There is also a recent Ph.D thesis at Glasgow that provides some
information.
INVESTIGATION OF LEAD AND ZINC DISPERSION
FROM AN ABANDONED MINE SITE
AT TYNDRUM, SCOTLAND
A thesis submitted for the degree of
Doctor of Philosophy
By
Nurlidia Mansor
MSc (Environmental Engineering)
BSc (Biotechnology)
Department of Environmental Chemistry
Faculty of Physical Science
University of Glasgow
August 2008
© Nurlidia
------------------------------
Roy Wares
============================
Roy Wares, P. Eng.
Mining Consulting
Vancouver, BC
----- Original Message -----
From: "Tony Brewis" <[log in to unmask]>
To: <[log in to unmask]>
Sent: Wednesday, August 19, 2009 11:18 AM
Subject: Re: Tyndrum
The November 1989 issue of Mining Magazine carried the following article on
page 353:
Gold at Tyndrum
The quest for gold during the current worldwide exploration boom has
extended to most
parts of the globe and Scotland has proved no exception. A number of
companies are
currently active and have been encouraged in no small measure by the success
of Dublin-based
Ennex International plc. Currently thwarted by the inability to use
conventional drill and blast
methods to exploit its substantial underground gold reserve at Curraghinalt
in the Sperrin
Mountains of Northern Ireland because of security considerations, Ennex is
now concentrating
its efforts in the British Isles on the development of its Cononish gold
property in the Scottish
Highlands near the old lean mining district centred on Tyndrum. It has
outlined a mineable gold
resource of some 0.9 Mt grading around 10 g/y and, subject to favourable
metallurgical testwork,
final feasibility and permitting, production could start by the end of next
year.
There are historic records of gold occurrences at a number of
Scottish localities dating
back to the thirteenth century but gold has never been mined on a
significant scale. Exploitation
has been limited to alluvial operations in the far north in Sutherland and
the leadhills district of
Lanarkshire in the south. Of the few recorded gold occurrences in the
Highlands the more
significant have been in the headwaters of the River Tay, near Tyndrum.
Lead mining at Tyndrum began in the mid-eighteenth century and
continued intermittently
until 1858 by which time several thousand tonnes of lead ore had been
recovered at grades
believed to be of the order of 5-10% Pb. The veins had been mined through a
vertical interval
of 230 m and the last attempt to re-open the mines was in the early 1920s.
Ennex's Cononish gold property is located about 3 km southeast
of the village of Tyndrum
at the site of the Eas Anie lead mine which exploited a southwesterly
striking vein structure accessed
by two adits driven into a cliff-face. In 1984 rock sampling near the adit
portals and subsequent
trenching over the adjacent hill-top showed the presence of gold and spurred
Ennex to launch a
10-hole drilling programme at the end of 1985 southwest along the strike of
the lead vein structure.
Gold was encountered in all holes down to a depth of 50 m but, with the
exception of two holes,
values were disappointing.
Following a review of all exploration data an intensive exploration
programme was relaunched
in 1987 and drilling was stepped back to test the lateral extent of the
earlier drilling intersections.
This rapidly led to the discovery of an auriferous quartz-sulphide structure
running parallel to, but a
few metres north of the main Eas Anie lode. The goldbearing structure,
which is hosted by a
succession of Dairadian psammites and pelites, was traced westwards over a
strike distance of
700 m with gold intersected in 35 of the 55 holes drilled. Gold grades
improved along the strike
with intercepts of up to 13.5 m at 29.14 g/t in the westernmost section. No
hole has been drilled
deeper than 300 m vertical depth and mineralization remains open at depth.
By the end of 1987 Ennex had secured exploration licences with
mining lease options over 100
km2 . A planning application was submitted for an underground operation
programme of drifting and
raising, the objective being to validate the ore reserve estimates above the
adit level and provide data
necessary for the full-scale feasibility study. Work on the adit began in
September 1988 and is progressing
at the rate of 20-30 m/week. To date it has reached 700 m and its planned
length of 900 m will be
completed by the end of 1989. Originally it was intended to extend the 'old
man's' adit along the structure
on the 448 m level but a decision was made to step back 200 m east and drive
a new adit on the 400 m
level. Although this has meant driving through several hundred metres of
barren ground initially, the surface
drilling had indicated that the gold structure plunges west so that locating
the adit at a lower level gives
access to 0.2 Mt more ore than would have been the case otherwise.
Thus far the underground exploration has borne out the surface
drilling, confirming the continuity
of grade and structure. The structure averages 1.65 in width in the section
developed to date and the
richest ore is concentrated along a well-defined hanging wall in the
psammite. Grades diminish away
from the hanging wall and tail off in a brecciated zone which forms an
ill-defined footwall. Mineralization
tends to favour the psammite rather than the pelite horizons because the
former are more competent and
the fracturing more open. Warp structures also give rise to thicker zones
and better grades.
Close to the hanging-wall the gold is sometimes visible but for
ore reserve calculation purposes,
where individual assay values exceed 60 g/t they have been cut to 60 g/t and
values between 30 g and
60 g have been cut to 30 g/t. Gold occurs as 5 to 100 micron-sized grains,
chiefly intergrown with
galena contained in microfractures in pyrite grains. Wallrock alteration
includes chloritization, sericitization
and haematization. A later episode of more widespread non-auriferous
quartz-carbonate-sulphide veining
forms the basis of the historical lead mining. Both appear to be shearzones
associated with the main regional
control, the Glen Fyne fault.
Bulk samples have been sent to Canada for metallurigcal
test-work and at this stage flotation seems
to be the most favoured route for ore treatment. For a 125,000 t/y
operation an appropriate processing
facility would cost an estimated E3.5 million with the total capital cost of
the project likely to be of the order
of E7 million. Mining costs should be less than E30/t and total operating
cash costs, not including financing
charges, around $ 230/oz.
The location of the mine in an area of outstanding natural
beauty means that great care will need to
be taken to ensure that tailings disposal, ore treatment methods and plant
installations have minimal impact
on the environment. Consultants W. J. Cairns of Edinburgh have been engaged
to undertake environmental
base-line studies and an environmental impact statement will be submitted to
the planning authorities by the
end of the year. Cononish could employ as many as 100 people of whom half
would be drawn from the
local communities. there seems no good reason why mining, as well as
forestry and tourism, should not make
a modest but valuable contribution to the Highlands economy.
Tony Brewis
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