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首页> 外文期刊>Journal of geodynamics >Late Cenozoic volcanism in the Almaludag region, Azerbaijan province, northwest Iran: Evidence for post-collisional extension
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Late Cenozoic volcanism in the Almaludag region, Azerbaijan province, northwest Iran: Evidence for post-collisional extension

机译：伊朗西北部阿尔马鲁加地区的半七代火山主义：局势延伸的证据

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We discuss the geology, petrology, and major and trace element geochemistry of Late Cenozoic volcanic rocks in the Almaludag region in the Western Azerbaijan province, northwest Iran. Geology of this region evolved through the northward subduction of the Neotethyan oceanic lithosphere and subsequent collision of the Arabian and Eurasian plates during the Alpine-Himalayan orogeny. Two different Late Cenozoic periods of volcanic activity are recognized: Episode I produced pyroclastic deposits and trachydacitic lava (1.47 Ma, U-Pb dating) and Episode II generated mafic lava and scoria cones (including spatter/cinder). Geochemical data indicate that Episode I lavas have high-silica adakitic compositions, similar to the post-collisional and continental adakites, that formed from the partial melting of the thickened lower crust. Episode II lavas vary in composition and fall into two distinct geochemical groups. The first group includes picrobasalt-basanite and tephrite compared to the more evolved trachybasalt and basaltic trachyandesite of the second group. Both of these groups show alkaline to shoshonitic affinities.The binary geochemical plots of the Episode II samples display compositional trends that indicate magmatic processes such as fractional olivine clinopyroxene crystallization. The major and minor elemental variations of these samples reflect a mantle source heterogeneity and minor crustal contamination. The REE (rare earth elements) patterns and spider diagrams indicate enrichment of the large ion lithophile elements (LILE) and depletion of the high field strength elements (HFSE) relative to the heavy rare earth elements (HREE), and reveal an enriched lithospheric mantle source which was previously metasomatized by subduction components. The mantle source of the Episode II lavas was enriched by fluids and melts which were released from a subducted slab between Late Mesozoic and Early Cenozoic in northwest Iran. The Si-undersaturated lavas of the first group of Episode II probably originated in the garnet stability field in the lithospheric mantle with carbonate residue or veins, suggesting that the mantle source probably underwent carbonate metasomatism. Geochemistry of the SiO2 rich lavas of the second group of Episode II is consistent with a melt extracted from a peridotitic mantle source. The compositional variation from the rocks of the first group to those in the second group suggests a diminishing degree of metasomatic veins-wallrock interactions.The Late Cenozoic mafic rocks in the Almaludag region probably formed through extension in a post-collision, post-orogenic setting. The extension was likely the result of the delamination of the thickened subcontinental lithospheric mantle (SCLM) and ensuing asthenospheric upwelling after the collision of the Arabian and Eurasian plates.
机译：西北伊朗西部阿尔马鲁德地区奥尔马鲁德地区后期新生代火山岩地球化学地球化学地球化学地球化学。该地区的地质通过Neotethyan海洋岩石圈的向北俯冲而演变，在高山 - 喜马拉雅山脉期间阿拉伯和欧亚板块的随后碰撞。识别出两种不同晚期新生代的火山活性：发作我生产的Pyroclastic沉积物和棘突式熔岩（1.47 mA，U-PB约会）和第II集生成的Mafic Lava和Scoria锥体（包括飞溅/煤渣）。地球化学数据表明，Iavas具有高二氧化硅脂肪组合物，其类似于碰撞和欧式粘液，由加厚的下外壳的局部熔化形成。第II集II熔岩在成分中变化，并落入两个不同的地球化学群体。第一个组包括与第二组的更进一体的曲囊和玄武岩颅骨和玄武岩鳞状和玄武岩雌蕊和Tepharite。这两组都显示出碱性至血管淋巴瘤。发作II的二元地球化学曲线样品显示组成趋势，表明岩石工艺如分数橄榄石冠状蛋白结晶。这些样品的主要和次要元素变化反映了地幔源异质性和轻微的地壳污染。 Ree（稀土元素）图案和蜘蛛图表明，相对于重稀土元素（HREE）的大离子型锂锂岩元素（含量）和耗尽高场强元件（HFSE），并揭示富含富含岩石的岩石罩以前通过俯冲组件弥思的来源。第II集II熔岩的地幔来源由流体和熔体富集，这些熔体在西北西北部的中生代和新生代早期之间的悬浮层中释放。第一组发作二世的Si-缺乏液体可能源于岩石岩石地幔的石榴石稳定性场，含有碳酸盐残留物或静脉，表明地幔源可能接受碳酸酯代索术。第二组发作II的SiO2富含熔岩的地球化学与从橄榄石岩石源源中提取的熔体一致。来自第一组岩石的组成变化与第二组中的组成变化表明，替代静脉 - 墙面相互作用的逐渐减少。almaludag区域的晚新生代MAFIC岩石可能通过突出后的延伸，眶后设定形成。延伸可能是分层增厚的亚丁型岩性地幔（SCLM）的结果，并在阿拉伯和欧亚板块碰撞后随着哮喘越来越多。

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