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首页> 外文期刊>Contributions to Mineralogy and Petrology >Fine-scale temporal recovery, reconstruction and evolution of a post-supereruption magmatic system
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Fine-scale temporal recovery, reconstruction and evolution of a post-supereruption magmatic system

机译：喷发后岩浆系统的精细时间恢复，重建和演化

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摘要

Supereruptions (> 10(15) kg approximate to 450 km(3) of ejected magma) have received much attention because of the challenges in explaining how and over what time intervals such large volumes of magma are accumulated, stored and erupted. However, the processes that follow supereruptions, particularly those focused around magmatic recovery, are less fully documented. We present major and trace-element data from whole-rock, glass and mineral samples from eruptive products from Taupo volcano, New Zealand, to investigate how the host magmatic system reestablished and evolved following the Oruanui supereruption at 25.4 ka. Taupo's young eruptive units are precisely constrained chronostratigraphically, providing uniquely fine-scale temporal snapshots of a post-supereruption magmatic system. After only similar to 5 kyr of quiescence following the Oruanui eruption, Taupo erupted three small volume (similar to 0.1 km(3)) dacitic pyroclastic units from 20.5 to 17 ka, followed by another similar to 5-kyr-year time break, and then eruption of 25 rhyolitic units starting at similar to 12 ka. The dacites show strongly zoned minerals and wide variations in melt-inclusion compositions, consistent with early magma mixing followed by periods of cooling and crystallisation at depths of > 8 km, overlapping spatially with the inferred basal parts of the older Oruanui silicic mush system. The dacites reflect the first products of a new silicic system, as most of the Oruanui magmatic root zone was significantly modified in composition or effectively destroyed by influxes of hot mafic magmas following caldera collapse. The first rhyolites erupted between 12 and 10 ka formed through shallow (4-5 km depth) cooling and fractionation of melts from a source similar in composition to that generating the earlier dacites, with overlapping compositions for melt inclusions and crystal cores between the two magma types. For the successively younger rhyolite units, temporal changes in melt chemistry and mineral phase stability are observed, which reflect the development, stabilisation and maturation of a new, probably unitary, silicic mush system. This new mush system was closely linked to, and sometimes physically interacted with, underlying mafic melts of similar composition to those involved in the Oruanui supereruption. From the inferred depths of magma storage and geographical extent of vent sites, we consider that a large silicic mush system (> 200 km(3) and possibly up to 1000 km(3) in volume) is now established at Taupo and is capable of feeding a new episode or cycle of volcanism at any stage in the future.
机译：超级喷发（> 10（15）kg大约是喷出的岩浆的450 km（3）），因为在解释如何以及在什么时间间隔内积累，储存和喷发如此大量的岩浆方面存在挑战，引起了人们的极大关注。但是，关于超火山爆发的过程，特别是那些围绕岩浆恢复的过程，没有得到充分的记录。我们提供了来自新西兰陶波火山喷发产物的全岩石，玻璃和矿物样品的主要和微量元素数据，以研究东岩浆系统在25.4 ka的奥鲁努伊火山爆发后如何重建和演化。陶波的年轻喷发单元在时间地层上受到严格的限制，为喷发后的岩浆系统提供了独特的精细尺度的时间快照。在奥拉努伊火山喷发后仅类似于静止5多年之后，陶波爆发了20.5到17 ka的三个小体积（约0.1 km（3））的达西热碎屑单元，随后又出现了一个类似于5年的时间断裂，然后以类似于12 ka的速度喷发25个流纹单元。 dacites显示出强烈的区域性矿物和熔体包裹体成分的广泛变化，这与早期岩浆混合，随后在大于8 km深度的冷却和结晶期一致，在空间上与较旧的Oruanui硅质糊状胶体系统的推断基础部分重叠。 dacites反映了新硅质系统的最初产物，因为火山口坍塌之后，大部分Oruanui岩浆根区的成分显着改变或被热铁镁质岩浆大量涌入而有效破坏。最初的流纹岩在12至10 ka爆发，是通过浅层冷却（4-5 km深度）和从与产生早期dacits的成分相似的成分中分离出熔体而形成的，在两个岩浆之间有重叠的熔体夹杂物和晶体核类型。对于相继年轻的流纹岩单元，观察到熔融化学和矿物相稳定性的时间变化，这反映了新的，可能是单一的硅质糊状体系的发展，稳定和成熟。这个新的糊状系统与组成与Oruanui超级喷发中涉及的熔体相似的底层镁铁质熔体紧密相连，有时还与其物理相互作用。从推断的岩浆储存深度和喷口部位的地理范围来看，我们认为陶波目前已经建立了一个大型的硅质淤浆系统（> 200 km（3），可能高达1000 km（3））。在未来的任何阶段提供新的火山事件或火山循环。

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