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首页> 外文期刊>Neues Jahrbuch fur Geologie und Palaontologie. Abhandlungen >Insights from the basalts of SE Lebanon into the nature of the Middle East Cenozoic Volcanic Province
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Insights from the basalts of SE Lebanon into the nature of the Middle East Cenozoic Volcanic Province

机译：黎巴嫩东南部玄武岩对中东新生代火山省性质的启示

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摘要

A component of the vast Middle East Cenozoic Volcanic Province is represented by lavas from SE Lebanon, occurring at the Dead Sea transform. The lavas are phyric alkali basalts, consisting of 45-50 vol.% labradorite (An_(60-68)), 30% clinopyroxene, 20% olivine, and minor opaque phases. They exhibit low silica values (ave. 46 wt% SiO2) and have a narrow range of major element compositions (Al_2O_3, 14.1-15.7 wt%; MgO, 5.9-8.9 wt%; CaO, 8.5-10.6 wt%). The rocks are alkaline in nature and are enriched in TiO_2 (2.2-3.1 wt%), Zr (175-237 ppm), Nb (32-57 ppm) and REE, thus reflecting strong OIB affinities. The primitive mantle-normalized patterns are strongly fractionated [(La/Yb)_N = 19.3] indicative of a garnet-bearing mantle source. The ~(87)Sr/~(86)Sr isotopic composition ranges from 0.70327-0.70339 and ~(143)Nd/~(144)Nd from 0.512848-0.512872 (ε_(Nd) = 4.1 to 4.6). The basatltic magma was more likely generated via adiabatic decompression and melting occurred along fractures developed during the Plio-Quaternary. Modeling using a variety of mantle source materials and different degrees of partial melting indicates that the magma was produced by a small degree of batch partial melting (F = 0.5%) of a primitive, garnet-lherzolite fertile mantle source. Judging from the nature of the Levantine crust, along with elemental ratios such as K/P (2.85) and La/Nb (1.06), the magma was subjected to minimal crustal contamination. Changes in the Arabian plate motion as it rotated to the northeast with respect to the Levantine sub-plate during the Plio-Quaternary may have initiated localized transtensional forces, thus provoking the development of deep-seated fractures along which basaltic lavas have erupted.
机译：来自中东黎巴嫩的熔岩代表了中东新生代火山省的一个组成部分，发生在死海改造中。熔岩是物理碱性玄武岩，由45％至50％（体积）的拉长石（An_（60-68）），30％的斜辉石，20％的橄榄石和次要的不透明相组成。它们表现出低的二氧化硅值（平均SiO 2为46重量％）并且具有窄范围的主要元素组成（Al 2 O 3，14.1-15.7重量％; MgO，5.9-8.9重量％; CaO，8.5-10.6重量％）。这些岩石本质上是碱性的，并富含TiO_2（2.2-3.1 wt％），Zr（175-237 ppm），Nb（32-57 ppm）和REE，因此反映出很强的OIB亲和力。原始的地幔归一化模式被强烈分割[（La / Yb）_N = 19.3]，表明带有石榴石的地幔源。 〜（87）Sr /〜（86）Sr同位素组成的范围为0.70327-0.70339，〜（143）Nd /〜（144）Nd的范围为0.512848-0.512872（ε_（Nd）= 4.1至4.6）。玄武岩浆更有可能是通过绝热减压而产生的，并且融化发生在上新世第四纪期间形成的裂缝上。使用各种地幔源材料和不同程度的部分熔融进行的建模表明，岩浆是由少量原始的石榴石-锂沸石可育地幔源的批量部分熔融（F = 0.5％）产生的。从黎凡特地壳的性质以及元素比（例如K / P（2.85）和La / Nb（1.06））来看，岩浆受到的地壳污染最小。在上古第四纪期间，阿拉伯板块相对于黎凡特次板块向东北旋转时，板块运动的变化可能引发了局部张拉力，从而激发了深部裂缝的发展，玄武质熔岩沿该裂缝破裂。

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