedly initiated fractures, providing finer grained, weaker, planar precursors that localized subsequent ductile shear zones. This intimate interplay between brittle and ductile deformation suggests a local source for lower crustal earthquakes, rather than downward migration of earthquakes from the shallower, usually more seismogenic part of the crust.

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An example of structural and metamorphic relationships in the Musgrave orogenic belt, central Australia

Cited by 41 publications

References 11 publications

The burning heart — The Proterozoic geology and geological evolution of the west Musgrave Region, central Australia

The burning heart — The Proterozoic geology and geological evolution of the west Musgrave Region, central Australia

Inverted distribution of ductile deformation in the relatively “dry” middle crust across the Woodroffe Thrust, central Australia

Weak and slow, strong and fast: How shear zones evolve in a dry continental crust (Musgrave Ranges, Central Australia)

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