Skip Navigation


Journal of Petrology Advance Access originally published online on November 7, 2008
Journal of Petrology 2008 49(11):1915-1929; doi:10.1093/petrology/egn047
This Article
Right arrow Full Text Freely available
Right arrow FREE Full Text (PDF) Freely available
Right arrow Supplementary Data
Right arrow All Versions of this Article:
49/11/1915    most recent
egn047v1
Right arrow Alert me when this article is cited
Right arrow Alert me if a correction is posted
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 Add to My Personal Archive
Right arrow Download to citation manager
Right arrowRequest Permissions
Google Scholar
Right arrow Articles by Crowley, J. L.
Right arrow Articles by Gibson, H. D.
Right arrow Search for Related Content
GeoRef
Right arrow GeoRef Citation
Social Bookmarking
Add to CiteULike   Add to Connotea   Add to Del.icio.us  
What's this?

© The Author 2008. Published by Oxford University Press. All rights reserved. For Permissions, please e-mail: journals.permissions@oxfordjournals.org

Assessing Inheritance of Zircon and Monazite in Granitic Rocks from the Monashee Complex, Canadian Cordillera

J. L. Crowley1,*, R. L. Brown2, F. Gervais2 and H. D. Gibson3

1Department of Geosciences, Boise State University, Boise, ID 83725, USA
2Department of Earth Sciences, Carleton University, Ottawa, ON, K1S 5B6, Canada
3Department of Earth Sciences, Simon Fraser University, Burnaby, BC, V5A 1S6, Canada

RECEIVED SEPTEMBER 5, 2007; ACCEPTED SEPTEMBER 10, 2008


  Abstract

Zircon and monazite from granitic sheets and dikes in the Monashee complex, Canadian Cordillera, were investigated to determine whether igneous crystallization occurred at 1·9 Ga or 50 Ma with 1·9 Ga inherited zircon and monazite. Four of the five samples are weakly deformed to undeformed, despite occurring in a gneiss dome at the structurally deepest exposed level of the orogen that elsewhere was strongly deformed and partly melted at 50 Ma. Based on U–(Th)–Pb ages from zircon and monazite, field relationships, and mineral composition and zoning, we conclude that the granitic rocks crystallized at 1·9 Ga and were metamorphosed at 50 Ma. All dated zircon is 1·9 Ga (except for 2·3–2·0 Ga inherited cores) and 1·9 Ga monazite makes up >90% of the population in four samples. The remainder of the monazite is 50 Ma and all monazite in one sample is 50 Ma. Composition and zoning of 1·9 Ga zircon and monazite are uniform within samples, yet differ between samples, indicating growth from 1·9 Ga magmas that are unique to each sample. This relationship is unlikely if the grains are inherited because the host rocks are heterogeneous 2·3–2·1 Ga gneisses. The 1·9 Ga zircon and monazite have zoning that is consistent with growth from magmas, whereas the 50 Ma monazite has variable composition and zoning that suggest growth from diverse metamorphic fluids. The results demonstrate that part of the Monashee complex was last strongly deformed and partly melted at 1·9 Ga, and thus largely escaped Cordilleran tectonism.

KEY WORDS: Canadian Cordillera; inheritance; monazite; U–Pb geochronology; zircon

*Corresponding author. Telephone: 208-407-8767. E-mail: jimcrowley{at}boisestate.edu


Add to CiteULike CiteULike   Add to Connotea Connotea   Add to Del.icio.us Del.icio.us    What's this?




Disclaimer: Please note that abstracts for content published before 1996 were created through digital scanning and may therefore not exactly replicate the text of the original print issues. All efforts have been made to ensure accuracy, but the Publisher will not be held responsible for any remaining inaccuracies. If you require any further clarification, please contact our Customer Services Department.