Search results for: Amy M. Gaffney

Items from 1 to 18 out of 18 results

article

Evaluating uranium radiochronometry by single-collector mass spectrometry for nuclear forensics: a multi-instrument investigation

Kerri C. Treinen, Kyle M. Samperton, Rachel E. Lindvall, Josh B. Wimpenny, more

Journal of Radioanalytical and Nuclear Chemistry > 2019 > 322 > 3 > 1627-1640

Radiochronometric data, a key signature in evaluating the provenance and process history of nuclear material out of regulatory control, are conventionally acquired via multi-collector mass spectrometry. Here we explore the potential of age-dating by single-collector mass spectrometry. To evaluate model age accuracy/precision across different instrument designs, we performed ²³⁰Th–²³⁴U and ²³¹Pa–²³⁵...

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Improved protactinium spike calibration method applied to ²³¹Pa–²³⁵U age-dating of certified reference materials for nuclear forensics

Kerri C. Treinen, Amy M. Gaffney, John M. Rolison, Kyle M. Samperton, more

Journal of Radioanalytical and Nuclear Chemistry > 2018 > 318 > 1 > 209-219

The application of multiple radiochronometers in a forensic investigation of bulk uranium provides increased confidence for interpreting age-dating results. We have developed a streamlined method for the purification of Pa and Th from bulk uranium and have applied this method in analyzing uranium certified reference materials (CRMs) IRMM-1000 and CRM U100, using the ²³¹Pa–²³⁵U and ²³⁰Th–²³⁴U radiochronometers...

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A case study in plutonium radiochronometry using multiple isotope systems

Amy M. Gaffney, Josh B. N. Wimpenny, Tashi Parsons-Davis, Ross W. Williams, more

Journal of Radioanalytical and Nuclear Chemistry > 2018 > 318 > 1 > 287-295

Radiochronometry analyses of two Pu metals were performed using the ²³⁷Np–²⁴¹Am–²⁴¹Pu, ²³⁴U–²³⁸Pu, ²³⁵U–²³⁹Pu, and ²³⁶U–²⁴⁰Pu decay series. For one sample, all radiochronometers yield concordant model dates in 1959–1960, indicating that the aqueous processing method used to purify Pu effectively removed U, Am and Np decay products from the bulk Pu. The second sample yields discordant model dates that...

article

New determination of the ²²⁹Th half-life

Richard M. Essex, Jacqueline L. Mann, Ronald Collé, Lizbeth Laureano-Perez, more

Journal of Radioanalytical and Nuclear Chemistry > 2018 > 318 > 1 > 515-525

A new determination of the ²²⁹Th half-life was made based on measurements of the ²²⁹Th massic activity of a high-purity solution for which the ²²⁹Th molality had previously been measured. The ²²⁹Th massic activity was measured by direct comparison with SRM 4328C using 4παβ liquid scintillation counting, NaI counting, and standard addition liquid scintillation counting. The massic activity was confirmed...

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The application of radiochronometry during the 4th collaborative materials exercise of the nuclear forensics international technical working group (ITWG)

Michael J. Kristo, Ross Williams, Amy M. Gaffney, Theresa M. Kayzar-Boggs, more

Journal of Radioanalytical and Nuclear Chemistry > 2018 > 315 > 2 > 425-434

In a recent international exercise, 10 international nuclear forensics laboratories successfully performed radiochronometry on three low enriched uranium oxide samples, providing 12 analytical results using three different parent-daughter pairs serving as independent chronometers. The vast majority of the results were consistent with one another and consistent with the known processing history of...

article

Application of the ²²⁶Ra–²³⁰Th–²³⁴U and ²²⁷Ac–²³¹Pa–²³⁵U radiochronometers to uranium certified reference materials

John M. Rolison, Kerri C. Treinen, Kelly C. McHugh, Amy M. Gaffney, more

Journal of Radioanalytical and Nuclear Chemistry > 2017 > 314 > 3 > 2459-2467

Uranium certified reference materials (CRM) issued by New Brunswick Laboratory were subjected to dating using four independent uranium-series radiochronometers. In all cases, there was acceptable agreement between the model ages calculated using the ²³¹Pa–²³⁵U, ²³⁰Th–²³⁴U, ²²⁷Ac–²³⁵U or ²²⁶Ra–²³⁴U radiochronometers and either the certified ²³⁰Th–²³⁴U model date (CRM 125-A and CRM U630), or the known...

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Chronologic implications for slow cooling of troctolite 76535 and temporal relationships between the Mg-suite and the ferroan anorthosite suite

Lars E. Borg, James N. Connelly, William S. Cassata, Amy M. Gaffney, more

Geochimica et Cosmochimica Acta > 2017 > 201 > C > 377-391

Ages have been obtained using the ⁸⁷Rb–⁸⁷Sr, ¹⁴⁷Sm–¹⁴³Nd, and ¹⁴⁶Sm–¹⁴²Nd isotopic systems for one of the most slowly cooled lunar rocks, Apollo 17Mg-suite troctolite 76535. The ¹⁴⁷Sm–¹⁴³Nd, ¹⁴⁶Sm–¹⁴²Nd, and Rb–Sr ages derived from plagioclase, olivine, and pyroxene mineral isochrons yield concordant ages of 4307±11Ma, 4299⁺²⁹/₋₃₅ Ma, and 4279±52Ma, respectively. These ages are slightly younger than...

article

Round-robin ²³⁰Th–²³⁴U age dating of bulk uranium for nuclear forensics

Amy M. Gaffney, Amélie Hubert, William S. Kinman, Masaaki Magara, more

Journal of Radioanalytical and Nuclear Chemistry > 2016 > 307 > 3 > 2055-2060

In an inter-laboratory measurement comparison study, four laboratories determined ²³⁰Th–²³⁴U model ages of uranium certified reference material NBL U050 using isotope dilution mass spectrometry. The model dates determined by the participating laboratories range from 9 March 1956 to 19 October 1957, and are indistinguishable given the associated measurement uncertainties. These model ages are concordant...

article

A review of lunar chronology revealing a preponderance of 4.34–4.37 Ga ages

Lars E. Borg, Amy M. Gaffney, Charles K. Shearer

Meteoritics & Planetary Science > 50 > 4 > 715 - 732

Data obtained from Sm‐Nd and Rb‐Sr isotopic measurements of lunar highlands’ samples are renormalized to common standard values and then used to define ages with a common isochron regression algorithm. The reliability of these ages is evaluated using five criteria that include whether: (1) the ages are defined by multiple isotopic systems, (2) the data demonstrate limited scatter outside uncertainty,...

article

Investigating uranium distribution in surface sediments and waters: a case study of contamination from the Juniper Uranium Mine, Stanislaus National Forest, CA

Theresa M. Kayzar, Adam C. Villa, Megan L. Lobaugh, Amy M. Gaffney, more

Journal of Environmental Radioactivity > 2014 > 136 > Complete > 85-97

The uranium concentrations and isotopic compositions of waters, sediment leachates and sediments from Red Rock Creek in the Stanislaus National Forest of California were measured to investigate the transport of uranium from a point source (the Juniper Uranium Mine) to a natural surface stream environment. The ( ²³⁴ U)/( ²³⁸ U) composition of Red Rock Creek is altered downstream of...

article

A young solidification age for the lunar magma ocean

Amy M. Gaffney, Lars E. Borg

Geochimica et Cosmochimica Acta > 2014 > 140 > C > 227-240

The time at which the lunar magma ocean solidified can be determined from the Lu–Hf isotope systematics of lunar rocks derived from magma sources that formed during crystallization of the lunar magma ocean. The final magma ocean crystallization product, termed urKREEP, is enriched in incompatible elements including K, REE and P. We have determined the initial Hf isotopic compositions of four samples,...

article

The origin of young mare basalts inferred from lunar meteorites Northwest Africa 4734, 032, and LaPaz Icefield 02205

Stephen M. Elardo, Charles K. Shearer, Amy L. Fagan, Lars E. Borg, more

Meteoritics & Planetary Science > 49 > 2 > 261 - 291

Northwest Africa (NWA) 4734 is an unbrecciated basaltic lunar meteorite that is nearly identical in chemical composition to basaltic lunar meteorites NWA 032 and LaPaz Icefield (LAP) 02205. We have conducted a geochemical, petrologic, mineralogic, and Sm‐Nd, Rb‐Sr, and Ar‐Ar isotopic study of these meteorites to constrain their petrologic relationships and the origin of young mare basalts. NWA 4734...

article

Disturbance of isotope systematics during experimental shock and thermal metamorphism of a lunar basalt with implications for Martian meteorite chronology

Amy M. GAFFNEY, Lars E. BORG, Yemane ASMEROM, Charles K. SHEARER, more

Meteoritics & Planetary Science > 46 > 1 > 35 - 52

Abstract– To better determine the effects of impact‐related processes on radiometric chronometers in meteorites, we undertook an isotopic study of experimentally shocked and heated samples of lunar basalt 10017. Shock experiments at 55 GPa were completed on one subsample, and a second subsample was heated in an evacuated quartz tube at 1000 °C for 170 h. A third subsample was maintained as a control...

article

Mechanisms for incompatible-element enrichment on the Moon deduced from the lunar basaltic meteorite Northwest Africa 032

Lars E. Borg, Amy M. Gaffney, Charles K. Shearer, Donald J. DePaolo, more

Geochimica et Cosmochimica Acta > 2009 > 73 > 13 > 3963-3980

The lunar meteorite Northwest Africa (NWA) 032 is a low-Ti basalt that has incompatible-element abundances and Th/Sm ratios characteristic of the involvement of late stage magma ocean crystallization products (urKREEP) in its petrogenesis. This sample is very fine-grained and contains terrestrial weather products. A progressive leaching procedure was therefore developed and applied to magnetic separates...

article

Uranium–lead isotope systematics of Mars inferred from the basaltic shergottite QUE 94201

Amy M. Gaffney, Lars E. Borg, James N. Connelly

Geochimica et Cosmochimica Acta > 2007 > 71 > 20 > 5016-5031

Uranium–lead ratios (commonly represented as ²³⁸ U/ ²⁰⁴ Pb=μ) calculated for the sources of martian basalts preserve a record of petrogenetic processes that were active during early planetary differentiation and formation of martian geochemical reservoirs. To better define the range of μ values represented by the source regions of martian basalts, we completed U–Pb elemental and isotopic...

article

The origin of geochemical diversity of lunar mantle sources inferred from the combined U–Pb, Rb–Sr, and Sm–Nd isotope systematics of mare basalt 10017

Amy M. Gaffney, Lars E. Borg, Yemane Asmerom

Geochimica et Cosmochimica Acta > 2007 > 71 > 14 > 3656-3671

The results of our combined U–Pb, Rb–Sr, and Sm–Nd isotope study of mare basalt 10017 contribute to the understanding of the petrogenetic processes involved in the origin of geochemical diversity in lunar mare basalt sources, as well as the U–Pb isotope systematics of the Moon. The Rb–Sr, Sm–Nd, and ²³⁸ U– ²⁰⁶ Pb isotope systems yield concordant crystallization ages of 3.633±0.057Ga,...

article

Constraints on source-forming processes of West Greenland kimberlites inferred from Hf–Nd isotope systematics

Amy M. Gaffney, Janne Blichert-Toft, Bruce K. Nelson, Martin Bizzarro, more

Geochimica et Cosmochimica Acta > 2007 > 71 > 11 > 2820-2836

Kimberlites from West Greenland have Hf–Nd isotope as well as major and trace element compositions that are similar to other Group I kimberlites, but that are distinctive in the spectrum of magmas sampled at Earth’s surface. The West Greenland kimberlites have ε _Ndi that ranges from +1.6 to +3.1 and ε _Hfi that ranges from −4.3 to +4.9. The samples exhibit ubiquitous negative Δε ...

article

Oxygen–osmium isotope systematics of West Maui lavas: A record of shallow-level magmatic processes

Amy M. Gaffney, Bruce K. Nelson, Laurie Reisberg, John Eiler

Earth and Planetary Science Letters > 2005 > 239 > 1-2 > 122-139

New δ ¹⁸ O and ¹⁸⁷ Os/ ¹⁸⁸ Os data from late shield-building stage lavas from West Maui volcano, Hawai'i, indicate that a range of distinct shallow-level processes can affect compositions of plume-generated ocean island magmas. The relative ages of the samples studied were determined either on the basis of field relationships, or from collection depth in a water well. The stratigraphically...

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Keywords

RADIOCHRONOMETRY (5)
NUCLEAR FORENSICS (4)
AGE-DATING (3)
PROTACTINIUM (2)
THORIUM (2)
230TH–234U AGE DATING (1)
226RA (1)
227AC (1)
229TH (1)
ACTINIDE DECAY SERIES (1)
AGE (1)
ALPHA SPECTROMETRY (1)
ASSIMILATION (1)
GAMMA SPECTROMETRY (1)
GEOCHEMISTRY (1)
HALF-LIFE (1)
HAWAII (1)
HIGHLANDS (1)
INDUCTIVELY COUPLED PLASMA MASS SPECTROMETRY (1)
ISOTOPE DILUTION ALPHA SPECTROMETRY (1)
LIQUID SCINTILLATION COUNTING (1)
LUNAR (1)
MASS SPECTROMETRY (1)
MC-ICP-MS (1)
MULTI-COLLECTOR MASS SPECTROMETRY (1)
NAI COUNTING (1)
OCEANIC LITHOSPHERE (1)
OSMIUM (1)
OXYGEN (1)
PLUTONIUM (1)
SEDIMENT CONTAMINATION (1)
SINGLE-COLLECTOR MASS SPECTROMETRY (1)
SM-ND ISOTOPES (1)
THERMAL IONIZATION MASS SPECTROMETRY (1)
U-SERIES RADIOCHRONOMETRY (1)
URANIUM (1)
URANIUM ISOTOPES (1)
URANIUM MINING (1)
URANIUM OXIDE (1)
WATER CHEMISTRY (1)
WEST MAUI (1)
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Elsevier (8)
Springer (7)
Wiley (3)

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Search results for: Amy M. Gaffney

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