Summary:
The Nyanzaga and Kilimani deposits are orogenic gold deposit types. The mineralisation is hosted by a cyclical sequence of chemical and clastic sediments (chert/sandstone/siltstone) interbedded volcaniclastic rocks bound by footwall and hanging wall volcanoclastic units.
The Nyanzaga and Kilimani deposits occur within a sequence of folded Nyanzian sedimentary and volcanic rocks. The current interpretation of the Nyanzaga deposit recognises a sequence of cyclic (C1, 2 etc) mudstone, sandstone and chert units folded into a northerly plunging anticline. The Kilimani deposit, located 450 m northeast of Nyanzaga, is developed in the fold hinge of an interpreted west-northwest striking double plunging anticline. The bulk of the Kilimani deposit occurs in the heavily weathered zone, within 140 m from surface.
Gold mineralisation at Nyanzaga is concentrated at the intersection point of the north-west trending Nyanzaga Fault Zone (Far Eastern and Eastern Faults); the Axial and Central Faults; and the north-northwest structures plunging Nyanzaga Anticline. The higher-grade mineralisation occurs in lodes associated with mid to late stage, sub-vertical second order north-west to north-northwest and/or reactivated north to north-northwest structures (Axial Fault Zone) relating to the second phase of deformation (D2) deformation.
Preferential grade enhancement occurs in selected altered units such as the thick cherts, silica-dolomite altered medium grained sandstones, brecciated silica-carbonate altered mudstones; or along the margin of late quartz veins as free gold.
Mineralisation at the Kilimani deposit is currently mostly defined in the oxidised to partially oxidised profile and implies secondary enrichment. The mineralisation style at Kilimani appears similar to the Nyanzaga, fault-controlled mineralisation. The mineralisation has an AuMo-As-Sb-Mn-Ba geochemical association, which is characteristic of the fault-controlled earlystage carbonate replacement mineralisation observed at Nyanzaga. It is reasonable to assume that the fluids between Nyanzaga and Kilimani are interconnected. Kilimani may have been a higher-level development of the Nyanzaga system now structurally juxtaposed.
At Nyanzaga, three key alteration assemblages have been identified; Stage 1, Crustiform carbonate stockwork; Stage 2, Silica – sericite - dolomite breccia replacement overprint; and Stage 3, Silica-sulphide-gold veins. At Kilimani, most of the recognised mineralisation occurs in the oxidised profile. Where intersected in fresh material, the mineralisation is associated with strongly carbonated stock work and disseminated replacement. Mineralisation at Kilimani is reported as stratigraphically controlled in chert, mudstone, sandstones and interbedded volcaniclastic rocks.
Dimensions
Nyanzaga MRE The Nyanzaga deposit area extends over a north - south strike length of 0.6km (from 9,672,735mN – 9,672,110mN), has a maximum width of 0.44km and extends 800m vertically from 1,300mRL – 500mRL.
Kilimani MRE
The extent of the Mineral Resource is approximately 1 km along strike, 300 m in plan width and 240 m in depth.