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Cretaceous age, composition, and microstructure of pseudotachylyte in the Otago Schist, New Zealand


Barker, SLL and Palin, M and Sibson, RH and FitzGerald, JD and Reddy, S and Warr, LN and van der Pluijm, BA, Cretaceous age, composition, and microstructure of pseudotachylyte in the Otago Schist, New Zealand, New Zealand Journal of Geology and Geophysics, 53, (1) pp. 15-29. ISSN 0028-8306 (2010) [Refereed Article]


Copyright Statement

Copyright 2010 The Royal Society of New Zealand. This is an Accepted Manuscript of an article published by Taylor & Francis in New Zealand Journal of Geology and Geophysics on 14 April 2010, available online:

DOI: doi:10.1080/00288301003631764


At Tucker Hill, in Central Otago, New Zealand, a series of pseudotachylyte veins are hosted in quartzofeldspathic schist. Chilled margins, microlites, flow banding, and the crystallisation of mineral phases absent from the host rock provide unequivocal evidence for melting during pseudotachylyte formation. Whole rock analyses of pseudotachylyte reveal c. 3 enrichment of K2O, Ba, and Rb, and similar depletion of Na2O, CaO, Sr, and Eu, as compared to host schist. Formation age of pseudotachylyte is 95.91.8 Ma as measured by total fusion 40Ar/39Ar analyses. Stepwise heating of pseudotachylyte matrix yields an excellently defined 40Ar/39Ar plateau age of 96.00.3 Ma. These well-defined ages are attributed to the presence of potassium feldspar, low abundance of inherited lithic material from the host rock, and few fluid inclusions containing extraneous Ar. We propose that formation of these pseudotachylyte veins was related to Cretaceous extensional uplift and exhumation of the Otago Schist.

Item Details

Item Type:Refereed Article
Keywords:pseudotachylyte, Ar-Ar, Otago Schist, geochronology, friction melting
Research Division:Earth Sciences
Research Group:Geology
Research Field:Structural geology and tectonics
Objective Division:Expanding Knowledge
Objective Group:Expanding knowledge
Objective Field:Expanding knowledge in the earth sciences
UTAS Author:Barker, SLL (Dr Shaun Barker)
ID Code:129311
Year Published:2010
Web of Science® Times Cited:7
Deposited By:CODES ARC
Deposited On:2018-11-22
Last Modified:2018-12-10
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