A high carbon content of the Hawaiian mantle from olivine-hosted melt inclusions
A high carbon content of the Hawaiian mantle from olivine-hosted melt inclusions
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DOI：
10.1016/j.gca.2019.04.001
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发表时间：
2019-06
影响因子：
5
通讯作者：
J. Tucker;E. Hauri;A. Pietruszka;Michael O. Garcia;J. Marske;F. Trusdell
中科院分区：
文献类型：
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作者：
J. Tucker;E. Hauri;A. Pietruszka;Michael O. Garcia;J. Marske;F. Trusdell
深部地幔碳含量和碳通量是了解全球挥发分循环和分布的基本量。在这里，我们提出了407橄榄石托管熔体包裹体从华拉莱，基拉韦厄，库劳，Loihi，和莫纳罗亚CO2浓度测量约束夏威夷地幔CO2含量和通量。量化的熔体夹杂物CO2是复杂的无处不在的蒸汽或“收缩”气泡的存在。从测量的气泡尺寸和CO2的状态方程，并添加到溶解CO2重建总熔体包裹体CO2浓度的贡献，从出溶收缩气泡CO2确定。气泡通常含有约90%的熔体夹杂物C，其中大部分可能被隔离在气泡壁上的沉淀相中，因此不适合通过拉曼光谱法进行测量。根据我们的总（溶解+气泡）CO2浓度的数据集，我们估计来自五个夏威夷火山的母体熔体的CO2浓度范围从3900到10，000 ppm CO2。在活火山中，CO2浓度向西北方向降低，可能反映了地幔源的异质性，尽管与岩浆房相对深度有关的CO2脱气差异也可能发挥作用。夏威夷火山的地幔来源范围从380到480 ppm的CO2表明，夏威夷羽至少是一个因素的104倍以上的C-丰富的上地幔中洋脊玄武岩采样。这种富集可能是由于夏威夷地幔中存在回收的表层碳和/或富含碳的原始物质。
The deep mantle carbon content and flux are fundamental quantities in understanding global volatile cycles and distributions. Here, we present CO2concentrations measured in 407 olivine-hosted melt inclusions from Hualalai, Kilauea, Koolau, Loihi, and Mauna Loa to constrain the Hawaiian mantle CO2content and flux. Quantification of melt inclusion CO2is complicated by the ubiquitous presence of vapor or “shrinkage” bubbles. The contribution from exsolved shrinkage bubble CO2was determined from the measured bubble size and a CO2equation of state, and added to the dissolved CO2to reconstruct total melt inclusion CO2concentrations. Bubbles typically contain ∼90% of melt inclusion C, much of which may be sequestered in precipitated phases on bubble walls, and thus not amenable to measurement by Raman spectroscopy. Based on our dataset of total (dissolved + bubble) CO2concentrations, we estimate that parental melts from the five Hawaiian volcanoes have CO2concentrations ranging from 3900 to 10,000 ppm CO2. Among the active volcanoes, CO2concentrations decrease to the northwest, likely reflecting mantle source heterogeneity, although differences in CO2degassing related to the relative depths of the magma chambers may also play a role. Mantle sources of the Hawaiian volcanoes range from 380 to 480 ppm CO2suggesting that the Hawaiian plume is at least a factor of ∼4 more C-rich than the upper mantle sampled by mid-ocean ridge basalts. This enrichment is likely due to the presence of recycled surficial C and/or C-rich primitive material in the Hawaiian mantle.