The Kipushi Project, also in the DRC's province of Katanga and southeast of the company's Kamoa discovery, is adjacent to the town of Kipushi and approximately 30 kilometres southwest of the provincial capital of Lubumbashi. Ivanhoe Mines acquired its 68% interest in the Kipushi Project in November 2011; the balance of 32% is held by the DRC's state-owned mining company, Gécamines.
The Kipushi Project is based on the high-grade, underground zinc-copper mine in the Central African Copperbelt, which mined approximately 60 million tonnes grading 11% zinc and 7% copper between 1924 and 1993. In addition to producing copper and zinc, the mine produced 12,673 tonnes of lead and approximately 278 tonnes of germanium between 1956 and 1978. The mine has been managed on a care and maintenance basis since 1993.
Gécamines discovered the Big Zinc Deposit before 1993 and the deposit remains unmined. Historical estimates of the Big Zinc's resources between the mine's 1,295- and 1,500-metre levels total 4.7 million tonnes averaging 39% zinc and 0.76% copper. Several exploration holes confirmed the continuation of the Big Zinc Deposit below the 1,640-metre level. Kipushi's historical resource estimates above the 1,500-metre level total approximately 17 million tonnes averaging 16.7% zinc and 2.3% copper, including the Big Zinc historical resources.
A Qualified Person has not done sufficient work to classify the historical estimates as current Mineral Resources and Ivanhoe Mines is not treating such estimates as current Mineral Resources. The historical resources noted above are derived from an estimate prepared by Techpro Mining and Metallurgy in 1997 and are presented at an indicated level. A discussion of the material assumptions, parameters and methods relating to the historical resource estimate, as well as a discussion of relevance, reliability and other information regarding the estimate, is included in the Kipushi Technical Report dated September 2012 prepared by IMC Group Consulting Ltd. and available at www.sedar.com
Click here to view the Kipushi Technical Report
Schematic of Kipushi cross-section showing mine infrastructure and the Big Zinc and Kipushi Fault Zones.
Project development and infrastructure
Work began in early March 2014 on the planned underground diamond-drilling program at the Kipushi Project, a major advance made possible by the ongoing dewatering program directed by Ivanhoe during the past three years following its acquisition in November 2011.
The mine, which had been placed on care and maintenance in 1993, flooded in early 2011 due to a lack of pump maintenance over an extended period. Water reached 851 metres below surface at its peak. A major milestone was reached in December 2013 when Ivanhoe restored access to the mine's principal haulage level at 1,150 metres below the surface.
Since then, crews have been upgrading underground and surface infrastructure to support the drilling program. Recent improvements have included the fabrication of an air deflector for ventilation Shaft #4 to reduce noise impact, tie-in of the water piping from shafts P1Ter and P15 to the 1,112-metre-level dam, and the start of the removal of corroded ventilation columns from Shaft #5.
Water levels are stabilized below the 1,150-metre-level haulway and 1,272-metre-level hanging wall drift, enabling access for drilling, with two rigs targeting the Série Récurrente and Big Zinc mineralization.
Exploration and development drilling
Ivanhoe's Kipushi underground drilling program is designed to confirm and update Kipushi's estimated historical resources and to further expand the resources along strike and at depth. More than 10,000 metres of drilling had been completed by the end of the third quarter.
A total of 5,148 metres, in 37 drill holes, were completed in Q3. Drilling during the quarter initially focused on the Série Récurrente Zone, with 2,361 metres drilled in 21 holes. The focus of drilling subsequently switched to the Big Zinc as the 1,272-metre-level drill drift was dewatered and rehabilitated, with 2,787 metres completed in 16 holes.
Série Récurrente exploration continued to test areas to the east and below the historical measured and indicated resources. A final drill section was completed from the 1,251-metre-level and three additional sections were completed from a drill station on the 1,261-metre-level. Two holes tested the Nord Riche area, where the Série Récurrente intersects the Fault Zone.
The first assays from Ivanhoe drilling program at Kipushi were received on July 14, 2014: Among the significant results received to that date:
- Three holes drilled to validate historical models of the down-plunge continuity of Big Zinc mineralization returned zinc grades of 40.9% over 348.5 metres, 44.8% over 339.4 metres, and 33.3% over 305.8 metres. The down-plunge geometry of the holes does not allow for estimation of true widths.
- Internal zones of exceptionally rich mineralization in the first two holes, KPU001 and KPU002, returned zinc grades of 60.4% over 35.1 metres, 56.3% over 18.0 metres, and 56.6% over 71 metres. These internal zones also returned germanium grades of 87.2, 120.4 and 111.9 grams per tonne (g/t), respectively.
- An internal copper-silver-germanium rich zone in the third hole KPU003 graded 6.1% copper, 44.5% zinc, 144 g/t silver and 66.9 g/t germanium over 31 metres from 197 metres. Historical resource estimates at Kipushi excluded silver and germanium.
- The third hole, KPU003, also discovered a zone grading 58.6% zinc and 293.8 g/t germanium over 22.3 metres, approximately 180 metres below the historical measured and indicated resources. This exceptional grade intersection may represent an extension to the Big Zinc or the start of a new zinc- and germanium-rich zone, and will be followed up by ongoing drilling.
- In addition, two holes from Ivanhoe's exploratory drilling program targeting the Série Récurrente ("Recurring Series") zone at the north end of the Kipushi deposit returned very high copper and silver grades. Hole KPU008 intersected 11.4 metres (estimated true width of 11.2 metres) grading 17% copper and 89.6 g/t silver.
Historical Resource Estimate
|Measured & Indicated
|- including Big Zinc zone
Note: A Qualified Person has not done sufficient work to classify these historical estimates as current Mineral Resources and Ivanhoe Mines is not treating such historical estimates as current Mineral Resources. For the material assumptions relating to the Kipushi Project historical resource estimate, please see note 2 in the appendix hereto. Source: Historical resource estimate by Techpro Mining and Metallurgy in 1997.
- Low grade: 1% < copper < 2% and 7% < zinc < 14%.
- Waste: copper < 1% and zinc < 7%.
Big Zinc's grade and tonnage potentially are higher than previously estimated, new review indicates
Ivanhoe recently received the findings of an independent review conducted by MSA Group (Pty.) Ltd., of Johannesburg, based on results of a comprehensive re-sampling program of historical Kipushi core collected from drilling by Gécamines into the Big Zinc Discovery in the early 1990s.
A total of 384 historical quarter-core (NQ-sized) samples were collected and dispatched to Bureau Veritas Minerals Pty. Ltd.'s laboratory in Australia. A total of 457 samples, including quality-control samples, were submitted to Bureau Veritas and analyzed for gold by fire assay, and for multi-elements, including zinc and copper, by sodium peroxide fusion and ICP-AES/MS finish. The re-sampling program was conducted over eight complete drill intersections of the Big Zinc from eight separate section lines and represented 18% of the total samples in the Big Zinc's historical assay database.
MSA's review of the recent re-sampling revealed that the zinc assay results generally report higher -- and averaged 5.5% higher -- than the assay results originally reported by Gécamines. MSA also concluded that density applied by Gécamines for estimating the tonnage in the Big Zinc Discovery was understated by an average of 9%. Despite the low bias, the review confirms that historical assay values reported by Gécamines are reasonable and can be replicated within a reasonable level of error by international, accredited laboratories under strict QA/QC control. This is an important milestone for Ivanhoe as part of its program to establish current resource estimates for its Kipushi Project.