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regional stresses during at least the latter part of the period of granitiza-
tion; the leucogranite sills and dykes, which apparently fill fractures and
thus imply rock movement in the earlier stages, but which also should
have recorded the effects of any deforming stresses active during their
consolidation, are mostly structureless.

(3) In the wake of the highly selective granitizing solutions came
others which, by contrast, were capable of wholesale, indiscriminate replace-
ment of rocks of various compositions and textures. These solutions,
apparently, had only limited power to replace the grey granodiorite, and
large quantities may have passed through narrow fractures now represented
by thin seams; but they were able to dissolve the granitized rocks to a
remarkable extent. They did not permeate the pores and foliation planes
of these rocks, which were, apparently, more or less sealed by granitization,
but they appear to have followed a multitude of fractures, perhaps con-
traction joints, in the relatively brittle migmatites and gneisses. These
fractures seem to have been enlarged by simultaneous, indiscriminate
replacement of the wall-rocks, the material of which was, apparently,
completely removed, and substituted by a variable, generally coarsely
crystalline aggregate of quartz, microcline microperthite, and muscovite.
In places, possibly because of a local loss of volatile content accompanying
the sudden opening of a fracture the coarse, variable crystallization did
not obtain, and a fine, sugary aplite resulted; in other places, typically in
irregular ‘pockets’ formed by the intersection of several sets of fractures,
a ‘pool’ of the pegmatitic fluid seems to have been able to crystallize
quietly, or the growing crystals to have suffered uniform, crystallographi-
cally controlled replacement (Spencer, 1945), to form patches of graphic
granite. The net result has been the development of an intersecting
system of pegmatite and aplite dykes, bodies of graphic granite, and high-
temperature quartz veins, which occupy as much as 50 per cent of the
exposed rock over large areas lying within a shell 1,000 feet or so thick
surrounding the granodiorite stocks (See Figure 5). The pegmatites have
apparently been emplaced by removing, in solution, the rock whose space
they occupy, without effecting any appreciable over-all increase in the
volume of the rock.

The pegmatite-forming solutions were obviously highly siliceous, and
rich in potash. At irregular intervals they carried small quantities of
iron and magnesium, forming irregular clusters of biotite and other minor
minerals. There is much evidence of deposition, solution, and redeposi-
tion of material within the dykes. The final solutions in many places
carried little but silica and a small amount of iron and copper; these
formed pockets of clear quartz within the dykes, and veins of transparent
to smoky quartz containing a few metallic sulphides transecting the dykes.
What peculiarities of the solutions or conditions of the invaded rock
caused the solutions to follow lines of mechanical weakness, such as
fractures, rather than enter the foliation planes and whatever pore
spaces remained in the granitized rocks, and yet enabled them to com-
pletely replace those rocks more or less independently of their composition
and texture, are unsolved problems.

(4) After the cessation of pegmatite-forming activities, the intruded,
granitized, pegmatite-bearing rocks suffered three periods of normal dyke