Identifying deformed pseudotachylyte and its influence on the strength and evolution of a crustal shear zone at the base of the seismogenic zone

Price, Nancy A.; Johnson, Scott E.; Gerbi, Christopher; West, David P.

doi:10.1016/j.tecto.2011.11.011

Cited by 62 publications

(64 citation statements)

References 77 publications

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“…3). When overprinted by subsequent ductile shearing, identification becomes more difficult and cannot always be confirmed (Kirkpatrick and Rowe, 2013;Price et al, 2012). The thickness of pseudotachylyte veins reaches up to 7 cm but is usually about 1 cm.…”

Section: Field Observationsmentioning

confidence: 99%

Pseudotachylyte as field evidence for lower-crustal earthquakes during the intracontinental Petermann Orogeny (Musgrave Block, Central Australia)

et al. 2018

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Abstract. Geophysical evidence for lower continental crustal earthquakes in almost all collisional orogens is in conflict with the widely accepted notion that rocks, under high grade conditions, should flow rather than fracture. Pseudotachylytes are remnants of frictional melts generated during seismic slip and can therefore be used as an indicator of former seismogenic fault zones. The Fregon Subdomain in Central Australia was deformed under dry sub-eclogitic conditions of 600-700 • C and 1.0-1.2 GPa during the intracontinental Petermann Orogeny (ca. 550 Ma) and contains abundant pseudotachylyte. These pseudotachylytes are commonly foliated, recrystallized, and cross-cut by other pseudotachylytes, reflecting repeated generation during ongoing ductile deformation. This interplay is interpreted as evidence for repeated seismic brittle failure and post-to inter-seismic creep under dry lower-crustal conditions. Thermodynamic modelling of the pseudotachylyte bulk composition gives the same PT conditions of shearing as in surrounding mylonites. We conclude that pseudotachylytes in the Fregon Subdomain are a direct analogue of current seismicity in dry lower continental crust.

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Section: Field Observationsmentioning

confidence: 99%

Pseudotachylyte as field evidence for lower-crustal earthquakes during the intracontinental Petermann Orogeny (Musgrave Block, Central Australia)

et al. 2018

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“…3). When overprinted by subsequent ductile shearing, identification becomes more difficult and cannot 116 always be confirmed (Kirkpatrick and Rowe, 2013;Price et al, 2012). The thickness of pseudotachylyte veins reaches 117 up to 7 cm but is usually about 1 cm.…”

Section: Introduction 22mentioning

confidence: 99%

Pseudotachylyte as field evidence for lower crustal earthquakes during the intracontinental Petermann Orogeny (Musgrave Block, Central Australia)

Hawemann¹,

Mancktelow²,

Wex³

et al. 2017

Preprint

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Geophysical evidence for lower continental crustal earthquakes in almost all collisional orogens is in conflict with the widely accepted notion that rocks, under high grade conditions, should flow rather than fracture. Pseudotachylytes are remnants of frictional melts generated during seismic slip and can therefore be used as an indicator of former seismogenic fault zones. The Fregon Domain in Central Australia, was deformed under dry sub-eclogitic conditions during the intracontinental Petermann Orogeny (ca. 550 Ma) and contains abundant pseudotachylyte. These pseudotachylytes are commonly foliated, recrystallized, and crosscut by other pseudotachylytes, reflecting repeated generation during ongoing ductile deformation under generally dry conditions. This interplay is interpreted as a cycle of seismic brittle failure and post- to inter seismic creep under dry lower crustal conditions. Thermodynamic modelling of the pseudotachylyte bulk composition gives conditions of shearing of 600-700 °C and 1.0-1.2 GPa, the same as in surrounding mylonites. We conclude that pseudotachylytes in the Fregon Domain are a direct analogue of current seismicity in dry lower continental crust.

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“…In this regard, tektites and impact -related glass, the most important products of collision, are worthy of our attention. Other types of natural glass are products of geological processes, such as volcanic glass, which is the product of rapidly cooling magma, and pseudotachylite, which is formed by frictional melting of wall rocks during rapid fault movement related to seismic shocks (Price et al, 2012) or impact events (Reimold, 1995); Such glass often experiences high temperature and/or pressure. Comparison of these natural glass types can help us understand the role played by the atmosphere in the formation of the glass.…”

Section: Introductionmentioning

confidence: 99%

Local structure of iron in tektites and natural glass: An insight through X-ray absorption fine structure spectroscopy

Wang¹,

Yoshiasa²,

Okube

et al. 2013

Journal of Mineralogical and Petrological Sciences

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The local structure of iron in tektites from six strewn fields, and impact -and non -impact -related glass were studied using the Fe K -edge X -ray absorption near edge structure (XANES) and extended X -ray absorption fine structure (EXAFS) techniques, in order to obtain quantitative data on Fe -O bond length and Fe coordination number. X -ray absorption fine structure (XAFS) spectra and Fe -O bonds in standard minerals such as hematite, fayalite, and magnetite were compared. The degree of oxidation was measured based on the valencies of iron in the samples. Tektites contain a greater proportion of ferrous than ferric iron [0.04 (1) /ƩFe] are higher than that in tektites. Based on the measured Fe -O distance, it was inferred that 4 -and 5 -coordinated Fe exist in tektites, whereas volcanic glass contains 5 -and 6 -coordinated Fe. Impact -related glass possesses various local structures caused by the combination of 4 -, 5 -, and 6 -coordinated Fe. During formation, tektites experience high temperatures and a reducing atmosphere when they were ejected into the outer space. In contrast, the impact -related glass, which was ejected into the atmosphere or which remained close to the crater, experienced a more complex environment, with air pressure, density, and temperature varying across the atmospheric layers. Thus, impact -related glass presents more complicated oxidation states and structure compared to tektites. Volcanic glass, on the other hand, has a relatively stable redox condition; and thus, it undergoes only a small change in the degree of oxidation. This study indicates that the local structure and oxidation state of Fe may change due to the environment that the glass experienced during its formation. These different kinds of natural glass can be distinguished from each other using the study of the local structure.

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Identifying deformed pseudotachylyte and its influence on the strength and evolution of a crustal shear zone at the base of the seismogenic zone

Cited by 62 publications

References 77 publications

Pseudotachylyte as field evidence for lower-crustal earthquakes during the intracontinental Petermann Orogeny (Musgrave Block, Central Australia)

Pseudotachylyte as field evidence for lower-crustal earthquakes during the intracontinental Petermann Orogeny (Musgrave Block, Central Australia)

Pseudotachylyte as field evidence for lower crustal earthquakes during the intracontinental Petermann Orogeny (Musgrave Block, Central Australia)

Local structure of iron in tektites and natural glass: An insight through X-ray absorption fine structure spectroscopy

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