Lithocap Structure-controlled feeder zone Lithology-controlled ...

Early convecting magma (30 -
50 % crystals), flux ~ equal to
White Island quiescent eruption
Later stagnant magma,
slow crystallization =
Low rate of fluid advection, fluid
rises slowly and loses heat, such
that it does not intersect solvus
Lower temperature, brittle
conditions at shallow depth
Late stagnant magma (>50%
crystals, advective flux sharply
decreases ~ 10x
Creation of the phyllic
(muscovite, “sericite”) stage
Shinohara & Hedenquist, 1997
Effect on fluid exsolution,
advection, and nature of fluid
ascent?
Early magmatic fluid =
Hot, plastic, lithostatic P (potassic,
A veins)
Rapid ascent, intersection of
solvus, forms brine plus vapor
Later magmatic fluid =
Cooler, brittle, hydrostatic P
(muscovite, D veins)
Critical fluid never intersects
solvus due to slow ascent and
cooling
Normal progression of exsolving
magma chambers, magma
convection early (fast
crystallization), to later stagnant
xstallization (conductive heat loss)
Shinohara and Hedenquist, 1997;
Hedenquist et al., 1998
Chang et al., 2011