Clinopyroxene Dissolution Records Rapid Magma Ascent ...

• Main Authors: Neave, DA, Maclennan, J
• Format: Article in Journal/Newspaper
• Language: English
• Published: Frontiers Media SA 2020
• Subjects: magma ascent rate; plumbing system; clinopyroxene dissolution; basalt; disequilibrium; Iceland; Borgarhraun; Ocean Island
• Online Access: https://dx.doi.org/10.17863/cam.52449; https://www.repository.cam.ac.uk/handle/1810/305366

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 modelling 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 crystallisation near the Moho (_800 MPa), whereas low-Al2O3 clinopyroxene rims and inclusion compositions are consistent with crystallisation at or near the surface. We interpret low-Al2O3 rims and inclusions as the crystallised remnants of boundary layers formed by the dissolution of high-Al2O3 clinopyroxene during magma ascent. By combining ...