The part of Central Skye investigated and described
in the present thesis consists of three adjacent areas the
geology of the three regions has not been correlated.
Beinn na Cro consists of a complex of Tertiary basic
rocks which are cut by hybrid and acidic net -veins, dykes and
great tongues, the latter extending into the basic rocks from
the Beinn na Cro granite mass. The rocks comprise lavas
which, it is postulated, have been metasomatised into granulite and gabbro and fluidised into dolerite as the result of
the uprise of hot supercritical fluids along vertical concentric sub -arcuate fractures. The hybrid and acidic net - veins and dykes appear to have been emplaced partially by the
metasomatic alteration of the country rock by acidic fluids
and partially as fluidised acidic systems. Quartz- porphyry
sheets of magmatic origin cut the other rocks.
bìrea.gan Dubh is formed of a complex of Tertiary
gneiss with pyroclastic and basic rocks overlain unconformably
by lavas, the entire succession being cut by transgressive
agglomerate and quartz -porphyry intrusions. It is suggested
that the gneiss has formed as the result of the preferential
alteration in situ of laminated and bedded tuff by ascending
acidic fluids without the operation of tectonic forces.
The transgressive agglomerate and quartz -porphyry are of
Glas Bheinn Bheag comprises Jurassic sediments in
which a metamorphic aureole around a Tertiary microgranite
has been detected. The introduction of heat, alkalies and
bases into the sediments from the microgranite has resulted
in the granulitisation and chemical alteration of the sediments. The microgranite is considered, at least at its margins, to be metasomatic in origin. Quartz -porphyry sills
and dykes of magmatic origin cut the other rocks.