The Nyanzaga Gold Project (NGP) consists of one Special Mining Lease (SML), nine granted prospecting licences, and one prospecting licence application. Through its subsidiary, Nyanzaga Mining Company Limited (NMCL), Perseus holds an 80% interest in Sotta Mining Corporation (SMCL). The SML was granted on 13 December 2021 to SMCL for an initial period of 15 years. The Treasury Registrar holds the 20% free carried interest of the Government of Tanzania in accordance with the Mining Act.
- subscription is required.
Summary:
The Nyanzaga project is situated on the north-eastern flank of the Sukumaland Greenstone Belt. Rock sequences comprise Nyanzian-aged sequences of mafic volcanics in the far south-west and banded-iron-formation, tuffs, mudstone, sandstone and epiclastics of general volcanogenic origin and massive sulfide lenses and volcanics of rhyodacitic to andesitic composition. The sequences are tightly folded and strike generally west-northwest.
The Nyanzaga and Kilimani deposits are orogenic gold deposit types.
Historical petrology work indicated the protolith types at Nyanzaga included volcanic arenite and tuffs; siliceous and ferruginous chemical sediments and reworked tuffs; pelite (mudstone, silty mudstone), calcarenite with primary carbonate matrix; and volcanogenic clastic sediments including andesitic crystal-lithic tuff, polymictic breccia and layered greywacke (Mason, 2011). The country rock suites at Nyanzaga show a dacitic to andesitic volcanogenic composition (Henkel, 2012).
In the central part of the project, the Nyanzaga and Kilimani groups are defined. The Nyanzaga Group is divided into a sequence of three broad mappable units from drill core and outcrop mapping and are in stratigraphical order as follows:
1. Nyanzaga Upper Volcaniclastic Formation.
2. Nyanzaga Central Formation (formerly Mine Formation).
3. Nyanzaga Lower Volcaniclastic Formation.
These three units are folded into the north-northwest plunging Nyanzaga Anticline. These sequences are in turn overlain by the Kilimani Group which appears to be tectonically dislocated from the underlying Nyanzaga Group by faulting and potential earlier thrusts.
The Kilimani deposit, located 450 m northeast of Nyanzaga, is developed in the fold hinge of an interpreted double plunging anticline. The bulk of the defined deposit occurs in the heavily weathered, upper 140 m from surface.
Mineralisation
The two mineralisation systems show similar alteration and mineralisation styles, though the Kilimani deposit is interpreted to have been emplaced at shallower levels than at Nyanzaga.
Typical alteration features include pervasive carbonate alteration, varying from distal ferroan-calcite to proximal ankerite-sericite dominated and quartz-pyrite alteration.
The interpretation indicates that there is a distinct lithological control and most of the gold appears to be hosted by iron rich sediments in the form of an extensive stock-work of carbonate, quartz veins, and quartz-carbonate breccias. 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 in the late quartz veins as free gold. High-gold grades occur in narrow 5 to 20 mm wide tensional quartz veins that developed as conjugate sets and dip moderately to the southwest and southeast. Evidence suggests these veins may have developed along the axis of plunging parasitic folds in the area of the cherts; or with an apparent preference for developing in dolomitised and silicified, medium to coarse grained sandstone host rocks.
Typical alteration features include pervasive carbonate alteration, varying from distal ferroan-calcite to proximal ankerite - sericite dominated and quartz-pyrite alteration. Three key alteration assemblages have been identified. These include:
• Stage 1: Crustiform carbonate stockwork. An initial, distinctive broad zone of crustiform carbonate veining and disseminated sulfide associated with low grade gold mineralisation.
• Stage 2: Silica-sericite-dolomite breccia replacement overprint. An overprinting breccia, dolomitisation and silica/sericite. Fine grained disseminated and minor veinlet pyrite/pyrrhotite disseminated moderate grade gold mineralisation. This stage is likely related to localised demagnetisation.
• Stage 3: Silica-sulfide-gold veins. A late, silica sulfide remobilisation event incorporating pyrrhotite veinlets, quartz-free gold tensional veinlets and late, subhedral coarser pyrite and in some instances, increased arsenopyrite concentration.
Dimensions
Nyanzaga
The Mineral Resource extends along a broadly north-south strike interpreted as centred on an anticlinal fold hinge with a moderately dipping western limb and steeply dipping (subvertical) eastern limb. Mineralisation extends approximately 650 m along strike, with mineralisation extending preferentially along the eastern limb up to approximately 750 m down dip. Typical widths vary from 10’s of metres to in excess of 200 m in the centre of the project area.
Kilimani
The Mineral Resource is interpreted to be variably mineralised along a 900 m strike length. Mineralisation is modelled as stratigraphically controlled along preferential lithologies within the gently folded strata. Typical widths vary from several metres up to 10 metres across several individual strata.