TY - JOUR
T1 - Formation of Anorthositic Rocks within the Blair River Inlier of Northern Cape Breton Island, Nova Scotia (Canada)
AU - Shellnutt, J. Gregory
AU - Dostal, Jaroslav
AU - Keppie, J. Duncan
AU - Keppie, D. Fraser
N1 - Funding Information:
We thank Sarah Roeske for editorial handling and comments J.S. Daly and an anonymous reviewer that helped to improve this manuscript. We are grateful to Carol Chuang and Terri Tang for their laboratory assistance. This research was supported by a funding provided by Ministry of Science and Technology (MOST) (Taiwan) grant 107-2628-M-003-003 to JGS and NSERC Discovery grant to JD.
Publisher Copyright:
© 2020. J. Gregory Shellnutt et al. Exclusive Licensee GeoScienceWorld. Distributed under a Creative Commons Attribution License (CC BY 4.0). All Rights Reserved.
PY - 2020
Y1 - 2020
N2 - Rocks from the Blair River inlier of Northern Cape Breton Island (Nova Scotia, Canada) have been correlated with either the Grenville basement of eastern Laurentia or the accreted Avalon terrane. Additional zircon U-Pb dates of spatially associated anorthositic dykes (425:1± 2:2 Ma) and a metagabbro (423:8± 2:5 Ma) from the Fox Back Ridge intrusion of the Blair River inlier reveal Late Silurian emplacement ages. Their contemporaneity suggests that they may be members of a larger intrusive complex. The anorthositic rocks have high Eu/Eu∗ values (>2.5), and bulk compositions are similar to the mineral compositions of labradorite (An50-70) and andesine (An30-50). The metagabbro is compositionally similar to alkali basalt and does not seem to have been affected by crustal contamination (Nb/U > 24; Th/NbPM ≤ 1:1) although it was metamorphosed. The high Tb/YbN (1.8-1.9) ratios suggest that the parental magma of the metagabbro was derived from a garnet-bearing peridotite. Fractional crystallization and mass balance calculations indicate that the anorthositic rocks can be derived by mineral accumulation from a mafic parental magma similar in composition to the metagabbro of this study. The Late Silurian ages suggest that the rocks were emplaced into the Avalon terrane after the closure of the Iapetus Ocean but before Early Devonian (415-410 Ma) sinistral transpression.
AB - Rocks from the Blair River inlier of Northern Cape Breton Island (Nova Scotia, Canada) have been correlated with either the Grenville basement of eastern Laurentia or the accreted Avalon terrane. Additional zircon U-Pb dates of spatially associated anorthositic dykes (425:1± 2:2 Ma) and a metagabbro (423:8± 2:5 Ma) from the Fox Back Ridge intrusion of the Blair River inlier reveal Late Silurian emplacement ages. Their contemporaneity suggests that they may be members of a larger intrusive complex. The anorthositic rocks have high Eu/Eu∗ values (>2.5), and bulk compositions are similar to the mineral compositions of labradorite (An50-70) and andesine (An30-50). The metagabbro is compositionally similar to alkali basalt and does not seem to have been affected by crustal contamination (Nb/U > 24; Th/NbPM ≤ 1:1) although it was metamorphosed. The high Tb/YbN (1.8-1.9) ratios suggest that the parental magma of the metagabbro was derived from a garnet-bearing peridotite. Fractional crystallization and mass balance calculations indicate that the anorthositic rocks can be derived by mineral accumulation from a mafic parental magma similar in composition to the metagabbro of this study. The Late Silurian ages suggest that the rocks were emplaced into the Avalon terrane after the closure of the Iapetus Ocean but before Early Devonian (415-410 Ma) sinistral transpression.
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U2 - 10.2113/2020/8825465
DO - 10.2113/2020/8825465
M3 - Article
AN - SCOPUS:85099884136
SN - 1941-8264
VL - 2020
SP - 1
EP - 21
JO - Lithosphere
JF - Lithosphere
IS - 1
ER -