Supplementary materials for PhD thesis - "Understanding ⁴⁰Ar/³⁹Ar age variations in basaltic lavas"
<p dir="ltr">This dataset comprises the files contained on a CD-ROM which was attached to the thesis when it was submitted in 2014. It was uploaded to ORDO in 2025 for preservation purposes. For more information, please refer to the thesis “Understanding ⁴⁰Ar/³⁹Ar age variations in...
محفوظ في:
| المؤلف الرئيسي: | |
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| منشور في: |
2025
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| الموضوعات: | |
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إضافة وسم
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| الملخص: | <p dir="ltr">This dataset comprises the files contained on a CD-ROM which was attached to the thesis when it was submitted in 2014. It was uploaded to ORDO in 2025 for preservation purposes. For more information, please refer to the thesis “Understanding ⁴⁰Ar/³⁹Ar age variations in basaltic lavas” via ORO. </p><h2>Abstract</h2><p dir="ltr">Previous radiometric studies of the Faroe Islands Basalt Group (FIBG) have identified 2 pulses of magmatism: ca. 62 Ma and ca. 55 Ma. Biostratigraphy studies on inter-basalt sedimentary horizons have only identified palynofloral assemblages indicative of 55 Ma. The <sup>40</sup>Ar/<sup>39</sup>Ar technique is the main high-precision dating technique applicable to basaltic rocks, but intra-lava age variations of ±10% have been observed. Being able to model the behaviour of K and Ar, as the elements essential for the technique, is crucial for understanding the causes of such highly variable <sup>40</sup>Ar/<sup>39</sup>Ar ages and consequently improving the likelihood of producing reliable and accurate <sup>40</sup>Ar/<sup>39</sup>Ar ages from basaltic rocks. Using a combination of field observations, geo-chemical analyses and alteration indices, this study unravels the processes responsible for K- and Ar- disturbance in subaerially erupted basaltic lavas which inevitably result in disturbed and therefore, unreliable <sup>40</sup>Ar/<sup>39</sup>Ar ages.<br><br><sup>40</sup>Ar/<sup>39</sup>Ar ages for 48 samples from 5 basaltic lavas erupted as part of the syn-breakup succession of the Faroe Islands are presented. Intra-lava variations of 10-20 Ma are observed. A criteria for assessing the reliability of an <sup>40</sup>Ar/<sup>39</sup>Ar age is proposed to evaluate each <sup>40</sup>Ar/<sup>39</sup>Ar age, which has decreased the inter-lava <sup>40</sup>Ar/<sup>39</sup>Ar age variability. However, even after the evaluation of <sup>40</sup>Ar/<sup>39</sup>Ar age reliability, significant inter-lava age variations are still observed and which have been related to inter-lava variations in geochemistry, loss on ignition values and other alteration indices. Consequently, a methodology for sample selection is presented in order to obtain more reliable and consistent <sup>40</sup>Ar/<sup>39</sup>Ar ages in basaltic provinces. The application of the criteria to this dataset dramatically reduced inter-lava <sup>40</sup>Ar/<sup>39</sup>Ar age variations to an age spread which is consistent with <sup>40</sup>Ar/<sup>39</sup>Ar age precision, suggesting that suitable sample collection is imperative to achieving reliable and accurate <sup>40</sup>Ar/<sup>39</sup>Ar ages.</p> |
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