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First evidence of Renlandian (c. 950-940 Ma) orogeny in Mainland Scotland: implications for the status of the Moine Supergroup and circum-North Atlantic correlations

Bird, Anna; Cutts, Kathryn; Strachan, Rob; Thirlwall, Matthew F.; Hand, Martin

Authors

Kathryn Cutts

Rob Strachan

Matthew F. Thirlwall

Martin Hand



Abstract

Central problems in the interpretation of the Neoproterozoic geology of the North Atlantic region arise from uncertainties in the ages of, and tectonic drivers for, Tonian orogenic events recorded in eastern Laurentia and northern Baltica. The identification and interpretation of these events is often problematic because most rock units that record Tonian orogenesis were strongly reworked at amphibolite facies during the Ordovician-Silurian Caledonian orogeny. Lu-Hf and Sm-Nd geochronology and metamorphic modelling carried out on large (>1 cm) garnets from the Meadie Pelite in the Moine Nappe of the northern Scottish Caledonides indicate prograde metamorphism between 950 and 940 Ma at pressures of 6–7 kbar and temperatures of 600 °C. This represents the first evidence for c. 950 Ma Tonian (Renlandian) metamorphism in mainland Scotland and significantly extends its geographic extent along the palaeo-Laurentian margin. The Meadie Pelite is believed to be part of the Morar Group within the Moine Supergroup. If this is correct: 1) the Morar Group was deposited between 980 ± 4 Ma (age of the youngest detrital zircon; Peters, 2001, youngest published zircon date is 947 ± 189 (Friend et al., 2003)) and c. 950 Ma (age of regional metamorphism reported here), 2) an orogenic unconformity must separate the Morar Group from the 883 ± 35 Ma (Cawood et al., 2004) Glenfinnan and Loch Eil groups, and 3) the term ‘Moine Supergroup’ may no longer be appropriate. The Morar Group is broadly correlative with similar aged metasedimentary successions in Shetland, East Greenland, Svalbard, Ellesmere Island and northern Baltica. All these successions were deposited after c. 1030 Ma, contain detritus from the Grenville orogen, and were later deformed and metamorphosed at 950–910 Ma during accretionary Renlandian orogenesis along an active plate margin developed around this part of Rodinia.

Journal Article Type Article
Publication Date Feb 1, 2018
Print ISSN 0301-9268
Publisher Elsevier
Peer Reviewed Peer Reviewed
Volume 305
Pages 283-294
APA6 Citation Bird, A., Cutts, K., Strachan, R., Thirlwall, M. F., & Hand, M. (2018). First evidence of Renlandian (c. 950-940 Ma) orogeny in Mainland Scotland: implications for the status of the Moine Supergroup and circum-North Atlantic correlations. Precambrian research, 305, 283-294. https://doi.org/10.1016/j.precamres.2017.12.019
DOI https://doi.org/10.1016/j.precamres.2017.12.019
Keywords Geology; Geochemistry and Petrology
Publisher URL https://www.sciencedirect.com/science/article/pii/S0301926817303753
Copyright Statement © 2018. This manuscript version is made available under the CC-BY-NC-ND 4.0 license http://creativecommons.org/licenses/by-nc-nd/4.0/
Additional Information This article is maintained by: Elsevier; Article Title: First evidence of Renlandian (c. 950–940 Ma) orogeny in mainland Scotland: Implications for the status of the Moine Supergroup and circum-North Atlantic correlations; Journal Title: Precambrian Research; CrossRef DOI link to publisher maintained version: http://dx.doi.org/10.1016/j.precamres.2017.12.019; Content Type: article; Copyright: © 2017 Elsevier B.V. All rights reserved.

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Copyright Statement
© 2018. This manuscript version is made available under the CC-BY-NC-ND 4.0 license http://creativecommons.org/licenses/by-nc-nd/4.0/



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