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| Titel |
Comparison of Zircon (Ti) Thermometry and Typology of the Cappadocian Ignimbrites |
| VerfasserIn |
Lutfiye Akin, Erkan Aydar, Axel K. Schmitt, H. Evren Çubukçu |
| Konferenz |
EGU General Assembly 2014
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 16 (2014) |
| Datensatznummer |
250086633
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| Publikation (Nr.) |
 EGU/EGU2014-537.pdf |
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| Zusammenfassung |
| The typological study of zircons is a valuable, convenient, reliable and economical tool since
this mineral is highly resistant to alteration and post-magmatic heating. The zircon
morphology yields information on temperature and the chemistry of magma hence can be a
perfect indicator of the origin of material (e.g., crustal, hybrid or mantle). Zircon typology
method has been applied to 8 different ignimbrite successions (Kavak-9.3 Ma, Zelve-9.2 Ma,
Sarimadentepe-8.4 Ma, Sofular-8.2 Ma, Cemilkoy-7.2 Ma, Tahar-6.1 Ma, Gordeles-6.4 Ma,
Kizilkaya-5.2 Ma) of Miocene-Pliocene in Central Anatolian Volcanic Province.
The growth of the pyramidal and prismal faces of zircon crystals, extracted from
pumices of each ignimbrite, has been examined and plot onto typology diagram. The
temperature index (I.T.), which depends on the relative change of the (110) and (100)
prismal faces and alkaline index (I.A.), which depends on the change of the (211)
and (301) pyramidal faces, are determined. Typological Evolution Trend (T.E.T)
which is used for granitoid classification, is drawn based on estimated I.T. and
I.A..
Furthermore, Ti-thermometry of zircons has been applied in order to estimate the
emplacement temperatures of the magmatic rocks. For that purpose, Ti concentrations of
zircons and host rocks are determined. Zircon evolution temperatures and zircon saturation
temperatures are calculated according to Ferry and Watson (2007) and Watson and
Harrison (1983). Obtained zircon geothermometry data have been correlated with the
zircon typology data. Zircon evolution temperature estimated from zircon crystals
are 741oC ( Tmin=-30oC and Tmax=16oC) for Kavak, 749oC (Tmin=-31oC and
Tmax=33oC) for Zelve, 811oC (Tmin=-37oC and Tmax=53 oC) for Sarimadentepe, 807oC
(Tmin=-24oC and Tmax=61oC) for Sofular, 739oC (Tmin=-58oC and Tmax=42oC) for
Cemilkoy, 768oC for Tahar, 806oC (Tmin=-37oC and Tmax=29oC) for Gordeles, 805oC
(Tmin=-35oC and Tmax=69oC) for Gordeles-B, 765oC (Tmin=-25oC and Tmax=48oC) for
Kizilkaya ignimbrites. Temperatures correspond to zircon typology temperature indices
are 714.29oC for Kavak, 740oC for Sarimadentepe, 775oC for Sofular, 730oC for
Cemilkoy, 830oC for Gordeles, 837.5oC for Gordeles-B, 757.14oC for Kizilkaya
ignimbrites.
Consequently, geothermometric assessmentes based on zircon typologies are
comparable with the zircon thermometry studies for some ignimbrite units (Gordeles,
Gordeles-B, Cemilkoy, Kizilkaya). For some ignimbrites, temperatures show differences
between 30-55oC which may be due to physical properties, variation of zircon
crystals in the rock, source of rock and generation processes. According to zircon
topology, Neogene Cappadocian ignimbrites are calc-alkaline hybrid. Since these units
approximate temperature values and alkaline indices, zircon typology studies on
Quaternary rhyolitic domes/lavas which are situated in Central Anatolian Volcanic
Province, indicate low temperature values and high alkaline indices. Therefore, it can be
concluded that from older to younger units, alkalinity increases and it shifts to
peralkaline.
Keywords: Zircon, Ti, thermometry, typology, Cappadocia, ignimbrite |
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