美国夏威夷大学Aaron J. Pietruszka研究组报道，Kama'ehuakanaloa熔岩化学的缓慢变化与夏威夷地幔柱边缘缓慢的地幔上涌有关。相关论文于2023年5月26日发表在《地质学》杂志上。

该研究组对Kama'ehuakanaloa (前Lō'ihi) 玄武岩中的²²⁶Ra-²³⁰Th不平衡进行了高精度测量，来估计夏威夷海底前盾状火山最近喷发的模型年龄。年龄范围从大约ca. 0到2300 yr (不包含两个更老的样本)，在过去150 yr 至少有5次喷发，揭示了Kama'ehuakanaloa (或“Kama'ehu”) 岩浆演化的两张快照。

首先，从碱性火山作用到拉斑玄武岩火山作用的长期转变几乎在大约 ca. 2 ka. 前完成。第二，峰顶熔岩不相容元素比率 (如Th / Yb) 的系统性短期波动发生在约1200 yr 的时间尺度上。这比邻近的地面火山 Kīlauea 约200 yr 的熔岩化学历史周期要长的多。Kama'ehu熔岩化学变化较慢的速度很可能是由夏威夷地幔柱边缘缓慢的地幔上涌控制的。

据悉，由于确定火山喷发时间是一个挑战，人们很难解释活海底火山熔岩化学的时间变化。

附：英文原文

Title: Slow changes in lava chemistry at Kama'ehuakanaloa linked to sluggish mantle upwelling on the margin of the Hawaiian plume

Author: Aaron J. Pietruszka, Michael O. Garcia, Richard W. Carlson, Erik H. Hauri

Issue&Volume: 2023-05-26

Abstract: Temporal variations in lava chemistry at active submarine volcanoes are difficult to decipher due to the challenges of dating their eruptions. Here, we use high-precision measurements of ²²⁶Ra-²³⁰Th disequilibria in basalts from Kama'ehuakanaloa (formerly Lō'ihi) to estimate model ages for recent eruptions of this submarine Hawaiian pre-shield volcano. The ages range from ca. 0 to 2300 yr (excluding two much older samples) with at least five eruptions in the last ~150 yr. Two snapshots of the magmatic evolution of Kama'ehuakanaloa (or “Kama'ehu”) are revealed. First, a long-term transition from alkalic to tholeiitic volcanism was nearly complete by ca. 2 ka. Second, a systematic short-term fluctuation in ratios of incompatible elements (e.g., Th/Yb) for summit lavas occurred on a time scale of ~1200 yr. This is much longer than the ~200-yr-long historical cycle in lava chemistry at the neighboring subaerial volcano, Kīlauea. The slower pace of the variation in lava chemistry at Kamaehu is most likely controlled by sluggish mantle upwelling on the margin of the Hawaiian plume.

DOI: 10.1130/G51350.1

Source: https://pubs.geoscienceworld.org/gsa/geology/article/doi/10.1130/G51350.1/623711/Slow-changes-in-lava-chemistry-at-Kama-ehuakanaloa