The volatile budget of Hawaiian magmatism: Constraints from melt inclusions from Haleakala volcano, Hawaii

Moore L. R.; Gazel E.; Bodnar R. J.

摘要

Pre-eruptive volatile contents recorded by melt inclusions from ocean island settings such as Hawaii constrain the extent of deep Earth outgassing on geologic timescales by mantle plume activity. However, melt inclusions trapped from a partially degassed magma will not reflect the original volatile content of the primary melt, and relatively silicic (45 wt% SiO2) shield-stage tholeiites are more likely to have been affected by degassing during fractionation at shallow depths. In contrast, magmas associated with post-shield volcanoes erupt volatile-rich melts that ascend quickly from the source region and crystallize in deep reservoirs. As a result, melt inclusions from post-shield volcanoes may be more likely to preserve undegassed melt compositions that can be used to determine the primary melt and source volatile contents. In this study, we analyzed melt inclusions from Haleakala Volcano (East Maui, Hawaii) to estimate the volatile budget of Hawaiian post-shield magmas. Melt inclusions from Haleakala contain up to 1.3 wt% CO2, 1.2 wt% H2O, and about 2000 ppm S. We calculate that melts from Haleakala were derived from a parental melt with-0.7 wt% H2O and-0.7 wt% CO2 and experienced-15-40% polybaric, fluid-saturated crystallization starting at 5-7 kbar. Post-shield melt inclusions from Haleakala have H2O/Ce and CO2/Ba compositions that are intermediate between shield-stage melt inclusions from Kilauea and the alkaline North Arch Volcanic Field, which is consistent with a scenario in which primary melts from Haleakala are influenced by the volatile-rich auto-metasomatized periphery of the composite plume source. (c) 2020 Elsevier B.V. All rights reserved.commentSuperscript/Subscript Available/comment

机译：来自海洋岛屿环境的熔体夹杂物记录的预发布挥发内容，如夏威夷，通过地幔羽流量限制了地质时间尺度的深层地球的范围。然而，从部分脱气的岩浆中捕获的熔体夹杂物不会反映初级熔体的原始挥发性含量，并且相对硅（> 45wt％SiO 2）屏蔽阶obleies更可能受到在浅深度的分馏期间脱气的影响更可能受到脱气。相比之下，与屏蔽后火山相关的岩浆爆发了富有的熔体熔体，从源区迅速提升并在深层储层中结晶。结果，来自屏蔽后火山的熔体夹杂物可能更容易保留可用于确定初级熔体和源挥发性含量的不可缩熔融组合物。在这项研究中，我们分析了Haleakala火山（东毛伊岛，夏威夷）的熔体夹杂物来估计夏威夷盾牌岩浆挥发性预算。 Haleakala的熔体夹杂物含有高达1.3wt％的CO 2，1.2wt％H 2 O，1.2重量％H 2 O，以及约2000ppm S.我们计算哈里亚哈拉的熔体衍生自与-0.7wt％H 2 O和-0.7wt％CO 2的亲本熔体和经验 - 15-40％的聚下压力，流体饱和结晶起始，起始于5-7 kbar。 Haleakala的屏蔽后熔体夹杂物具有H 2 O / Ce和CO 2 / BA组合物，其来自基尔拓和碱性北拱火山场的屏蔽级熔体夹杂物之间的中间，这与哈拉贝拉的主要熔化的情况一致复合羽流源的富挥发的自动偏析周边。（c）2020 Elsevier B.v.保留所有权利。<注释>上标/下标可用

The volatile budget of Hawaiian magmatism: Constraints from melt inclusions from Haleakala volcano, Hawaii

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