Magma ascent rates control volcanic eruption styles. However, the rates at which basaltic magmas ascend through the crust remain highly uncertain. Although recent studies have successfully exploited records of decompression driven degassing to estimate the rates at which H₂O-rich basalts ascend, such approaches cannot readily be applied to primitive and H₂O-poor basalts that erupt in ocean island and mid-ocean ridge settings. Here we present magma ascent rates obtained by modeling the dissolution of clinopyroxene crystals in a wehrlitic nodule from the primitive Borgarhraun lava flow in North Iceland. High-Al₂O₃ clinopyroxene core compositions are consistent with crystallization near the Moho (~800 MPa), whereas low-Al₂O₃ clinopyroxene rims and inclusion compositions are consistent with crystallization at or near the surface. We interpret low-Al₂O₃ rims and inclusions as the crystallized remnants of boundary layers formed by the dissolution of high-Al₂O₃ clinopyroxene during magma ascent. By combining characteristic rim dissolution lengths of 50–100 μm with published experimental calibrations of clinopyroxene dissolution behavior, we estimate that the Borgarhraun magma most likely decompressed and ascended at rates of 3.0–15 kPa.s⁻¹ and 0.11–0.53 m.s⁻¹, respectively. These rates are slightly faster than published estimates obtained by modeling the diffusive re-equilibration of olivine crystals, suggesting that the Borgarhraun magma either accelerated upwards or that it stalled briefly at depth prior to final ascent. Comparisons with other basaltic eruptions indicate that the H₂O-poor magma that fed the dominantly effusive Borgarhraun eruption ascended at a similar rate to some H₂O-rich magmas that have fed explosive eruptions in arc settings. Thus, magma ascent rates do not appear to correlate simply with magma H₂O contents. Overall, our findings confirm that primitive and H₂O-poor basalts can traverse the crust within days, and may erupt with little precursory warning of magma ascent.

岩浆上升速率控制着火山喷发的样式。但是，玄武岩浆通过地壳上升的速度仍然非常不确定。尽管最近的研究已经成功地利用减压驱动的脱气记录来估算富含H ₂ O的玄武岩的上升速率，但是这种方法不能轻易应用于在大洋岛屿和中洋脊喷发的原始和富含H ₂ O的玄武岩。设置。在这里，我们介绍了通过模拟北冰岛原始的Borgarhraun熔岩流中的辉绿结核中斜辉石晶体溶解而获得的岩浆上升速率。高Al ₂ O ₃斜茂铁芯组成与Moho附近（〜800 MPa）的结晶相一致，而低Al ₂O ₃ Clinopyroxene边缘和内含物的组成与表面处或附近的结晶相一致。我们将低Al ₂ O ₃边缘和夹杂物解释为岩浆上升过程中由高Al ₂ O ₃斜辉石溶解而形成的边界层的结晶残留物。通过将特征轮缘溶解长度为50–100μm与已公布的斜柏石溶解行为实验标定相结合，我们估计，Borgarhraun岩浆最有可能以3.0–15 kPa.s ^-1和0.11–0.53 ms ^-1的速率减压和上升。， 分别。这些速率比通过对橄榄石晶体的扩散性重新平衡进行建模而获得的公开估算值稍快，这表明Borgarhraun岩浆要么向上加速，要么在最终上升之前短暂停顿在深处。与其他玄武岩喷发的比较表明，以博格哈龙喷发为主的贫H ₂ O岩浆上升的速度与某些在电弧环境下爆炸性喷发的富H ₂ O岩浆相似。因此，岩浆上升速率似乎并不简单地与岩浆H ₂ O含量相关。总体而言，我们的发现证实了原始和H ₂贫瘠的玄武岩可以在几天之内穿越地壳，并且可能在没有岩浆上升预警的情况下爆发。