Gülin GENÇOG˘LU Korkmaz, H. Kurt, Kürşad Asan, Maurizio Petrelli, Matthew Leybourne
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引用次数: 0
Abstract
This study investigates the mantle source characteristics of the Quaternary Karapınar Basalts from the southwestern part of the Cappadocia Volcanic Province (CVP) in Central Anatolia using a combination of whole-rock and olivine major-and trace-element geochemistry as well as olivine oxygen isotope composition. Petrographic features and trace element distributions demonstrate that the Karapınar basalts can be classified into two sub-groups as basalt-1 (KB1/ alkaline–calc-alkaline) and basalt-2 (KB2/calc-alkaline). Although these two types of basalts are petrographically, texturally and geochemically different, they exhibit similar “orogenic type” incompatible trace element patterns in MORB-normalized diagrams. KB1 basalts are relatively primitive (e.g., up to 12 wt. % MgO) and calc-alkaline to mildly alkaline (Ne-normative content up to 5 %) in character, whereas KB2 basalts are enclave-bearing, calc-alkaline (hypersthene-normative plus quartz or olivine) ones with the more evolved composition. The most primitive olivine from the KB1 exhibits normal zoning, from core compositions of Fo 89 to rim compositions of Fo 86, with a concomitant decreasing in Ni and increasing MnO and CaO contents. On the contrary, the KB2 olivines show both inverse and normal zoning in terms of CaO and MnO contents. Moreover, the studied olivine phenocrysts have enriched rims and/or growth zones in Li, Zn, Cr, Ti, Sc, and V contents, which indicates a source containing recycled continental crust and/or magma recharging processes. The olivine from the most primitive samples (KB1; MgO > 10 wt. %) has high Zn/Fe, Fe/Mn, Co, Zn, Ni, Ca, and low Mn/Zn, Co/Fe values indicating melt addition from a pyroxenitic source. Calculations based on the olivine chemistry indicate that the most primitive nepheline normative KB1 rocks originated from the melting of mixed pyroxenitic-peridotitic source that shows the average proportion of ~70 % and ~30 %, respectively. The mean δ 18 O values of olivine phenocrysts (+ 6.4 ‰; n = 8) from the Karapınar basaltic rocks are higher than typical mantle olivine (+ 5.1–5.4 ‰) but overlap known OIB-EMII sources (+ 5.4–6.1 ‰). Collected data indicate that the Karapınar basalts are the mixing products of partial melts from mantle peridotite and metasomatic pyroxenite generated by the reaction of the subducted oceanic slab-derived melts with the surrounding peridotite, related to the convergence system of the Eurasian and Afro–Arabian plates.
期刊介绍:
The Journal of Geosciences is an international peer-reviewed journal published by the Czech Geological Society with support from the Czech Geological Survey. It accepts high-quality original research or review papers dealing with all aspects of the nature and origin of igneous and metamorphic rocks. The Journal focuses, mainly but not exclusively, on:
-Process-oriented regional studies of igneous and metamorphic complexes-
Research in structural geology and tectonics-
Igneous and metamorphic petrology-
Mineral chemistry and mineralogy-
Major- and trace-element geochemistry, isotope geochemistry-
Dating igneous activity and metamorphic events-
Experimental petrology and mineralogy-
Theoretical models of igneous and metamorphic processes-
Mineralizing processes and mineral deposits.
All the papers are written in English, even though they may be accompanied by an additional Czech abstract. Each contribution is a subject to peer review by at least two independent reviewers, typically at least one from abroad. The Journal appears 2 to 4 times a year. Formally it is divided in annual volumes, each of them including 4 issues.