The origin of volcanic flux variations along Pacific hotspot tracks: Plume-lithosphere interaction vs. plume pulsations

近30~80 Ma以来，夏威夷热点地区的火山通量普遍增大，10~15 Ma呈二阶变化。这一显著的增长仍然无法用经典的烟柱理论解释，该理论预测，伴随着大规模火山活动的烟柱头部阶段之后是活动不断减少的烟柱尾部阶段。特别是，25-30 Ma以前，夏威夷火山通量急剧增加了~4倍，这似乎与太平洋板块运动从~60公里/Ma增加到~100公里/Ma有关。几乎在同一时间，南太平洋地区出现了一股年轻的低流量热点轨道的浪潮。从我们对采样较差的夏威夷轨迹的理解来看，尚不清楚这些火山通量变化是与太平洋板块的加速有关，还是与夏威夷羽流的脉动有关。为了解释板块速度加快和火山流量增加的耦合观测，我们打算探索三个年轻的、相对低流量的太平洋热点轨迹。多个热点轨道的高精度地质年代学数据是从板内记录中提取有关夏威夷热点轨道采样较差的年轻端的基本新信息的唯一途径。我们建议使用下一代多收集器质谱仪对来自基金会、复活节和普卡普卡-拉诺拉希火山轨迹的111个样品进行高精度年龄测定。我们将利用这些新数据来(1)准确地确定太平洋板块速度增加的时间和热点火山通量的变化，以及(2)了解控制太平洋热点火山通量变化的潜在机制。

The volcanic flux at the Hawaiian hotspot generally increased over the last 30-80 Ma, with second-order variations over 10~15 Ma. This significant increase remains unexplained by classic plume theory, which predicts that a plume-head stage with massive volcanic activity is followed by a plume- tail stage with ever decreasing activity. In particular, 25-30 Ma ago there was a sharp increase in the Hawaiian volcanic flux by a factor ~4 that appears to be associated with an increase in Pacific plate motion from ~60 km/Ma to ~100 km/Ma. At about the same time there was a surge across the South Pacific of young low-volume hotspot tracks. It is unclear from our understanding of the poorly sampled Hawaiian track if these volcanic flux variations are related to speed up of the Pacific plate or to pulsations of the Hawaiian plume. In order to explain the coupled observations of faster plate speed and increased volcanic flux we aim to explore three young, relatively low-volume Pacific hotspot tracks. High–precision geochronological data for multiple hotspot tracks is the only way of extracting fundamental new information from the intraplate record about the poorly-sampled young end of the Hawaiian hotspot track. We propose to determine high-precision ages using the next generation of multi-collector mass spectrometer for 111 samples from the Foundation, Easter and Pukapuka-Rano Rahi volcanic tracks. We will use these new data to (1) pinpoint the timing of Pacific plate-speed increases and variations in hotspot volcanic flux, and (2) understand the underlying mechanisms controlling volcanic flux variations at Pacific hotspots.