Mineral Resource Update at the Mikei Gold Project, Kenya (JORC, 2012)
Mineral Resource of 723 koz at 1.49 g/t Reported
22 February 2021
Red Rock Resources Plc (“Red Rock” or “the Company”), the natural resource development company with interests in gold, copper/cobalt, manganese and minerals, announces the completion of a Mineral Resource estimate (“MRE”) updated to comply with the 2012 edition of the Code published by the Australasian Joint Ore Reserves Committee (“JORC”) over parts of Red Rock’s exploration license at Mikei, Migori, Kenya comprising the Mikei Gold Project (“MGP”). The supporting documentation (the “Report”) was prepared by CSA Global (UK) Limited (“CSA Global”).
The Report documents the results of Mineral Resource estimation work initially conducted in 2011 and 2012 and revised in 2021 in order to report the Mineral Resource according to JORC (2012) guidelines. MGP was assessed for reasonable prospects for eventual economic extraction (RPEEE) by applying conceptual benchmarked costs to calculate conceptual reporting pit shells. Any material outside or below the reporting pit shell was updated as “Not Classified” since it did not meet the criteria to be reported as a Mineral Resource.
The total Mineral Resource, for both Inferred and Indicated categories at a 0.5 g/t Au cut-off, is estimated at:
15.13 Mt @ 1.49 g/t Au with contained metal content of 723 koz Au
· MRE covered the five prospect areas covered by the 2012 MRE
· Application of RPEEE principles required by JORC (2012) led to the exclusion of some previously estimated Mineral Resource areas and a consequent 39% reduction in reported ounces of gold
· Gold grade of the MRE for the same reason increased by 18% to 1.49 g/t
· Some material previously stated as Indicated in the oxidised zone has been downgraded to Inferred, reflecting uncertainties relating to the terrain model and the extent of artisanal activity since 2012
· Detailed recommendations for a first stage step-out drilling programme made to potentially increase the size of the MRE
Red Rock Chairman Andrew Bell comments: “We are delighted to announce an updated Mineral Resource at Mikei, with a higher gold grade. These conceptual pit shells used to test for reasonable prospects of extraction will now act as a springboard for our future exploration which will be focused on Resource enhancement.
After having been for several years prevented from carrying out work on the property while other nearby projects in Tanzania and Kenya progressed, the first necessary steps on our return were to conduct updated baseline and Resource studies, and to prepare an immediate programme to upgrade and extend our Mineral Resource.
Updating our Mineral Resource Estimate to JORC (2012) was essential if we were to make public reference to it, and the exercise of complying with it has been invaluable in two ways.
First, the application of conceptual benchmarked costs to calculate conceptual reporting pit shells ensures that the reported Mineral Resource is aligned with a modern, industry-recognised method of testing for reasonable prospects for eventual economic extraction. This together with the higher grade within the conceptual pit shells enables us to report a Mineral Resource that looks more robust in the context of current gold prices.
Secondly, the exercise of working out what, on the assumptions made, lay outside the pit shell but nearby or along strike showed us where targeted step-out drilling might prove effective in extending the pit, and so gave us our first 14, and mainly shallow, new drill hole locations. These we can test without delay while planning further programmes for infill and step-out drilling and for testing mineralisation at depth.
We now have the opportunity to build on this solid base and it is our belief that the potential for expansion at and around Mikei is strong”.
The MGP comprises two prospecting licences which cover approximately 245 km2, namely PL/2018/0202 and PL/2018/0203, over the Migori Greenstone Belt, and are located along the northern margin of the Tanzanian Craton. The licences extend 63 km along strike of the belt, which also hosts the Kilimapesa Gold Mine. The North Mara Gold Mine, which is operated by Barrick Gold, is located 30 km to the south of the MGP in Tanzania.
Regional exploration in the project area began in the early 1930s and culminated in the identification and subsequent mining of the Macalder volcanogenic massive sulphide (VMS) base metal mine.
In 2010, Red Rock began the extensive task of file organisation, data digitisation and compilation of available historical data, following which CSA Global performed cross-checks and validation steps prior to loading it into a Structured Query Language (SQL) database using Datashed. During 2011 and 2012, Red Rock undertook an infill drilling programme at all five of the lode gold prospects; MK, Kakula-Kalange-Munyu (KKM), Kakula-Kalange-Munyu West (KW), Nyanza (NZ), and Gori Maria (GM) within PL/2018/0202.
http://www.rns-pdf.londonstockexchange.com/rns/0738Q_1-2021-2-23.pdf [Figure 1: Total field aeromagnetic imagery for the Mikei area collected by Red Rock, with drill collars annotated in yellow and surface structural dip and dip-directions as red triangles]
The Report documents the results of Mineral Resource estimation work initially conducted in 2011 and 2012 and revised in 2021 in order to report the Mineral Resources according to JORC (2012) guidelines. No new data is available since the 2012 report, and as such, those estimates remain valid and disclosure to JORC (2012) is the focus of the Report.
Mineral Resource Estimate and Comparison with Previous Estimate
The Mineral Resource has been estimated using geological models developed by Red Rock and CSA Global. The MRE has been undertaken using ordinary kriging (OK) on volume block models for all prospects. Consideration of natural grade populations, along with top cutting, compositing and variography has been completed for all prospects. This has produced robust 3D grade models for each prospect, that can be used for conceptual mine planning studies and further exploration planning.
The MRE is reported in accordance with JORC (2012) guidelines, following the application of reasonable prospects of eventual economic extraction by means of pit shells supported by conceptual cost and gold price forecast parameters. The Mineral Resource is reported at a cut-off of 0.5 g/t Au.
The JORC Code (2012) defines a Mineral Resource as a concentration or occurrence of solid material of economic interest in or on the Earth’s crust in such form, grade (or quality), and quantity that there are reasonable prospects for eventual economic extraction. The location, quantity, grade (or quality), continuity and other geological characteristics of a Mineral Resource are known, estimated, or interpreted from specific geological evidence and knowledge, including sampling. Mineral Resources are subdivided, in order of increasing geological confidence, into Inferred, Indicated and Measured categories.
The Mineral Resource estimate for all MGP prospects is reported according to the JORC (2012) guidelines. The geology for each prospect is broadly understood. Sectional interpretations were undertaken using geological information, structural measurements, and grade relationships. The statistical grade characteristics of the individual prospects are generally well understood, and a reasonable amount of density determinations were conducted to ensure an acceptable level of confidence in the bulk density of the material being reported as Mineral Resources.
Prior to Mineral Resource classification, a review of all historical and modern supporting data was undertaken. CSA Global concluded that there is adequate confidence in both the historical and Red Rock data to classify areas of the Mineral Resource as either Indicated or Inferred. Classification was further reviewed on a prospect-by-prospect basis, following consideration of data quality, data spacing, continuity of mineralised domains, and confidence in the grade estimate.
Where appropriate, a coherent zone of mineralisation, located around the more densely sampled core, was assigned an Indicated classification. The extremities of each block model, that were supported by fewer data and were therefore less reliably informed, were classified as Inferred.
All prospects, except GM, were classified as Indicated and Inferred Mineral Resources. GM was classified as Inferred only, mainly due to the relatively low average RC drill recovery of 62%.
Due to the uncertain lateral extent and depth of artisanal mining at the Mikei prospects, and the lack of topographic data to accurately deplete the Mineral Resource, all oxidised material was classified as Inferred Mineral Resources.
The term “reasonable prospects for eventual economic extraction” (RPEEE) implies a realistic inventory of mineralisation which, under assumed and justifiable technical, economic and development conditions, might, in whole or in part, become economically extractable. The assumption is that the Mikei prospects will be extracted by open pit mining. The MGP block models were assessed for RPEEE by applying conceptual benchmarked costs to calculate reporting pit shells. The following conceptual parameters were applied for open pit mining:
· Mining cost: US$3/tonne
· Processing cost: US$22/tonne ore
· Pit slope angle: 52°
· Recovery: 90%
· Royalty: 7%
· Gold price: US$ 1,800/troy ounce.
The Mineral Resource is reported as that material within the RPEEE pit shells, and above a cut-off grade of 0.5 g/t Au. The Mineral Resource is reported as of 18 January 2021
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