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40Ar/39Ar dating of Quaternary feldspar: Examples from the Taupo Volcanic Zone, New Zealand

Geology

By:
, , , , and
https://doi.org/10.1130/0091-7613(1992)020<0531:AADOQF>2.3.CO;2

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Abstract

Using a continuous laser and resistance furnace, we have measured ages on Quaternary plagioclase with an absolute precision of about ±30 ka and on Quaternary sanidine with a relative precision of better than 1%. Such precision was achieved by using low-temperature heating steps to remove much of the nonradiogenic argon contamination. Plagioclase is one of the most common mineral phases in volcanic rocks; thus, these procedures will be widely applicable to many problems for which precise radiometric age control has not been available. We studied plagioclase and plagioclase-sanidine concentrates from the oldest and the three largest silicic ash-flow deposits of the Taupo Volcanic Zone, New Zealand, one of the world's largest and most active volcanic systems. The results are in close agreement with new magnetostratigraphic data, suggest that existing fission-track age determinations significantly underestimate the age of older units, and shift the inception of Taupo Volcanic Zone volcanism back to at least 1600 ka. The improved precision has permitted the first correlations between proximal and distal units; previous correlations with deep-sea ash flows in the western Pacific require major revision.

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Additional publication details

Publication type:
Article
Publication Subtype:
Journal Article
Title:
40Ar/39Ar dating of Quaternary feldspar: Examples from the Taupo Volcanic Zone, New Zealand
Series title:
Geology
DOI:
10.1130/0091-7613(1992)020<0531:AADOQF>2.3.CO;2
Volume:
20
Issue:
6
Year Published:
1992
Language:
English
Publisher:
Geological Society of America
Description:
4 p.
First page:
531
Last page:
534
Country:
New Zealand