Cretaceous age, composition, and microstructure of pseudotachylyte in the Otago Schist, New Zealand
MetadataShow full item record
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 95.9±1.8 Ma as measured by total fusion 40Ar/39Ar analyses. Stepwise heating of pseudotachylyte matrix yields an excellently defined 40Ar/39Ar plateau age of 96.0±0.3 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.
Copyright 2010 The Royal Society of New Zealand
Showing items related by title, author, creator and subject.
Scott, J.; Auer, A.; Muhling, J.; Czertowicz, T.; Cooper, A.; Billia, M.; Kennedy, Allen (2015)Metamorphic mineral compositions of a staurolite-bearing greyschist from the middle reaches of the Moeraki River valley in south Westland reveal peak equilibration at c. 558 ± 50 °C and c. 6.1 ± 1.2 kbar. Two c. 83 Ma ...
Associations between sulfides, carbonaceous material, gold and other trace elements in polyframboids: Implications for the source of orogenic gold deposits, Otago Schist, New ZealandHu, Si-Yu; Evans, Katy; Fisher, L.; Rempel, Kirsten; Craw, D.; Evans, Noreen; Cumberland, S.; Robert, Aileen; Grice, Kliti (2016)Intimately intergrown micron-scale framboidal pyrite, carbonaceous material (CM), chalcopyrite, sphalerite and cobaltite form polyframboids in prehnite-pumpellyite facies rocks of the Otago Schist, New Zealand. This study ...
Raman characterization of carbonaceous material in the Macraes orogenic gold deposit and metasedimentary host rocks, New ZealandHu, Siyu; Evans, Katy; Craw, D.; Rempel, Kirsten; Bourdet, J.; Dick, Jeffrey; Grice, Kliti (2015)Raman spectroscopic and petrographic analyses were performed on samples collected from zones distal and proximal to the Macraes gold deposit in the Otago Schist of New Zealand to characterize the features and possible ...