scholarly journals A Sample Characterization Toolkit for Carbonate U-Pb Geochronology

2020 ◽  
Author(s):  
E. Troy Rasbury ◽  
Theodore M. Present ◽  
Paul Northrup ◽  
Ryan V. Tappero ◽  
Antonio Lanzirotti ◽  
...  
Keyword(s):  
Laser Ablation ◽  
Reference Material ◽  
Best Practices ◽  
Sr Isotope ◽  
Turkana Basin ◽  
Spatially Resolved ◽  
Dolomite Sample ◽  
Three Samples ◽  
Sample Characterization ◽  
Barstow Formation

Abstract. Laser ablation U-Pb analyses of carbonate (LAcarb) samples has greatly expanded the potential for U-Pb dating to a variety of carbonate producing settings. Carbonates that were previously considered impossible to date using isotope dilution methods may preserve domains that are favorably interrogated when using spatially resolved laser ablation geochronology techniques. Work is ongoing to identify reference materials and to consider best practices for LAcarb. In this study we apply standard and emerging characterization toolsets on three natural samples with the dual goal of enhancing the study of carbonates and in establishing a new set of precisely characterized natural standards for LAcarb studies. We start with the existing carbonate reference material WC-1 from the Permian Reef Complex of Texas, building on the published description to offer a deeper look at U and fluids. We consider a tufa sample from the Miocene Barstow Formation of the Mojave Block, California, as a possible secondary calcite reference material due to its well-behaved U/Pb systematics. There are currently no natural dolomite standards. We present an unusual dolomite sample with very well-behaved U-Pb systematics from the Miocene of the Turkana Basin of Kenya as a possible dolomite reference material for LAcarb dating. In addition to using XRF mapping and spectroscopy to better understand U in these natural samples, we have analyzed multiple aliquots of each of them for 87Sr/86Sr. The Sr isotope compositions are reasonably homogeneous in all three samples, so that these could be used as Sr isotope standards as well. This combination could streamline split stream analyses of 87Sr/86Sr and U/Pb geochronology.

scholarly journals Tools for uranium characterization in carbonate samples: case studies of natural U–Pb geochronology reference materials

Geochronology ◽  
2021 ◽  
Vol 3 (1) ◽  
pp. 103-122
Author(s):  
E. Troy Rasbury ◽  
Theodore M. Present ◽  
Paul Northrup ◽  
Ryan V. Tappero ◽  
Antonio Lanzirotti ◽  
...  
Keyword(s):  
Laser Ablation ◽  
Reference Material ◽  
Reference Materials ◽  
Ionization Mass ◽  
Sr Isotope ◽  
Turkana Basin ◽  
Spatially Resolved ◽  
Dolomite Sample ◽  
Three Samples ◽  
Homogeneous Regions

Abstract. Laser ablation U–Pb analyses of carbonate (LAcarb) samples has greatly expanded the potential for U–Pb dating to a variety of carbonate-producing settings. Carbonates that were previously considered impossible to date using isotope dilution methods may preserve radiogenic domains that can be dated using spatially resolved laser ablation geochronology techniques. Work is ongoing to identify reference materials and to consider best practices for LAcarb. In this study we apply standard and emerging characterization tool sets on three natural samples with the dual goal of enhancing the study of carbonates and establishing a new set of well-characterized natural reference materials for LAcarb studies. We start with the existing carbonate reference material WC-1 from the Permian Reef Complex of Texas, building on the published description to offer a deeper look at U and associated trace elements. We consider a tufa sample from the Miocene Barstow Formation of the Mojave Block, California, as a possible secondary calcite reference material due to its well-behaved U–Pb systematics. There are currently no natural dolomite standards. We present an unusual dolomite sample with very well-behaved U–Pb systematics from the Miocene of the Turkana Basin of Kenya as a possible dolomite reference material for LAcarb dating. In addition to using X-ray fluorescence (XRF) mapping and spectroscopy to better understand U in these natural samples, we have analyzed multiple aliquots of each of them for 87Sr/86Sr by thermal ionization mass spectrometry (TIMS). The Sr isotope compositions are analytically homogeneous within petrographically homogeneous regions of all three samples, and thus these materials could be used as Sr isotope standards as well. While not part of the current contribution, this combination could streamline simultaneous LA analyses of 87Sr/86Sr and U–Pb geochronology.

Accuracy of laser-ablation (LA)-MC-ICPMS Sr isotope analysis of (bio)apatite – a problem reassessed

2016 ◽  
Vol 31 (1) ◽  
pp. 259-269 ◽  
Author(s):  
Wolfgang Müller ◽  
Robert Anczkiewicz
Keyword(s):  
Laser Ablation ◽  
Isotope Analysis ◽  
Sr Isotope ◽  
Plasma Laser ◽  
Interference Correction

Accurate in situ Sr isotope analysis of (bio)apatite via ‘robust-plasma’ laser-ablation MC-ICPMS with negligible 40Ca31P16O and reliable 87Rb interference correction.

785 nm femtosecond laser ablation for improved precision and reduction of interferences in Sr isotope analyses using MC-ICP-MS

2011 ◽  
Vol 26 (2) ◽  
pp. 341-351 ◽  
Author(s):  
Zhaoping Yang ◽  
Brian J. Fryer ◽  
Henry P. Longerich ◽  
Joel E. Gagnon ◽  
Iain M. Samson
Keyword(s):  
Laser Ablation ◽  
Femtosecond Laser ◽  
Femtosecond Laser Ablation ◽  
Sr Isotope ◽  
Icp Ms ◽  
Isotope Analyses

scholarly journals Assessment of Five Monazite Reference Materials for U-Th/Pb Dating Using Laser-Ablation ICP-MS

Geosciences ◽  
2019 ◽  
Vol 9 (9) ◽  
pp. 391
Author(s):  
Richter ◽  
Nebel-Jacobsen ◽  
Nebel ◽  
Zack ◽  
Mertz-Kraus ◽  
...  
Keyword(s):  
Laser Ablation ◽  
Reference Material ◽  
Reference Materials ◽  
Operational Conditions ◽  
Inductively Coupled ◽  
Phosphate Mineral ◽  
Icp Ms ◽  
Wide Range ◽  
Absolute Age ◽  
Key Aspects

Monazite is a common accessory phosphate mineral that occurs under a wide range of pressure and temperature conditions in sedimentary, metamorphic and igneous rocks. Monazite contains high amounts of Th and U, rendering single monazite grains suitable for in-situ U-Th/Pb dating using laser ablation inductively-coupled mass spectrometry (LA-ICP-MS). Two key aspects of monazite dating that are critical for accurate age data with maximum precision are (i) optimized instrumental conditions to minimize analytical scatter and (ii) a well characterized reference material to ensure the accuracy of the obtained aged. Here, we analyzed five monazite reference materials (USGS 44069, 94-222, MAdel, Moacir and Thompson Mine Monazite) for their U-Th/Pb ages using LA-ICP-MS technique and applied a variety of laser spot diameters and repetition rates to find the best operational conditions to achieve accurate age data while maintaining maximum precision. We find that a spot diameter of 10 µm and a repetition rate of 10 Hz yield the most precise ages with a deviation of ±2.0% from their respective high-precision U/Pb literature age data. Ages were reproduced in three different LA-ICP-MS laboratories using these parameters. Each reference material was tested for its suitability as a matrix-matched age reference material. For this, a rotating, iterative approach was adopted in which one reference monazite was used as calibration reference material against all others, which were treated as unknowns. The results reveal that USGS 44069, 94-222, Thompson Mine Monazite and MAdel all agree with their respective calculated ages and ID-TIMS reference ages and thus are suggested as suitable calibration reference materials. Moacir, however, appears slightly older than previously suggested (up to 4%), thus, caution is advised here when using Moacir as reference material for U-Th/Pb LA-ICP-MS dating in the absence of further absolute age calibration.

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