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Mumbwa

The Mumbwa Project is located in west central Zambia, approximately 200 km west of the Country’s capital, Lusaka. The Mumbwa tenement (8589-HQ-LPL) covers an area of approximately 250 sq km, and is being explored for Iron Oxide Copper Gold (“IOCG”) style mineralisation, similar to Prominent Hill and Olympic Dam in South Australia, and Ernest Henry in Queensland.

Within the Mumbwa tenement the main focus is on the Kitumba Deposit with combined Indicated and Inferred Mineral Resources of over 2 million tonnes of contained copper (0.5% Cu cut-off, 187 Mt @ 1.14% Cu). Regional satellite targets have also been identified, the highest priority of which is known as the Kakozhi prospect. Located 5 Km to the northwest of Kitumba, Kakozhi has coincident FALCON™ gravity and copper in soil anomalies.

Tenure and Location

The Mumbwa Project, previously held in joint venture with BHP Billiton, is now owned 100% by Blackthorn Resources with BHP Billiton retaining a 2% production royalty following its decision to exit from direct involvement in the Project in 2011.

The Mumbwa project includes four exploration licenses covering approximately 790 sq km. The details of these licenses are set out in the table below with the locations shown in the figure below.

TABLE 1: Mumbwa Project large-scale prospecting licences (LPL)

Name Licence Number
        
Area Sq Kms
       
Mumbwa 8589-HQ-LPL 248.3
Musafwa 14265-HQ-LPL 186.0
Kachindu 14266-HQ-LPL 208.8
Kabwera 14267-HQ-LPL 147.0

Mumbwa Licences Granted

IMAGE 1 : Mumbwa Project licences


Exploration History

The Mumbwa area has numerous historic artisanal copper mines dating from the late 19th century and has been explored for large Iron Oxide Copper Gold (IOCG) style deposits since the mid 1990’s. The region was originally identified using early era airborne magnetic data commissioned by the United Nations Development Program (UNDP). This data was followed up by ground reconnaissance sampling and mapping. A relationship between copper and gold anomalism and the Hook intrusive suite was identified and an IOCG style of mineralisation, similar to Olympic Dam and Prominent Hill postulated.

Phase 1

With a regional scale anomaly identified in the UNDP airborne magnetic data and encouraging field results, a Falcon airborne gravity gradiometer (AGG) survey was commissioned to acquire high-resolution gravity, magnetic and radiometric data. Using the abundance of differing datasets and increasing resolution of data, three targets were identified; Kitumba, Mushingashi (or the “Worm”) and Mutoya (see figure below) forming a 25 Km long structural corridor with associated gravity and magnetic anomalism. Based on this, a drilling program consisting of 11 holes for 5700 m was proposed.

Kitumba AGG

IMAGE 2 : Falcon AGG data showing the original Kitumba, Mutoya (now Kakozhi) and Mushingashi target areas


Phase 2


At Kitumba, the Phase 2 drilling program in 2006-2007 completed 8 holes for a total 4,105.17 m, including what is now considered the discovery hole S36-001. This hole was drilled by joint venture partners AIM Resources (now Blackthorn Resources) and BHP Billiton as the penultimate hole of the 2006/7 drill season, and intersected 655.4m at an average 0.46% Cu from 42m, including:

  • 317m @ 0.79% Cu,
  • 18m @ 0.20g/t Au,
  • 42m @ 2.01% Cu, including
    • 4m @ 5.56% Cu.

Phases 3 and 4

Phase 3 involved grid drilling around S36-001 including 27 holes for a total of 14,700 m. Phase 4 targeted the Mutoya and Mushingashi anomalies and involved drilling under the covering “Karoo” sediments. With improved geological confidence both regionally and at Kitumba, a maiden Mineral Resource estimate was released in October 2009 stating; 87 Mt @ 0.94% Cu using a 0.5% Cu cut-off in the Inferred category.

Phase 5

Phase 5 included 10,934 meters of drilling in 21 holes and included the “break-out” hole for Kitumba, S36-033 which failed at 463 m and was twinned in hole S36-038. Best results from S36-038 include;

  • 223m at 4.67% Cu between 188m and 411m, including:
    • 23m at 11.28% Cu between 205m and 228m
    • 23m at 9.06% Cu between 231m and 254m
    • 36m at 8.84% Cu between 260m and 296m
  • 30m at 0.99% Cu between 465m and 495m


Updated Mineral Resource


Blackthorn Resources commissioned The MSA Group to conduct an updated Mineral Resource estimate for the Kitumba area. The updated Mineral Resource was estimated and reported in accordance with guidelines of the 2004 JORC code. The updated estimate includes Mineral Resources at the Indicated and Inferred levels, representing a 160% improvement in contained copper on the October 2009 maiden Mineral Resource Estimate.

TABLE 2: In-situ Indicated Mineral Resource:

Copper
cut-off
(%)
Resource
Tonnes
(Mt)
Average
Grade Cu
(%)
Average
Grade Au
(g/t)
Average
Grade Ag
(g/t)
Average
Grade U
(ppm)
0.25 164.4 0.83 0.04 1.01 43
0.50 79.9 1.33 0.04 0.90 43
0.75 52.4 1.71 0.04 0.89 43
1.00 36.3 2.08 0.04 0.91 44

TABLE 3: In-situ Inferred Mineral Resource

Copper
cut-off
(%)
Resource
Tonnes
(Mt)
Average
Grade Cu
(%)
Average
Grade Au
(g/t)
Average
Grade Ag
(g/t)
Average
Grade U
(ppm)
0.25 274.7 0.60 0.05 0.96 44
0.50 107.1 1.00 0.04 0.86 45
0.75 63.5 1.27 0.04 0.84 46
1.00 40.6 1.51 0.04 0.85 46

TABLE 4: Total (Indicated and Inferred) In-situ Mineral Resource

Copper
cut-off
(%)
Resource
Tonnes
(Mt)
Average
Grade Cu
(%)
Average
Grade Au
(g/t)
Average
Grade Ag
(g/t)
Average
Grade U
(ppm)
0.25 439.1 0.68 0.05 0.98 44
0.50 187.0 1.14 0.04 0.88 44
0.75 116.0 1.47 0.04 0.86 45
1.00 76.9 1.78 0.04 0.88 45

Scoping Study

Results from the updated Mineral Resource estimate and first pass metallurgical test work were integrated into a scoping study – the results of which were released in the middle of September 2012.

Highlights from the scoping study include;

  • Economic support for a potential large open cut mine.
  • Estimated mineable ore of 84.5 Mt Run of Mine (ROM) at 1.19% Cu and a strip ratio of 2.4:1 (tonnes of waste per ROM tonne of ore).
  • Ore production of approximately 7.5 Mt pa to produce a 30% Cu copper concentrate.
  • Copper metal production potential ranges from 55 kt pa in early years ramping up to 75 kt pa in the latter years.
  • Open cut production mine life of approximately 14 years.
  • Cash cost estimate of US$31.45/ROM t (US$1.49/lb. Cu)
  • Estimated start-up capital expenditure of US$377M.
  • The metal recovery is estimated at 80% based on scoping study level test work


The proposed open pit could  be mined in a series of staged cutbacks detailed in the table and figure below.

TABLE 5: Proposed pit stages

Name Ore
(Mt)
Cu
(%)
Waste
(Mt)
Strip
Ratio
Contained Cu
(kt)
1 15.8 1.16 11.5 0.73 183.3
2 10.3 0.78 16.9 1.64 80.1
3 20.6 0.95 52.9 2.56 196.0
4 21.7 1.28 69.8 3.22 276.9
Final Stage 16.1 1.69 38.8 2.41 271.8
Total Pit 84.5 1.19 189.9 2.41 1,008


Proposed Pit Cross Section

IMAGE 3 : Proposed pit cross section


The figure below shows a sliced 3D model representing a north-south long section through the deposit with the 0.5% Cu and 1% Cu grade shells and the ultimate pit shell.

Long Section Final 

IMAGE 4 : Long section looking east through the Kitumba Deposit


Geological Context


Kitumba Geology Landscape

IMAGE 5 : Mumbwa geology map shoing the 0.15% Cu grade shell


The Mumbwa Project area is located approximately 200km west of Zambia’s capital, Lusaka. The region is largely underlain by metasedimentary rocks of the Kundulungu Group of the Neoproterozoic Katanga Sequence. These are intruded by syn- to post-tectonic granitic and related rocks of the Hook Granitoid Complex, with associated regional iron-oxide alteration. The Mumbwa Project is underlain by a giant mineralised iron-oxide alteration system extending over a 25km long north-south trending structural corridor, with associated large scale magnetic and gravity anomalies. The Kitumba and Kakozhi (previously referred to as “Target A”) areas are the main target areas for exploration, with on-going exploration work in progress.

The Kitumba IOCG deposit is expressed on surface by a north-south trending massive haematite replacement breccia system. Copper and gold mineralisation is spatially associated with faults and lineaments that cross-cut the region.

Copper mineralisation at Kitumba comprises a primary disseminated to semi-massive pyrite-chalcopyrite assemblage that has been extensively modified by deep weathering and oxidation. This has resulted in a redistributed supergene assemblage comprising secondary copper minerals in the form of malachite, chalcocite, copper phosphate minerals, cuprite, covellite, digenite, chrysacolla, and bornite, as well as native copper. The potential for an extensive hypogene zone of primary sulphide mineralisation consisting of chalcopyrite and pyrite is currently been explored.

Remobilisation of copper commonly occurs down fracture networks and as linings in cavities and supergene alteration has been observed down structures at over 700 m depth. The high-grade copper zone largely associated with supergene enrichment but also including deeper hypogene mineralisation is situated between 150m and 600m vertical depth from surface, and extends along strike for a distance of ~450m and across strike for ~170 meters.