Study of temporal and spatial variation of Hawaiian plume

在这里，我们总结了我们最近对夏威夷五座火山恢复活力的熔岩进行未加钉K-Ar定年的结果。(1)西毛伊岛（Sherrod et al., in press）：下面的后盾层有9个年龄，盾层阶段单位有28个年龄，分别为1.8-1.3 Ma和1.3-1.2 Ma。因此，在西毛伊岛，火山在恢复活力之前的静止时间约为0.6毫秒，比以前估计的要长得多。(2) Koolau, Oahu (Ozawa等，2005)：对32个恢复期火奴鲁鲁火山的41个样品和8个下伏盾状期Koolau火山样品的新时代分析表明，盾状火山作用结束于2.1 Ma，恢复期火山作用开始于0.8 Ma，导致火山活动中断1.3 Ma。火奴鲁鲁火山活动在0.8 ~ 0.35 Ma和~ 0.1 Ma有两个明显的脉冲。(3) Kahoolawe （Sano et al.，本次会议并提交）：最年轻的火山喷发留下了5个小的岩脉煤渣沉积物和稀疏的熔岩流，这些沉积物以前没有确定年代，但在大量侵蚀不整合的基础上被认为是一个复兴阶段的一部分。来自最南端的两个样本和来自下一个北端的一个样本显示年龄在1.0到1.4 Ma之间，这表明后盾和最年轻的爆发之间有一个短暂的间隔。(4) Kauai (Sano et, in prep.)：来自Koloa火山岩的23个样品的新年龄在0.15 ~ 3.9 Ma之间，而来自Waimea Canyon玄武岩晚期的5个样品的新年龄在4.1 ~ 4.5 Ma之间。因此，恢复活力前的火山静息期最多约为0.3毫秒。考艾岛恢复活力阶段可分为至少5次喷发脉冲。

Here we summarize below our recent results of unspiked K-Ar dating on rejuvenated lavas from five Hawaiian volcanoes.(1) West Maui (Sherrod et al., in press) : Nine ages for the underlying postshield and 28 for shield stage units range from 1.8-1.3 Ma and 1.3-1.2 Ma, respectively. Therefore, the duration of volcanic quiescence prior to rejuvenation is about 0.6 m.y. at West Maui, much longer than estimated previously.(2) Koolau, Oahu (Ozawa et al., 2005) : New ages, on 41 samples from 32 vents of rejuvenated-stage Honolulu Volcanics and on eight samples of underlying shield-stage Koolau Volcanics show that shield volcanism ended at 2.1 Ma and that rejuvenated volcanism started at 0.8 Ma, resulting in a 1.3 m.y. hiatus in volcanic activity. Two distinct pulses were found for Honolulu volcanism at 0.8-0.35 and 〜0.1 Ma.(3) Kahoolawe (Sano et al., this meeting and submitted) : youngest eruptions left five small deposits of dike-fed cinders and sparse lava flows, which were previously undated but thought part of a rejuvenated stage on the basis of a substantial erosional unconformity. Two samples from the southernmost site and one sample from the next site northward show ages of 1.0 to 1.4 Ma, suggesting a short gap between the postshield and youngest eruptions.(4) Kauai (Sano et al., in prep.) : New ages of 23 samples from rejuvenated Koloa Volcanics range from 0.15 to 3.9 Ma, whereas ages of five samples from late shield-stage Waimea Canyon Basalt are 4.1-4.5 Ma. Hence, the volcanic quiescence before rejuvenation is at most about 0.3 m.y. The Kauai rejuvenated-stage can be divided into at least five eruptive pulses.