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Proterozoic anorthosite-granite Nain Batholith; structure and intrusion processes in an active lithosphere-scale fault zone, northern Labrador

John S. Myers, Ronald J. Voordouw and Tanya A. Tettelaar
Proterozoic anorthosite-granite Nain Batholith; structure and intrusion processes in an active lithosphere-scale fault zone, northern Labrador
Canadian Journal of Earth Sciences = Revue Canadienne des Sciences de la Terre (August 2008) 45 (8): 909-934

Abstract

We present field evidence of the structure and evolution of a typical Proterozoic massif-type anorthosite. The anorthosite forms a batholith composed of numerous plutons and ring complexes intruded episodically in two main sequences, each producing anorthositic rocks and monzonite-ferrodiorite followed by granite. The batholith is located where a lithosphere-scale fault zone, approximately 50 km wide and extending over 1000 km from Greenland to Labrador, intersected an older continental suture. Intermittent episodes of mainly sinistral transtension along this Gardar-Voisey's Bay fault zone were associated with the generation of a number of pulses of magmatism and controlled the rise of magmas to middle and upper crustal levels between approximately 1363 and 1289 Ma. Both the large- and small-scale structures and magma intrusion processes are similar to those of many cordilleran batholiths, with tabular plutons associated with ring dykes emplaced by cauldron subsidence, and basin-shaped plutons associated with cone sheets. These structures are well known in subvolcanic situations but little known at the mid-crustal depth of the Nain batholith. The location of these structures within the batholith was controlled by intersecting, externally generated faults and shear zones. We conclude that this typical massif-type anorthosite is an intracratonic structural equivalent of cordilleran batholiths of continental margins.


ISSN: 0008-4077
EISSN: 1480-3313
Coden: CJESAP
Serial Title: Canadian Journal of Earth Sciences = Revue Canadienne des Sciences de la Terre
Serial Volume: 45
Serial Issue: 8
Title: Proterozoic anorthosite-granite Nain Batholith; structure and intrusion processes in an active lithosphere-scale fault zone, northern Labrador
Affiliation: Memorial University, Department of Earth Sciences, St. John's, NL, Canada
Pages: 909-934
Published: 200808
Text Language: English
Summary Language: French
Publisher: National Research Council of Canada, Ottawa, ON, Canada
References: 151
Accession Number: 2009-006630
Categories: Igneous and metamorphic petrology
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. sects., 2 tables, geol. sketch maps
N56°00'00" - N57°00'00", W62°00'00" - W61°40'00"
Country of Publication: Canada
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute.
Update Code: 200904
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