Lyell Collection
Geological Society, London, Special Publications
Lyell Centre  |   Lyell Collection  |   Subscriptions   |   Geological Society  |   Email alerts  |   Online bookshop  |   Help

Keywords:
Author:
Advanced search>>
This Article
Right arrow Full Text (PDF)
Right arrow References
Right arrow Alert me when this article is cited
Right arrow Alert me if a correction is posted
Right arrow Citation Map
Services
Right arrow Email this article to a friend
Right arrow Similar articles in this journal
Right arrow Alert me to new issues of the journal
Right arrow Download to citation manager
Right arrow Request Permissions
Citing Articles
Right arrow Citing Articles via HighWire
Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by Rudnick, R. L.
Right arrow Articles by Taylor, S. R.
Right arrow Search for Related Content
GeoRef
Right arrow GeoRef Citation
Geological Society, London, Special Publications; 1986; v. 24; p. 179-191;
DOI: 10.1144/GSL.SP.1986.024.01.17
© 1986 Geological Society of London

Geochemical constraints on the origin of Archaean tonalitic-trondhjemitic rocks and implications for lower crustal composition

R. L. Rudnick & S. R. Taylor

Research School of Earth Sciences, Australian National University, Canberra, A.C.T., Australia. 2600

The rare earth element (REE) concentrations of high-grade trondhjemitic gneisses from the Archean Kapuskasing Structural Zone, central Ontario, are similar to REE concentrations of Archaean tonalites and trondhjemites world-wide: REE patterns are steeply fractionated (La/Yb)N = 20–100), with variable positive Eu anomalies and fractionated HREE ((Gd/Yb)N = 2–4). Calculated models for the melting of a mafic source with a flat REE pattern and variable mineralogy show that amphibole alone is not capable of producing the large amount of REE fractionation observed in Archaean tonalites; garnet amphibolite (with >20% garnet), mafic garnet granulite or eclogite are the most likely sources. The presence of garnet constrains the mafic source to be within the lower crust (deeper than 25 km) or upper mantle. Such crustal or upper mantle melting depths are not geochemically distinguishable, yet have important implications for the composition of the Archaean lower crust.





This article has been cited by other articles:


Home page
 Geological Society, London, Special PublicationsHome page
A. Gerdes, G. Worner, and F. Finger
Hybrids, magma mixing and enriched mantle melts in post-collisional Variscan granitoids: the Rastenberg Pluton, Austria
Geological Society, London, Special Publications, 2000; 179: 415 - 431.
[Abstract] [PDF]