Kavango Resources - Results of drilling undertaken on the KSZ Botswana
("Kavango" or "the Company")
RESULTS OF DRILLING UNDERTAKEN ON THE KSZ
· The drilling has provided valuable geological information to management to assist in the understanding of the potential of the KSZ to host large Cu-Ni mineral deposits.
· The assays from the core show elevated copper and nickel values against what might be expected in a non-mineralised gabbro.
· Three gabbro sills were intersected and analysed during the programme. These were from holes:
RIT50DH1 - at 58m depth, for 14m - average Cu 134ppm, Ni 205ppm
RIT50DH2 - at 58m depth, for 13m - average Cu 132ppm, Ni 226ppm
RIT08DH2 - at 121m depth, for 16m - average Cu 163ppm, Ni 181ppm.
· Peak values were: 415ppm Ni, 189ppm Cu.
· Discussions were held with several major mining companies at the recent
COMMENT AND INTERPRETATION
· Kavango's exploration effort is currently directed towards confirming that the conditions necessary for the formation of metal sulphide orebodies existed during the emplacement of gabbroic intrusives associated with a major volcanic episode during the late Karoo geological era (180 Ma).
· The 1,100m drilling programme, undertaken in
o The gabbro sills contain "primary" sulphides, which suggests that the molten magma was in a condition of "sulphur saturation" at the time of emplacement.
o The sills appear to favour emplacement within the coal and shaley-coal bearing sediments of the Ecca (geological) formations. Thus a source of additional sulphur would have been available to encourage the development of metal sulphides within the cooling magma.
o The existence of multiple (and relatively thin) gabbro sills and dykes lying above a large gabbroic magma chamber, suggests the development of a complex "plumbing system" feeding volcanic vents on the ancient (paleo-) surface.
o Drill core logging confirms that these relatively thin gabbroic bodies are associated with extensive heat alteration halos (several metres) into the host rocks, which suggests that molten magma was flowing through these "conduits" over prolonged periods. This would allow for the accumulation of (heavy) metal sulphides in physical traps during magma flow.
· The assays from the core show slightly elevated copper and nickel values against what would be expected in a non-mineralised gabbro. This probably reflects the enrichment of these metals in the fine disseminated sulphides seen in the thin sections (taken from the core). However, these metals would have been leached out of the crystalising silicate minerals by sulphur and probably deposited elsewhere thus reducing the overall metal value in the core. Polished thin sections and the whole rock geochemistry needs to be undertaken to confirm this.
· What was not confirmed was the ability of Kavango's CSAMT geophysical system to identify massive sulphide bodies associated with the gabbro sills. This is almost certainly due to the presence of ground water contaminated with salt in and around the gabbroic intrusions.
o Salty water absorbs electrical current and acts as an EM conductor, which would tend to mask massive sulphide minerlisation.
o Geophysical consultants have now advised Kavango that the use of down-hole EM surveying and/or the use of much more powerful transmitters from surface should be employed to discriminate between the mildly conductive salty water and the much more conductive massive sulphide mineralization.
· The Company is now in discussion with our geophysical consultants to develop a geophysical method, either down-hole or from surface that will discriminate between conductors caused by saline groundwater and massive sulphide mineralization. Such systems are available and need to be tested on the KSZ.
· Down-hole EM surveys have the potential to search 300m from the probe when placed in existing boreholes.
· Additional tasks include:
o Generate computerized 3-D models of the geology of the KSZ and combine this with the data obtained from the airborne EM surveys.
o Complete polished thin sections to aid identification of metal sulphide species.
o Commission a full analysis and report on the whole rock geochemistry of the drill core by a recognised authority on magmatic sulphide deposits.
"There is now a large body of evidence suggesting that the accumulation of nickel and copper bearing metal sulphides occurred within the high level gabbroic intrusions of the KSZ. The 3-D modelling of the geological information obtained from the drilling, together with all the geophysical surveys that have been completed, is providing Kavango with much valuable information concerning the genesis of the intrusives, the mechanisms of magma transport and the chemistry of the magma itself. The next stage is to identify and assess the value of these metal sulphide accumulations."
For further information please contact:
Turner Pope Investments (Joint Broker) +44 20 3657 0050
Andy Thacker and Zoe Alexander
Glossary of Terms
· CSAMT: Kavango uses a ground based geophysical technique known as Controlled Source Audio frequency Magneto Tellurics (CSAMT) to identify the exact location of the conductors identified in the airborne electromagnetic (AEM) survey. The shape, orientation and depth of the conductors will determine if the conductor should be drilled.
· When a deposit consists almost entirely of sulphides it is termed "massive". When it consists of grains or crystals of sulphide in a matrix of silicate minerals, it is termed "disseminated".
· Magmatic sulphide deposit: The accumulation of metal sulphides and their deposition within the intrusive is largely dependent on the volume of magma that passes through the conduit. The formation of a magmatic sulphide deposit requires the precipitation of small amounts of metal sulphide from large amounts of magma (lava) over a considerable time period
· Gabbro/gabbroic: A coarse grained, medium to dark coloured rock, formed from the intrusion of mantle derived molten magma into the earth's crust.
· Gabbroic sills: Relatively thin, planar bodies of solidified gabbroic magma that intruded into layers of sedimentary rock whilst still molten.
· High level sills: Are sills that are emplaced in the upper levels of the earth's crust, close to the surface.
· Sulphide mineralisation: If there is sufficient sulphur in the molten magma, it will tend to combine with metals (Cu, Zn, Ni, Co, Pb, PGEs etc.) to form metal sulphide complexes, which may coalesce to form massive sulphide deposits. If the melt is sulphide poor, the metals will be taken up into the silicate minerals that form as the magma cools and will not usually form economic deposits.
· Primary sulphides: Are sulphide complexes (or crystals) that form as the magma cools and are composed of elements that are present at the time of initial crystallization.
· Secondary sulphides may form after the magma has solidified either by the introduction of new elements into the rock or by re-mobilising elements already present through changes in pressure, heat etc.
· Magma conduits: Beneath a volcano or multiple volcanic vents and fissures there will exist a complex "plumbing system" of (vertical) dykes and (horizontal) sills transporting magma (lava) to the surface. In some cases these "conduits" can remain active for hundreds of years accumulating metal sulphides in traps or along the floor. These accumulations solidify to become massive sulphide deposits
· Electromagnetic (EM) surveys: are used to detect a wide variety of mineral deposits, especially base metal sulphides (such as copper and nickel), via detection of conductivity anomalies which can be generated around sulphide bodies in the subsurface. On a regional scale they are carried out via airborne methods, at ground level for detailed follow-up work, or down a drill hole to identify a body of mineralization under the conductive layers above.
· Downhole EM surveying: Downhole EM will be able to detect any massive sulphide which the drill hole may have missed (off hole) as well as beyond the extent of the drill hole. Since the receiver of the downhole EM unit will be much closer to the source, it will be able to detect bodies beyond the reach of surface and airborne methods with less interference from Kalahari and Karoo sediments. Radius of search is typically 300m.
This information is provided by RNS, the news service of the
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