Deposit Types & Mineralization
Mineral Deposit Type/Model for the Property
Quartz bearing veins in the Andavakoera region are in strong and persistent shear or fault systems
containing iron and base metal sulphides. The presence of barite, coxcomb textures and a base metal
sulphide association with gold is consistent with an epithermal origin. The strength of controlling
structures allows gold bearing veins to continue to depth with better gold potential expected to
occur in areas of cross structures, dilation zones and intersecting veins.
Disseminations of very fine gold occur in weakly altered carbonaceous Permian sediments.
Similar geology and mineralization is found in the Carlin trend in Nevada. Paleozoic sedimentary
rocks in the Andavakoera project area should be prospected for Carlin type mineralization. The BRGM
identified anomalous lead and zinc concentrations in Triassic strata near Betsiaka, and reported that
conditions were favorable for stratabound sedex type lead-zinc mineralization.
Mineralization (Mineralized Zones Encountered)
Surface Mineralization
Gold mineralization occurs in eluvial deposits developed by extensive workings in the
Betsiaka-Andavakoera region with some of the workings on PAMM ground. Christopher examined several
old workings accessible from the main road in the southwest area of the property. Veins exposed by
these workings average more than a meter in width, extend to three meters or more and are visible
over several hundred meters along strike. Veins are barite rich and many show rust staining. Some
workings on the PAMM ground are over-grown while others are relatively recent (Plate 1, 2 & 3).
Sulphides have generally been leached and workings are in the oxidized surface layer. A number of mineral
inventory occurrences are shown on the PAMM project area but the main workings are on BRGM held ground.
Mineralization In Permian Sediments
BRGM exploration at Korimalandy found gold associated with weak hydrothermal alteration of arkosic
sandstones. Some areas display moderate amounts of fine, iron stained quartz stockwork. A grab-sample
of quartz stockwork collected by the BRGM graded 10.5 g/t Au (BRGM 1988). The BRGM observes that while
weak gold values were obtained in the majority of drill cuttings, there was no correlation between gold
grades and the degree of silicification, and concluded that gold is found in weakly altered, permeable
sandstone layers. The fine gold is difficult to recover using gravity methods.
Mineralization In Gneissic Basement
Gold bearing quartz veins are fault controlled and follow the general Andavakoera trend. Most veins
average less than a meter in width though some are reported to exceed 3m. Besairie reports that large
veins can give way to zones of narrow stringers when approaching the sandstone contact and that these
extend through the overlying sandstones.
Veins and stringers share a number of common characteristics. Quartz is usually the dominant
mineral with barite present in varying proportions, often as laminar bands alternating with quartz.
A few veins are almost entirely barite. Cox-comb textures are common, occurring as vuggy open space
fillings and as massive intergrowths. Sulphide mineralization includes pyrite, arsenopyrite,
chalcopyrite, galena, and sphalertie with some associated carbonates. Gold averages 750 fine and
economic mineralization was confined to bodies rich in galena and honey colored sphalerite.
The gold bearing part of the structure extends from Ankitokazo in the southwest to Betakilotra
in the northeast with the most productive zones found between Ranomafana and Betakilotra. The fault
system northeast of Betakilotra is obscured by Permian sediments and has not been mapped.
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