TORONTO, Aug. 02, 2022 (GLOBE NEWSWIRE) — Xanadu Mines Ltd (ASX: XAM, TSX: XAM) (Xanadu or the Company) is pleased to update the market on its on-going metallurgical test program at the Kharmagtai Copper-Gold Project in the South Gobi region of Mongolia.
- Preliminary metallurgical test work completed on partially oxidised material from surface to 30 metres depth.
- Glycine and cyanide leach tests delivered metallurgical recoveries of up to 91% gold and 46% copper, with head grades ranging between 0.52 g/t to 2.25 g/t Au and 0.12% to 0.67% Cu.
- All partially oxidised material leached readily at a coarse P80 > 2mm particle size, indicating the potential for a heap leach treatment.
- Indicates a potential treatment path for approx. 90 million tonnes (Mt) of oxidised material treated as waste in the Scoping Study1 due to low flotation recovery.
- First step in evaluating a material uplift opportunity identified in the Scoping Study, to generate additional cash flow by leaching partially oxidised, near surface material.
- Further mineralogical studies required to confirm viability and optimise the process.
Xanadu’s Executive Chairman & Managing Director, Colin Moorhead said:
“These preliminary results are a very positive, first step as we test the uplift opportunities in the Kharmagtai Scoping Study. The base case assumed that all ore is processed through a standard sulphide circuit, which means that the partially oxidised material at the surface, which does not float, ends up being treated as zero value waste. If we can turn that material into cash generating ore by leaching with glycine and cyanide, it has potential to drive significant value uplift for the Kharmagtai project.”
Results from bottle roll tests at varying cyanide and glycine addition rates were conducted using 2.5 kilograms per tonne (kg/t) cyanide and 2.5kg/t glycine tests over a 48-hour conventional leach time, shown in Table 1.
Table 1: Gold, silver and copper recoveries at 2.5kg/t cyanide and 2.5kg/t glycine addition
These results demonstrate achievement of high gold recoveries at modest cyanide addition rates and in the presence of significant cyanide soluble copper. The coarse particle size indicates that heap leach treatment may be feasible.
Generally, gold leaching increases with decreasing particle size, providing a larger specific surface area for solution contact. Gold recoveries are expected to improve by grinding to 150 micrometre (µm) particle size, typically used for Carbon in Leach (CIL) processing.
Cyanide and glycine consumption was relatively low, indicating high potential for recovering and recycling of both reagents via the eventual optimal processing route. The addition of glycine reduced the cyanide consumption versus the cyanide consumption when leached using traditional cyanidation. Actual cyanide consumption rates ranged from 1.6kg/t to 2.1kg/t.
Test Program Scope
There is up to 90Mt of partially oxidised material at Kharmagtai, with 80% located near surface at Stockwork Hill, White Hill and Golden Eagle. If this material was processed as ore rather than pre-stripping, it could reduce waste rock production by approx. 10%.
The scope of the test program included head grade analysis and combined cyanide and glycine leach test work on four composite samples of previously untested, partially oxidised material from the upper 30m across the Kharmagtai mineralised system. The objective of the leach tests was to determine metallurgical recovery of gold and copper, and gauge potential of glycine addition to enhance recovery and reduce cyanide consumption. These results will inform future variability test work to evaluate an optimal processing route for this material.
Leaching with Glycine and Cyanide
Cyanide and glycine leaching was investigated on this partially oxidised material. Low cyanide addition, coupled with a glycine-dominant lixiviant, has many beneficial properties, particularly for leaching of precious metals with elevated copper content. This occurs due to copper preferentially bonding to glycine rather than cyanide, thus freeing the cyanide to leach gold.
Glycine is a widely available bulk reagent with characteristics favourable for use in mineralogical processing; non-toxic, water soluble, stable, non-volatile and can be recycled. Under alkaline conditions, glycine forms stable complexes with precious and base metals but not with iron, magnesium, or manganese.
Metallurgical test work was undertaken by Perth based Mining and Process Solutions (MPS), who hold the rights for leaching metals using glycine with cyanide.
Sample Selection and Preparation
Four composite samples were collected from Stockwork Hill, White Hill and Golden Eagle deposits at Kharmagtai project, as being representative of each of these zones. Samples were coarse rejects (P80>2mm particle size), consisting of mixed oxide and sulphide material taken from previously drilled diamond core holes. There is a risk that aged diamond core will deliver lower metallurgical recovery than test work on newly drilled material, due to post-drilling oxidation. Care was taken during sample selection to avoid those exhibiting evidence of post-drilling oxidation.
Sample preparation consisted of homogenising and splitting samples “as received” into their respective composites and labelling “Sample 1” through to “Sample 4”, with no further crushing or grinding. Each split was rotary split and homogenised for head analysis and sub-samples taken for test work. Head assays for Au, Silver (Ag) & Cu were conducted by fire assay for each sample. Prior to leach test work, samples were cured in 10k grams per tonne (g/t) sulfuric acid for 24 hours to improve copper extraction.
Metallurgical sample locations, zones and head assay grades are detailed in Table 2. Drill hole sample details are outlined in Table 3, and collar locations for drill holes sampled are outlined in Figure 1.
Table 2: Metallurgical sample details for partially oxidised test work program
|Sample||Sample drill holes||Zone||Head assay grade|
|g/t Au||g/t Ag||% Cu|
|1||KHDDH393, KHDDH415, KHDDH491, KHDDH499||Stockwork Hill (South)||2.25||3.0||0.66|
|2||KHDDH246, KHDDH266, KHDDH267, KHDDH359, KHDDH527||Stockwork Hill (North)||0.95||2.0||0.67|
|3||KHDDH401, KHDDH514, KHDDH517, KHDDH518||Golden Eagle||1.39||1.0||0.12|
|4||KHDDH230, KHDDH340, KHDDH437, KHDDH480, KHDDH489||White Hill||0.52||2.0||0.45|
Table 3: Drill hole sample details for partially oxidised test work program
|Hole ID||Easting (m)||Northing (m)||Height (m)||Azimuth (°)||Dip (°)||Sample True Depth (m)|
1 Golden Eagle has 25m barren cover overlaying mineralisation, such that partially oxidised material commences at 25m true depth.
2 Sample true depth exceeds 30m for each of these drill holes given each deposit has a different depth from surface to base of oxidation.
Future Test Work
Leaching of partially oxidised material will be further investigated as follows:
- Characterise partially oxidised material to quantify copper species present.
- Optimise cyanide and glycine reagent addition to maximise metallurgical recovery and minimise cyanide consumption.
- Undertake variability test work across the mineralised partially oxidised zones to understand leaching kinetics.
- Undertake grind variability assessment as part of glycine and cyanide leaching to understand liberation and maximum achievable metal recovery.
- Determine suitable flowsheet options.
Partially oxidised material test work is a subset of the broader Kharmagtai metallurgical test work program. A comprehensive metallurgy program during the Pre-Feasibility Study over next 12 to 18 months will investigate flotation and comminution properties of the mineralisation and alteration styles at Kharmagtai, aiming to determine optimum flowsheet and generate inputs for engineering design. This will also generate data to inform the copper and gold recovery models, and allow operating costs estimates to be calculated. Concentrate samples will be generated for marketing studies as part of the broader metallurgy program.
About Xanadu Mines
Xanadu is an ASX and TSX listed Exploration company operating in Mongolia. We give investors exposure to globally significant, large-scale copper-gold discoveries and low-cost inventory growth. Xanadu maintains a portfolio of exploration projects and remains one of the few junior explorers on the ASX or TSX who control a globally significant copper-gold deposit in our flagship Kharmagtai project. For information on Xanadu visit: www.xanadumines.com.
This Announcement was authorised for release by Xanadu’s Executive Chairman & Managing Director.
Appendix 1: Statements and Disclaimers
Competent Person Statements
The information in this Announcement that relates to exploration results is based on information compiled by Dr Andrew Stewart, who is responsible for the exploration data, comments on exploration target sizes, QA/QC and geological interpretation and information. Dr Stewart, who is an employee of Xanadu and is a Member of the Australasian Institute of Geoscientists, has sufficient experience relevant to the style of mineralisation and type of deposit under consideration and to the activity he is undertaking to qualify as the “Competent Person” as defined in the 2012 Edition of the Australasian Code for Reporting Exploration Results, Mineral Resources and Ore Reserves and the National Instrument 43-101. Dr Stewart consents to the inclusion in the report of the matters based on this information in the form and context in which it appears.
The information in this Announcement that relates to metallurgy and metallurgical test work has been reviewed by Andrew Goulsbra, AusIMM, B.App Sci (Met). Mr Goulsbra is not an employee of the Company but is employed as a contract consultant. Mr Goulsbra is a member of the Australasian Institute of Mining and Metallurgy; he has sufficient experience with the style of processing response and type of deposit under consideration, and to the activities undertaken, to qualify as a competent as defined in the 2012 Edition of the Australasian Code for Reporting Exploration Results, Mineral Resources and Ore Reserves and the National Instrument 43-101. Mr Goulsbra consents to the inclusion in this report of the contained technical information in the form and context as it appears.
Certain statements contained in this Announcement, including information as to the future financial or operating performance of Xanadu and its projects may also include statements which are ‘forward‐looking statements’ that may include, amongst other things, statements regarding targets, estimates and assumptions in respect of mineral reserves and mineral resources and anticipated grades and recovery rates, production and prices, recovery costs and results, capital expenditures and are or may be based on assumptions and estimates related to future technical, economic, market, political, social and other conditions. These ‘forward-looking statements’ are necessarily based upon a number of estimates and assumptions that, while considered reasonable by Xanadu, are inherently subject to significant technical, business, economic, competitive, political and social uncertainties and contingencies and involve known and unknown risks and uncertainties that could cause actual events or results to differ materially from estimated or anticipated events or results reflected in such forward‐looking statements.
Xanadu disclaims any intent or obligation to update publicly or release any revisions to any forward‐looking statements, whether as a result of new information, future events, circumstances or results or otherwise after the date of this Announcement or to reflect the occurrence of unanticipated events, other than required by the Corporations Act 2001 (Cth) and the Listing Rules of the Australian Securities Exchange (ASX) and Toronto Stock Exchange (TSX). The words ‘believe’, ‘expect’, ‘anticipate’, ‘indicate’, ‘contemplate’, ‘target’, ‘plan’, ‘intends’, ‘continue’, ‘budget’, ‘estimate’, ‘may’, ‘will’, ‘schedule’ and similar expressions identify forward‐looking statements.
All ‘forward‐looking statements’ made in this Announcement are qualified by the foregoing cautionary statements. Investors are cautioned that ‘forward‐looking statements’ are not guarantee of future performance and accordingly investors are cautioned not to put undue reliance on ‘forward‐looking statements’ due to the inherent uncertainty therein.
For further information please visit the Xanadu Mines’ Website at www.xanadumines.com.
Appendix 2: Kharmagtai Table 1 (JORC Code, 2012)
Set out below is Section 1 and Section 2 of Table 1 under the JORC Code, 2012 Edition for the Kharmagtai project. Data provided by Xanadu. This Table 1 updates the JORC Table 1 disclosure dated 8 December 2021.
JORC TABLE 1, SECTION 1 – SAMPLING TECHNIQUES & DATA
(Criteria in this section apply to all succeeding sections).
|Drill sample recovery||
|Sub-sampling techniques and sample preparation||
|Quality of assay data and laboratory tests||
|Verification of sampling and assaying||
|Location of data points||
|Data spacing and distribution||
|Orientation of data in relation to geological structure||
|Audits or reviews||
JORC TABLE 1, SECTION 2 – REPORTING OF EXPLORATION RESULTS
(Criteria in this section apply to all succeeding sections).
and land tenure status
|Exploration done by other parties||
|Drill hole information||
|Data aggregation methods||
Copper equivalent (CuEq or eCu) grade values were calculated using the following formula: CuEq or eCu = Cu + Au * 0.60049 * 0.86667,
Gold equivalent (AuEq or eAu) grade values were calculated using the following formula: AuEq or eAu = Au + Cu / 0.60049 * 0.86667.
Where: Cu – copper grade (%), Au – gold grade (g/t), 0.60049 – conversion factor (gold to copper), 0.86667 – relative recovery of gold to copper (86.67%)
The copper equivalent formula was based on the following parameters (prices are in USD):
|Relationship between mineralisation on widths and intercept
JORC TABLE 1, SECTION 3 – ESTIMATION & REPORTING OF MINERAL RESOURCES
Mineral Resources are not reported so Section 4 is not applicable to this Announcement.
JORC TABLE 1, SECTION 4 – ESTIMATION & REPORTING OF ORE RESERVES
Ore Reserves are not reported so Section 4 is not applicable to this Announcement.
1 ASX/TSX Announcement, 6 April 2022 – Scoping Study – Kharmagtai Copper-Gold Project