Base Metal Exploration confirms prospectivity of the Migori Project, SW Kenya
Dated: 02 July 2012
Base Metal Exploration confirms prospectivity of the Migori Project, SW Kenya
Red Rock Resources Plc ("Red Rock" or the "Company"), an exploration and mining company with a producing gold mine in Colombia, advanced gold exploration in Kenya and iron ore interests in Greenland, announces exploration and drilling updates for the base metal exploration on the Migori Project in south west Kenya.
Recent work on the Macalder Belt, an Archaean volcano-sedimentary sequence to the north of Red Rock's Mikei Gold Project (Dec 2011 JORC Indicated & Inferred Resource of one deposit: 17.8Mt @ 1.01g/t Au; more updates due shortly), has confirmed the prospectivity of the 20km strike length of the belt for base metal mineralisation.
A comprehensive study of historic results and re-logging of recently-discovered historic drill core combined with detailed mapping of the immediate area around the historic Macalder Mine (Estimated historic production ~2.0 Mt @ 2.3% Cu, 3.2% Zn, 3.3 g/t Au), itself the subject of Red Rock's Macalder Tailings Retreatment Project (October 2011 JORC Measured Resource: 1.28Mt @ 1.65g/t Au, 33.5g/t Ag), has resulted in revised interpretations and confirmed the prospectivity of both the immediate vicinity of the mine and VMS potential elsewhere within the belt.
While massive sulphides were not intersected, drill results from a new prospect called Barnabas based on one of the unexplored airborne electromagnetic conductors within the Macalder Belt, have confirmed the presence of prospective stratigraphy, and the sediment-hosted volcanogenic sulphides with anomalously high Cu, Pb, Zn, Au and Ag results suggest enrichment potentially related to as yet undiscovered nearby mineralisation.
Regional Base Metal Exploration
In the Migori Project Red Rock is exploring for gold and base metals in an Archaean greenstone belt parallel to the Tanzanian border. In addition to extensive gold mineralisation greenstone belts throughout the world also host volcanogenic massive sulphide deposits, often in clusters or 'camps' of separate deposits around a volcanic centre. Until recently Macalder (~2.0 Mt @ 2.3% Cu, 3.2% Zn, 3.3 g/t Au) was the only know VMS deposit in the greenstone belts of the North Tanzanian craton, however the recent discovery of the Bumbo VMS deposit (Aviva Ltd ASX: AVA September 2011 1.68 Mt @ 1.8% Cu, 5.4% Zn, 0.7g/t Au and 37g/t Ag) in the Ndori greenstone belt 140km away confirms that there is further VMS potential in Kenyan greenstones.
A comprehensive study by a consultant expert in VMS deposits around the world, Dr Rob Willan, of the geological setting and mineralisation style of the Macalder mine area has been undertaken to generate targets within and near the Macalder system, and to determine geological features which may be used to evaluate the VMS potential of targets and prospects generated within the Macalder Belt. The key findings from the study suggest that potential proximal VMS deposits may be found in the direction of the thickest development of basaltic volcanic rocks, such as are found to the northwest at Nyatworo, and also on the palaeoslopes distal to the main volcanic centre associated with lower temperature VMS -style deposits and sulphidic carbonaceous black shale. Stratigraphic horizons of sulphide-bearing carbonaceous black shale and pillow basalts occur along strike from the known Macalder VMS and have been intersected during the recent drilling.
Also, as Red Rock has previously reported, an airborne electromagnetic (AEM) geophysical survey was flown at 100m line spacing over the area surrounding the Macalder Mine (Fig. 1) to detect remnant conductors and evaluate the along-strike potential for other Macalder-style massive sulphide deposits concealed at depth. Two high priority AEM targets were highlighted during the survey (Fig. 1) and have been the focus of follow-up exploration.
FIGURE 1. AEM Survey area showing high priority targets at Macalder and Barnabas and detailed IP anomaly map showing location of geophysical modelled bodies & drill holes.
The largest AEM conductor was adjacent to the known deposit at the historic Macalder Mine, somewhat offset from the historical workings, and will be worked up as a drill target in combination with the testing of structural and stratigraphic ideas generated by the VMS expert's comprehensive study.
A second significant AEM anomaly was located on the south eastern edge of the survey in an unexplored area called Barnabas, 4 km southeast of Macalder. Since the anomaly was located on the edge of the airborne survey area, a follow-up Induced Polarisation (IP) ground survey was carried out to better localise and characterise the depth and extent of the conductor. The IP work identified both chargeable and low resistivity bodies, consistent with conductive material at depth (Fig. 1).
At Macalder the ore body conductive target projects to surface and is characterised by intense surface oxidation of massive sulphides and development of a gossanous cap, however at Barnabas the conductive units are concealed at a depth of ~50 meters with no outcrop exposure. The geophysical anomaly is consistent with a strongly conductive unit and has similarities to the anomaly associated with the known Macalder VMS.
Exploration drilling results
Three exploration drillholes at Barnabas were designed to intersect the concealed geophysical targets, to better understand the stratigraphic context of the anomalies, and to assess the VMS potential of the area. BNDD001, BNRC002 and BNRC003 intersected sequences of meta-basalt, meta-andesite and carbonaceous black shale with up to 80% blebby sulphides including pyrite, chalcopyrite, pyrrhotite and sphalerite with anomalous intersection intervals of up to 9 meters (Table 1 & Fig. 2). These zones, including maximum results of 0.7g/t Au, 44g/t Ag, 0.09% Cu, 0.1% Pb and 0.3% Zn, are intimately associated with the sulphide-bearing carbonaceous black shale, locally extending into adjacent meta-andesites. These element concentrations are considered anomalous and are notably higher than typical element concentrations for non-mineralised rocks.
Notes: Assays completed at the ALS Minerals Laboratory in Johannesburg, using fire assay analysis for gold and ICP-AES analysis for base metals. Holes 1 & 3 were NQ diamond drillholes, Hole 2 was drilled using reverse circulation percussion. Grades are expressed as average grades across the measured interval.
FIGURE 2. Geological cross sections from BNDD001, BNRC002 and BNRC003 showing weighted average grades through anomalous intersections.
In addition, the geological relationships between sulphide-bearing carbonaceous shale and VMS deposits are recognised as occurring contemporaneously the world over, with Cu, Pb and Zn sourced from VMS systems concentrated in proximal black shales due to the anoxic reducing environment in which they are deposited. At Barnabas the source of the anomalous Cu, Pb and Zn is unknown however the geological setting and results are analogous to Precambrian age black shale host base metal deposits in the Zambian Copper Belt and the well known shale host base metal deposits at Macarthur River, Mount Isa and Hilton in Australia.
Throughout the Macalder Belt a combination of techniques will be used to assess regional base metal potential, further test the Macalder system and generate new volcanogenic massive sulphide (VMS) gold-base metal targets. The findings of the recent study will be integrated into on-going assessments of historic data and mapping; drill targets will be defined within the Macalder Mine area to test the eastern AEM conductors with the principal aim of locating potential along-strike extensions of the VMS lenses not discovered during mining; historic reports of base metal minerals and occurrences from Red Rock's recent aircore survey of the Nyatworo area (RRR release: 11 April 2012) will be systematically assessed. Regional geophysical surveys to assess the base metal potential of the remainder of the Macalder Belt will be considered.
At Barnabas follow-up work will continue to evaluate the area's VMS potential, and will include detailed mapping, comparative geochemistry to the known VMS deposit at Macalder, with particular emphasis of host rock compositions, stratigraphic correlation, minor element analysis and the character of mineralisation on the periphery of the known mineralisation. The geophysical anomalies will be re-examined in light of the geology encountered in drilling and assessed for indications of the possible development of massive sulphides at depth. Follow-up drilling will be designed on the basis of the integration of the results of all this work.
The Macalder study has indicated that the stratigraphic sequence found in the Macalder Belt suggests that further lower temperature VMS -style deposits may be found associated with sulphide-bearing carbonaceous black shales.
At Barnabas the sequence of volcano-sedimentary rocks intersected in the three exploration drillholes reported here also show a stratigraphic sequence that is prospective for VMS-style deposits. There are elevated levels of typical VMS-suite metals in the system, and the geophysics indicates there is an east-west strike continuity of the conductors seen at the Barnabas Prospect.
Based on the above results, follow-up work will be designed to determine the origin of the sulphide mineralisation and evaluate the prospectivity for a concealed VMS deposit not intersected during the recent drilling.
Also, during the recent reappraisal of the geology of the Macalder Mine Area it is clear that conductive material exists outside the known, mined VMS lens and so represents a high priority target, and that a further conductor, Bushells, occurs along strike from Macalder; and regionally there is still much untested potential along the whole of the 20km long Macalder Belt.
Competent Person Statements
The information in this report that relates to Exploration Results is based on information compiled by Jamie McCreath PhD based on additional work by Rob Willan PhD, and is approved for release by Mr Richard Evans, who is a Member of The Australasian Institute of Mining and Metallurgy. Mr Evans is an employee of the Red Rock Group of Companies and has sufficient experience which is relevant to the style of mineralisation and type of deposit under consideration and to the activity which he is undertaking, to qualify as a Competent Person as defined in the 2004 Edition of the "Australasian Code for Reporting of Exploration Results, Mineral Resources and Ore Reserves". Mr Evans consents to the inclusion in the report of the matters based on his information in the form and context in which it appears.
Forward Looking Statements
This report contains 'forward-looking information' that is based on the Company's expectations, estimates and projections as of the date on which the statements were made. This forward-looking information might include, among other things, statements with respect to the Company's business strategy, plans, objectives, performance, outlook, growth, shareholder value, projections, targets and expectations, Mineral Reserves and Resources, results of exploration and related expenses, property acquisitions, mine development, mine operations, drilling activity, sampling and other data, grade and recovery levels, future production, capital costs, expenditures for environmental matters, life of mine, completion dates, uranium prices, demand for uranium, and currency exchange rates. Generally, this forward-looking information can be identified by the use of forward-looking terminology such as 'outlook', 'anticipate', 'project', 'target', 'likely', 'believe', 'estimate', 'expect', 'intend', 'may', 'would', 'could', 'should', 'scheduled', 'will', 'plan', 'forecast' and similar expressions. Persons reading this report are cautioned that such statements are only predictions, and that the Company's actual future results or performance may be materially different.
Forward-looking information is subject to known and unknown risks, uncertainties and other factors that may cause the Company's actual results, level of activity, performance or achievements to be materially different from those expressed or implied by such forward-looking information. Forward-looking information is developed based on assumptions about such risks, uncertainties and other factors set out herein, including but not limited to the risk factors set out in the Company's Annual Report. This list is not exhaustive of the factors that may affect our forward-looking information. These and other factors should be considered carefully and readers should not place undue reliance on such forward-looking information. The Company disclaims any intent or obligations to update or revise any forward-looking statements whether as a result of new information, estimates or options, future events or results.
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