Calibration of GA1550 biotite standard for K/Ar and 40Ar/39Ar dating

McDougall, Ian; Wellman, Peter

doi:10.1016/j.chemgeo.2010.10.001

Cited by 74 publications

(75 citation statements)

References 26 publications

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“…Ages were calculated using decay constants established by Steiger and Jäger (1977) at a 95% confidence level. The GA1550 (MD2) biotite standard, with a 98.5±0.5 Ma recommended age (McDougall & Wellman, 2011), was analyzed simultaneously; two aliquots averaged 99.7 ± 0.5 Ma (age-probability spectrum, MSWD = 1.65, P = 0.04, N = 19).…”

mentioning

confidence: 99%

Melanite-bearing nepheline syenite fragments and 40Ar/39Ar age of phlogopite megacrysts in conduit breccia from the Poços de Caldas Alkaline Massif (MG/SP), and implications

Vlach

Ulbrich

et al. 2018

Braz. J. Geol.

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mentioning

confidence: 99%

Melanite-bearing nepheline syenite fragments and 40Ar/39Ar age of phlogopite megacrysts in conduit breccia from the Poços de Caldas Alkaline Massif (MG/SP), and implications

Vlach

Ulbrich

et al. 2018

Braz. J. Geol.

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“…J-values were calculated assuming an age of 98.79 ±0.96 Ma (Renne et al, 1998). We note the existence of updated ages for GA1550 (Spell and McDougall, 2003;Schwarz and Trieloff, 2007;McDougall and Wellman, 2011), but as this study is investigating the presence or lack of variation within a single sample, calculation of the precise absolute age is unimportant. 40 Ar/ 39 Ar UV-laser ablation analysis was carried out on all fragments.…”

Section: Samples and Methodologymentioning

confidence: 99%

Disturbance to the 40Ar/39Ar system in feldspars by electron and ion beam irradiation

et al. 2013

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The extent to which intracrystalline microtextures influence the diffusion of radiogenic Ar within alkali feldspars from slowly cooled igneous rocks is a long standing question in thermochronology. By combining highresolution electron microscopy with in-situ UV-laser ablation microprobe 40 Ar/ 39 Ar analysis the interplay of microtextures with isotope ages can be studied directly, enabling some of the assumptions underlying 40 Ar/ 39 Ar thermochronological techniques to be tested and allowing deduction of thermochronological and geological histories. However, there are numerous potential mechanisms by which a sample can be damaged and its Ar-isotope system disturbed by such microscopy techniques. To test this hypothesis, perthitic alkali feldspars from the 270-280 Ma Dartmoor Granite, UK, and gem-quality orthoclase from Itrongay, Madagascar (~470 Ma) were polished with colloidal silica or etched with hydrofluoric acid and irradiated with electrons and Ga + ions. The accelerating voltages and currents used were typical of those for electron beam imaging by scanning electron microscopy, X-ray analysis and mapping by electron probe, and for extraction of foils using the focused ion beam technique. No disturbance to the Ar-isotope system was observed for Ga + ion irradiation, or for low-resolution SEM imaging, but electron irradiation of small areas for long durations, as occurs during extended high-magnification SEM imaging, was found to disturb the Ar-isotope system over hundreds of micrometre sized areas by the addition of K and atmospheric Ar, producing anomalously young apparent 40 Ar/ 39 Ar ages. The best explanation for this age disturbance is electromigration of K and implantation of atmospheric Ar during sample charging.

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“…Recoil model ages are reported for the discordant results following Fleck et al (2014). All results have been recalculated to current standards relative to a first-principles GA1550 biotite age of 98.79 ± 0.96 Ma (McDougall and Wellman, 2011). This yields a standard age of 28.345 Ma for Taylor Creek sanidine (Fleck and Calvert, 2016).…”

Section: Geochronologymentioning

confidence: 99%

Pleistocene volcanism and shifting shorelines at Lake Tahoe, California

et al. 2018

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In the northwestern Lake Tahoe Basin, Pleistocene basaltic and trachy andesitic lavas form a small volcanic field comprising ~1 km 3 of lava that erupted from seven vents. Most of these lavas erupted subaerially and produced lava flows. However, where they flowed into an early Lake Tahoe ( ProtoTahoe), they produced deltas consisting of hydrovolcanic breccias as well as pillow lavas draped downslope, pillow breccias, hyaloclastites, and mixtures of lava and wet sediments.

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Calibration of GA1550 biotite standard for K/Ar and 40Ar/39Ar dating

Cited by 74 publications

References 26 publications

Melanite-bearing nepheline syenite fragments and 40Ar/39Ar age of phlogopite megacrysts in conduit breccia from the Poços de Caldas Alkaline Massif (MG/SP), and implications

Melanite-bearing nepheline syenite fragments and 40Ar/39Ar age of phlogopite megacrysts in conduit breccia from the Poços de Caldas Alkaline Massif (MG/SP), and implications

Disturbance to the 40Ar/39Ar system in feldspars by electron and ion beam irradiation

Pleistocene volcanism and shifting shorelines at Lake Tahoe, California

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