KEY PROJECT PERSONNEL RESUME
Tenyears Gumede – Holder of a Masters in Exploration Geophysics degree from the University of Zimbabwe and ITC, Deft Netherlands. BSc Honours in Physics degree from the University of Zimbabwe. 19 years industry experience as a graduate/staff/senior/expatriate geophysicist with Anglo American Corporation for 10 years and expatriate geophysicist for Mineral Search of Africa/Norilsk Nickel Burundi for 4 years. Involved in a number of Anglo Projects and part of the team that discovered and evaluated Bubi Gold Mine(Zimbabwe), McKays Gold Mine (Zimbabwe), WHEN Gold Mine (Zimbabwe). Involved in evaluation of Unki Platinum Mine and Hunters Road low grade high tonnage nickel deposit in Zimbabwe. Member of the Geological Society of Zimbabwe and Society of Exploration Geophysicist (United States of America).
Knowledge Factory P/L limited carried out a ground magnetic survey on Joker Claims, Tafuna Hill, Shamva at the request of Mr. and Mrs. Mtisi and Mrs. Midzi, to aid in geological mapping of the claims area and subsequently identify zones of potential gold mineralization. The survey planning was based on previous known strike extents of reefs such that at least two survey lines profiled over the potential reefs. In general, reef in the Shamva, Bindura, Glendale area are known to be up to 300m in strike with the short strike length reefs up to 70m in strike. As such, a 50m line spacing magnetic survey was adopted across the regional geological strike, which is north south.
1.1 PROPERTY DESCRIPTION AND LOCATION
The mining claims are situated in the Harare Mining District of Zimbabwe, North East of the City of Harare, some 40km straight line distance on a 35˚ heading from Harare. Access is by a wide tarred road from Harare to Shamva town, some 70km north, then turn left into a gravel road towards the old Joking Mine some 3600m above sea level (see Figure 1).
The claims lies some 5km (see Figure 2) northwest of Shamva Mine and 20km southeast of Freda Rebecca Mine, where an estimated 1429 833Oz of gold valued at £ 6 446 832 were extracted by 1930.
The climate is warm to hot humid summers (October to March) with temperatures rising into the 30s. Winter months, April to September are cooler but temperatures seldom fall below 12˚C.
Figure 1 – General Locality Map of Zimbabwe indicating Joker Claims
Figure 2 – Joker Claims overlain on regional geological map
1.3 GENERAL GEOLOGY AND MINERALISATION
The Tafuna Hill covers some 14km2 and is 5km southeast of Shamva Mine. The topographical feature is known for its concentrations of auriferous veins. It exists as a mafic island enclosed within the Shamvaian sediments and comprise metabasaltic/metadoleritic greenstones and agglomerates that are part of Tafuna formation. Some 7473kg of gold were produced up to the 1984 period averaging 13.8g/t and 15.45kg of scheelite.
Joking Mine, which lies to the southeast of claims area has been the largest producer of all mines on Tafuna Hill, the production being 37324 oz. from 60199 tonnes, while Joker Mine worked from 1905 to 1925 produced 27674 oz. from 23095 tonnes of ore representing an
average recovery rate of 1 oz/t (Biscoe, 1931). The reef was mapped 70m on strike at a bearing of 28˚and a west-north-westerly dip ˜40˚ and stoping was to sixth level.
Figure 3 – Simplified Geology Map of License Area
On the other hand, Shamva Mine, at the end of May 1930, 1429833oz of gold worth £6 446 832 had been extracted from 9.6 million tonnes of ore. Shamva Mine is hosted in Shamvaian sediments similar to sediments covered by Joker Claims.
The claims straddle between Chancit and Tip Top Mines. Chancit lies west of Joker Mine within Tafuna Hill, and a reef dipping eastwards at 50˚ was mined in the 1930s, where 660 tonnes were crushed and 3Kg of gold recovered at an average recovery grade of 6.6g/t.
58417 tonnes of ore were crushed at Tip Top Mine yielding some 19039 oz of gold during 1921 to 1924 period. The calculated recovery grade is 9.8g/t on a reef that strikes N S for approximately 125m at first level. The average width of 75cm is reported on a reef where
development was to sixth level (Stidolph, The Geology of the Country around Shamva). This reef could be the northerly extension of Chancit reef that lies to the south of the claims.
1.4 MINERAL OCCURRENCES
1.5 SURVEY SPECIFICATIONS
The survey utilized a GSM 19 magnetometer of sensitivity ±0.01nT as a roving machine while the Geometrics G856 of sensitivity ±0.1nT was a base machine. The base machine is programmed to acquire reading at 15s interval on the same place to monitor variations of the magnetic field with time and assess the likelihood of magnetic storms or secular variations.
2 SURVEY DATA PROCESSING AND PRESENTATION
2.1 Data Reduction and Compilation
Data compilation and reduction to IGRF was carried out by Fugro and presented as GEOSOFT *.GDB, and GEOSOFT/ER- MAPPER grid files. The data was gridded on a 75m square cell basis with line-to-line correlation.
2.2 Data Processing
2.2.1 Interpretive Map Generation
Interpretative maps were generated in order to facilitate the interpretation exercise and were aimed at:
a) Improving the spatial mapping resolution of the litho-magnetic/radiometric units
b) Enhancing subtle features of limited amplitude and continuity
Transforms in frequency and space domain were effected using MapInfo mapping packages.
Based on prospect areas supplied by Perola Mining Limitada, the area of interest was clipped from the original GEOSOFT *.grd files using MapInfo mapping package. The following data routines were applied:
Reduction-to-the pole: This transform generates a total field data whose magnetic field anomaly is commensurate with a 90° inclination of the earth’s magnetic field for the induced magnetisation of the prospect area. The effect is to simplify the magnetic map and render anomalies independent of strike direction, and generating symmetrical anomalies over steeply dipping dyke like magnetic sources.
Anomalies asymmetric (significant LOs) then reflect flatly dipping sources, or those with a strong remanent magnetization.
Gradient Data: Gradient data emphasise shallow source responses at the expense of broader regional features, and allow for the recognition of low amplitude, short wavelength magnetic anomalies (dykes, pegmatites, zoning and structures) in areas of significant magnetic relief. Vertical gradients are less complex over steeply dipping magnetic sources and visual inspection of the resulting HI/LO ratios allows for a further check on the dip of the magnetic source.
Second vertical derivative further boosts the response of shallow targets but higher noise levels are experienced. Note: Over isolated bodies, second derivative data has the advantage that zero level contours approximate contacts of magnetic body, rendering this data of some significant use in semi-quantitatively outlining the plan position of stratigraphic units.
Analytical Signal: This is a scalar sum of the vertical and the two horizontal gradients. It yields a wholly positive bell-shaped anomaly over any magnetic source irrespective of
its dip, or magnetization history and is useful in mapping the strike trace of long magnetic sources or the centre of plug-like sources.
Image processed data: Relief Shading highlights short wavelength, low amplitude anomalies at shallow depths in total field and other related data sets. Steep features generate sharp, intense shadows. Where the azimuth is at a large angle to the strike (perpendicular), the process allows for the visual confirmation of strike continuity along sectors where anomalies are poorly developed.
Gridded radiometric data was subjected to image enhancement techniques to map lineaments. The contents of radioelements are changed in hydrothermal processes. Potassic alteration often results in elevated K – radiation particularly in mafic rocks and anomalous K/Th ratios along local shear and fracture zones may be indicative of gold bearing mineralisation. On the other hand, high U/Th ration within meta-sedimentary units may point out prospects of sulphidization. Radioelement ratioing to map hydrothermal alteration was achieved through Grid Calculator module in Encom Discover Version 10.
3 REGIONAL AEROMAGNETIC REMOTE SENSING IMAGERY
3.1. ANALYSIS OF AIRBORNE DATA
Prior to data interpretation of the airborne data within the license area, a study of the gold belt and mines was undertaken in order to develop an analytical framework that aided in geophysical signatures in known gold mineralisation. The Shamva, Joker, Joking, and other gold mine shaft positions, whose co-ordinates were extracted from 1:100000 geology maps, were plotted on the regional magnetic map and seen to be hosted in a major regional and micro structures interpreted as a shear zone (see Figures 4, and 5).
Figure 4 – Regional Total Magnetic Intensity Map of License Area
Figure 5 – Regional Total Magnetic Intensity Map of License Area Overlain by Mines
The study allowed the selection of possible target zones based on the following criteria:
i) Evident structures that displace magnetic anomalies
ii) Low magnetic anomalies relating to fracture zones, filled with none magnetic quartz zones
iii) Short strike low magnetic zones
An analysis of mining activities was done through google image, where satellite imagery acquired over a period from 2007 to 2013 showed the mining activities over the span. Of interest
is the elluvial activities observed during field work to the west of the licence area, where huge mounds of soil derived from sand washing were observed but are no evident in all images (see Figures 6, 7, 8 and 9). It is therefore concluded that these elluvial activities are for the 2013 to 2014 rain season. These elluvial deposits should be evaluated with a view of operating a suitable size mining operation. A testing plant to assess the deposits which are known in the area to thicken from 0.5 to 5m, 300m or so from the hill is recommended.
Figure 6 – Google Image dated 6/4/2007 Overlain by Claims showing major structure to the north
3.1.1 GEOPHYSICAL ANOMALIES
The magnetic survey covered the license area; save for a few hectares that seem to fall onto other claims that did not belong to client (see Figure 10). However, the survey extended to cover camp area which does not fall within the client claims but client has been active in that part of the land without dispute. The area is constituted of moderate magnetic anomalies (45nT) mapped as
metabasaltic/metadoleritic greenstone but re-interpreted in some sections as fissures/fracture or shear zone. The anomaly is mapped on geological data as single massive epidiorite dissected by N S dolerite. The moderate magnetic anomaly of 45nT is evidence that the survey is mapping variations of magnetic mineralogy within the epidiorite. This variation is due to tectonic effects which tend to destroy magnetic on shear/fissure and fracture zones
Figure 7 – Google Image dated 8/11/2011 Overlain by Claims showing major structure to the north
Five magnetic horizons, that exhibit low magnetism within the mapped epidiorite formation have been identified and interpreted as possible shear zones. The units have been labelled SH, SH1, SH2, SH3 and SH4. Potentially pegmatitic zones SH/P and P have also been identified and exhibit same magnetic properties as the potential shear. Identifies of pegmatite exploration for tantalite are observable in the field over a considerable strike associated with the P horizon.
188.8.131.52 SH1 ANOMALY
The anomaly lies on the westerly end of the claims Joking 2 (33558), Joking 4 (33556) and Joking 5 (33557) and has been worked for elluvial gold as evidenced by mounds of gravel and numerous pits to the gravel layer. It is a winding feature (see Figure 10 and 11) lying on flat ground to the west of the Tafuna Hill. Source of gold could be from the reefs on hill top or weathered in situ reef. A small washing plant is recommended to exhaust the elluvial resources and proceeds used to fund hard rock mining. Within the zone, islands of magnetic anomalies are mapped indicating concentration of remnant magnetite from the epidiorite.
Figure 8 – Google Image dated 8/21/2012 Overlain by Claims showing major structure to the north
184.108.40.206 SH ANOMALY
The anomaly lies the Joking1, 2 and 3 claims and trends NE SW open ended on either ends (see Figure 10, 11 and 12). The anomaly is interpreted as a potential shear zone that pinches and swells along strike and is dissected by NW SE fracture system. Outcrop of quartz reefs were observed to the north of anomaly where one arm of the anomaly strike swings to a NW SE trend and intersects SH1 anomaly while the other continues in a NE SW trend. Zones that exhibit a drag due to fracture system have a high prospectivity for gold mineralization. In general, areas where the conjugate structures intersect the SH anomaly are highly prospective for gold mineralization.
Figure 9 – Google Image dated 10/19/2007 Overlain by Claims showing major structure to the north
220.127.116.11 SH2 and SH4 ANOMALIES
SH2 is a lowly magnetic horizon that has a WWN EES strike towards SH/P and SH4 and is interpreted is a potential shear and is dissected by NW SE short wavelength anomaly observable from shaded relief data. It is dissected by a NE SW structure to its east and NE SW structure where it splays to give SH4. The splay is an area of interest (AOI) that should be followed up for
gold mineralization. SH4, also interpreted as a potential shear is a splay anomaly of SH2 and has a N S strike and is host to a N S small wavelength structure. It is also host to micro-magnetic high anomalies to the north that have a NW SE strike and area affected by the N S short wavelength structure.
Figure 10 – TMI Image overlain by Claims area
18.104.22.168 SH3 AND S5 ANOMALY
SH3 anomaly lies to the NE of the survey area but was not fully resolved by the magnetic survey as it spills outside the Tip Top Claims. It shows a near E W strike with low magnetic intensity characteristics synonymous with other mapped potential shear zones. It is therefore, also interpreted as a potential shear zone within the epidiorite. Equally, SH5, which lies on the SE
edge of the survey area, partly within the Tip Top claims but spilling outside, is interpreted as a potential shear. SH5 is synonymous with SH3 in strike but is dissected by NE SW strike that has affected SH2 to the north. It is also dissected by an interpreted NW SE structure that is host to some pits/reefs currently exploited by the claims holders. It is worthy of mention that these pits fall outside the claims area and client needs to rectify the anomaly with the ministry. To the immediate east of the anomaly SH5 lies a NE SW, mirror image anomaly that has a short strike, separated from SH5 by an intermediate magnetic anomaly. This anomaly is interpreted as part of SH5 separated from its parent anomaly but a later age structure.
Figure 11 – TMI Image overlain by interpreted magnetic signatures
22.214.171.124 SH/P ANOMALY
The anomaly lies within the Joking Claim and trends NE SW towards Tip Top Claims. It pinches and swells along its strike, and the swelling is associated with sinistral faulting. It is interpreted as potentially a shear zone or a quartz core of a pegmatite, which may host tantalite. Some
exposures of the pegmatitic quartz core where identified in the field and fall within this anomaly to its north. It is sub-parallel anomaly to SH which also swells due to the effect of the NW SE structures that dissect both anomalies. To the north of the anomaly, a N S short wavelength anomaly related to the extension of the Old Tip Top reef is identified and cuts across the anomaly towards Chancit Reef to the south (see Figures 3, 10, 11, 12 and 13).
Figure 12 – Residual Magnetics overlain by interpreted structures
Figure 13 – Shaded Relief Magnetics overlain by interpreted structures
126.96.36.199 P ANOMALY
This is NW SE striking anomaly that falls immediate south of a major sinistral fault. It exhibits the characteristics of a shear zone but is a quartz core of a zoned pegmatite (see Plate 1) and may be host to tantalite mineralization. It is of short strike length and terminated to its north by a major fault structure (see Figure 11).
Plate 1 – Pegmatitic Quartz, Joking Claim, Tafuna
4 CONCLUSIONS AND RECOMMENDATIONS
Five zones that are potential host to gold mineralization have been identified by the magnetic survey and are dissected by three fracture systems, the N S, NW SE and the NE SW systems. Zones where the fracture systems dissect the anomalies may be high prospective for gold mineralization. On the other hand, 2 zones that are potential pegmatites have been mapped and are prospective for tantalite mineralization.
It is recommended that anomaly SH be investigated by a pilot washing plant to exploit the elluvial gold potential. Proceeds from the elluvial mining maybe used to fund hard rock mining/ underground gold reef mining. It is also recommended that additional claims pegging/verification be undertaken to cover anomalies that spill outside the current jurisdiction.
Biscoe, R. T. (1931). The Geology of the Country around Shamva, Mazoe District. Salisbury: The Rhodesian Printing and Publishing Company. Ltd.
Songea. (n.d.). Retrieved 10 10, 2014, from Shanta: www.shantagold.com/operations/songea
Sperinck, M. J. (2009). Tecnical report on the mineral assets of Tantalum Mineracao and Prospeccao Limitada. Bull Creek.
Stidolph, P. A. (The Geology of the Country around Shamva). Bulletin 78, 1977, Salisbury