Exploration for porphyry-style copper mineralisation near Llandeloy

Correlations > 99.95 significance.
Highest positive correlations of variables with no
-- association > 99.95 significance level.
Figure 5 Diagram matic illustration of highly significant
positive correlations within the drainage survey data
.
dispersion train of anomalies downstream of the copper
mineralisation located by soil sampling. One marginally
anomalous copper in stream sediment result is the only
indication of the mineralisation about Treffynnon. The
isolated position, small magnitude and absence of an
anomaly in concentrate, but association with anomalous
levels of elements concentrated in hydrous oxide
precipitates, are reasons to suggest that this weak Cu
anomaly would not have been followed up during a
routine survey.
The failure of the drainage survey to outline the area
of hidden copper mineralisation about Treffynnon
indicates the ineffectiveness of the technique for
mineral exploration in geographically similar terrains.
Regional geophysics
The Llandeloy and Middle Mill areas are covered by the
national aeromagnetic and gravity surveys and by a
recent helicopter-borne magnetic and very low
frequency electromagnetic (VLF-EM) survey of part of
west Dyfed. Mean terrain clearance was 60 m for the
magnetic and 75 m for the VLF-EM sensors (Cornwell
and Cave, in press). Extra gravity stations, including two
detailed traverses, were occupied to supplement existing
data in the area.
Magnetic surveys
The national aeromagnetic map (IGS, 1980) shows the
survey areas lying at the eastern end of a NE-SW
elongated magnetic high (Fig. 6), one of a series of
similar features extending along the south Welsh coast
from Ramsey Island to the Vale of eath. These may be
fragments of an original single linear feature which has
been broken up by postulated NESW transform faults
active intermittently during the Caledonian and
Figure 6 Aeromagnetic anomaly map of west Wales (IGS 1980). Contours at 10 nT intervals with magnetic lows stippled