Compositional Layering in Io Driven by Magmatic Segregation and Volcanism

• Published in: Journal of geophysical research. Planets 2020-09, Vol.125 (9), p.n/a
• Main Authors: Spencer, Dan C., Katz, Richard F., Hewitt, Ian J., May, David A., Keszthelyi, Laszlo P.
• Format: Article
• Language: English
• Subjects: Ascent; compaction; Evolution; heat pipes; Heating; High temperature; Jupiter; Lava; Low temperature; Lower mantle; Melting; Melts; planetary compositions; planetary volcanism; Rocks; Stratification; tidal heating; Volcanic activity; Volcanic eruptions
• ISSN: 2169-9097; 2169-9100
• DOI: 10.1029/2020JE006604

The compositional evolution of volcanic bodies like Io is not well understood. Magmatic segregation and volcanic eruptions transport tidal heat from Io's interior to its surface. Several observed eruptions appear to be extremely high temperature (≥1600 K), suggesting either very high degrees of melting, refractory source regions, or intensive viscous heating on ascent. To address this ambiguity, we develop a model that couples crust and mantle dynamics to a simple compositional system. We analyze the model to investigate chemical structure and evolution. We demonstrate that magmatic segregation and volcanic eruptions lead to stratification of the mantle, the extent of which depends on how easily high temperature melts from the more refractory lower mantle can migrate upwards. We propose that Io's highest temperature eruptions originate from this lower mantle region and that such eruptions act to limit the degree of compositional stratification. Plain Language Summary Io is vigorously heated by the tides it experiences from Jupiter. This heating causes the interior to melt, feeding volcanic eruptions onto the surface. When a rock is heated, some chemical components enter the melt at lower temperatures than others. In this work we use a new model to show that low‐melting‐point magmas form and rise toward the surface, leaving behind a deep mantle composed of high‐melting‐point rock. This deep high‐melting‐point rock eventually melts and must also rise upward in order to allow the lower mantle to lose heat. We propose that high‐temperature magmas formed in the deep mantle can rise all the way to the surface, providing an explanation for the highest temperature eruptions. Key Points We present a model of Io that couples crust and mantle dynamics to a simplified compositional system Magmatic segregation and volcanism cause rapid stratification, leading to the formation of refractory melts in the lower mantle Io's highest temperature eruptions can be explained as deep refractory melts that migrate to the surface