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Koppers, A.A.P., Staudigel, H. and Wijbrans, J.R. (2000). Dating crystalline groundmass separates of altered Cretaceous seamount basalts by the Ar-40/Ar-39 incremental heating technique. Chemical Geology 166(1-2): 139-158. doi: 10.1016/S0009-2541(99)00188-6. |
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Alteration of submarine basalts compromises geochronology using conventional K/Ar and Ar-40/Ar-39 techniques. To help overcome these problems, we re-evaluated the potential of groundmass dating techniques. Incremental heating on acid-leached groundmass samples, following an overnight bakeout at 200 degrees C and using high-resolution heating schedules, eliminated most of the low temperature alteration effects in the submarine basalts studied. More than 75% of the groundmass analyses (n = 32) display accurate age plateaus consisting of 30-70% of the total amount of Ar-39(kappa) released. More than 50% of the analyses have plateau ages concordant with their total fusion ages implying minor or proportional loss of radiogenic Ar-40* and Ar-39(kappa). Overall, we could show a high degree of coherence between ages of groundmass separates and comagmatic phenocrysts. This suggests that the dating of aphyric basalts, which previously has proven problematic, can be accomplished with increasing confidence as well. Adding these rock types to the list of datable submarine basalts significantly enhances our ability to understand the eruptive history of linear submarine volcanic chains. (C) 2000 Elsevier Science B.V. All rights reserved. |
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| BACKGROUND DATA FILES |
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Abstract |
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Criteria for 40Ar/39Ar Experiments |
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Groundmass Geochemistry |
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Table 1 |
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Table 2 |
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Table 3 |
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Geological Setting & Sampling |
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Mineral Separation |
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Incremental Heating Technique |
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Chemical Analyses |
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Keywords
ar-40/ar-39 geochronology, seamount basalts, groundmass, incremental heating, seawater alteration, recoil, squared weighted deviation, statistical distribution, age, pacific, argon, geochronology, isochrons, volcanism, islands, samples |
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Publisher
Elsevier Science
P.O. Box 211
1000 AE Amsterdam
The Netherlands
(+31) 20 485 3757
(+31) 20 485 3432
nlinfo-f@elsevier.com |
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