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Metamorphosed Gabbroic Dikes Related to Opening of Iapetus Ocean at the St. Lawrence Promontory: Blair River Inlier, Nova Scotia, Canada

Brent V. Miller and Sandra M. Barr
The Journal of Geology
Vol. 112, No. 3 (May 2004), pp. 277-288
DOI: 10.1086/382759
Stable URL: http://www.jstor.org/stable/10.1086/382759
Page Count: 12
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Metamorphosed Gabbroic Dikes Related to Opening of Iapetus Ocean at the St. Lawrence Promontory: Blair River Inlier, Nova Scotia, Canada
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Abstract

Abstract Metamorphosed mafic dikes in the Laurentian Blair River inlier of northern Cape Breton Island, Nova Scotia, are related to the opening of the Iapetus Ocean during the breakup of the supercontinent Rodinia. The dikes were metamorphosed during a Paleozoic (likely Silurian) thermal event related to Appalachian orogenesis but were not deformed significantly. Two dikes yielded U‐Pb zircon ages of \documentclass{aastex} \usepackage{amsbsy} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{bm} \usepackage{mathrsfs} \usepackage{pifont} \usepackage{stmaryrd} \usepackage{textcomp} \usepackage{portland,xspace} \usepackage{amsmath,amsxtra} \usepackage[OT2,OT1]{fontenc} \newcommand\cyr{ \renewcommand\rmdefault{wncyr} \renewcommand\sfdefault{wncyss} \renewcommand\encodingdefault{OT2} \normalfont \selectfont} \DeclareTextFontCommand{\textcyr}{\cyr} \pagestyle{empty} \DeclareMathSizes{10}{9}{7}{6} \begin{document} \landscape $581\pm 6$ \end{document} and \documentclass{aastex} \usepackage{amsbsy} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{bm} \usepackage{mathrsfs} \usepackage{pifont} \usepackage{stmaryrd} \usepackage{textcomp} \usepackage{portland,xspace} \usepackage{amsmath,amsxtra} \usepackage[OT2,OT1]{fontenc} \newcommand\cyr{ \renewcommand\rmdefault{wncyr} \renewcommand\sfdefault{wncyss} \renewcommand\encodingdefault{OT2} \normalfont \selectfont} \DeclareTextFontCommand{\textcyr}{\cyr} \pagestyle{empty} \DeclareMathSizes{10}{9}{7}{6} \begin{document} \landscape $576\pm 6$ \end{document} Ma, have the chemical characteristics of subalkaline basalt generated at rift environments, and have initial εNd values of +4.9. Metagabbro dikes of the Blair River inlier are contemporaneous with and geochemically similar to other Iapetus rift‐related, mafic rocks in eastern North America. A block of Laurentia “missing” from the Quebec embayment should also contain rift‐related dikes of this age and basement of similar character to the Blair River inlier. If this block could be identified, much as the Argentine Precordillera has been identified as a block derived from southern Laurentia, then these new data will aid in Neoproterozoic paleogeographic reconstructions of Rodinia.

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