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Valentine - Technical Review Report . W . Mugomo, G.S Chagondah July 2013 Caledonia Mining Corporation Blanket Mine Division Gwanda, Zimbabwe. Preamble.
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Valentine - Technical Review Report W. Mugomo, G.S Chagondah July 2013 Caledonia Mining Corporation Blanket Mine Division Gwanda, Zimbabwe
Preamble • Valentine prospect, comprising Valentine North and Valentine South, are brown fields projects previous worked by Germans and illegal artisanal miners (makorokoza) and later by Blanket Mine. • The Prospect forms part of Blanket Mine’s minerals claim portfolio which has several satellite gold claims within the Gwanda Greenstone Belt that have been explored and developed to different stages. These blocks of claims are all within 50km radius of Blanket Mine. • Valentine North and Valentine South have a recorded combined production of 457ozs from 1 566 tons representing a recoverable grade of 10g/t. • Follow up “first pass” surface diamond drilling carried out by Blanket Mine on anomalies defined by grass roots exploration (geological mapping, soil & rock geochem, geophysical surveys) at Valentine North indicated significant intersections. A total of 503.45m were completed at Valentine North in 2002 on 4 drilling sites. • There is scope that Valentine Prospect presents an opportunity for application of high tonnage, low grade and low cost mining methods to feed extra capacity in the stone’s throw away Blanket Mine process plant. • Open pit mining should be given consideration given broad surface and near surface mineralization in the Prospect.
Report objective To review the available Valentine Prospect technical information as part of a scopying study before a full feasibilty study of the mining project is carried out. This technical reappraisal is necessary against a backdrop of change in resource modifying conditions since the last internal estimate was done in 2002.
VALENTINE PROSPECT • Location & Access • Valentine Prospect is located within the Gwanda Greenstone Belt. The claims cover a gently rolling relief. • The Prospect is approximately 2.7km (straight distance) NNE of Blanket Mine (Figure 1). • It comprises of Valentine North and Valentine South claims separated by a river and lying within a radius of 500m of each other.
Ground Tenure Status • Blanket Mine purchased the mining claims from FDA Payne and are registered in the Bulawayo Mining District. • The claims occupy a total area of 270.6ha and are confined to the former Sheet Farm. • Production History • Valentine North and Valentine South prospects have old workings presumably located at known high grade sites by the old timers. • The two properties have a recorded combined production of 457ozs from 1 566 tons representing a recoverable grade of 10g/t.
Deposit Model The deposit model envisaged at Valentine Prospect is a broad (high tonnage) mineralized zone at the contact of mafic volcanics of the Gwanda Greenstone Belt and flanking granite intrusives e.g. as in Horn, Princess Betty, Jessie, Coatbridge and Olympus Mines (all in Gwanda) and Eureka Mine (Guruve).
Previous work done includes: • Mining by old timers and makorokoza. • Geological mapping @ 1: 2 500 scale (Figure 2). • Rock chip geochem – on surface outcrops & grab samples • Au, Pb & As in-soil geochem • Geophysical work – airborne and follow-up ground magnetics, and airborne radiometric (K/Th alteration index). • Trenching & sampling (Figures 3 & 4). • Surface drill testing of selected targets in Valentine north – 4 holes (VNS 01 to VNS 04, Figures 5,6,7 & 8) • Resource estimation
Prospect Geology & Structure • The prospect comprises a package of interbedded mafic and felsic volcanics flanked by gneissic granites, see figure 2. • NW trending regional stratigraphy with a system of foliation parallel quartz veins and stringers. Most important veins are hosted in hornblende-chlorite schist and to a lesser extent gneissic granite and metagabbro. • Valentine Prospect hosts gold mineralization in quartz veins and altered shear zones which are located within the Gwanda Greenstone Belt. • Valentine North consists of multiple (>5) ore shoots of variable width that characteristically pinch and swell on strike. • The pay shoots from both Valentine North and Valentine South trend north-west while dipping south-west (@ approx. 45-55˚) • On plan view longitudinally, the ore zones are spatially associated with a series of left-stepping en-echelon shear zones. • The two prospects are separated by a curvi-linear river course which is reckoned to represent a fault (figure 3).
Figure 2. Geology of Valentine North Prospect showing trenches .
Trenching Trenching and the subsequent limited drill testing confirmed potential down-dip and strike continuity of ore shoots (Figures 3 to 8 ). • Valentine North: number of trenches =17, total metres = 1057m • Valentine South: number of trenches = 21, total metres = 940m
Figure 3. Valentine North & Valentine South trench plan & intersections
Valentine North diamond drilling • Total metreage of 503.45m completed over 4 holes. • Drill sections for Valentine North are presented below (Figures 5 to 8).
Alteration & Mineralization • Silicification within the sheared gold hosting hornblende–chlorite schists is the predominant alteration type. Carbonation and biotitization are subsidiary. • Valentine North is a mixed burger comprised of a broad mineralized hornblende-chlorite schist (mafic schist wall-rock) that occasionally return economic but lower Au grades when compared to the relatively high tenor (sweetener) in the multiple NW trending parallel quartz reefs(Mean-1.38g/t). • Mineralization is also associated with lithological contacts.
Drill intersections • Valentine North drill hole intersections are summarized in Table 1.
Table 1. Summary of Valentine North diamond drilling intersections
What is known about Valentine?At the desk top level Valentine North is more prospective than Valentine South.Valentine North Details(a) Diamond Drilling & Sampling* Total BQ metres drilled on 4 sections -503.45m. * Average hole depth-125.9m, Max-141.6m and Mini-110.4m.* Total samples analysed - 404.(b) Mineralization* Drilled strike length-74m.* Average width covered by quartz reefs- 20m(South) and 60m (North).*Sulphide minerals present are pyrite, pyrrhotite and minor galena * Valentine North average reef width 1.58m* Approx. quartz reef frequency/density-6-10m*Grades: Mean -1.38g/t; Max-14.17g/t & Mini- 0.23g/t* Average deepest reef intersection – 80m *Reefs dip at 50 SW and strike NW-SE(c)Mineral Resources Drill Indicated-35 053t @ 6.18g/t over 1.35mInferred Resource- 155 620@6.05g/t over 1.28m(d ) Infrastructure* Proximal to Blanket Mine(2.7km straight distance) and therefore accrues benefits by association e.g. power, roads, water, etc.
Proposed work: Valentine North Resource Growth Strategies • Potential strike extensions: • Plan a soil geochemical sampling program to chase for the open ended NW extension of Valentine North, number of drill intersections appear to be increasing from south to north. • Infill trenching in Valentine North prospect e.g. between trenches VN3 & VN5 and also between trenches VN2 & VN4. Short trenches should be extended to cover the entire ore body cross section. (Figure 9). • Plan drill holes in same section line of trenches. • Potential down dip extensions: • Maintain and extend VNS 01 to VNS 04 drill fence and target 40mL and 120mL depths on proposed dip step-in and step-out drill holes (Figure 5 to 9). • Deepen VNS 04 which was prematurely ended while it was returning encouraging grades. • Potential economic mineralization of the reef middlings • Carry out an ore resource inventory sensitive test based on changing ore outlines owing to the inclusion of unpay mineralized HCS unit. • Valentine North Potential Prospectivity of the Prospect- Rated high . Mines on the same geological setting – sheared granite gneissic terrain/ Gwanda greenstone contact include Horn, Princess Betty, Coatbridge and Olympus. Elsewhere in Zimbabwe Eureka Mine (Guruve) is a classical example.
Figure 9. Valentine North map showing drilling proposal & ore intersections
Scope For Open Cast Mining Method Taken into account are the following Valentine North attributes: • Moderate dip angle(50˚) • Shallow to outcropping nature of occurrence • Relatively high reef density over a reasonable span • Resource availability with estimated above economic cut off Au values returned on 10m benches • An estimated 5.7:1.0 waste to ore ratio • Short hauling distance to the mill • Competent ground conditions
Recommendations • Valentine North could reasonably be considered for a high tonnage, low grade and low cost 10m bench open cast with mining advancing from the hanging wall to the footwall to minimise dilution. • To define a mineable ore reserve block complete with a forecast grade, 20m deep holes could be drilled on 15m centres using an RC drill ahead of mining.
Proposed work :Valentine South • Underground Valentine South plans need to be reviewed in detail to establish the extend of mining before a fair assessment of the property can be presented. • Relatively big dumps on Valentine Prospect appear to suggest that considerable mining of resource occurred underground. • There are however reports that the dumps also represent ore hauled from Sabiwa and other satellite projects then.
References Nyagumbo, J. (2001). Surface Exploration over and around the Valentine Mines, Kinross Holdings Zimbabwe (Private) (Unpublished internal company report). Ndebele, G. (2001). Proposed Grassroots Exploration & Trenching Authorization for expenditure (A.F.E). (Unpublished internal company report). Tyndale-Biscoe, R., (1940). The geology of the country around Gwanda, Southern Rhodesia Geological Survey, Bulletin No. 36, 204p.
Appendix 1. Gwanda Greenstone Belt showing location of Blanket Mine claims
