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| Titel |
Volcanic facieses and mineral chemistry of Tertiary alkaline volcanic rocks in the eastern Pontides, NE Turkey |
| VerfasserIn |
Cem Yücel, Mehmet Arslan, Emel Abdioğlu, İrfan Temizel, Gilles Ruffet |
| Konferenz |
EGU General Assembly 2011
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 13 (2011) |
| Datensatznummer |
250045747
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| Zusammenfassung |
| The eastern Pontides (NE Turkey) represent a paleo-island arc formed during subduction of
Tethyan oceanic crust from Jurassic to Cretaceous time. On the basis of lithological and
petrochemical differences of Tertiary volcanics, two volcanic sub-provinces are identified,
a northern alkaline and a southern calcalkaline one (Arslan et al., 1997; Arslan
& Aliyazi ci oÄlu, 2001; Temizel & Arslan, 2008, 2009). Furthermore, Tertiary
volcanics in the north are subdivided as Trabzon Group and Tonya Group (Arslan et al.,
1997).
The studied Tertiary aged volcanics of Trabzon-Giresun areas in the north of the eastern
Pontides were divided, on the basis of the volcanic facieses; as pyroclastics, subvolcanics and
lava flows. Furthermore, volcanic chemo-stratigraphy analyses reveal three suites: (1)
basalt, trachy-basalt and basaltic trachy-andesite (BTB) suite including basaltic
dikes and sills, basaltic lavas, pillow lavas and basaltic breccias, (2) trachyte and
trachy-andesite (TT) suite containing andesitic dikes and domes, trachytic dikes, (3)
basanite-tephrite (BT) suite containing foid bearing brecciated lavas and foid bearing
breccias.
Petrographically, the studied volcanics exhibit evidences of disequilibrium crystallization
such as oscillatory zoning, sieve texture and corrosion in plagioclase phenocrysts, zoning and
inclusions in clinopyroxene phenocrysts. Based on mineral chemistry data as well as
optical observations, the common mineral phases in all suites are clinopyroxene,
plagioclase and Fe-Ti oxides. Clinopyroxenes are named as augite in composition
from Wo39En44Fs20 to Wo44En47Fs9 with Mg number 0.59-0.81 and diopsite in
composition from Wo45En33Fs22 toWo50En37Fs13 with Mg number 0.60-0.91.
Feldspars generally exhibit wide range of compositions from sanidine to albite or
anorthite with weak normal and reverse compositional zoning. Fe-Ti oxides are
generally described as magnetite and titanomagnetite. Olivines with Fo68-92 in
composition are observed only in the BTB suite rocks. Hornblendes which are
classified as pargasite owing to their higher Al(V I) atomic ratio than Fe3+ with Mg
numbers ranging from 0.92 to 0.96 are observed only in the BT suite rocks. The foid
minerals in the BT suite rocks are classified as analcime, possibly derived from
leucite.
Volatile enrichment and silica saturation of primary magma(s) as well as possible
polybaric evolutionary paths of each suite may be responsible for the mineral chemistry and
related chemo-stratigraphy of the Tertiary alkaline volcanics in NE Turkey.
References
Arslan, M. & Aliyazi ci oÄlu, Ä°. (2001) Geochemical and petrochemical characteristics of
the Kale (Gümüşhane) volcanic rocks: Implications for the Eocene evolution of Eastern
Pontide arc volcanism, Northeast Turkey. International Geological Review, 43, 7,
595-610.
Arslan, M., Tüysüz, N., Korkmaz, S. & Kurt, H. (1997) Geochemistry and petrogenesis
of the Eastern Pontide Volcanic Rocks, Northeast Turkey. Chemi der Erde, 57,
157-187.
Temizel, Ä°. & Arslan, M. (2008) Petrology and geochemistry of Tertiary volcanic
rocks from the Ä°kizce (Ordu) area, NE Turkey: implications for the evolution of the
eastern Pontide paleo-magmatic arc. Journal of Asian Earth Sciences, 31(4-6),
439-463.
Temizel, Ä°. & Arslan, M. (2009) Mineral Chemistry and Petrochemistry of
Post-Collisional Tertiary Mafic to Felsic Cogenetic Volcanics in the Ulubey (Ordu)
Area, Eastern Pontides, NE Turkey. Turkish Journal of Earth Science, 18, 29-53. |
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