Time Scales of Magmatic Processes from Modeling the Zoning Patterns of Crystals

Warm storage for arc magmas

“…The preservation of sharp compositional gradients in plagioclase phenocrysts, assumed to have crystallized >10 ka before eruption, has recently been interpreted to indicate that arc volcanic reservoirs characteristically remain in "cold storage" at temperatures below the eruption window, possibly below the solidus, and thus only capable of erupting during brief recharge events (<10 ka) (1). In contrast, zircon dating and heat budget considerations are difficult to reconcile with this scenario; instead, they are consistent with continuously partially molten reservoirs capable of erupting (i.e., with melt portion ≥40%) over long durations (>>10 ka) (6)(7)(8)(9)(10)(11)(12). Whatever these differences, all agree that understanding the thermal history of the magmatic reservoir is key to constraining the duration of the eruption window (3,12).…”

“…volcano | eruption | arc magma | zircon D etermining the timescale of magma storage and remobilization in the upper crust is key to understanding the tempo and magnitude of volcanic eruptions (1)(2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13). Whether a volcano can erupt is controlled by the recharge rate to the magma reservoir (13) (reservoir in this context refers to the portion of the igneous complex that is potentially eruptible), which in turn determines the duration of the "eruption window" [generally defined as the rheological state during which the subvolcanic reservoir is below ∼60% crystals and hence capable of eruption (4)].…”

“…Whether a volcano can erupt is controlled by the recharge rate to the magma reservoir (13) (reservoir in this context refers to the portion of the igneous complex that is potentially eruptible), which in turn determines the duration of the "eruption window" [generally defined as the rheological state during which the subvolcanic reservoir is below ∼60% crystals and hence capable of eruption (4)]. However, estimates for how long this eruption window remains open vary over four orders of magnitude; this suggests either profound problems in assumptions underlying one or more of these estimates or a continuum of physical mechanisms that resist formulation of a unified model for the state of magma reservoirs before eruption (1)(2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13). The preservation of sharp compositional gradients in plagioclase phenocrysts, assumed to have crystallized >10 ka before eruption, has recently been interpreted to indicate that arc volcanic reservoirs characteristically remain in "cold storage" at temperatures below the eruption window, possibly below the solidus, and thus only capable of erupting during brief recharge events (<10 ka) (1).…”

Short time scales of magma-mixing processes prior to the 2011 eruption of Shinmoedake volcano, Kirishima volcanic group, Japan

“…Zoning profiles of phenocrysts have been often analyzed to estimate time scales of various magmatic processes (e.g., Costa et al 2008). Olivine is one of the most useful minerals for such studies (e.g., Gerlach and Grove 1982;Nakamura 1995;Martin et al 2008) because it commonly occurs in mafic magma, and its rapid Mg-Fe interdiffusion enables timescales to be estimated at less than 1 month.…”

“…Olivine is one of the most useful minerals for such studies (e.g., Gerlach and Grove 1982;Nakamura 1995;Martin et al 2008) because it commonly occurs in mafic magma, and its rapid Mg-Fe interdiffusion enables timescales to be estimated at less than 1 month. Recently, Mg in plagioclase has been used to provide time scales of days to years (e.g., Costa et al 2003Costa et al , 2008Druitt et al 2012;Ruprecht and Cooper 2012). Magnetite phenocrysts are particularly useful in silicic magma systems for detecting the processes within days to months before eruption (e.g., Nakamura 1996; Devine et al 2003;Chertkoff and Gardner 2004;Tomiya and Takahashi 2005) because of their rapid diffusion (Van Orman and Crispin 2010) and common occurrence in various types of magma.…”