My investigations into the processes attending the ascent and emplacement of magmas into the crust follow naturally from my desire to understand the overall displacement history of an orogen.  Not to mention Scott R. Paterson was my Ph.D. advisor and most discussions on geology with his research group would normally migrated to that topic at some point.  Seriously, however, as a Paterson student I was made very much aware of the role the various mass transfer processes must play to accommodate the ascent of magma.  During my mapping in northern Baja California I happened to discover a relatively small pluton located ~5 km southwest of the ancestral Agua Blanca fault, a suture juxtaposing the Alisitos arc with the Santiago Peak arc.  This pluton was named Balbuena after my gracious hosts during my time mapping in that area.  At the level of exposure the Balbuena pluton is composed of three phases (I,II, & III) with a relatively mafic (gabbro to diorite) middle phase (II) which was being intruded out by the tonalitic outer and inner phases (I & III) at the time of final crystallization.  This is demonstrated by the observation of the tonalitic magmas intruding and mechanically disintegrating the middle phase (II).  However, one of the most unique and interesting aspects of this intrusion are the relationships in the surrounding country rocks.    
     The Alisitos Formation comprises the volcanic host rock to the Balbuena pluton.  At distances greater than two kilometers from the margin of the Balbuena the Alisitos Fm. is characterized by a strong and consistent northwest strike of bedding as formed by tight to isoclinal, upright to slightly overturned (to the southwest) folds.  However, within a few hundred to as much as two kilometers from the margin of the pluton these regionally consistent trends are deflected in opposite senses on opposite sides of the pluton.  For example, to the northwest of the Balbuena an overturned syncline is deflected from a regional trend of ~315 (or 135)  to ~65 (or 245), for a net counterclockwise rotation of ~70 degrees.  Concomitant with this deflection the fold is rotated into an upright orientation and the intensity of strain measured from these rocks increases dramatically over that in the surrounding Alisitos Fm. unaffected by the Balbuena.  In a recent GSA abstract Wetmore et al. (2001) argued that the dramatic and wide structural aureole of the Balbuena pluton resulted from the emplacement of the middle phase (II) due to the observation that the deflected host rocks were in concordance with the trend of the middle phase along the northwest side of the pluton and because the outer and inner phases cut discordantly across this aureole in almost every exposure.  Furthermore, mechanically disintegrated (stoped) blocks of the Alisitos Fm. are volumetrically abundant (locally as great as 30-40%) along the northwestern and southeastern margins of the pluton.

Geologic map of the Balbuena pluton.  Red lines are the axial traces
of folds, thin black lines are trend lines of bedding, and black ellipses are
strain ellipses showing the YZ plane (uncorrected for primary fabric).

Preemplacement fold with axial surface rotated >80 degrees counterclockwise in the northwest margin of the Balbuena pluton

Mechanical disintegration of middle quartz diorite phase (II) within the outer tonalite phase (III). Note that most blocks have globular

margins and discreet fractures (many with clear offsets).

Elongate and flattened mafic enclaves