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Title
The Port Mouton Shear Zone : intersection of a regional fault with a crystallizing granitoid pluton
Related
Lithos, Vol. 61, Issue 3-4, p.141-159
DOI
http://dx.doi.org/10.1016/S0024-4937(02)00077-4
Publisher
Elsevier Science
Date
2002
Author/Creator
Clarke, D. Barrie
Author/Creator
McCuish, Krista L
Author/Creator
Vernon, Ron H
Author/Creator
Maksaev, Victor
Author/Creator
Miller, Brent V
Description
The peraluminous tonalite–monzogranite Port Mouton Pluton is a petrological, geochemical, structural, and geochronological anomaly among the many Late Devonian granitoid intrusions of the Meguma Lithotectonic Zone of southern Nova Scotia. The most remarkable structural feature of this pluton is a 4-km-wide zone of strongly foliated (040/subvertical) monzogranites culminating in a narrow (10–30 m), straight, zone of compositionally banded rocks that extends for at least 3 km along strike. The banded monzogranites consist of alternating melanocratic and leucocratic compositions that are complementary to the overall composition of that part of the pluton, suggesting an origin by mineral–melt and mineral–mineral sorting. Biotite and feldspar are strongly foliated in the plane of the compositional bands. These compositional variations and foliations originated by a process of segregation flow during shearing of the main magma with a crystallinity of 55–75%. Subsequent minor brittle fracturing of feldspars, twinning of microcline, development of blocky sub-grains in quartz, and kinking of micas demonstrate overprinting by a high-temperature deformation straddling the monzogranite solidus. Small folds and late sigmoidal dykes indicate dextral movement on the shear zone. This Port Mouton Shear Zone (PMSZ) is approximately co-linear with the only outcrops of Late Devonian mafic intrusions in the area, two of which are syn-plutonic with well-developed mingling textures in the marginal tonalite of the Port Mouton Pluton. Also closely co-linear with the mafic intrusions are a granitoid dyke that extends well beyond the outer contact of the Port Mouton Pluton, a swarm of large aligned angular xenolithic slabs, a zone of thin wispy schlieren banding, a large Be-bearing pegmatite, and a breccia pipe with abundant garnetiferous metapelitic xenoliths. In various ways, the shear zone may control all of these features. The Port Mouton Shear Zone is parallel to many other NE-trending faults and shear zones in the northern Appalachians, probably related to the docking of the Meguma Zone along the Cobequid–Chedabucto Fault system.
Description
19 page(s)
Subject Keyword
shear zone
Subject Keyword
granite
Subject Keyword
magma
Subject Keyword
segregation banding
Subject Keyword
schlieren
Subject Keyword
mingling
Subject Keyword
breccia
Subject Keyword
pegmatite
Resource Type
journal article
Organisation
Macquarie University. Dept. of Earth and Planetary Sciences
Organisation
Macquarie University. National Key Centre for Geochemical Evolution and Metallogeny of Continents (GEMOC)
Identifier
http://hdl.handle.net/1959.14/37912
Identifier
ISSN:0024-4937
Identifier
mq-rm-2002015404
Language
eng
Peer Reviewed
Peer Reviewed