Geology
Property and Local Geology
The entire region is underlain by Precambrian metamorphic rocks of the "Graphite System".
The Graphite System is locally subdivided into the gneiss and schist dominated Ambatolampy
Group on the west and the migmatite dominated Manampontsy Group on the east. The Ambatolampy
Group is locally composed of strongly micaceous schist containing subordinate amounts of gneiss,
quartzite, marble and granitic dykes.
Schists consist of biotite, sillimanite, garnet and graphite. Related gneiss is usually
biotite rich and grades in and out of a schistose facies and often carries sillimanite and garnet.
Quartzites, ranging from thick-bedded ridge-forming units to fine interbeds following the rock
fabric, contain varying amounts of garnet, sillimanite, pyroxene, tourmaline, graphite and
magnetite. Marble beds are occasionally seen and generally associated with graphitic zones
and skarn.
Compositional layering and rock fabric trend northeast and dips 45°NW. The region is
deeply weathered and fresh outcroppings of most rock types are rare. Geological maps show
general trends but contain little detail. The tectonic setting is poorly understood because
structural elements are obscured by surface weathering. The effects of proximity to the
Angavo Tectonic Belt and the Antananarivo Virgation are unknown since neither structural
belt was considered in the preparation of geological maps and the relationship of gold
mineralization to regional structure has not been studied.
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