Experimental and textural constraints on mafic enclave formation in volcanic rocks

Thermal and rheological controls on the formation of mafic enclaves or banded pumice

“…Magma mixing is recorded from the microscale in geochemically zoned crystals (Clynne 1999;Tepley et al 1999Tepley et al , 2000Coombs et al 2003;Browne et al 2006;Davidson et al 2007;Ruprecht and Woerner 2007;Andrews et al 2008) to the magma-chamber scale in plutons and batholiths (e.g., Chappell 1996;Wiebe et al 1997). At centimeter to meter scales, mixing style is recorded in volcanic rocks by enclaves and banded pumice (e.g., Eichelberger 1980;Vernon 1984;Koyaguchi 1985;Bacon 1986;Freundt and Tait 1986;Koyaguchi 1986;Campbell and Turner 1989;Clynne 1999;Coombs et al 2003;Browne et al 2006;Waythomas et al 2010;Sylvester 2011).…”

“…At centimeter to meter scales, mixing style is recorded in volcanic rocks by enclaves and banded pumice (e.g., Eichelberger 1980;Vernon 1984;Koyaguchi 1985;Bacon 1986;Freundt and Tait 1986;Koyaguchi 1986;Campbell and Turner 1989;Clynne 1999;Coombs et al 2003;Browne et al 2006;Waythomas et al 2010;Sylvester 2011). Enclaves are discrete inclusions of one magma hosted within another magma (Fig.…”

“…Studies of magma mixing have long recognized that mixing textures and compositional zoning result from the interaction between two magmas with different temperatures, compositions, densities, viscosities, and solidii (e.g., Eichelberger 1980;Koyaguchi 1985;Bacon 1986;Campbell and Turner 1986;Koyaguchi 1986;Campbell and Turner 1989;Koyaguchi and Blake 1989;Jellinek et al 1999;Blake and Fink 2000;Snyder 2000;Coombs et al 2003;Humphreys et al 2006;Martin et al 2006). Injection of one magma into another, thermal and compositional contrasts of the magmas, and buoyancy forces can drive mixing between the two magmas (Eichelberger 1980;Freundt and Tait 1986;Clynne 1999;Blake and Fink 2000;Snyder 2000;Coombs et al 2003;Ruprecht et al 2008).…”

“…Injection of one magma into another, thermal and compositional contrasts of the magmas, and buoyancy forces can drive mixing between the two magmas (Eichelberger 1980;Freundt and Tait 1986;Clynne 1999;Blake and Fink 2000;Snyder 2000;Coombs et al 2003;Ruprecht et al 2008). Viscosity contrasts and solidification inhibit mixing Blake and Fink 2000;Martin et al 2006;Hodge and Jellinek 2012;Hodge et al 2012a, b).…”

“…In those models, injection of a typically hotter, mafic magma into a cooler, silicic host results in the formation of either enclaves or banding depending on magma properties and injection conditions. In general, for low injection rates, because the mafic intruder is denser than the host, the intruder is assumed to pool at the base of the silicic magma body (Pallister et al 1996;Clynne 1999;Snyder 2000;Coombs et al 2003). As the intruder crystallizes, it can become volatile saturated, resulting in vesiculation and a decrease in density (Eichelberger 1980;Turner and Campbell 1986;Clynne 1999;Pallister et al 1996;Coombs et al 2003;Ruprecht et al 2008).…”