The Hasan Dagi stratovolcano (Central Anatolia, Turkey): evolution from calc-alkaline to alkaline magmatism in a collision zone
The Hasan Dagi stratovolcano (Central Anatolia, Turkey): evolution from calc-alkaline to alkaline magmatism in a collision zone
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DOI：
10.1016/s0377-0273(98)00097-3
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发表时间：
1998-12-01
影响因子：
2.9
通讯作者：
Gourgaud, A
中科院分区：
文献类型：
--
作者：
Deniel, C;Aydar, E;Gourgaud, A
哈桑达吉火山是卡帕多西亚（土耳其安纳托利亚中部）两座大型上新世-第四纪火山之一。该火山有三个建造阶段：古火山、中火山和新火山。哈桑达吉火山的大多数样品都是钙碱性的，并确定了从玄武安山岩到流纹岩的几乎完整的趋势。然而，最近的（新火山）镁铁质样品是碱性玄武岩。最古老的熔岩（Kecikalesi（13 Ma）和Paleo-Hasan Dagi（7 Ma））的矿物学和地球化学特征与较年轻的熔岩（Meso-和Neo-Hasan Dagi（< 1 Ma））的矿物学和地球化学特征明显不同。在这些较老的熔岩中通常可以观察到钙质斜长石和钙黄长石。古火山玄武岩贫碱，并显示拉斑玄武岩的倾向，而分化的熔岩贫Na 2 O，但丰富的K2 O相比，年轻的熔岩。随着时间的推移，TiO 2、Fe 2 O3 *、MgO、Na 2 O和K2 O含量逐渐升高，Al 2 O3和SiO2含量逐渐降低，这反映在玄武岩的成分中。所有的玄武岩显示出典型的大陆边缘岩浆的多元素模式，具有显着富集LILE（K，Rb，Ba和Tn）和LREE和强（古火山）到中等（中-和新火山）负Nb，Zr和Ti异常。然而，年轻的玄武岩是最丰富的不相容元素，在协议与他们的碱性亲和力，并没有系统地显示负HFSE异常，稀土元素数据表明含水角闪石含结晶历史的中，新火山熔岩。微量元素Nb/Y、Ti/Y和Th/Y比值也有明显区别。这些比率表明了俯冲成分+/-地壳污染在哈桑达吉熔岩成因中的作用，特别是对于最古老的熔岩（Kecikalesi和古哈桑达吉）。在过去的6-7百万年里，随着时间的推移，这一成分的影响逐渐减弱，Sr、Nd、Pb同位素比值变化范围虽小（0.70457-0.70515; 0.51262-0.51273; 18.80-18.94; 15.64-15.69; 38.87-39.10），但也反映了岩浆源区的演化。事实上，最年轻的（新火山）和最原始的玄武岩显示显着较低的Sr-87/Sr-86比古和中火山玄武岩，而中火山玄武岩显示更多的放射性铅比古火山样品。最初的异质性和/或岩浆污染的岩浆之间的岩浆混合过程可以解释的成因，少分化和中间熔岩（48- 57%SiO2）。中-新火山分异熔岩（60- 68%SiO2）要么来自分析的玄武岩，要么来自更原始和更贫化的岩浆，通过分离结晶+/-一些地壳污染（AFC）。此外，高度分化的样品（72- 75%SiO2）没有受到严重污染。在没有同期俯冲作用的情况下，哈桑山火山熔岩的强钙碱性特征一定反映了非洲-阿拉伯板块在欧亚板块之下的早期俯冲的遗产。碱性成分随时间的演化显然与中新世晚期安纳托利亚中部伸展构造的发展有关。(C)1998 Elsevier Science B. V.保留所有权利。
The Hasan Dagi volcano is one of the two large Plio-Quaternary volcanoes in Cappadocia (Central Anatolia, Turkey). Three stages of edifice construction have been identified for this volcano: Paleovolcano, Mesovolcano and Neovolcano. Most samples from Hasan Dagi volcano are calc-alkaline and define an almost complete trend from basaltic andesite to rhyolite. However, the more recent (Neovolcano) mafic samples are alkaline basalts. The mineralogical and geochemical characteristics of the oldest lavas (Kecikalesi (13 Ma) and Paleo-Hasan Dagi (7 Ma)) are significantly different from those of the younger lavas (Meso- and Neo-Hasan Dagi (< 1 Ma)). Calcic plagioclase and pigeonite are typically observed in these older lavas. The Paleovolcano basalts are depleted in alkalis and display a tholeiitic tendency whereas the differentiated lavas are depleted in Na2O but enriched in K2O compared to younger lavas. There is an evolution through time towards higher TiO2, Fe2O3*, MgO, Na2O and K2O and lower Al2O3, and SiO2, which is reflected in the basalt compositions. All the basalts display multi-element patterns typical of continental margin magmas with a significant enrichment in LILE (K, Rb, Ba and Tn) and LREE and strong (Paleovolcano) to moderate (Meso- and Neovolcano) negative Nb, Zr and Ti anomalies. However, the younger basalts are the most enriched in incompatible elements, in agreement with their alkaline affinities and do not systematically display negative HFSE anomalies, REE data suggest an hydrous amphibole-bearing crystallization history for both Meso- and Neovolcano lavas. The distinction between the older and younger lavas is also apparent in trace element ratios such as Nb/Y, Ti/Y and Th/Y. These ratios indicate the role of a subducted component +/- crustal contamination in the genesis of the Hasan Dagi lavas, particularly for the oldest lavas (Kecikalesi and Paleo-Hasan Dagi). The decreasing influence of this component through time, over the last 6-7 m.y., has been accompanied by an increasing contribution of melt-enriched lithosphere, Although the range of variation of Sr, Nd and Pb isotopic ratios is small (0.70457-0.70515; 0.51262-0.51273; 18.80-18.94; 15.64-15.69; 38.87-39.10), it also reflects the evolution of the magma sources through time. Indeed, the youngest (Neovolcano) and most primitive basalts display significantly lower Sr-87/Sr-86 than the Paleo- and Mesovolcano basalts, whereas the Mesovolcano basalts display more radiogenic Pb than Paleovolcano samples. Magma mixing processes between initially heterogeneous and/or variably contaminated magmas may account for the genesis of the less differentiated and intermediate lavas (48-57% SiO2). Meso- and Neovolcano differentiated lavas (60-68% SiO2) are either derived from the analyzed basalts or from more primitive and more depleted magmas by fractional crystallization +/- some crustal contamination (AFC). Furthermore, the highly differentiated samples (72-75% SiO2,) are not strongly contaminated. The strong calc-alkaline character of Hasan Dagi lavas, in the absence of contemporaneous subduction, must reflect the heritage of the early subduction of the Afro-Arabian plate under the Eurasian plate. The evolution towards alkaline compositions through time is clearly related to the development of extensional tectonics in Central Anatolia in the Late Miocene. (C) 1998 Elsevier Science B.V. All rights reserved.