Differentiation and magma mixing on Kilauea's east rift zone: a further look at the eruptions of 1955 and 1960. Part II. The 1960 lavas
Differentiation and magma mixing on Kilauea's east rift zone: a further look at the eruptions of 1955 and 1960. Part II. The 1960 lavas
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基拉韦厄东部裂谷带的分异和岩浆混合：进一步观察 1955 年和 1960 年的火山喷发。第二部分。
DOI：
10.1007/s004450050115
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发表时间：
1992
影响因子：
3.5
通讯作者：
R. T. Helz
中科院分区：
文献类型：
--
作者：
T. L. Wright;R. T. Helz
摘要：新的、详细的岩相观察、矿物成分数据以及全岩与玻璃成分趋势记录了 1960 年基拉韦厄东部裂谷带喷发的熔岩中的岩浆混合。证据包括异质斑晶组合的出现，包括熔岩中被推断为混合体的再吸收和反向分区矿物。计算表明，这种混合发生在 1955 年喷发结束时补充的岩浆库内，涉及引入四种不同的岩浆。这些岩浆起源于基拉韦厄山顶下方，并在喷发开始 10 天后开始进入裂谷储层。我们使用玻璃的微探针分析来计算 1955 年和 1960 年喷发液体的温度。然后，我们使用计算出的储存成分和补给成分的比例来估计补给成分的温度，并发现这些温度与基拉韦厄山顶出现的相同岩浆的温度一致。我们的研究强化了之前基拉韦厄岩浆管道研究中得出的结论。我们推断，岩浆进入基拉韦厄山顶下方的浅层储层，并横向移动到东部裂谷带的流体核心。在此过程中，如果存在具有独特化学性质的岩浆，它们会保留其化学特性，并且冷却量与向上或横向输送到喷发地点的岩浆相当。地表几公里内的侵入物冷却并结晶，产生分馏岩浆。岩浆混合既发生在先前分馏的岩浆体内，也发生在新的岩浆与预先存在的储层相交时。否则，通过围岩隔膜或连续岩浆批次的不同热和密度特性，可以防止岩浆混合。
Abstract New and detailed petrographic observations, mineral compositional data, and whole-rock vs glass compositional trends document magma mixing in lavas erupted from Kilauea's lower east rift zone in 1960. Evidence includes the occurrence of heterogeneous phenocryst assemblages, including resorbed and reversely zoned minerals in the lavas inferred to be hybrids. Calculations suggest that this mixing, which is shown to have taken place within magma reservoirs recharged at the end of the 1955 eruption, involved introduction of four different magmas. These magmas originated beneath Kilauea's summit and moved into the rift reservoirs beginning 10 days after the eruption began. We used microprobe analyses of glass to calculate temperatures of liquids erupted in 1955 and 1960. We then used the calculated proportions of stored and recharge components to estimate the temperature of the recharge components, and found those temperatures to be consistent with the temperature of the same magmas as they appeared at Kilauea's summit. Our studies reinforce conclusions reached in previous studies of Kilauea's magmatic plumbing. We infer that magma enters shallow storage beneath Kilauea's summit and also moves laterally into the fluid core of the East rift zone. During this process, if magmas of distinctive chemistry are present, they retain their chemical identity and the amount of cooling is comparable for magma transported either upward or laterally to eruption sites. Intrusions within a few kilometers of the surface cool and crystallize to produce fractionated magma. Magma mixing occurs both within bodies of previously fractionated magma and when new magma intersects a preexisting reservoir. Magma is otherwise prevented from mixing, either by wall-rock septa or by differing thermal and density characteristics of the successive magma batches.