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Constraints on incipient charnockite formation from zircon geochronology and rare earth element characteristics

Rimsa, Andrius LU ; Johansson, Leif LU and Whitehouse, M. J. (2007) In Contributions to Mineralogy and Petrology 154(3). p.357-369
Abstract
We present high spatial resolution ion-microprobe U-Th-Pb geochronology and rare earth element (REE) data combined with cathodoluminescence (CL) and back-scattered electron (BSE) imaging for complex zircons in incipient charnockites from Sondrum, SW Sweden. Examination of closely paired samples across the dehydration zone demonstrates that incipient charnockite formation at Sondrum is a zircon-forming process. We determined the age of the dehydration event (i.e. charnockitisation) to 1,397 +/- 4 Ma (2 sigma, MSWD = 1.7). This is the first successful attempt to date incipient charnockite formation using U-Pb systematics of zircon. Internal structure, chemical and isotopic characteristics of zircon indicate that the granitic pegmatite in the... (More)
We present high spatial resolution ion-microprobe U-Th-Pb geochronology and rare earth element (REE) data combined with cathodoluminescence (CL) and back-scattered electron (BSE) imaging for complex zircons in incipient charnockites from Sondrum, SW Sweden. Examination of closely paired samples across the dehydration zone demonstrates that incipient charnockite formation at Sondrum is a zircon-forming process. We determined the age of the dehydration event (i.e. charnockitisation) to 1,397 +/- 4 Ma (2 sigma, MSWD = 1.7). This is the first successful attempt to date incipient charnockite formation using U-Pb systematics of zircon. Internal structure, chemical and isotopic characteristics of zircon indicate that the granitic pegmatite in the core of the incipient charnockite is a melting zone. Commonly observed bulk rock HREE depletion in incipient charnockites is not caused by zircon dissolution but by involvement of garnet as a reactant in the dehydration reactions. Moreover, REE patterns of the newly formed zircon are HREE-enriched, indicating non-concurrent growth and suggesting that the degree of charnockite depletion in HREE might be controlled by the volume of newly formed zircon. (Less)
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author
organization
publishing date
type
Contribution to journal
publication status
published
subject
keywords
REE, zircon, (incipient) charnockite, Sondrum, geochronology
in
Contributions to Mineralogy and Petrology
volume
154
issue
3
pages
357 - 369
publisher
Springer
external identifiers
  • wos:000248300400007
  • scopus:34547697746
ISSN
0010-7999
DOI
10.1007/s00410-007-0197-5
language
English
LU publication?
yes
id
52bbb858-c23e-4b00-a512-53abd50a2775 (old id 689540)
date added to LUP
2007-12-14 11:23:32
date last changed
2017-07-23 03:35:10
@article{52bbb858-c23e-4b00-a512-53abd50a2775,
  abstract     = {We present high spatial resolution ion-microprobe U-Th-Pb geochronology and rare earth element (REE) data combined with cathodoluminescence (CL) and back-scattered electron (BSE) imaging for complex zircons in incipient charnockites from Sondrum, SW Sweden. Examination of closely paired samples across the dehydration zone demonstrates that incipient charnockite formation at Sondrum is a zircon-forming process. We determined the age of the dehydration event (i.e. charnockitisation) to 1,397 +/- 4 Ma (2 sigma, MSWD = 1.7). This is the first successful attempt to date incipient charnockite formation using U-Pb systematics of zircon. Internal structure, chemical and isotopic characteristics of zircon indicate that the granitic pegmatite in the core of the incipient charnockite is a melting zone. Commonly observed bulk rock HREE depletion in incipient charnockites is not caused by zircon dissolution but by involvement of garnet as a reactant in the dehydration reactions. Moreover, REE patterns of the newly formed zircon are HREE-enriched, indicating non-concurrent growth and suggesting that the degree of charnockite depletion in HREE might be controlled by the volume of newly formed zircon.},
  author       = {Rimsa, Andrius and Johansson, Leif and Whitehouse, M. J.},
  issn         = {0010-7999},
  keyword      = {REE,zircon,(incipient) charnockite,Sondrum,geochronology},
  language     = {eng},
  number       = {3},
  pages        = {357--369},
  publisher    = {Springer},
  series       = {Contributions to Mineralogy and Petrology},
  title        = {Constraints on incipient charnockite formation from zircon geochronology and rare earth element characteristics},
  url          = {http://dx.doi.org/10.1007/s00410-007-0197-5},
  volume       = {154},
  year         = {2007},
}