Age of high-grade gneisses south of Grand Lake, Newfoundland

Authors

  • K. L. Currie Geological Survey of Canada, 601 Booth Street, Ottawa, Ontario K1A OE8, Canada
  • O. van Breeman Geological Survey of Canada, 601 Booth Street, Ottawa, Ontario K1A OE8, Canada
  • P. A. Hunt Geological Survey of Canada, 601 Booth Street, Ottawa, Ontario K1A OE8, Canada
  • J. T. van Berkel geological Survey of Canada, 601 Booth Street, Ottawa, Ontario K1A OE8, Canada; Present address: Department of Earth Sciences, Free University, P.O. Box 7161, 1007 MC Amsterdam, The Netherlands

DOI:

https://doi.org/10.4138/1857

Abstract

Crystalline rocks of the Steel Mountain Subzone of the Humber Zone in southwest Newfoundland give an age for granulite-grade metamorphism of 1498+9/-8 Ma, similar to ages from the Long Range inlier and northwestern Cape Breton Island. Peralkaline leucogranite was emplaced at 608 ± 4 Ma. The emplacement of anorthosite-gabbro complexes and amphibolite-grade metamorphism took place between these dates. The southern part of the Dunnage Zone (Central Gneiss Subzone), in contact with the Steel Mountain Subzone at the Long Range Fault, lacks Precambrian crystalline rocks, but was intruded by charnockitic plutons and metamorphosed to granulite facies at 460 ±10 Ma. This subzone was exhumed before 435 Ma. In the Meelpaeg Subzone of the Gander Zone, which is in contact with the Central Gneiss Subzone along the Victoria River Fault, the oldest intrusive component of a granoblastic migmatitic gneiss was emplaced at 418 ± 4 Ma. These data demonstrate that both the Long Range and Victoria River faults form major tectonic boundaries. Subzones appear to have been thrust westward in Silurian or later time. RÉSUMÉ Les roches cristallines de la sous-zone du mont Steel, dans la zone de Humber du sud-ouest de Terre-Neuve, ont donné des âges de 1498+9/-8 Ma pour le métamorphisme de haul grade, similaires à ceux de la boutonnière de Long Range et du nord de l'ile-du-Cap-Breton. Un leucogranite peralcalin s'est mis en place à 608 ± 4 Ma. L'intrusion des complexes à anorthosite-gabbro et le métamorphisme au faciès amphibolite se sont produits entre ces deux évènements. La partie sud de la zone de Dunnage (sous-zone de gneiss centrale), en contact avec la sous-zone du mont Steel a la faille de Long Range, ne contient pas de roches cristallines précambriennes mais à 616 recouped par des plutons charnockitiques et à 616 métamorphisée au faciès granulite à 460 ± 10 Ma. Cette sous-zone a été exhumge avant 435 Ma. Dans la sous-zone Mulpaeg de la zone de Gander, qui est mise en contact avec la sous-zone de gneiss centrale par la faille de la rivière Victoria, la phase intrusive la plus ancienne d'un gneiss migmatitique et granoblastique s'est mise en place à 418 ± 4 Ma. Ces données démontrent que les failles de Long Range et de la rivière Victoria sont des frontières tectoniques majeures. Les sous-zones semblent avoir subi un chevauchement vers l'ouest au plus tard au Silurien. [Traduit par le journal]

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Published

1992-07-01

How to Cite

Currie, K. L., van Breeman, O., Hunt, P. A., & van Berkel, J. T. (1992). Age of high-grade gneisses south of Grand Lake, Newfoundland. Atlantic Geoscience, 28(2). https://doi.org/10.4138/1857

Issue

Vol. 28 No. 2 (1992)

Section

Articles

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