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首页> 外文期刊>Journal of Asian earth sciences >Small-volume melts of lithospheric mantle during continental collision: Late Cenozoic lavas of Mahabad, NW Iran
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Small-volume melts of lithospheric mantle during continental collision: Late Cenozoic lavas of Mahabad, NW Iran

机译：大陆碰撞中岩石圈地幔的小体积熔体：伊朗西北部马哈巴德的新生代晚期熔岩

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摘要

Basanites and alkali basalts from Mahabad in the West Azerbaijan province of Iran are part of a widespread series of Late Miocene-Quaternary mantle-derived magmas erupted within the Turkish-Iranian orogenic plateau, itself part of the active Arabia-Eurasia collision zone. New elemental and Sr-Nd isoto-pic results are combined with geophysical and geological constraints to suggest that these lavas formed predominantly by small degrees of partial melting of the thick (》100km) Eurasian lithospheric mantle within the garnet facies. Samples are highly enriched in large ion lithophile elements (LILE) and the light rare earth elements (LREE), up to 600 times chondritic values. They mostly possess negative primitive mantle-normalised Rb, K, Nb-Ta, Zr-Hf and Ti anomalies, with an overall signature that indicates a mantle source metasomatised by fluids or melts derived from crust during continental collision or the Teth-yan oceanic subduction that preceded it. Sr-Nd isotopic values are similar to other Quaternary centres in NW Iran; ~(87)Sr/~(86)Sr is slightly depleted with respect to Bulk Silicate Earth, at ～0.7045, and ~(143)Nd/~(144)Nd is slightly enriched, at ～0.5127. Crustal contamination does not appear to be an important process in the chemistry of these samples. Possible triggers for melting may include: breakdown of hydrous phases during lithospheric thickening; hydration of the mantle lithosphere by underthrusting of the Arabian passive margin; small-scale sub-lithospheric convection due to a significant thickness gradient in the Zagros lithosphere. Such processes may account for small-volume syn-collisional mantle-derived magmatism elsewhere in regions of thick lithosphere where recent slab break-off or lithospheric delamination cannot be proven.
机译：伊朗西阿塞拜疆省马哈巴德的玄武岩和碱玄武岩是土耳其-伊朗造山带爆发的一系列中新世-第四纪地幔衍生岩浆的一部分，而土耳其-伊朗造山带本身就是活跃的阿拉伯-欧亚大陆碰撞区的一部分。新的元素和Sr-Nd同位素结果与地球物理和地质约束条件相结合，表明这些熔岩主要是由石榴石相内厚达100 km的欧亚岩石圈地幔小程度的部分熔融形成的。样品高度富集大型离子亲石元素（LILE）和轻稀土元素（LREE），是软骨素值的600倍。它们大多具有负原始地幔归一化的Rb，K，Nb-Ta，Zr-Hf和Ti异常，其总体特征表明，地幔源被大陆碰撞或Teth-yan海洋俯冲过程中的地壳流体或熔体交代了在它之前。 Sr-Nd同位素值类似于伊朗西北部的其他第四纪中心。相对于块状硅酸盐地球，〜（87）Sr /〜（86）Sr略微耗尽，约为〜0.7045，〜（143）Nd /〜（144）Nd略微富集，约为〜0.5127。在这些样品的化学过程中，地壳污染似乎并不是重要的过程。融化的可能触发因素包括：岩石圈增厚过程中水相的破坏；通过对阿拉伯被动缘的逆冲作用使地幔岩石圈水化； Zagros岩石圈中明显的厚度梯度，导致小尺度次平流层对流。这样的过程可能解释了厚岩石圈其他地方无法证实近期板块破裂或岩石圈分层的小体积同碰撞地幔源岩浆。

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  • 来源
    《Journal of Asian earth sciences》 |2013年第25期|37-49|共13页
  • 作者

    M. Kheirkhah; I. Neill; M.B. Allen; K. Ajdari;

  • 作者单位

    Research Institute for Earth Sciences, Geological Survey of Iran, Azadi Square, Meraj Avenue, Tehran, Iran;

    Department of Earth Sciences, Durham University, Durham DH1 3LE, UK;

    Department of Earth Sciences, Durham University, Durham DH1 3LE, UK;

    Research Institute for Earth Sciences, Geological Survey of Iran, Azadi Square, Meraj Avenue, Tehran, Iran;

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  • 正文语种 eng
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  • 关键词

    Lithosphere; Iran; Basalt; Geochemistry; Melting;

    机译：岩石圈;伊朗;玄武岩地球化学;融化;

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