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Geochemical and isotopic constraints on petrogenesis of the beypazarı granitoid, nw ankara,.
| Content Provider | CiteSeerX |
|---|---|
| Author | Helvaci, Cahi̇t Satir, Muharrem Öztürk, Yeşi̇m Yücel |
| Abstract | units, on the basis of petrography and geochemical composition; these are granodiorite and diorite. Th e granitoid is subalkaline, belonging to the high-K calc-alkaline I-type granite series, which have relatively low initial 87Sr/86Sr ratios (0.7053–0.7070). All these characteristics, combined with major, trace element geochemical data as well as mineralogical and textural evidence, reveal that the Beypazarı granitoid formed in a volcanic arc setting and was derived from a subduction-modified and metasomatized mantle-sourced magma, with its crustal and mantle components contaminated by interaction with the upper crust. Th e rocks have εNd(75Ma) values ranging from –5.5 to –2.0. Th ese characteristics also indicate that a crustal component played a very important role in their petrogenesis. Th e moderately evolved granitoid stock cropping out near Beypazarı, Ankara, was studied using the oxygen and hydrogen isotope geochemistry of whole rock, quartz and silicate minerals. δ18O values of the Beypazarı granitoid are consistently higher than those of normal I-type granites. Th is is consistent with field observations, petrographic and whole-rock geochemical data, which indicate that the Beypazarı granitoid has significant crustal components. However, the δ18O relationships among minerals indicate a very minor infl uence of hydrothermal processes in sub-solidus conditions. Th e oxygen isotope systematics of the Beypazarı granitoid samples results from the activity of high-δ18O fl uids (magmatic water), with no major involvement of low-δ18O fl uids (meteoric water) evident. Th e analysed four quartz-feldspar pairs have values of Δqtz-fsp between 0.5–2.0, which are consistent with equilibrium under close-system |
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| Access Restriction | Open |
| Content Type | Text |
