Loss of 40Ar(rad) from leucite-bearing basanite at low temperature: Implications on K/Ar dating

K. Balogh, Károly Németh, Tetsumaru Itaya, F. Molnár, Robert Stewart, Ngo Thanh, Hironobu Hyodo, L. Daróczi

Research output: Contribution to journalArticle

6 Citations (Scopus)

Abstract

The Bakony-Balaton Highland Volcanic Field (BBHVF) is located in the central part of Transdanubia, Pannonian Basin, with over 50 alkali basaltic volcanoes. The basanite plug of Hegyestu erupted in the first phase of volcanic activity. K/Ar and Ar/Ar ages were published for the BBHVF. K/Ar and Ar/Ar ages of the leucite-bearing basanite of Hegyestu were conflicting. This is caused by the special Ar retention feature of leucite in this basanite.K/Ar ages measured in the usual way were 25-45% younger, but after HCl treatment of the rock, or after reducing the baking temperature of the argon extraction line from 250°C to 150°C, they became similar to the Ar/Ar ages. All Ar/Ar determinations were performed after HF treatment.HCl treatment dissolved olivine, nepheline, leucite, magnetite and from 1-1 sample analcime or calcite. K dissolution studies from different locations of Hegyestu have shown that K content is mostly ~2%, but it may decrease to ~0.3%. HCl treatment dissolved 28.0-63.5% of the K content. The calculated K concentration for the dissolved part of samples with ~2%K was 4.02-6.42%: showing that leucite is responsible for the low temperature loss of 40Ar(rad).Ar may release at low temperature from very fine-grained mineral, or when the Ar release mechanism changes. A 40Ar(rad) degassing spectrum has been recorded in the 55-295°C range of baking temperature and the data were plotted in the Arrhenius diagram. The diagram shows that a change of the structure in the 145-295°C range caused the loss of 40Ar(rad). On fractions of HCl treated rock 7.56±0.17 Ma isochron K/Ar age has been determined. This is regarded as minimum age of eruption and it is similar to the Ar/Ar isochron age (7.78±0.07 Ma).

Original languageEnglish
Pages (from-to)385-398
Number of pages14
JournalCentral European Journal of Geosciences
Volume2
Issue number3
DOIs
Publication statusPublished - Sep 1 2010

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basanite
leucite
diagram
analcime
nepheline
degassing
argon
dating
loss
rock
magnetite
olivine
calcite
volcano
volcanic eruption
temperature
dissolution
mineral
basin

Keywords

  • Ar retentivity
  • basanite
  • K/Ar dating
  • leucite

ASJC Scopus subject areas

  • Earth and Planetary Sciences(all)

Cite this

Loss of 40Ar(rad) from leucite-bearing basanite at low temperature : Implications on K/Ar dating. / Balogh, K.; Németh, Károly; Itaya, Tetsumaru; Molnár, F.; Stewart, Robert; Thanh, Ngo; Hyodo, Hironobu; Daróczi, L.

In: Central European Journal of Geosciences, Vol. 2, No. 3, 01.09.2010, p. 385-398.

Research output: Contribution to journalArticle

Balogh, K. ; Németh, Károly ; Itaya, Tetsumaru ; Molnár, F. ; Stewart, Robert ; Thanh, Ngo ; Hyodo, Hironobu ; Daróczi, L. / Loss of 40Ar(rad) from leucite-bearing basanite at low temperature : Implications on K/Ar dating. In: Central European Journal of Geosciences. 2010 ; Vol. 2, No. 3. pp. 385-398.
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