Early activity of the largest Cenozoic shield volcano in the circum-Mediterranean area: Mt. Karacadag, SE Turkey
Early activity of the largest Cenozoic shield volcano in the circum-Mediterranean area: Mt. Karacadag, SE Turkey
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DOI：
10.1127/0935-1221/2010/0022-2024
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发表时间：
2010-06
影响因子：
2.1
通讯作者：
M. Lustrino;M. Keskin;M. Mattioli;V. Lebedev;A. Chugaev;E. Sharkov;O. Kavak
中科院分区：
文献类型：
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作者：
M. Lustrino;M. Keskin;M. Mattioli;V. Lebedev;A. Chugaev;E. Sharkov;O. Kavak
火山活动在Mt。土耳其东南部的Karacadag在~11 ~0.01 Ma之间发育。在本文中，我们调查的最古老的产品（年龄超过2.6马），创造了一个大的火山高原和南北对齐的火山机构的形式盾状火山。这些火成岩是弱碱性到过渡性橄榄石-单斜辉石斑状玄武岩，具有少量夏威夷岩、碧玄岩和非常罕见的差异化岩性（mugearites和benmoreites）。这些熔岩中的主要元素与MgO的相关性较差，这与岩浆产生的多压深度、不同程度的部分熔融（从~ 2%到~ 10%）、异质地幔来源和分馏晶体组合的差异在定性上是一致的。原始地幔标准化模式类似于典型的非造山岩浆成分，在HFSE（Nb，Ta，Hf，Zr）和高HFSE/LILE比值的峰值。稀土元素含量与石榴子石-尖晶石混合相橄榄岩经~ 2%部分熔融后形成的碧玄岩相一致。碱性玄武岩与来自同一类型来源的较高熔融度（5 - 10%）相容。初始87 Sr/ 86 Sr比值范围为0.70349至0.70522，而143 Nd/ 144 Nd比值范围为0.512853至0.512659。与高原期熔岩相比，早期熔岩具有较高的87 Sr/ 86 Sr和较低的143 Nd/ 144 Nd。Sr-Nd同位素的变化及其与常量和微量元素的关系不能用涉及平均地壳岩性的AFC（同化和分步结晶）过程来解释。更有可能的是，Sr-Nd同位素比值与非均质地幔源的存在，只有轻微的AFC类过程的参与。安纳托利亚东南部卡拉苏山谷和叙利亚-伊拉克-土耳其边界之间200 x 800 km区域内的新生代熔岩形成了一个独特的火成岩省，其特征可根据Sr同位素特征来确定。该地区岩石圈地幔具有明显的87 Sr/ 86 Sr富集（高达0.7055）和同位素亏损（87 Sr/ 86 Sr降至0.7030）的特征。
Volcanic activity at Mt. Karacadag, SE Turkey, developed between ~11 and ~0.01 Ma. In this paper we investigate the oldest products (older than 2.6 Ma) that created a large volcanic plateau and a N-S aligned volcanic edifice in the form of a shield volcano. These igneous rocks are mildly alkaline to transitional olivine-clinopyroxene phyric basalts with minor hawaiites, basanites and very rare differentiated lithologies (mugearites and benmoreites). The poor correlation of major elements with MgO in these lavas is qualitatively consistent with polybaric depths of magma production, variable degrees of partial melting (from ~2 to ~10 %), heterogeneous mantle sources and differences in the fractionating crystal assemblage. Primitive mantle-normalized patterns resemble typical anorogenic magma compositions, with peaks at HFSE (Nb, Ta, Hf, Zr) and high HFSE/LILE ratios. REE contents are compatible with derivation of the basanites from a mixed garnet-spinel facies peridotite after ~2 % partial melting. Alkali basalts are compatible with higher degrees of melting (between 5 and 10 %) from the same type of source. Initial 87 Sr/ 86 Sr ratios range from 0.70349 to 0.70522 while those of 143 Nd/ 144 Nd range from 0.512853 to 0.512659. Early-stage lavas show higher 87 Sr/ 86 Sr and lower 143 Nd/ 144 Nd compared to plateau-stage lavas. The Sr-Nd isotopic variations and their relation with major and trace elements cannot be explained by AFC-like (Assimilation and Fractional Crystallization) processes involving average crustal lithologies. More likely, the Sr-Nd isotopic ratios are related to the existence of heterogeneous mantle sources with only minor involvement of AFC-like processes. The Cenozoic lavas in a 200 x 800 km area between the Karasu Valley and the Syria-Iraq-Turkey border in south-eastern Anatolia form a distinct igneous province which can be characterised on the basis of Sr-isotope signatures. The lithospheric mantle beneath this area is characterized by anomalously enriched 87 Sr/ 86 Sr compositions (up to 0.7055) as well as more isotopically depleted compositi o ns ( 87 Sr/ 86 Sr down to 0.7030).