Ages and petrogenetic significance of igneous mangerite-charnockite suites associated with massif anorthosites, Grenville Province

Journal Article · Thu Mar 01 04:00:00 EST 1990 · Journal of Geology; (USA)

DOI:https://doi.org/10.1086/629394· OSTI ID:6286243

Emslie, R F; Hunt, P A ^[1]

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1. Geological Survey of Canada, Ottawa, Ontario (Canada)

U-Pb ages of zircon fractions of major anorthosite-mangerite-charnockite-granite (AMCG) igneous suites imply that this magmatism inaugurated what is widely regarded as the Grenvillian event between about 1.16 and 1.12 Ga ago over about two-thirds of the Grenville Province east, northeast, and southeast of the Central Metasedimentary Belt. Pre-Grenvillian AMCG suites about 1.36 and 1.64 Ga old have much more restricted distribution. An apparent time lag of about 0.05 to 0.10 Ga is indicated between culmination of AMCG magmatism and the widely recognized Grenvillian metamorphic peak (about 1.10 to 1.03 Ga), perhaps the most distinctive hallmark of the Grenville event. The time lag is consistent with conductive heating of thick subcontinental lithosphere that began with initiation of AMCG magmatism and continued until geotherms rose sufficiently to produce granulites in much of the lower to middle crust. Tectonic crustal thickening did not likely occur until later in the sequence of events, perhaps after some cooling from the metamorphic peak. Compressive forces were externally applied, possibly at a distant plate margin, while the continental lithosphere was still thermally weakened from preceding magmatic-metamorphic culminations.

• OSTI ID: 6286243
• Journal Information: Journal of Geology; (USA), Journal Name: Journal of Geology; (USA) Vol. 98:2; ISSN JGEOA; ISSN 0022-1376
• Country of Publication: United States
• Language: English

Related Subjects

58 GEOSCIENCES
580000* -- Geosciences
ACTINIDE ISOTOPES
AGE ESTIMATION
ANORTHOSITES
CANADA
COMPRESSION
CONTINENTAL CRUST
EARTH CRUST
GABBROS
GEOLOGIC FORMATIONS
GEOLOGIC HISTORY
GRANITES
HEATING
IGNEOUS ROCKS
ISOTOPE DATING
ISOTOPES
LEAD ISOTOPES
MAGMATISM
METAMORPHISM
MINERALS
NORTH AMERICA
OXYGEN COMPOUNDS
PLUTONIC ROCKS
ROCKS
SILICATE MINERALS
SILICATES
SILICON COMPOUNDS
TECTONICS
TRANSITION ELEMENT COMPOUNDS
URANIUM ISOTOPES
ZIRCON
ZIRCONIUM COMPOUNDS
ZIRCONIUM SILICATES