Interpretation & Conclusion
The Andavakoera region is a gold producing area of Madagascar. Mining companies and informal workers
exploited surface concentrations of gold using unsophisticated methods that provide financial returns
with a minimum of investment. The gold source, possibly in bedrock below areas of surface gold mining,
remains an untested exploration target.
Vein Mineralization
Mineralization is controlled by linear quartz-barite veins ranging from a few centimeters to a meter
in width. The veins often extend for over several hundred meters. Gold mineralization is accompanied
by a pyrite, galena and sphalerite. Gold grades are difficult to ascertain because meaningful records
were never kept. Exploited veins generally graded from 20 to >60 g/t gold and 10 g/t gold was below cut-off.
Veins have Carboniferous radiometric ages but are known to cut Permian strata and possibly the
lower Triassic, an age of <250 Ma is more likely. Barite is a major vein constituent and combined with
the presence of galena and honey colored sphalerite suggests epithermal conditions of emplacement.
Mineralization was only tested down-dip, from underground workings, to a depth of about 60m.
Vein patterns, internal structures and alteration are not well known, but mineralization in the
Andavakoera region resembles that found at the Yankee Girl and Ymir mines in the Kootenay district of
British Columbia where productive veins extend to depths of >300m.
Disseminated Gold Mineralization
Stockworks quartz-stringer mineralization in Permian sandstone near Korimalandy is related to broad
zones of weak hydrothermal alteration and a coincident gold anomaly in soil that extends over more
than 1.2 km. The BRGM reports these findings but fails to recognize a similarity between gold
mineralization in these carbonaceous sandstones and similarities to gold mineralization along the
Carlin Trend in Nevada. Strata favorable for Carlin type mineralization extends onto the PAMM ground
northeast of Betsiaka where Jourde found anomalous cinnibar in pan concentrates. This region has never
been explored systematically or examined for Carlin Type gold mineralization.
Sedex Type Lead-Zinc Mineralization
Bretizel suggests that zinc anomalies associated with the Ranomafana area pyrite-rich Triassic schists
have potential for sedimentary lead-zinc mineralization. He concludes that this horizon is favourable
to the deposition of massive sulphides and the mineralization would be masked by deep weathering and
leaching. If potential for this type of mineralization can be established for the region, the sedimentary
strata located on PAMM permits to the northeast of Andavakoera will be particularly prospective.
Exploration Potential
Quartz veins and stringers on PAMM exploration permit southwest of Betsiaka and Andavakoera have not
been systematically explored. The amount of gold recovered from workings in lag or oxide zones on the
A5 project is not known but the near surface deposits represent significant areas of anomalous gold and
justify testing for bedrock sources. Informal workings, on the PAMM ground, are indications of possible
bedrock gold potential.
The potential for disseminated gold mineralization in Permian carbonaceous sediments as demonstrated
by the BRGM in the Betsiaka region should be evaluated. The potential for Carlin Type gold mineralization
provides justification for regional silt sampling and prospecting of Permian sedimentary rocks. The sedex
type mineralization potential warrants further evaluation.
Conclusions
The Andavakoera region was one of Madagascar's main gold mining centers in the early 20th century with most
of production derived from surfaced enriched lag deposits. Mineralization occurs in parallel and orthogonal
sets of quartz and quartz-barite veins that locally carry from 20 to 60g/t gold. PAMM holds exploration
permits over more than 1900 km square of the northeast and southwest extensions of the main historic
workings on BRGM's Betsiaka property. Informal gold production and quartz and quartz-barite veins
observed in the southwest part of the A5 project provide sufficient evidence of gold potential to
justify an initial exploration program using modern geochemical and geophysical methods and overburden
drilling. Permian sediments to the west of Betsiaka have many features of Carlin type gold mineralization
and should be prospected for fine grained gold in carbon bearing rocks. Potential for stratiform
lead-zinc mineralization in overlying Triassic strata, suggested by the BRGM, warrants further evaluation.
Stream silt sampling and examination of known prospects provide cost effective methods of selecting target areas.
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