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Petrology and Isotopic Composition of a Grenvillian Basement Fragment in the Northern Appalachian Orogen: Blair River Inlier, Nova Scotia, Canada.

Authors :
MILLER, BRENT V.
BARR, SANDRA M.
Source :
Journal of Petrology. Dec2000, Vol. 41 Issue 12, p1777-1804. 28p. 1 Black and White Photograph, 2 Diagrams, 4 Charts, 8 Graphs.
Publication Year :
2000

Abstract

Mesoproterozoic metaplutonic rocks in northern Cape Breton Island, Nova Scotia, occur in a tectonic inlier within the Appalachian orogen. Although they have been multiply metamorphosed and variably deformed, the petrology and geochemistry of these rocks provide insight into the tectonomagmatic evolution of easternmost Laurentia. Anorthosite, syenite, and granitoid plutons (1100–980 Ma) intruded the Sailor Brook and Polletts Cove River gneisses. New Nd isotopic data are presented from a biotite-rich part of the Sailor Brook gneiss (εNdi = −0·7), two anorthosite samples (εNdi = +2·1 and +2·8), and a charnockite unit (εNdi = −0·4). New U–Pb zircon data from the anorthosite yield 207Pb/206Pb ages between 975 and 1095 Ma. Disrupted U–Pb systematics preclude a unique age interpretation, but the ∼1095 Ma single-grain date is a minimum age for the anorthosite. Field relations, major and trace-element geochemistry, and isotopic characteristics indicate that the anorthosite and charnockite were probably coexisting melts, but not differentiates of a single parent magma. The lithological and chemical characteristics of the Lowland Brook Syenite are similar to those of a contemporaneous belt of ultrapotassic plutons in the southern Grenville Province, and both have the chemical characteristics of certain modern continental-margin arc magmas. These data indicate that the Mesoproterozoic units in the Blair River inlier were juvenile crustal additions to eastern Laurentia during Grenville-related orogenic events. [ABSTRACT FROM PUBLISHER]

Details

Language :
English
ISSN :
00223530
Volume :
41
Issue :
12
Database :
Academic Search Index
Journal :
Journal of Petrology
Publication Type :
Academic Journal
Accession number :
44403240
Full Text :
https://doi.org/10.1093/petrology/41.12.1777