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Thor Mining PLC - Mineral Resource Estimates Bonya Tungsten & Copper

RNS Number : 2729B
Thor Mining PLC
29 January 2020
 

29 January 2020

 

THOR MINING PLC

MAIDEN RESOURCE ESTIMATES - BONYA TUNGSTEN AND COPPER

 

Thor Mining Plc ("Thor") (AIM, ASX: THR) and Arafura Resources Limited ("Arafura") (ASX: ARU) are pleased to advise maiden mineral resource estimates for the White Violet and Samarkand tungsten and copper deposits at Bonya, adjacent to the Thor Mining Molyhil tungsten and molybdenum project.

The project is held in joint venture between Arafura (60%) and Thor (40%) with Thor acting as manager, and each party contributing to the cost according to their equity holding.

Highlights:

•     White Violet;

•    Inferred Resources of 495,000 tonnes, grading 0.22% Tungsten Trioxide (WO₃) and 0.06% copper (Cu), containing 1,090 tonnes of WO₃, and 300 tonnes Cu.

•     Samarkand;

•      Inferred Resources of 245,000 tonnes, grading 0.19% Tungsten Trioxide (WO₃) and 0.13 % copper (Cu), containing 465 tonnes of WO₃, and 320 tonnes Cu.

•        Both deposits outcrop and remain open at depth, while Samarkand, in particular, shows potential for strike extension to the copper mineralisation.

•        Each deposit considered amenable to open cut extraction for significant components of the resource.

•        Both deposits situated in close proximity to the Thor Mining Molyhil tungsten and molybdenum project, and potentially therefore within economic trucking distance.

These resources add to previously announced Inferred Resources at Bonya Copper of 230,000 tonnes, grading 2.0% Cu, containing 4,600 tonnes Cu (ref Table B and announcement of 24 November 2018).

 

Mr Mick Billing, Executive Chairman, commented: 

"These maiden resources are very significant when combined with the mining inventory of the nearby proposed Molyhil development."

"More work is required, to convert these inferred resources to, at least, Indicated classification, along with other technical, environmental, and social impact assessments, however we have taken very good first steps."

The Bonya project hosts additional known tungsten and copper deposits, and some high tenor copper strike extension at Samarkand.  These will be tested in due course, and we expect that they will further contribute to the life and value of the greater Molyhil project."

"A solid improvement in the tungsten price during the December quarter is also a very positive sign."

 

Gavin Lockyer, Managing Director of Arafura Resources, commented:

"We are pleased to deliver the project's first tungsten resources at White Violet and Samarkand, and feel quietly confident the JV can build further value over time through the discovery and delineation of additional tungsten and/or copper resources."

 

Table A: Bonya Tungsten Mineral Resources (15 January 2020)



Oxidation

Tonnes

WO3

Cu





%

Tonnes

%

Tonnes

White Violet

Inferred

Oxide

25,000

0.41

90

0.16

40


Fresh

470,000

0.21

980

0.06

260

Sub Total


495,000

0.22

1,070

0.06

300

Samarkand

Inferred

Oxide

25,000

0.11

30

0.07

20


Fresh

220,000

0.20

430

0.13

290

Sub Total


245,000

0.19

460

0.13

310

Combined

Inferred

Oxide

50,000

0.26

120

0.14

60


Fresh

690,000

0.21

1,410

0.08

550

Total


740,000

0.21

1,530

0.09

610

Notes:

·       0.05% WO3 cut-off grade.

·       Totals may differ from the addition of columns due to rounding.

Table B: Bonya Copper Mineral Resources (announced 26 November 2018)


Tonnes

Cu




%

Tonnes

Inferred

Oxide

25,000

1.0

200

Fresh

210,000

2.0

4,400

Total


230,000

2.0

4,600

Notes:

·      0.2% Cu cut-off grade.

·      Totals may differ from the addition of columns due to rounding.

·      The Company is not aware of any information or data which would materially affect this previously announced resource estimate, and all assumptions and technical parameters relevant to the estimate remain unchanged.

 

A link to the Thor Mining website showing a map of the Bonya deposits and proximity to Molyhil may be accessed via:

https://www.thormining.com/sites/thormining/media/maps/15-001-1d-bonya-resources.jpg

 

Summary of Resource Estimate and Reporting Criteria (White Violet and Samarkand)

 

Geology and geological interpretation

The White Violet and Samarkand deposits are located approximately 350km ENE of Alice Springs and approximately 30km east of Thor's 100% owned Molyhil deposit.

Mineralisation at  White Violet and Samarkand is interpreted as being hosted predominantly within metamorphic calc-silicate skarns and sheared hornfels associated with mafic intrusives, granites and pegmatites. The target deposits are analogous to the nearby Molyhil tungsten and molybdenum deposit which also contains some copper.

The tungsten mineralisation is predominantly scheelite and copper is most often present as chalcopyrite.

Drilling techniques and hole spacing

The drill hole database used for the mineral resource estimate (MRE) contains a total of 21 RC holes for 1,762.2m of drilling at White Violet and 17 RC holes for 1,202m of drilling at Samarkand.

The majority of holes have been drilled at angles of between 50 - 75° and approximately perpendicular to the strike of the mineralisation. Geological and assay data for all drill holes was used in the geological interpretation and MRE.

Sampling and sub-sampling

Samples from RC drilling were collected over an average 1m interval and submitted for assay. Barren zones were sampled as 4m composites. RC samples were homogenised and subsampled by either rotary or riffle splitting.

Sample analysis method

All samples were sent to Nagrom in Perth for preparation and analysis. The samples were sorted and dried. Primary preparation involved crushing the whole sample. The samples were split to obtain a sub-fraction which was then pulverized to 80% passing 75µm. For the April drilling, preliminary analysis was via mixed four acid digest and then ICP-OES. Samples with initial tungsten results >0.1% were then assayed via peroxide fusion and ICP-MS. For the October and November drilling all samples were analysed via peroxide fusion and ICP_MS. Internal laboratory QA uses CRM's, blanks, splits and replicates. A limited number of field standards, blanks and duplicates have all been applied in the QAQC methodology. Sufficient accuracy and precision have been established for the type of mineralisation encountered and is appropriate for QAQC in the Resource Estimation.

Cut-off grades

The current MRE for the White Violet and Samarkand deposits have been reported at a cut-off grade of 0.05% WO3. Top cuts were applied as follows: White Violet, WO3 - 1.5% Cu - 0.5%, Samarkand, WO3 - 1.45% Cu - 1.5%.

Estimation methodology

Mineralisation wireframes were generated in Micromine software using drill hole data supplied by Thor. Resource data was flagged with unique mineralisation domain codes as defined by the wireframe and composited to 1m lengths.

At White Violet, grade continuity analysis was undertaken in Micromine software for WO3 and Cu for the mineralised domain and variogram models were generated in all three directions. Parameters were used in the block model estimation. A block model with a parent block size of 8x4x8m with sub-blocks of 2 x 1 x 2m has been used to adequately represent the mineralised volume, with sub blocks estimated at the parent block scale.

At Samarkand, the data did not support the development of meaningful variograms.  Grade estimation for WO3 and Cu was completed using the Inverse Distance squared (ID2) technique. A block model with a parent block size of 4x8x8m with sub-blocks of 1 x 2 x 2m has been used to adequately represent the mineralised volume, with sub blocks estimated at the parent block scale.

Molybdenum (Mo) has not been estimated despite the fact that it can be an element of interest when considering tungsten deposits. The reason for this is that Mo levels are very low across both deposits. However, further work should be undertaken to better understand the distribution of Mo within the deposit.

Detailed downhole geophysics was collected from 15 drill holes across the two prospects. This included 2 sets of in-situ bulk density measurements (SSDG and BRDG). Both sets of data were collected at 0.01m intervals. The data was loaded into Micromine, composited to 1m intervals and averaged to provide an average bulk density down hole. The density varied down hole and it was clear that the mineralised skarn zones corresponded with elevated density values. This average 1m density data was paired up with the flagged composite assay file. As there was only data for some of the drill holes an average density was determined for the fresh and oxide mineralised domains for each deposit. At White Violet, a value of 3.16 g/cm3 has been assigned to all fresh mineralisation and a value of 1.95 g/cm3 to all oxidised mineralisation. At Samarkand, a value of 2.95 g/cm3 has been assigned to all fresh mineralisation and a value of 2.60 g/cm3 to all oxidised mineralisation.

There have been no direct measurements of any drill samples to confirm the accuracy or appropriateness of this calibration. However, the value for fresh mineralisation compares favourably with the densities reported for the nearby Molyhil tungsten deposit that is within the range of 2.78 - 3.5 g/cm3 (based on an iron grade calibration).

 

Classification criteria

The resource classification has been applied to the MRE based on the drilling data spacing, grade and geological continuity, and data integrity. Both White Violet and Samarkand models have low levels of confidence in the estimation or potential impact of modifying factors and have been classified as Inferred Mineral Resources under JORC (2012). The classification reflects the view of the Competent Person.

Mining and metallurgy

It has been assumed that the traditional open cut mining method of drill, blast, load and haul will be used. No other mining assumptions have been made.

No metallurgical recoveries have been applied to the Mineral Resource Estimate.

Eventual economic extraction

It is the view of the Competent Person that at the time of estimation there are no known issues that could materially impact on

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