Stratabound barium-zinc mineralisation in Dalradian schist near Aberfeldy, Scotland. Final report

The discovery and preliminary assessment of stratabound
barium-zinc mineralisation in Dalradian metamorphic rocks
near Aberfeldy (outlined in MRP Report No. 26) resulted
from co-ordinated geological, geochemical, geophysical and
mineralogical studies, full details of which are presented
here. The presence of an extensive zone of mineralisation
in the area was recognised initially by a geochemical
drainage survey and , reconnaissance geological mapping.
Subsequently, more detailed mapping and drainage sampling
were supplemented by VLF-EM geophysical surveys, overburden
and rock sampling, and shallow drilling. The
VLF-EM technique successfully delineated resistive rocks
within the generally conductive graphitic schists and proved
a valuable mapping aid in areas of poor exposure.
The mineralised zone is defined by the presence of
bedded baryte, sulphide concentrations, quartz-celsian rock
and micaceous schists in which the muscovite is barium-rich.
It varies in thickness from about 60 m to 110 m and
extends, at least intermittently, over 7 km of strike and
through a vertical interval of 370 m. Individual baryte bands
are 2.3-l 5.5 m thick and may extend along strike for up to
1.8 km. The greatest sulphide concentration is in carbonate
rock assaying 8.5% Zn and 3.6% Pb over 4.3 m. Other
unusual constituents of the mineralised zone are the barium
silicates hyalophane and cymrite and the chromian muscovite
fuchsite.
It is concluded that the mineralisation is of synsedimentary
origin, involving the introduction of metal-rich
hydrothermal brine into an euxinic basin.