Age of the Cabonga nepheline syenite, Grenville Province, western Quebec

2006 ◽  
Vol 43 (9) ◽  
pp. 1237-1249 ◽  
Author(s):  
Pierre Hudon ◽  
Richard M Friedman ◽  
Gilles Gauthier ◽  
Jacques Martignole
Keyword(s):  
Nepheline Syenite ◽  
Thermal Ionization Mass Spectrometry ◽  
Ionization Mass ◽  
Grenville Province ◽  
X Ray ◽  
Electronic Imaging ◽  
Isotopic Analyses ◽  
Thermal Ionization Mass ◽  
Granite Magmatism

This study presents isotope dilution – thermal ionization mass spectrometry (ID–TIMS) U–Pb data for megacrystic zircon from the Cabonga Nepheline Syenite Complex of the Réservoir Cabonga terrane (Grenville Province). This terrane is an allochthonous slab metamorphosed under granulite-grade conditions ~1.18–1.14 Ga and transported onto migmatites of the Grenvillian Parautochthon at about 1.02 Ga. The very low uranium and lead concentrations of zircon from the Cabonga nepheline syenite (CNS) did not permit determination of a statistically significant crystallization age using laser ablation microbeam techniques. Consequently, extensive microsampling (15 zircon chips), guided by X-ray and electronic imaging, followed by ID–TIMS analyses were carried out on a single megacrystic zircon. A regression of 13 out of 15 U–Pb isotopic analyses results in a crystallization age of 1171 ± 3 Ma for the CNS. Criteria based on zircon morphologies, zoning patterns, varying Th/U ratios (0.3–0.9), and a highly fractionated Zr/Hf ratio (68) suggest an igneous derivation for the CNS. The Cabonga alkaline rocks, intruded under high-grade metamorphic conditions, preceded the onset of the widespread and ubiquitous (1.15 ± 0.01 Ga) anorthosite–mangerite–charnockite–granite magmatism in the southern part of the Grenville Province.

Calibration of an Energy Dispersive X-Ray Fluorescence Spectrometer

1975 ◽  
Vol 19 ◽  
pp. 473-486 ◽  
Author(s):  
A. R. Stiles ◽  
T. G. Dzubay ◽  
R. M. Baum ◽  
R. L. Walter ◽  
R. D. Willis ◽  
...  
Keyword(s):  
Thermal Ionization Mass Spectrometry ◽  
Ionization Mass ◽  
National Bureau ◽  
Average Deviation ◽  
X Ray ◽  
Elemental Concentrations ◽  
Thermal Ionization Mass ◽  
Commercial Sources ◽  
Thickness Variations ◽  
Fluorescence Spectrometer

The purpose of this work was to develop accurate calibration standards which were fully characterized in terms of uniformity and concentration using fundamental measuring methods. Three similar sets of vacuum deposits were commercially made, each set containing the single deposits CuS, KCl, CaF2, Cr, Fe, Cu, RbNO3, SrF2, MoO3 , BaF2, and Pb. Thickness variations in each deposit were measured with PIXEA (proton induced x-ray excitation analysis) measurements taken at 6 to 8 positions along the deposit diameters. Relative elemental concentrations on corresponding deposits from each set were measured using multiple XRF intercomparisons. One set of deposits was destructively analyzed at the National Bureau of Standards with isotope dilution thermal ionization mass spectrometry (IDMS) in order to calibrate the remaining sets of vacuum deposits. The calibrated deposits were compared with standards from two commercial sources. For seven elements heavier than chlorine there was an average deviation of 13.5% between the calibrated deposits and the commercial standards. Disagreements as large as 15% were observed between standards from the two commercial suppliers.

Environmental Monitoring of Hanford Nuclear Facility Effluents by Thermal Ionization Mass Spectrometry

1994 ◽  
Vol 48 (11) ◽  
pp. 1326-1330 ◽  
Author(s):  
J. J. Stoffel(S) ◽  
J. F. Wacker ◽  
J. M. Kelley ◽  
L. A. Bond ◽  
R. A. Kiddy ◽  
...  
Keyword(s):  
Mass Spectrometry ◽  
Environmental Monitoring ◽  
Thermal Ionization Mass Spectrometry ◽  
Nuclear Material ◽  
Thermal Ionization ◽  
Ionization Mass Spectrometry ◽  
Ionization Mass ◽  
Material Production ◽  
Isotopic Analyses ◽  
Thermal Ionization Mass

Thermal ionization mass spectrometry (TIMS) is a sensitive method for environmental monitoring of effluent radionuclides around nuclear material production facilities. Isotopic analysis by positive and negative TIMS is an essential tool for the assessment of both the inventory and migration of radionuclides in the environment. Instrumentation used for trace-level isotope ratio measurements is described. Examples are given of environmental measurements of plutonium and radioiodine at the Hanford Site, a former nuclear material production site. In favorable cases, complete isotopic analyses are obtained on total analytes in the femtogram range, and minor isotopes in the attogram range are measured. The method of direct particle-inlet mass spectrometry (PIMS) for real-time analysis of airborne particles is also described, along with PIMS instrumentation. Examples are given that demonstrate the capability of PIMS to measure uranium isotope ratios in individual particles without isolating them from complex, heterogeneous samples.

scholarly journals Dating minerals by ID-TIMS geochronology at times of in situ analysis: selected case studies from the CPGeo-IGc-USP laboratory

2009 ◽  
Vol 81 (1) ◽  
pp. 73-97 ◽  
Author(s):  
Cláudia R. Passarelli ◽  
Miguel A.S. Basei ◽  
Oswaldo Siga Jr. ◽  
Kei Sato ◽  
Walter M. Sproesser ◽  
...  
Keyword(s):  
Thermal Ionization Mass Spectrometry ◽  
Age Determination ◽  
Isotopic Dilution ◽  
Ionization Mass ◽  
System Behavior ◽  
Rock Types ◽  
Geological Processes ◽  
Thermal Ionization Mass

Since 1964, the Center for Geochronological Research - CPGeo, one of the interdepartmental centers of the Instituto de Geociências (IG) of São Paulo University, has developed studies related to several geological processes associated with different rock types. Thermal Ionization Mass Spectrometry Isotopic Dilution (ID-TIMS) has been the technique widely used in the CPGeo U-Pb Laboratory. It provides reliable and accurate results in age determination of superposed events. However, the open-system behavior such as Pb-loss, the inheritance problem and metamictization processes allow and impel us to a much richer understanding of the power and limitations of U-Pb geochronology and thermochronology. In this article, we present the current methodology used at the CPGeo-IGc-USP U-Pb laboratory, the improvements on ID-TIMS method, and report high-precision U-Pb data from zircon, monazite, epidote, titanite, baddeleyite and rutile from different rock types of several domains of the Brazilian south-southeast area, Argentina and Uruguay.

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