Effects of fluid flow, cooling and deformation as recorded by 40 Ar/ 39 Ar, Rb–Sr and zircon fission track ages in very low- to low-grade metamorphic rocks in Avalonian SE Cape Breton Island (Nova Scotia, Canada)
Abstract 40 Ar/ 39 Ar in situ UV laser ablation of white mica, Rb–Sr mineral isochrons and zircon fission track dating were applied to determine ages of very low- to low-grade metamorphic processes at 3.5±0.4 kbar, 280±30°C in the Avalonian Mira terrane of SE Cape Breton Island (Nova Scotia). The Mi...
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2014
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Online Access: | http://dx.doi.org/10.1017/s0016756814000508 https://www.cambridge.org/core/services/aop-cambridge-core/content/view/S0016756814000508 |
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crcambridgeupr:10.1017/s0016756814000508 2024-09-15T18:00:25+00:00 Effects of fluid flow, cooling and deformation as recorded by 40 Ar/ 39 Ar, Rb–Sr and zircon fission track ages in very low- to low-grade metamorphic rocks in Avalonian SE Cape Breton Island (Nova Scotia, Canada) WILLNER, ARNE P. BARR, SANDRA M. GLODNY, JOHANNES MASSONNE, HANS-JOACHIM SUDO, MASAFUMI THOMSON, STUART N. VAN STAAL, CEES R. WHITE, CHRIS E. 2014 http://dx.doi.org/10.1017/s0016756814000508 https://www.cambridge.org/core/services/aop-cambridge-core/content/view/S0016756814000508 en eng Cambridge University Press (CUP) https://www.cambridge.org/core/terms Geological Magazine volume 152, issue 5, page 767-787 ISSN 0016-7568 1469-5081 journal-article 2014 crcambridgeupr https://doi.org/10.1017/s0016756814000508 2024-07-31T04:04:15Z Abstract 40 Ar/ 39 Ar in situ UV laser ablation of white mica, Rb–Sr mineral isochrons and zircon fission track dating were applied to determine ages of very low- to low-grade metamorphic processes at 3.5±0.4 kbar, 280±30°C in the Avalonian Mira terrane of SE Cape Breton Island (Nova Scotia). The Mira terrane comprises Neoproterozoic volcanic-arc rocks overlain by Cambrian sedimentary rocks. Crystallization of metamorphic white mica was dated in six metavolcanic samples by 40 Ar/ 39 Ar spot age peaks between 396±3 and 363±14 Ma. Rb–Sr systematics of minerals and mineral aggregates yielded two isochrons at 389±7 Ma and 365±8 Ma, corroborating equilibrium conditions during very low- to low-grade metamorphism. The dated white mica is oriented parallel to foliations produced by sinistral strike-slip faulting and/or folding related to the Middle–Late Devonian transpressive assembly of Avalonian terranes during convergence and emplacement of the neighbouring Meguma terrane. Exhumation occurred earlier in the NW Mira terrane than in the SE. Transpression was related to the closure of the Rheic Ocean between Gondwana and Laurussia by NW-directed convergence. The 40 Ar/ 39 Ar spot age spectra also display relict age peaks at 477–465 Ma, 439 Ma and 420–428 Ma attributed to deformation and fluid access, possibly related to the collision of Avalonia with composite Laurentia or to earlier Ordovician–Silurian rifting. Fission track ages of zircon from Mira terrane samples range between 242±18 and 225±21 Ma and reflect late Palaeozoic reburial and reheating close to previous peak metamorphic temperatures under fluid-absent conditions during rifting prior to opening of the Central Atlantic Ocean. Article in Journal/Newspaper Breton Island Cambridge University Press Geological Magazine 152 5 767 787 |
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Abstract 40 Ar/ 39 Ar in situ UV laser ablation of white mica, Rb–Sr mineral isochrons and zircon fission track dating were applied to determine ages of very low- to low-grade metamorphic processes at 3.5±0.4 kbar, 280±30°C in the Avalonian Mira terrane of SE Cape Breton Island (Nova Scotia). The Mira terrane comprises Neoproterozoic volcanic-arc rocks overlain by Cambrian sedimentary rocks. Crystallization of metamorphic white mica was dated in six metavolcanic samples by 40 Ar/ 39 Ar spot age peaks between 396±3 and 363±14 Ma. Rb–Sr systematics of minerals and mineral aggregates yielded two isochrons at 389±7 Ma and 365±8 Ma, corroborating equilibrium conditions during very low- to low-grade metamorphism. The dated white mica is oriented parallel to foliations produced by sinistral strike-slip faulting and/or folding related to the Middle–Late Devonian transpressive assembly of Avalonian terranes during convergence and emplacement of the neighbouring Meguma terrane. Exhumation occurred earlier in the NW Mira terrane than in the SE. Transpression was related to the closure of the Rheic Ocean between Gondwana and Laurussia by NW-directed convergence. The 40 Ar/ 39 Ar spot age spectra also display relict age peaks at 477–465 Ma, 439 Ma and 420–428 Ma attributed to deformation and fluid access, possibly related to the collision of Avalonia with composite Laurentia or to earlier Ordovician–Silurian rifting. Fission track ages of zircon from Mira terrane samples range between 242±18 and 225±21 Ma and reflect late Palaeozoic reburial and reheating close to previous peak metamorphic temperatures under fluid-absent conditions during rifting prior to opening of the Central Atlantic Ocean. |
format |
Article in Journal/Newspaper |
author |
WILLNER, ARNE P. BARR, SANDRA M. GLODNY, JOHANNES MASSONNE, HANS-JOACHIM SUDO, MASAFUMI THOMSON, STUART N. VAN STAAL, CEES R. WHITE, CHRIS E. |
spellingShingle |
WILLNER, ARNE P. BARR, SANDRA M. GLODNY, JOHANNES MASSONNE, HANS-JOACHIM SUDO, MASAFUMI THOMSON, STUART N. VAN STAAL, CEES R. WHITE, CHRIS E. Effects of fluid flow, cooling and deformation as recorded by 40 Ar/ 39 Ar, Rb–Sr and zircon fission track ages in very low- to low-grade metamorphic rocks in Avalonian SE Cape Breton Island (Nova Scotia, Canada) |
author_facet |
WILLNER, ARNE P. BARR, SANDRA M. GLODNY, JOHANNES MASSONNE, HANS-JOACHIM SUDO, MASAFUMI THOMSON, STUART N. VAN STAAL, CEES R. WHITE, CHRIS E. |
author_sort |
WILLNER, ARNE P. |
title |
Effects of fluid flow, cooling and deformation as recorded by 40 Ar/ 39 Ar, Rb–Sr and zircon fission track ages in very low- to low-grade metamorphic rocks in Avalonian SE Cape Breton Island (Nova Scotia, Canada) |
title_short |
Effects of fluid flow, cooling and deformation as recorded by 40 Ar/ 39 Ar, Rb–Sr and zircon fission track ages in very low- to low-grade metamorphic rocks in Avalonian SE Cape Breton Island (Nova Scotia, Canada) |
title_full |
Effects of fluid flow, cooling and deformation as recorded by 40 Ar/ 39 Ar, Rb–Sr and zircon fission track ages in very low- to low-grade metamorphic rocks in Avalonian SE Cape Breton Island (Nova Scotia, Canada) |
title_fullStr |
Effects of fluid flow, cooling and deformation as recorded by 40 Ar/ 39 Ar, Rb–Sr and zircon fission track ages in very low- to low-grade metamorphic rocks in Avalonian SE Cape Breton Island (Nova Scotia, Canada) |
title_full_unstemmed |
Effects of fluid flow, cooling and deformation as recorded by 40 Ar/ 39 Ar, Rb–Sr and zircon fission track ages in very low- to low-grade metamorphic rocks in Avalonian SE Cape Breton Island (Nova Scotia, Canada) |
title_sort |
effects of fluid flow, cooling and deformation as recorded by 40 ar/ 39 ar, rb–sr and zircon fission track ages in very low- to low-grade metamorphic rocks in avalonian se cape breton island (nova scotia, canada) |
publisher |
Cambridge University Press (CUP) |
publishDate |
2014 |
url |
http://dx.doi.org/10.1017/s0016756814000508 https://www.cambridge.org/core/services/aop-cambridge-core/content/view/S0016756814000508 |
genre |
Breton Island |
genre_facet |
Breton Island |
op_source |
Geological Magazine volume 152, issue 5, page 767-787 ISSN 0016-7568 1469-5081 |
op_rights |
https://www.cambridge.org/core/terms |
op_doi |
https://doi.org/10.1017/s0016756814000508 |
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Geological Magazine |
container_volume |
152 |
container_issue |
5 |
container_start_page |
767 |
op_container_end_page |
787 |
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1810437586531909632 |