Whakaari is New Zealand’s most active volcano, and its last major magmatic eruption occurred during a protracted episode between 1976 and 2000. This eruption episode involved a sustained phase of heightened unrest, punctuated by regular, and small-volume, phreatic, magmatic and phreatomagmatic eruptions. We examine the scoria sample suite erupted throughout this period to develop a model for the storage conditions and the underlying cause of this long-lived activity. From our analysis of the major element composition of minerals, groundmass glass and phenocryst-hosted melt inclusions, along with the volatile content of melt inclusions, Whakaari magmas are relatively hot and dry arc andesites when compared globally. Based on a combination of plagioclase hygrometry, volatile contents of phenocryst-hosted melt inclusions and thermodynamic modelling, we conceptualize a distributed magmatic system that is dominated by andesite. We find that the 1976–2000 eruption episode was largely driven by volatile poor andesite-dacite magma that was periodically intruded by a relatively primitive mafic magma throughout this period. This andesite-dacite crustal magma reservoir (to at least 9 km) is capped by a shallow storage reservoir at ~1- to 2-km depth, where magmas stalled before erupting. Mafic magma/s periodically intruded the andesite-dacite reservoir providing heat, melt, volatiles, and mafic minerals, including olivine, into the system. Finally, we show that the volatile budget during this small-volume eruption episode released significant S and Cl into the atmosphere, similar in scale to large basaltic eruptions.

华卡里火山是新西兰最活跃的火山，其最后一次主要岩浆喷发发生在1976年至2000年之间的旷日持久的事件中。该爆发事件包括持续的加剧的动荡阶段，其特征是定期，小批量，潜水，岩浆和岩浆岩喷发。 。我们检查了在此期间爆发的scoria样本套件，以开发一个模型来确定这种长期活动的存储条件和根本原因。从我们对矿物，地基玻璃和隐晶系熔体夹杂物的主要元素组成的分析以及熔体夹杂物的挥发性成分来看，全球范围内，华卡里岩浆是相对热干的弧形安山岩。基于斜长石吸湿法，苯晶类熔体夹杂物的挥发物含量和热力学模型，我们概念化了以安山岩为主的分布式岩浆系统。我们发现，1976-2000年的喷发事件主要是由不稳定的安山岩-ite石-岩浆岩浆驱动的，该岩浆岩在整个这段时期内定期被相对原始的镁铁质岩浆侵入。这个安山岩-ac石的地壳岩浆储集层（至少9 km）被一个约1至2 km深度的浅层储集层封盖，岩浆在喷发前就停滞了。镁铁质岩浆周期性地侵入安山岩-针铁矿储层，向系统中提供热量，熔体，挥发物和镁铁质矿物（包括橄榄石）。最后，我们证明了在小规模喷发期间波动的预算将大量的S和Cl释放到了大气中，其规模与大型玄武岩喷发相似。我们发现1976-2000年的喷发事件主要是由不稳定的安山岩-d石-岩浆岩浆驱动的，该岩浆岩在整个这段时期内定期被相对原始的镁铁质岩浆侵入。这个安山岩-ac石的地壳岩浆储集层（至少9 km）被一个约1至2 km深度的浅层储集层封盖，岩浆在喷发前就停滞了。镁铁质岩浆周期性地侵入安山岩-针铁矿储层，向系统中提供热量，熔体，挥发物和镁铁质矿物（包括橄榄石）。最后，我们证明了在小规模喷发期间波动的预算将大量的S和Cl释放到了大气中，其规模与大型玄武岩喷发相似。我们发现1976-2000年的喷发事件主要是由不稳定的安山岩-d石-岩浆岩浆驱动的，该岩浆岩在整个这段时期内定期被相对原始的镁铁质岩浆侵入。这个安山岩-ac石的地壳岩浆储集层（至少9 km）被一个深度约为1至2 km的浅层储集层封盖，岩浆在喷发前就停滞了。镁铁质岩浆周期性地侵入安山岩-针铁矿储层，向系统中提供热量，熔体，挥发物和镁铁质矿物（包括橄榄石）。最后，我们证明了在小规模喷发期间波动的预算将大量的S和Cl释放到了大气中，其规模与大型玄武岩喷发相似。