Quick Search:    advanced search

GSW Home   GeoRef Home   My GSW Alerts   Contact GSW   About GSW   Journals List   Help

This Article Figures Only Full Text Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Owen, J. V. Articles by Greenough, J. D. Search for Related Content GeoRef GeoRef Citation

Petrology of the Cormacks Lake Complex, Newfoundland: decompressional reaction relations in cordierite+orthoamphibole-bearing gneisses and associated rocks

¹ Department of Geology, Saint Mary’s University, Halifax, Nova Scotia, Canada B3H 3C3
² Department of Geological Sciences, Okanagan University College, 3333 College Way, Kolowna, British Columbia, Canada V1V 1V7

^* E-mail: victor.owen{at}stmarys.ca

Cordierite+orthoamphibole (Crd+Oam)-bearing gneisses in the Cormacks Lake complex are regionally associated with metapelites containing prismatic sillimanite and K-feldspar, metabasites that locally contain metamorphic orthopyroxene, and other high-grade rocks in the Central Gneiss (Dashwoods) subzone, in the southwestern Newfoundland Appalachians. Retrograde features formed at the expense of the granulite-facies assemblages are ubiquitous. For example, in some migmatitic rocks, garnet is resorbed by Crd+Oam, and in metapelites, cordierite separates corroded garnet and sillimanite. Mineral thermobarometry suggests that, following granulite-facies metamorphism (T<785°C, P<7.5 kbar), retrogression occurred as the Cormacks Lake gneisses cooled through Mg-Fe diffusional blocking temperatures as they decompressed to a pressure of ~3–4 kbar. Given the absence of Barrovian (or higher pressure) mineral assemblages in the metapelites, regional tectonic reconstructions involving the thrusting of a neighbouring terrane (Notre Dame subzone) over the Central Gneiss subzone appear to be supported only by the moderate pressure determined for the granulite facies event. Although scarcely discernible given re-equilibration effects and the imprecision of thermobarometers, subsequent decompression nonetheless had a marked impact on the mineralogy of the gneisses.

KEYWORDS: cordierite-orthoamphibole-bearing gneiss, Cormacks Lake Complex, Newfoundland

This article has been cited by other articles:

				P. Pitra, P. Boulvais, V. Antonoff, and H. Diot Wagnerite in a cordierite-gedrite gneiss: Witness of long-term fluid-rock interaction in the continental crust (Ile d'Yeu, Armorican Massif, France) American Mineralogist, February 1, 2008; 93(2-3): 315 - 326. [Abstract] [Full Text] [PDF]

				C.R. van Staal, J.B. Whalen, V.J. McNicoll, S. Pehrsson, C.J. Lissenberg, A. Zagorevski, O. van Breemen, and G.A. Jenner The Notre Dame arc and the Taconic orogeny in Newfoundland Geological Society of America Memoirs, January 1, 2007; 200(0): 511 - 552. [Abstract] [Full Text] [PDF]