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Tanzanian Royalty Confirms Indicator Minerals Likely Sourced From Diamondiferous Kimberlite
Vancouver, Canada (ots/PRNewswire) - The Company is pleased to report that laboratory analysis has confirmed the presence of a range of kimberlite indicator minerals in drill hole samples from its Nyamigunga prospecting license (PL) in Tanzania.
The suite of indicator minerals identified by a scanning electron microscope (SEM) includes G10 garnets and chromites, all of which point to a diamondiferous kimberlite source.
"From an exploration perspective, knowledge of the composition and relative abundance of garnets and chromites in kimberlite - the primary source rock for diamonds throughout the world - allows assumptions to be made about the proximity and economic diamond potential of a kimberlite," noted the Company's president, John Deane.
The Nyamigunga PL is known to host five kimberlite bodies within an area of approximately two square kilometres. These carrot-shaped bodies are believed to have been intruded along a dominant north-south fault zone that provided a pathway to surface for diamonds and their genetically-related kimberlite indicator minerals.
Visual results from Mineral Services in South Africa were received in March 2006 and subsequently reported in a news release on April 3rd. SEM analysis was initiated immediately thereafter to confirm the visual results.
Mantle-derived garnets and chromites are considered the most important kimberlite and diamond indicators. The pioneering work of Dawson and Stephens (1975), Gurney (1984) and Fipke (1989) formed the basis for using garnets as well as chromites as tools to focus exploration on areas that are prospective for diamonds.
The origin of diamond is more closely related to fragments of peridotite (a coarse grained plutonic rock) and eclogite (a granular rock composed primarily of garnet) which are derived from the Upper Mantle, the thick shell surrounding the earth's outer core. In order for diamonds to form, they require extremely high pressures and temperatures which are only found deep in the earth. It is here that eclogite forms consisting of red pyrope garnet and green clinopyroxene. Diamond crystals develop alongside the garnet and pyroxene crystals.
Because diamonds have a close affinity to specific fragments (eclogite, peridotite) and their respective source areas, they can be subdivided into ones that have a peridotitic origin (P-type) and others that have an eclogitic origin (E-type). Even though a diamond may be found as a single crystal within a kimberlite rock mass, inclusions or flaws within the diamond crystal can identify its origins.
The flaws or "inclusions" within diamonds often include associated minerals such as garnet, pyroxene, olivine, chromite, and sulphides such as pyrrhotite. The chemistry of the mineral inclusions can be compared with those present in the eclogite and peridotite fragments in order to determine their source. These inclusions also provide valuable information regarding the pressure and temperature under which the diamonds formed as well as their age.
The overall assessment of geochemical information relies on the recognition of those minerals that are co-genetic with diamonds and comparing their mineral geochemistry with those of diamond inclusions.
Two important garnet types are associated with diamondiferous pipes:
- G10 garnets: Ca-poor, Cr-diopside free, with elevated Cr2O3.
- Group 1 eclogitic garnets: characterised with elevated Na and Ti.
Potential chromites indicating a diamondiferous content for kimberlite have a chrome content between 60 and 70 wt % Cr2O3, with an average MgO concentration of between 8 and 16 wt% and a TiO2 content of less than 0.7 wt%. Discrimination plots are therefore used to define these geochemical boundaries and these plots are available on our website at: www.TanzanianRoyaltyExploration.com.
Poor ground conditions, including heavy water inflows, produced surface contamination in the drill holes which could explain some of the low indicator mineral grain counts in the K3, K4, K5 and K6 pipes. (Please refer to the Company's April 03, 2006 press release for details).
Nevertheless, kimberlite bodies within Tanzania often have variable indicator mineral chemistry without diminishing their economic potential.
"While much more work remains to be done, the progress we have made on the diamond exploration front in the past two years has been nothing short of phenomenal," said Jim Sinclair, the Company's Chairman and CEO.
"In the past year alone, we have drilled 11 kimberlites, six of which were brand new discoveries. I take great pride in saying that we are leading the charge that could one day see Tanzania reinstated as a major diamond producer," he added.
Analytical results from the K1 and K2 pipes, which provided statistically sound indicator mineral populations for analysis, are summarised below.
A total of 106 visually identified garnet grains were micro-probed and SEM results indicated that 12 are G10 garnets (approx 11%). A total of 45 visually identified chromite grains were micro-probed and SEM results indicate that all are kimberlitic chromites. A total of four grains (8.9%) have Cr2O3 above 60 wt% and hence plot within the diamond inclusion and intergrowth field.
The presence of G10 garnets and chromites that plot in the diamond inclusion and intergrowth field, supports the conclusion that this kimberlite sampled a potentially diamond bearing depleted harzburgite in the mantle on the way to the surface. Hence this kimberlite is highly ranked and warrants further follow up.
A total of 171 visually identified garnet grains were micro-probed with SEM results indicating that 22 are G10 garnets (approx 13%). A total of 52 visually identified chromite grains were micro-probed and SEM results indicated that all are kimberlitic chromites. A total of five grains have Cr2O3 wt% above 60 wt% and thus plot within the diamond inclusion and intergrowth field. Two of them have TiO2 less than 0.7wt% and plot within the diamond inclusion field.
The presence of G10 and DI chromites support the conclusion that this kimberlite sampled a potentially diamond bearing depleted harzburgite and eclogite in the mantle on the way to surface. As a result, this kimberlite is highly ranked and warrants further follow up.
Follow up work associated with these positive results is presently under way. The Company is currently extending the ground magnetic survey to the immediate south of these pipes to search for further kimberlites along the north-south fault zone.
A bulk sample of the kimberlites and gravels lying above the pipes is planned this year to confirm diamond concentration, quality and grade. "This will determine the future of this exciting prospect," said Deane
"Alluvial diamonds are the best indicator mineral for diamondiferous kimberlites," he added. "In fact, alluvial stones in gravels of the Orange and Vaal river systems led to the initial discovery of diamondiferous pipes in South Africa."
The Company's Qualified Person is Mr. John Deane, the President of Tanzanian Royalty Exploration Corporation Limited. He has a M.Sc. from the University of Cape Town (1993) and is a registered scientist with SACNASP (Reg. No.400005/05).
The Toronto Stock Exchange and American Stock Exchange have not reviewed and do not accept responsibility for the adequacy or accuracy of this release.
Cautionary Note to US Investors - The United States Securities and Exchange commission permits US mining companies, in their filings with the SEC, to disclose only those mineral deposits that a company can economically and legally extract or produce. We use certain terms on this news release, such as "measured", "indicated", and "inferred" "resources" that the SEC guidelines strictly prohibit US registered companies from including in their filings with the SEC. US Investors are urged to consider closely the disclosure in our Form 20-F, File No. 0- 50634, which may be secured from us, or from the SEC's website at http://www.sec.gov/edgar.shtml.
ots Originaltext: Tanzanian Royalty Exploration Corporation
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