RT Journal Article
SR Electronic
T1 A Grenville cross section from Port Cartier to Mount Reed, Quebec, Canada
JF American Journal of Science
JO Am J Sci
FD American Journal of Science
SP 693
OP 712
DO 10.2475/ajs.261.8.693
VO 261
IS 8
A1 Lepp, Henry
A1 Goldich, Samuel S.
A1 Kistler, Ronald W.
YR 1963
UL http://www.ajsonline.org/content/261/8/693.abstract
AB A traverse across the Grenville province from Port Cartier on the St. Lawrence River to Mt. Reed just S. of the Grenville front indicates that the bedrocks are a sequence of paragneisses intercalated with gneissic rocks and granofelses of uncertain origin. Minor masses of gabbro and granite were locally intruded in the gneisses. There is no regular pattern of metamorphic zones; the gneisses are principally in the amphibolite metamorphic facies, but local areas of granulite facies rocks occur throughout the region, particularly in the northern and southern parts. The average K-Ar age for the 13 samples from the Grenville province is 970 m.y. with a range of from 860-1000 m.y. Rb-Sr ages on 9 specimens average 950 m.y. and range from 860-1140 m.y. These ages date the Grenville orogeny. Geologic evidence conclusively indicates that some of the rocks involved in this orogeny formed at a much earlier period. Possibly some of the gneisses along the traverse were formed from sediments of the Grenville geosyncline, but these cannot be distinguished from the recrystallized older rocks by the present data.