The region is tightly folded, with fold axes trending NNE.Licenses have been selected proximal to strong aeromagnetic anomalies, believed to be an important stratigraphic control on Ni-Cu-PGE mineralization in the region, and known gabbro / norite bodies.
Kabanga property optioned to Songshan Mining Co. Ltd. (See news release dated March 10, 2009).
Physiography
The Kabanga Nickel project area falls within the highland country lying to the SW of the Lake Victoria depression. In the centre is the high rolling country of the Ngara ridge which is succeeded in the east by a broad dissected plateau. Within this area the persistent NNE strike of the rocks has controlled the strike direction of the ridges and their associated drainage.
Regional Geology:
The Kabanga project area is located within the Mesoproterozoic Karagwe-Ankolean sequence within the Kibaran Fold Belt of NW Tanzania. The Karagwe-Ankolean sequence covers the northwestern part of Tanzania on the border zone between the Western Internal Domain and the Eastern External Domain of this orogen. The rocks are predominantly metasediments characterized by the intrusion of mafic intrusive bodies at ~1275 Ma (mainly basic sheets), A-type granitoids at ~1250 Ma and post-orogenic tin granites with an age of approximately 1000 Ma.
The sedimentary features of the Karagwe-Ankolean rocks are massive, current bedded, ripple-marked sandstones and interbedded rhythmically laminated shales and siltstones. Individual units can be mapped out over tens of kilometers. The sediments reflect shallow-water deposition, with argillites, phyllites, low-grade sericite schists and quartzites.
During orogenisis the sediments were metamorphosed and are now quartzites, argillites, phyllites, slates and schists. Despite the low grade of metamorphism considerable migration of silica has taken place with the localization of quartz reefs near the basic sills and in the axial planes of minor folds.
The Karagwe-Ankolean sequence has been sub-divided into an Upper, Middle and Lower Division based on 1: 50 000 scale regional mapping carried out by the Mineral Resources Division of the Ministry of Energy and Minerals in the 1960's and early 1970's. The division is broken down as follows:
Kishanda beds
Upper Division Mtagata Quartzite (q3)
Mabira beds
-------------------------------------------
Kafulu Quartzite (q2)
Middle Division Arena beds
-------------------------------------------
Lower Division (q1)
Figure 1 is a schematic diagram illustrating a simplified version of the principle quartzite units (q1 to q3) within the fold belt. Folding makes it difficult to give an estimate of the true thickness of the Karagwe-Ankolean sequence but 10 to 20 km seems a good estimate.
Many highly ferruginized bodies are found interbedded with the metasediments, these are of igneous composition and are the main host to the nickel in the area. They are interpreted as transgressive sills of basic composition and are generally folded. These bodies are generally absent in the upper part of the succession.
Towards the end of the main folding, extensive bodies of undifferentiated gabbro were intruded as conformable sheets at the base of the main Upper Division quartzite formation (Figure 1). These meta-gabbros predate the intrusive granites and represent a phase of more widespread Proterozoic igneous activity of Bukoban age. Globally nickel, platinum and chromium tend to occur in similar geological environments that are generally:
- Layered mafic igneous intrusives such as gabbro and norite.
- Ultramafic rocks such as peridotites, dunites and serpentinites.
At Kabanga Nickel (26.4 Mt @ 2.6% Ni - Barrick website) nickel sulphides with minor chrome and platinum occur in a differentiated mafic - ultramafic sill (Opportunities for Mineral Resource Development, Tanzania, page 72). This sill forms a prominent aeromagnetic anomaly, and is located within middle to upper division Karagwe-Ankolean rocks. Pyrrhotite, pentlandite and chalcopyrite are the principal sulfides. Along strike to the N of the Kabanga nickel deposit sporadic magnetic highs can be seen on the government aeromagnetics that are believed to represent similar layered gabbro and norite bodies.
The Kapalagulu deposit, located 340km S of Kabanga, shows many similarities to the Kabanga deposit with nickel and copper mineralization occurring at the base of a layered norite. The deposit has a strike of over 8km. Goldstream Mining is presently exploring Kapalagulu as part of a larger exploration program covering some 2000 square kilometers of ground. Goldstream are also studying the Musongati Intrusion located 230km to the N of Kapalagulu. The Musongati Intrusion is poorly explored at depth but is covered by a major lateritic nickel deposit estimated at 183 million tonnes at 1.31% nickel (Goldstream website).
Exploration completed in 2003 confirmed the presence of three distinct styles of potentially economic mineralization at Kapalagulu;
- Primary PGE reefs associated with chromite and disseminated sulphide.
- Massive Nickel Sulphide.
- Lateritic Nickel with PGE and Copper.
In 2004, the Company applied for open ground on the stratigraphy that favours these magnetic anomalies. The largest of these anomalies, occurs in the north just south of the Tanzanian border (Figure 1). The Company has acquired the bulk of this ground, and these magnetic targets will form the Companies main nickel exploration focus. It is believed that the United Nations, and BHP has carried out work, including drilling, on some of these targets but there are no known reports.
The second targeted area is to the W of the main magnetic trend where the Ministry of Energy and Minerals have recorded anomalous nickel in soil anomalies that coincide with layered norite/gabbro bodies (Figure 1).
Figure 1: Tectonic setting of the Kibara Fold Belt with the main Karagwe-Ankolean
quartzite marker horizons and Tanzanian Royalty PL's.
Principal Structures:
Published regional mapping (Tanzania Geological Survey), supported by an aeromagnetic interpretation, shows the project area to be tightly folded, with fold axes following a general NNE trend. Dips are generally steep and the folding tight to isoclinal (Figure 1). The eastern boundary of the Karagwe-Ankolean sequence is also cut by a major rift fault, which forms the eastern shoreline of Lake Victoria.
Geology of the Prospecting Areas:
The geology of the prospecting areas are presented below in the order from south to north, and are extracted from various 1: 100 000 and 1: 125 000 maps from the Mineral Resources Division, Tanzania.
The Kabanga nickel stratigraphy is tightly folded in this vicinity and is located mainly in the northeastern and central portion of the one licence. The Ruvuvu Valley granite has led to contact metamorphic effects in the area. The government magnetics supports the mapping. There may be some hidden Kabanga geology in the east under surfical cover. This too is supported by the magnetics.
The main Burundi road passes diagonally through the licence and the border town of Ngara occurs in the central portion of the PL. The original interest in the PL was two fold:
- The Ministry of Energy and Minerals reports abundant nickel in soil anomalies in the area.
- The Opportunities for Mineral Resource Development (2nd Edition UNDP) records a layered norite/gabbro body on the licence with a coincident aeromagnetic anomaly.
A closer look at the 1: 125 000 geological map shows the Kabanga stratigraphy to be present in two areas:
- In the west of the PL on the Burundi border is a 10km long zone of deformed Kabanga rocks forming outcrops within the Kagera river (Tanzanian boundary) mbuga floodplain. Associated with this are intrusive gabbroic bodies.
- In the central portion of the PL is a NS trending, intensely folded unit of Kabanga stratigraphy which coincides with the original gabbro/norite intrusive identified in the UNDP report.
There are further linear gabbroic bodies that have intruded along the contact between interbedded quartzites and pelitic rocks / phyllites that appear to be older than the Kabanga units, but of the same sequence. It is probable that these dykes may be the source of the nickel in soil anomalies.
The original interest in one PL was its location within the zone of two parallel magnetic highs that extend down to Kabanga Nickel. On the government geological maps a few gabbro sills are recorded, and the stratigraphy is of middle Karagwe-Ankolean age.
The original interest in the PL was its position adjacent another PL where the eastern magnetic zone is located. Graphitic phyliites are recorded interbedded with quartzites of middle Karagwe-Ankolean age. A few small gabbro sills are also evident on the geological maps.
The licence has an area of 694.2 square kilometers. The original interest in the PL is the presence of two large gabbro / norite bodies illustrated on the Opportunities for Mineral Resource Development map. A study of the 1: 125 000 geological map shows the Kabanga stratigraphy to be located in the W, near the Tanzanian border covering a strike of some 20km with a width of 5km. This area has moderate nickel in soil anomalies as illustrated on maps from the Ministry of Energy and Minerals and forms the main target on the licence.
The original interest in the PL is the presence of two magnetic bodies
that have a similar signature to the Kibanga Nickel signature. A close look at the 1: 100 000 geological map suggests that the stratigraphy is of the lower to middle division of the Karagwe-Ankolean sequence, being of a similar age and composition to the Kabanga stratigraphy forming a large regional synclinal structure. There are numerous low order nickel in soil anomalies in the west of the licence area as illustrated on maps from the Ministry of Energy and Minerals.
The Ruiza river transects the licence in the E and flows into Lake Burigi in the N. Ferricretes and laterites cover approximately 50% of the licence area.
The original interest in one PL is the presence of a large magnetic anomaly with a similar intensity as Kabanga Nickel, having a strike length of some 50km. The majority of this anomaly occurs under lacustrine sediments of Lake Victoria. The Kagera river transects the licence and flows towards Lake Victoria in the east.
A study of the 1: 100 000 geological survey maps shows that the magnetic structure mimics a large southerly plunging antiform with the nose being just off the property in the south. Lower to middle division stratigraphy of the Karagwe-Ankolean sequence occur over the majority of the eastern portion of the PL. The lake sediments (mainly mbuga) have formed a blanket over the stratigraphy and this area is therefore geochemically quiet. Alternative exploration methods such as biogeochemistry will have to be carried out to detect mineralization under the sediments. This area provides the biggest and best target for locating a new nickel and/or PGE deposit.
In the W of the licence area in the more mountainous terrain are numerous moderate nickel in soil anomalies located within middle to upper Karagwe-Ankolean sequence lithologies.
Exploration Completed:
A regional evaluation of public domain aeromagnetic data and government issued geological maps was undertaken, as part of the initial property selection process. Selection was also made on the Geological Survey of Tanzania nickel in soil anomaly map. No other work has been done on this project area to date.
Geophysics:
The area has been covered by a UNDP/government sponsored airborne magnetic and radiometric survey. The entire belt was flown by BHP in the early 1990s'. This information is not available at the present time.
Back to Top
Future Activities
Detailed soil and geological mapping is scheduled to be undertaken towards the last quarter of 2005, in addition to systematic conventional soil sampling and a biogeochem sampling program over lacustrine and lake sediments.
The government maps comprise hand coloured copies. These will be digitized in the near future and a compilation map will be placed on the website as soon as this is complete.
A trip to Dodoma will be required as part of an on going literature survey to see what exploration work has been carried out in the area.
Back to Top
