Dynamics of an unusual cone-building trachyte eruption at Pu‘u Wa‘awa‘a, Hualālai volcano, Hawai‘i
Dynamics of an unusual cone-building trachyte eruption at Pu‘u Wa‘awa‘a, Hualālai volcano, Hawai‘i
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夏威夷花莱火山普阿乌瓦瓦瓦阿不寻常的锥形粗面岩喷发的动力学
DOI：
10.1007/s00445-017-1106-z
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发表时间：
2017
影响因子：
3.5
通讯作者：
Parsons, Elliott
中科院分区：
文献类型：
--
作者：
Shea, Thomas;Leonhardi, Tanis;Giachetti, Thomas;Lindoo, Amanda;Larsen, Jessica;Sinton, John;Parsons, Elliott
Pu'u Wa'awa'a 火山碎屑锥和 Pu'u Anahulu 熔岩流是两个突出的单成因喷发特征，被认为是由华拉莱火山（夏威夷）以粗面岩为主的早期后盾阶段的单次喷发造成的。 Pu'u Wa'awa'a 由富含深色致密碎屑的粗糙交叉层状单元的复杂重复组成，这些单元相反地分级为富含浮石的较粗单元。锥体中的火山碎屑的结构极其多样，除了完全结晶的端元之外，从玻璃状黑曜石到泡状矿渣或浮石。相比之下，>100 米厚的 Pu’u Anahulu 流完全是全晶质的。本研究通过现场观察和整体岩石分析，旨在测试 Pu'u Wa'awa'a 火山灰流和 Pu'u Anahulu 熔岩流是否如之前假设的那样源自同一喷发。晶体和囊泡结构以及间质玻璃的挥发性含量被表征，以确定 Pu'u Wa'awa'a 粗面岩中结构变化的起源（例如，岩浆混合与脱气起源）。我们发现（1）这两次喷发很可能起源于不同的喷口和岩浆库，尽管它们距离很近且年龄相似，（2）形成 Pu'u Wa'awa'a 的火山碎屑的结构多样性可以通过管道内不同的岩浆脱气和排气来充分解释，（3）Pu'u Wa'awa'a 锥体是在猛烈的斯特龙博利期和武尔干期之间风格过渡的爆炸期间形成的，涉及形成一个大锥体并反复破坏导管塞，但不产生大的火山碎屑密度流（PDC），以及（4）夏威夷粗面岩的对比喷发类型（流动型、锥体型和 PDC 形成）可能与岩浆到达地表之前的排气能力差异有关，而不是与内在成分或温度特性有关。这些结果进一步强调，与英安岩或流纹岩相比，粗面岩是“动力学更快”的岩浆，可能脱气和结晶更快。
The Pu‘u Wa‘awa‘a pyroclastic cone and Pu‘u Anahulu lava flow are two prominent monogenetic eruptive features assumed to result from a single eruption during the trachyte-dominated early post-shield stage of Hualālai volcano (Hawaiʻi). Puʻu Wa‘awa‘a is composed of complex repetitions of crudely cross-stratified units rich in dark dense clasts, which reversely grade into coarser pumice-rich units. Pyroclasts from the cone are extremely diverse texturally, ranging from glassy obsidian to vesicular scoria or pumice, in addition to fully crystalline end-members. The >100-m thick Pu‘u Anahulu flow is, in contrast, entirely holocrystalline. Using field observations coupled with whole rock analyses, this study aimed to test whether the Pu‘u Wa‘awa‘a tephra and Pu‘u Anahulu lava flows originated from the same eruption, as had been previously assumed. Crystal and vesicle textures are characterized along with the volatile contents of interstitial glasses to determine the origin of textural variability within Pu‘u Waʻawaʻa trachytes (e.g., magma mixing vs. degassing origin). We find that (1) the two eruptions likely originated from distinct vents and magma reservoirs, despite their proximity and similar age, (2) the textural diversity of pyroclasts forming Pu‘u Wa‘awa‘a can be fully explained by variable magma degassing and outgassing within the conduit, (3) the Pu‘u Wa‘awa‘a cone was constructed during explosions transitional in style between violent Strombolian and Vulcanian, involving the formation of a large cone and with repeated disruption of conduit plugs, but without production of large pyroclastic density currents (PDCs), and (4) the contrasting eruption styles of Hawaiian trachytes (flow-, cone-, and PDC-forming) are probably related to differences in the outgassing capacity of the magmas prior to reaching the surface and not in intrinsic compositional or temperature properties. These results further highlight that trachytes are “kinetically faster” magmas compared to dacites or rhyolites, likely degassing and crystallizing more rapidly.
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DOI：
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发表时间：
1980
期刊：
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2001
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DOI：
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发表时间：
2007
期刊：
Chemical Geology 242
影响因子：
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