Active and ongoing gold exploration and mining in ... - IAGS 2011

Geophysics (apart from radiation spectrometry) do
not appear to be effective in locating the mineralisation
(Fig. 2). This is likely due to the lack of sulphides
associated with the mineralisation, and although
there is some magnetite, there are also other magnetic
units that mask any subtle magnetic response in
the area. Geochemistry of soils and till is potentially
useful at defining mineralisation beneath shallow till
cover. So far, several Au anomalies in soil and organics
have been defined, but are yet to be drill tested.
Three different scale surface geochemical
surveys have been performed within the area
of interest, of which 90–95 % is covered by till.
These are 1) a regional C-horizon till geochemical
survey collected over 500 km 2 within the central
northern part of the Peräpohja Schist Belt; 2)
a semi-regional C-horizon till survey that concentrated
over the main mineralised trend within an
area of 150 km 2; and 3) a detailed local-scale survey
over the immediate strike extent of the mineralised
zone. The local-scale survey consisted of
three different sample media: C-horizon till, in-situ
weathered bedrock samples, and organic samples.
Results of the geochemical surveys show
that there are discrete, coherent anomalies in all
scales inspected, and some anomalies are directly
related to mineralisation. The geochemical pathfinder
associations at Rompas are Au with Te, and
U with Se and REE; also, the sample media perform
differently according to the geomorphologic
substrate. Although Rompas is at the very early
stages of exploration, surface geochemical data corresponds
well with known mineralisation and is an
effective exploration method to identify targets for
further geochemical in-fill sampling and drilling.
Mineralisation appears to be hydrothermal in
nature and shear or fracture-controlled, hosted mainly
by metavolcanic rocks which may, in part, be skarnified
and/or hornfelsed. Uranium is found in the form
of uraninite. Native gold and uraninite are generally
identified at surface in limonitic fractures within the
metavolcanic host rocks. It seems that the target is
a large, bulk-tonnage, and of shear or fracture-controlled
nature, that is probably related to a buried
intrusive that may be an apophyse or a down-dip extension
of the granitoid complex that occurs just a
few kilometres to the north of the property. The possibility
of finding potentially economic high-grade
vein structures must also be considered. Rompas can
be classified as a U-Au skarn or metasomatic vein
deposit in metasedimentary and igneous bedrock.
Rompas is a part of a broader mineralised
trend, or camp. Rumavuoma, about 5 km south-east
of Rompas (Fig. 20), is a lower-grade Au-U mineralised
trend. Nine historic samples taken by Areva NC
within an area of 3.5 kilometres by 400 metres assayed
0.1–1.8 g/t gold, averaged 0.3 g/t gold, and 5–3860
g/t (0.39 %) uranium and averaged 517 g/t uranium.
Mustamaa is located approximately 30 km
south, along strike, of the Rompas mineralised trend.
There, uranium is hosted by a phosphatic breccia
unit. The breccia is contained within more than 500
m long and up to 40 m wide apatite-bearing dolomite
unit. Better drill intersections include: R13:
55.4 m @ 0.03 % U 3O 8 from 104 m, including 4.1
m @ 0.08 % U 3O 8 from 120 m, and R10: 18.1 m @
0.03 % U 3O 8 from 65 m, including 8.4 m @ 0.04 %
U 3O 8 from 73 m. Additionally at Mustamaa, a glacial
boulder sampled by Mawson and located approximately
500 m west of the drilled breccia unit assayed
0.5 g/t gold and 165 g/t uranium. This boulder is not
sourced from the breccia unit detected in the local
bedrock suggesting the potential for further gold
mineralisation to be discovered between Rompas,
Rumavuoma and Mustamaa.
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