Journal article
Leucogranites and the time of extension in the East Greenland Caledonides
The Journal of geology, Vol.113(4), pp.399-417
07/2005
DOI: 10.1086/430240
Abstract
Leucogranites provide timing estimates for deformation, particularly extension, in many orogens. On this basis, the time of extension in the East Greenland Caledonides has been estimated at 420-430 Ma. U-Pb SHRIMP (sensitive, high-resolution ion-microprobe) analysis of zircon and monazite from selected leucogranites was undertaken to establish the age of the Payer Land detachment zone, an extensional structure that places low-grade metasedimentary rocks on granulite facies gneisses that record high-pressure (1.4-1.6 GPa) metamorphism at ca. 405 Ma. Deformed equigranular granites associated with upper plate lithologies give ages of 426+ or -3 to 413+ or -3 Ma, consistent with the regional leucogranite suite. A second suite of deformed pegmatitic granites occur as sills and dikes with respect to the extensional mylonitic fabrics that are superimposed on high-pressure granulites of the lower plate and therefore must be younger than the age of high-pressure metamorphism at 405 Ma and the more voluminous 415-440 Ma granite suite. Older ages for both zircon and monazite indicate that both minerals are inherited components within the pegmatitic granites. These observations suggest that inheritance, particularly of metamorphic monazite from the source rocks, can make it very difficult to establish meaningful emplacement ages for leucogranites in the absence of corroborative evidence. Although multiple periods of extension are permissible, current timing relationships established in Payer Land suggest that much of the extension responsible for exhumation of deep-level rocks in the East Greenland Caledonides is younger than 405 Ma.
Details
- Title: Subtitle
- Leucogranites and the time of extension in the East Greenland Caledonides
- Creators
- Jane A Gilotti - University of IowaWilliam C McClelland - University of Idaho
- Resource Type
- Journal article
- Publication Details
- The Journal of geology, Vol.113(4), pp.399-417
- Publisher
- University of Chicago Press
- DOI
- 10.1086/430240
- ISSN
- 0022-1376
- eISSN
- 1537-5269
- Language
- English
- Date published
- 07/2005
- Academic Unit
- Earth and Environmental Sciences
- Record Identifier
- 9984229302102771
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