The University of Dublin | Trinity College -- Ollscoil Átha Cliath | Coláiste na Tríonóide
Trinity's Access to Research Archive
Home :: Log In :: Submit :: Alerts ::

TARA >
School of Natural Science >
Geology >
Geology (Scholarly Publications) >

Please use this identifier to cite or link to this item: http://hdl.handle.net/2262/64063

Title: Chemical abrasion applied to SHRIMP zircon geochronology: An example from the Variscan Karkonosze Granite (Sudetes, SW Poland)
Author: CROWLEY, QUENTIN G
Author's Homepage: http://people.tcd.ie/crowleyq
Keywords: Geology
Zircon
SHRIMP geochronology
Chemical abrasion
Radiogenic lead loss
Karkonosze Granite
Issue Date: 2012
Publisher: Elsevier
Citation: Ryszard Kryza, Quentin G. Crowley, Alexander Larionov, Christian Pin, Teresa Oberc-Dziedzic, Ksenia Mochnacka, Chemical abrasion applied to SHRIMP zircon geochronology: An example from the Variscan Karkonosze Granite (Sudetes, SW Poland), Gondwana Research, 21, 2012, 757-767
Series/Report no.: Gondwana Research;21
Abstract: Thermal annealing followed by acid etching of zircon (chemical abrasion or CA) can be successfully utilised to minimize or eliminate the effects of major and cryptic Pb-loss for SIMS U–Pb zircon dating. The procedure is demonstrated by applying the U–Pb SIMS technique to both untreated and chemically abraded zircons from the Karkonosze Granite, Sudetes, SW Poland. Conventional U–Pb SIMS dating of untreated zircons yields an apparently coherent age population (n = 9) with a weighted mean 206Pb/238U age of 306 ± 4 Ma. Some untreated zircons display anomalously young 206Pb/238U ages (c. 225 and 238 Ma) and are likely to have suffered substantial Pb-loss. A sub-set of zircons from the same sample was chemically abraded. Physically, zircons treated in this manner display a range in the degree of etching and partial dissolution. Extreme examples developed a 3D network of sub-μm channels which follow high-U (dark CL) zones or linear defects, such as micro fractures or indistinct cleavage planes. U–Pb SIMS dating of treated zircons (n = 11) yields a mean 206Pb/238U age of 322 ± 3 Ma. Two analyses of treated zircons still display younger 206Pb/238U ages (c. 297 and 301 Ma) ascribed to the effects of Pb-loss. For the analysed sample, U–Pb ages determined from chemically abraded zircons are c. 5 % older than those from untreated zircons. This is attributed to effective removal of metamict domains susceptible to Pb-loss. The CA technique also removes micro-inclusions thus lowering common Pb and reducing matrix effects. A cryptic Pb-loss in untreated zircons is only recognised when compared with chemically abraded counterparts or ages determined using other isotope techniques. This clearly demonstrates the utility of CA to high-spatial resolution methods and stresses that Pb-loss is detectable at a range of scales, regardless of the analytical technique used.
Description: PUBLISHED
URI: http://hdl.handle.net/2262/64063
Related links: http://dx.doi.org/10.1016/j.gr.2011.07.007
Appears in Collections:Geology (Scholarly Publications)

Files in This Item:

File Description SizeFormat
Chemical abrasion applied to SHRIMP zircon geochronology- An example from the Variscan Karkonosze Granite (Sudetes, SW Poland).pdfPublished (author's copy) - Peer Reviewed859.17 kBAdobe PDFView/Open


This item is protected by original copyright


Please note: There is a known bug in some browsers that causes an error when a user tries to view large pdf file within the browser window. If you receive the message "The file is damaged and could not be repaired", please try one of the solutions linked below based on the browser you are using.

Items in TARA are protected by copyright, with all rights reserved, unless otherwise indicated.

 

Valid XHTML 1.0! DSpace Software Copyright © 2002-2010  Duraspace - Feedback