The role of peridotite and pyroxenite melts in the origin of the Karapınar basalts, Cappadocia Volcanic Province, Central Anatolia

IF 1.1 4区 地球科学 Q3 GEOCHEMISTRY & GEOPHYSICS
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.
橄榄岩和辉石岩熔体在安纳托利亚中部卡帕多西亚火山省Karapınar玄武岩起源中的作用
本研究采用全岩和橄榄石主元素和微量元素地球化学以及橄榄石氧同位素组成相结合的方法,研究了安纳托利亚中部卡帕多西亚火山省西南部第四纪卡拉普纳尔玄武岩的地幔源特征。岩石学特征和微量元素分布表明,Karapınar玄武岩可分为玄武岩-1(KB1/碱性-钙碱性)和玄武岩-2(KB2/钙碱性)两个亚组。尽管这两种类型的玄武岩在岩石、结构和地球化学上不同,但在MORB归一化图中,它们表现出类似的“造山型”不相容微量元素模式。KB1玄武岩是相对原始的(例如,高达12wt.%MgO)和钙碱性到弱碱性(Ne标准含量高达5%),而KB2玄武岩是含包体的钙碱性(紫苏标准加石英或橄榄石)玄武岩,成分更为演化。KB1中最原始的橄榄石表现出正常的分带,从Fo 89的核心成分到Fo 86的边缘成分,伴随着Ni的减少和MnO和CaO含量的增加。相反,KB2橄榄石在CaO和MnO含量方面显示出反分区和正分区。此外,所研究的橄榄石斑晶在Li、Zn、Cr、Ti、Sc和V含量方面具有富集的边缘和/或生长带,这表明其来源包含再循环的大陆地壳和/或岩浆补给过程。来自最原始样品(KB1;MgO>10wt.%)的橄榄石具有高Zn/Fe、Fe/Mn、Co、Zn、Ni、Ca和低Mn/Zn、Co/Fe值,表明辉石来源的熔体添加。基于橄榄石化学的计算表明,最原始的霞石规范KB1岩石起源于混合辉橄榄岩源的熔融,其平均比例分别为~70%和~30%。Karapınar玄武岩中橄榄石斑晶的平均δ18O值(+6.4‰;n=8)高于典型的地幔橄榄石(+5.1–5.4‰),但与已知的OIB-EMII来源(+5.4–6.1‰)重叠。收集的数据表明,Karapınar玄武岩是地幔橄榄岩部分熔体和交代辉石岩的混合产物,由俯冲大洋板衍生的熔体与周围的橄榄岩反应产生,与欧亚和非洲-阿拉伯板块的会聚系统有关。
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来源期刊
Journal of Geosciences
Journal of Geosciences GEOSCIENCES, MULTIDISCIPLINARY-MINERALOGY
CiteScore
2.30
自引率
7.10%
发文量
15
审稿时长
>12 weeks
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.
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