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首页> 外文期刊>Contributions to Mineralogy and Petrology >Mechanisms driving polymagmatic activity at a monogenetic volcano, Udo, Jeju Island, South Korea
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Mechanisms driving polymagmatic activity at a monogenetic volcano, Udo, Jeju Island, South Korea

机译：在韩国济州岛宇都市的单基因火山中推动多岩浆活动的机制

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High-resolution, stratigraphically ordered samples of the Udo tuff cone and lava shield offshore of Jeju Island, South Korea, show complex geochemical variation in the basaltic magmas that fed the eruption sequence. The eruption began explosively, producing phreatomagmatic deposits with relatively evolved alkali magma. The magma became more primitive over the course of the eruption, but the last magma to be explosively erupted had shifted back to a relatively evolved composition. A separate sub-alkali magma batch was subsequently effusively erupted to form a lava shield. Absence of weathering and only minor reworking between the tuff and overlying lava implies that there was no significant time break between the eruptions of the two magma batches. Modelling of the alkali magma suggests that it was generated from a parent melt in garnet peridotite at c. 3 to 3.5 GPa and underwent mainly clinopyroxene + olivine ± spinel fractionation at c. 1.5 to 2 GPa. The sub-alkali magma was, by contrast, generated from a chemically different peridotite with residual garnet at c. 2.5 GPa and evolved through olivine fractionation at a shallower level compared to its alkali contemporary. The continuous chemostratigraphic trend in the tuff cone, from relatively evolved to primitive and back to evolved, is interpreted to have resulted from a magma batch having risen through a single dyke and erupted the batch’s head, core and margins, respectively. The alkali magma acted as a path-opener for the sub-alkali magma. The occurrence of the two distinct batches suggests that different magmatic systems in the Jeju Island Volcanic Field have interacted throughout its history. The polymagmatic nature of this monogenetic eruption has important implications for hazard forecasting and for our understanding of basaltic field volcanism.
机译：韩国济州岛近海的Udo凝灰岩锥和熔岩护盾的高分辨率，地层有序样本显示了注入喷发序列的玄武岩浆中复杂的地球化学变化。爆发开始爆发，产生具有相对演化的碱岩浆的岩浆沉积。在喷发过程中，岩浆变得更加原始，但是最后一次爆发爆发的岩浆已经转移回相对演化的成分。随后，爆发性地喷出了一个单独的碱下岩浆批次，形成了熔岩护盾。缺乏风化作用，凝灰岩和上覆熔岩之间只有很小的返工，这意味着在两个岩浆批次之间没有明显的时间间隔。碱岩浆的建模表明它是由c的石榴石橄榄岩中的母体熔体产生的。 3至3.5 GPa，在c时主要进行clinopyroxene +橄榄石±尖晶石分馏。 1.5至2 GPa。相比之下，碱下岩浆是由化学性质不同的橄榄岩生成的，在橄榄石上残留石榴石。 2.5 GPa，并通过橄榄石分馏而比其碱性当代盐析浅。凝灰岩锥中的连续化学地层趋势，从相对演化到原始，再回到演化，被解释为是由一个岩浆批次上升通过一个堤坝并分别喷出了该批次的头部，岩心和边缘所致。碱岩浆是次碱岩浆的开路者。这两个不同批次的出现表明，济州岛火山场中不同的岩浆系统在整个历史过程中都发生了相互作用。这种单相喷发的多岩浆性质对灾害预报和我们对玄武岩田间火山作用的理解具有重要意义。

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