Moxico Resources owns 85% of Mimbula which contains a JORC Resource of 61.1Mt at 1.18% Cu
Mimbula is a former Zambia Consolidated Copper Mines (ZCCM) project situated in Chingola, Copperbelt Province, Zambia.
Moxico plans to complete a pre-feasibility study (PFS) and feasibility study (FS) including metallurgical test work to confirm the mineral processing flow sheet and undertake drilling to expand the mineral resource.
The company is currently undertaking a pre-IPO capital raise to fund the PFS and FS, resource expansion and development financing costs. A capital raise for development of the Mimbula mine and processing facilities through potential IPO is targeted for 2018.
Drilling at Mimbula commenced in 1926. By 1932, 16 drill holes (totalling 2,798m) had been drilled, determining the existence of the Mimbula ore body (Table 1). A follow-up drilling programme commenced in 1958 when 40 holes were drilled (totalling 4,124m). Two separate (contiguous) orebodies were defined – Mimbula 1 and Mimbula 2. Removal of overburden from Mimbula 1 commenced in April 1967 and production from the pit commenced in February 1968. The Mimbula 1 high-grade ore portions were substantially mined, and the pit allowed to flood in 1973. In 2007, SRK denoted in its report entitled "Geological Modelling and Estimation of Mineral Resources, Mimbula Orebody, Chingola, Zambia" that this part of the Mimbula Resource as ‘Area 1’. Area 1 (Mimbula 1) was not included in the 2007, nor, 2012 Mineral Resource Estimations by SRK and Golder respectively.
Mining of the Mimbula 2 Open Pit was undertaken in 1974, and overburden was removed down to the 55m bench, (extracting an estimated 1.5-2.0Mt of material) at which point mining operations were suspended while metallurgical investigations determined the treatability of the exposed mineralised material. The production figures for Mimbula 1 & 2 are not available at this time. There is no evidence of any mine activity or production from the Mimbula deposit post-1974.
SRK prepared a SAMREC-compliant Mineral Resource Estimate for Mimbula in 2007 (the SAMREC Code is a resource classification guideline widely used in South Africa and has the same standards, and is based on, the JORC Code). The database used in the 2007 model contained a total of 242 drill holes (totalling 46,382m) of which 188 holes were drilled prior to 1971 and 54 holes drilled by KCM in the period 2004-2006. All the ‘pre-1971’ holes were diamond drill holes. Of the 54 KCM holes, drilled for a total of 7,931m, 10 were reverse circulation holes and 56 were diamond drill holes. The target was the area between the existing Mimbula 1 and 2 orebodies.
The drilling at the Mimbula Deposit was on section lines with fences at varying spacing from 60m to 100m apart. Holes along the fence lines varied from 30m to 50m spacing. On the basis of the review of field sections, SRK were of the opinion that the variability of the mineralisation and hence the quality of the mineral resources would be better understood with additional closer spaced drilling.
Golder Associates (Golder) completed an audit (using SAMREC guidelines) of the SRK 2007 Mineral Resource Estimate for AMC in 2012, on the basis of which AMC prepared a PFS (2012) with the emphasis on mining the sulphide portion of the Mimbula 2 orebody as a stand-alone operation. The deposit was defined as a SAMREC compliant ‘Inferred Resource’, rather than an ‘Indicated Resource’, due to the absence of metallurgical test-work on the different ore material types.
In 2011 CSA Global Pty Ltd (CSA) was engaged by Zambezi Resources Ltd (Zambezi) to complete a JORC-compliant Mineral Resource Estimate of the acid-soluble copper mineralization for the Mimbula SP11 rock dump situated adjacent to the Mimbula 2 Open Pit. This was part of a broader regional study, aimed at examining the reclamation of low-grade rock dumps, by Zambezi. The 2011 JORC Indicated Resource for Mimbula SP11 Stockpile was 1,695,870 t at 0.94% Cu (0.65% acid soluble Cu) and it has so far been unmined. This stockpile is in addition to the in-situ resources shown in Table 2.
Based on AMC’s recommendations in the 2012 PFS, additional drilling was completed by KCM from 2012 to 2014. This more recent drilling data has been used to update the 2012 Mineral Resource Estimate (Golder, 2012); this work was completed in December 2016, by David Stock, an independent Competent Person (CP) as per the JORC Guidelines who published a JORC Inferred Resource for Mimbula.
Neither AMC, nor Stock have, in the current scope of works, audited this 2012-2014 drilling information to the level stipulated in the JORC 2012 Code so the resource can only be classified as Inferred under JORC.
Kanchana Resources (David Stock as Qualified Person) was retained by Moxico Resources Plc to undertake a new resource estimate for the Mimbula copper deposit, Chingola, Zambia. The report entitled "Mimbula Copper Project, Chingola, Zambia Mineral Resource Estimate December 2016" details the methodology and parameters used in the December 2016 resource. This resource is a revision of the February and June 2016 estimates by the same author with revised isosurfaces, an improved surface DTM, updated variography using the full database, and incorporating recommendations from the SRK 2016 review. The author has not visited the Mimbula property and this work calls upon the work previously undertaken by SRK 2007, African Mining Consultants (AMC) 2012 and LTI Advisory 2015. Without visiting the property, and given the absence of access to the QAQC data from the most recent drill programme 2011-14, together with the concerns expressed by SRK (2007) on the results of duplicate assays from the 2004-2006 drilling and pre-1971 drilling programmes the Mimbula resource cannot be classified as anything but an inferred resource under JORC 2012 guidelines. To move beyond inferred the check sampling needs to be completed on the 2011-14 drilling, particularly as it comprises some 32% of the samples used in this estimate. It should also be noted that the resource estimation detailed in this report is contained within both an existing licence held by Moxico Resources through its Zambian subsidiary and within an extension to the licence applied for but as yet not granted. The metallurgical route needs more work, particularly regarding the direct convertibility of laboratory acid soluble copper assay results to acid heap leach mining recoveries. The new total in-situ mineral resource is tabulated above, both total copper and optimised for acid soluble copper.
LOCAL GEOLOGY AND MINERALISATION
The Mimbula Deposit is hosted within the Lower Roan Subgroup, the host for the majority of the economic copper mineralisation of the Zambian Copperbelt, for a strike length of approximately 1.5km. The deposit is part of a suite of ‘Footwall’ orebodies hosted by the Arkose Formation common in the Chingola-Mimbula-Fitula areas. Mimbula is situated where the cupriferous Lower Roan Subgroup is draped around the corrugated southwest flank of the ‘Basement Complex’ that forms the Kafue Anticline.
The Lower Roan Subgroup strata comprise mainly arkose, greywacke, quartzite, shale, micaceous banded sandstone, feldspathic quartzite and schist and occur folded into major north-westerly plunging, asymmetrical synclines and anticlines, draped around the Nchanga Granite.
The three principal structural features are the Nchanga Syncline, the Chingola Anticline and the Mimbula-Chabwanyama Syncline within which more than 14 known orebodies occur at seven different horizons in a wide variety of sedimentary rock types, extending over a vertical interval of 150m from the base of the Lower Roan Subgroup. In the Mimbula area, the arkose is sub-divided into recognisable lithological units consisting of up to six superimposed lenses in argillaceous feldspathic arenites. The bulk of the mineralisation is generally found within the F2(4)(0) and F2(4) units. The thickness of ore in these ‘Footwall’ orebodies is highly variable ranging from a few metres to greater than 100m.
Structurally, the mineralised zones within the Mimbula area occur in subsidiary synclines of the main Mimbula-Chabwanyama Syncline. The syncline trends between 310° to 330° and plunges approx. 15° to the northwest. The orebody occurs asymmetrically around the fold axis and is considered to be a secondary concentration of leached metals from the flanks which have re-deposited in the hinge of the syncline. The mineralisation and copper grades appear to be controlled by, and increase in proximity to, an interpreted basement fault (trending 330°) which can be mapped in the north-eastern flank of the Mimbula-Chabwanyama Syncline. The base of the F2(4)0 unit marks the key copper-rich fluid influx. The orebody is closed off to the east and southeast although the down-plunge limits (Target 1 - Mimbula Extension) have not been defined. This provides the potential to increase resources down-dip by up to 20% within the current licence. AMC recommends additional drilling to the northwest, which may potentially increase the tonnage, and the grade of the 2016 MRE.
Bulk density determinations on selected cores from the various rock types were undertaken. The bulk density database contains 320 data points divided according to rock type as indicated in the table.
SRK (2007) was of the opinion that the bulk density average values are representative of the expected values within each of the lithologies. Stock (2016) has used these same average values for the conversion of volume to tonnages for the respective lithologies in the resource block model.
ACQUISITION AND PLANS
The property containing the Mimbula Deposit was initially held and operated by Zambian Consolidated Copper Mines (ZCCM) until 2000 at which point it was acquired by Anglo-American during the privatisation process of the ZCCM-held mines in Zambia.
The process of privatisation was protracted, and the largest stake was awarded to KCM, in which Anglo-American held a 65 percent stake, for a net payment of US$60 million. Anglo-American requested that the area containing Mimbula was excised from the Large Scale Mining License. In 2004, Vedanta Ltd bought a controlling stake (79.4%) in KCM, and remain the current operators of the nearby Nchanga and Konkola mines and smelting facilities.
In 2007 Rephidim Mining Supplies & Technical Services Ltd (Rephidim) applied for and was granted a small-scale mining licence over the area containing the Mimbula Deposit (8441-HQ-SML). This title was subject to a later dispute with KCM, and was fully resolved in August 2015, in favour of Rephidim, by the Mines Development Department.
In October 2015, Moxico Resources Zambia Ltd, a subsidiary of Moxico Resources plc, entered into an option agreement with Rephidim to earn an interest of up to 85% in the small-scale mining licence. Moxico subsequently exercised its option and signed a joint-venture agreement with Rephidim to earn 85% of the Licence, on 30th April 2016.
The Small Scale Mining Licence (SML) was renewed in January 2017 and in February formal notification was received from the Minister of Mines that the SML for Mimbula is to be extended to over 15 square kilometres and the validity increased to 25 years.
In March 2017 the extension to the mining lease was ratified and a Large Scale Mining Lease granted over the entire Mimbula Mining Lease for a period of 25 years was issued in May 2017. This significant step forward provided the platform to take Mimbula forward.
Moxico plans to complete PFS and FS including met test work to confirm the mineral processing flow sheet and undertake drilling to expand the mineral resource. Moxico intends to complete a Pre-IPO capital raising to fund this PFS and FS and development financing costs.
The company has completed a pre-IPO capital raise to fund metallurgical test work and a Feasibility Study. A capital raise for development of the Mimbula mine and processing facilities through to potential IPO is targeted for 2018.