1974 Prospecting
Following the increase in gold prices in the 1970's, Maurice Rantoanina published results of
a limited stream sediment survey in the Miandrivazo mining district that covered seven well
known past producers including those of the Dabolava area. He identified a number of gold
anomalies but concluded that only the Dabolava River drainage had placer gold potential.
1984 Reconnaissance
This work focused on both the bedrock and alluvial potential for the area. Bretizel attempted
to examine old workings but found them collapsed and obscured by lateritic cover. Their program
consisted of geological mapping, locating old workings, and underground, auger and pan-concentrate
sampling. Two main E-W directions, with past production, were identified as exploration targets.
The Ambohipisaka-Ankotrofotsy structure was recognized as four parallel mined-out trenches
having a total width of 70m and a strike length of 1500m. Narrow gold bearing veins follow the
margins of pegmatite dykes and five of these systems were worked in the past. The sampling did
not identify significant gold anomalies. A second mineralized system, the Ankaboka-Takodara axis,
was traced as a series of narrow trenches and pits for more than 2 km.
1985 & 1986 Programs
Regional stream geochemistry by Y. Symeon covered >200 square km with 736 samples analyzed for gold.
The silt survey produced anomalous locations considered worthy of additional testing. A small soil
sampling program consisting of 390 samples on a 50 meter grid conducted on the Dabolava mine site
near Ambohipisaka, produced two significant anomalies.
The north-west anomaly, defined by the 60 ppb contour, is slightly oblique to the trace of
old workings, and extends over a strike of 150 meters on a width of 50 meters. The Central Anomaly
is composed of two zones, one 600 m long and 250 m wide, and a second, 150m long and 50m wide that
strike at right angles to E-W trending veins and pegmatite dykes, and coincides with the trace of
a magnetic lineament. Maximum gold values are in the order of 1600 ppb but detailed results of
the geochemical and magnetic surveys are not available.
1987 Detailed Soil and Auger Sampling
An exploration program, conducted jointly by the BRGM and MDG in 1987 is summarized as follows.
Ambohipisaka (Dabolava workings)
This program focused on the old workings, the coincident crosscutting geochemical anomalies and
the magnetic anomalies recognized earlier. Auger drilling was conducted at 100 m line spacing
and 10 m intervals across the 600 m long anomalous area. The crosscutting anomalies were explored
unsuccessfully with self-potential, resistivity and magnetic surveys. The geochemistry failed to
show a consistent pattern of elevated gold and values did not approach economic levels. The soil
profiles were examined by 57 auger holes averaging about 3 m. in depth and probably failed to
penetrate lateritic cover or test bedrock.
Andimaka
This target corresponds with the "Mountain of Gold" zone of mineralization examined by
Pan African Mining in August of 2003. The BRGM conducted auger drilling on this area as a follow-up
to favorable stream geochemistry results obtained in 1986. An initial l00m by 50m grid was
selectively in-filled with 10m or 25m spacing, with 3m holes penetrating a meter into saprolite.
Four anomalous zones of greater than 200 ppb Au were obtained with maximum intensities of 850,
1000, 495 and 895 ppb gold. The anomalous gold values form an en echelon pattern following an E-W axis.
Mineralization is related quartz veins in a major E-W structure. The strength of the anomaly in
saprolite was greater than that obtained from surface samples. This strong target was never explored
by trenching or deep auger drilling.
Kiranomena
A soil grid established near the main highway west of Kiranomena tested favorable results obtained
from stream sediment sampling in 1986. The multi-element soil survey covers an area about 3.5 km
long and 1 km wide. A small gossan cap was mapped near the western limits of the grid area.
The program identified three gold anomalies above a 100 ppb threshold. Two anomalies, near
the village of Kiranomena, attain maximum values of 510 and 600 ppb Au and the third encloses
the gossan and attains a maximum of 4100 ppb Au. Copper values, to a maximum of 8000 ppm Cu, are
tightly constrained to the gossan. The copper anomaly follows a northwest striking, silicified and
mylonitized fault zone that contains pyrite, chalcopyrite and copper oxides.
A one kilometer copper anomaly located west of Kiranomena is outlined by a 200 ppm Cu contour
that includes values to 500 ppm Cu. This system strikes to the northwest, following the general
trend of gneissic country rocks and is marked by an abundance of quartz stringers, veinlets and
lenses. Elevated copper values, above 100 ppm, cover much of the remaining map area.
Summary
- The BRGM conducted a broad regional stream-geochemistry exploration program covering the entire Dabolava/Kiranomena Gold Camp. Results produced six significant anomalies.
- From 1983 to 1988, BRGM made a token effort to test four of the anomalies using surface geochemistry and some geophysical methods on widely spaced grids.
- A broad crosscutting zone of anomalous gold in soil and coincident anomalous magnetics found at Ambohibisaka was never adequately tested and remains unexplained.
- Strongly anomalous gold in soils found at Andimaka was confirmed by shallow auger sampling. High-grade gold veins actively worked by local artizanal miners, provides an exploration target.
- At Kiranomena, a multi-element soil survey revealed strongly anomalous copper for about 3.5 km and a one km section carries strong values. Details of analytical results were not available to the Company, but anomalous gold values partly coincide with copper anomalies. This target remains unexplored and has possible strike extensions.
- Two remaining regional stream anomalies, Ambaratakely and Antsaily, have not been tested or examined.
