USA Graphite Inc fka USGT

[DITRstocks]

$USGT The mylonitic zone is considered to represent a deep expression of middle Tertiary extensional shearing that led to unroofing of the middle crust (Snoke and Lush, 1984; Snoke and Howard, 1984; Howard, 1987). Patterns of Oligocene to middle Miocene cooling ages from fissiontrack and biotite 40Ar/39Ar studies on the metamorphic and granitic rocks suggest that much of the footwall was at elevated temperatures, typical of midcrustal levels, until it was rapidly cooled in the early Miocene (Kistler and others, 1981; Dokka and others, 1986; Dallmeyer and others, 1986). Stratigraphic evidence from surrounding areas as well as the geochronologic and structural evidence supports a model that ascribes this cooling to extensional unroofing during progressive rise of the footwall.