The high frequency of historical eruptions at Kīlauea Volcano presents an exceptional opportunity to address fundamental questions related to the transport, storage, and interaction of magmas within rift zones. The Nāpau Crater area on Kīlauea’s East Rift Zone (ERZ) experienced nine fissure eruptions within 50 years (1961–2011). Most of the magma intruded during these frequent eruptions remained stored within the rift zone, creating a potential magma mixing depot within the ERZ. The superbly monitored and sampled 2011 eruption (Puʻu ʻŌʻō episode 59) presents an extraordinary opportunity to evaluate magma mixing processes within the ERZ. Whole-rock, glass, and olivine compositions were determined, not only for lava from the 2011 eruption, but also for a new suite of Nāpau Crater area samples from the 1963, 1965, 1968, 1983, and 1997 eruptions, as well as the previously undocumented 1922 eruption. Whole-rock XRF data revealed two geochemically distinct magma batches for episode 59: one less evolved (∼6·6 wt % MgO, 0·46 wt % K₂O) than the other (∼6·2 wt % MgO, 0·58 wt % K₂O). Episode 59 lava is remarkably aphyric (∼0·1 vol. % phenocrysts), making use of mineralogy to identify parent magma affinities problematic. Linear compositional trends of whole-rock major and trace elements, and reversely zoned olivine crystals indicate episode 59 lavas underwent magma mixing. Least squares regression calculations and plots of major and trace element data, were used to evaluate whether the episode 59 samples are products of mixing summit-derived magma with residual magma from previous Nāpau Crater area eruptions. The regression results and trace element ratios are inconsistent with previously proposed mixing scenarios, but they do support mixing between summit-derived magma and residual magma from the 1983 and 1997 Nāpau Crater area eruptions. These magmas were stored in physically and chemically distinct pods at depths of 1·6–3·0 km prior to mixing with new magma intruded from the summit to produce the episode 59 lava. One pod contained a fractionated equivalent of 1983 lava, and the other a hybrid of compositions similar to 1983 and 1997 lavas. The petrology of episode 59 lava demonstrates that magmas from two previous eruptions (1983 and 1997) were available to mix with magma intruded from the summit region. This study clarifies the pre-eruptive history of the mixed episode 59 lava, and elucidates the evolution of the volcano's magmatic system in a region of frequent eruptions.

中文翻译：

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2011年夏威夷基拉韦厄火山喷发对裂谷岩浆相互作用的岩石学见解

基拉韦厄火山的历史喷发频繁，为解决与裂谷区内岩浆的运输，储存和相互作用有关的基本问题提供了绝佳的机会。基拉韦厄东大裂谷带（ERZ）的Nāpau火山口地区在50年内（1961-2011年）经历了9次裂隙喷发。在这些频繁喷发过程中侵入的大部分岩浆仍保留在裂谷带中，从而在ERZ内形成了一个潜在的岩浆混合库。出色的监测和采样2011年喷发（PuʻuʻŌʻō第59集）为评估ERZ内的岩浆混合过程提供了绝佳的机会。确定了整个岩石，玻璃和橄榄石的成分，不仅针对2011年喷发的熔岩，还针对1963年，1965年，1968年，1983年和1997年喷发的一组新的NāpauCrater地区样本，以及先前未记录的1922年喷发。全岩XRF数据显示第59集有两个地球化学不同的岩浆批次：少一个演化（〜6·6 wt％MgO，0·46 wt％K₂ O）比其他（〜6·2 wt％MgO，0·58 wt％K ₂O）。第59集熔岩具有明显的亲水性（〜0·1体积％的表晶），利用矿物学来确定母岩浆亲和力存在问题。整个岩石主要元素和微量元素的线性组成趋势，以及反向划的橄榄石晶体表明，第59集熔岩经历了岩浆混合。最小二乘回归计算以及主要元素和痕量元素数据的图用于评估第59集样本是否是峰顶衍生岩浆与先前Nāpau火山口地区喷发的残留岩浆混合的产物。回归结果和痕量元素比率与先前提出的混合情景不一致，但它们确实支持了1983年和1997年Nāpau火山口地区喷发的山顶衍生岩浆和残留岩浆之间的混合。在与从山顶侵入的新岩浆混合以产生第59集熔岩之前，将这些岩浆储存在物理和化学上不同的豆荚中，深度为1·6-3·0 km。一个豆荚包含1983年熔岩的等分部分，另一个包含类似于1983年和1997年熔岩的成分混合体。第59集熔岩的岩石学表明，以前两次喷发（1983年和1997年）的岩浆可与从山顶地区侵入的岩浆混合。这项研究阐明了混合事件59熔岩的喷发前历史，并阐明了火山喷发系统在频繁喷发区域的演变。另一种是类似于1983年和1997年熔岩的成分混合体。第59集熔岩的岩石学表明，以前两次喷发（1983年和1997年）的岩浆可与从山顶地区侵入的岩浆混合。这项研究阐明了混合事件59熔岩的喷发前历史，并阐明了火山喷发系统在频繁喷发区域的演变。另一种是类似于1983年和1997年熔岩的成分混合体。第59集熔岩的岩石学表明，以前两次喷发（1983年和1997年）的岩浆可与从山顶地区侵入的岩浆混合。这项研究阐明了混合事件59熔岩的喷发前历史，并阐明了火山喷发系统在频繁喷发区域的演变。