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APPLICATION NOTE

Porphyry Copper-Gold – OREAS 503c

SUMMARY

The application note summarizes the digestion of OREAS 503c, a Porphyry Copper-Gold Certified Reference Material using ColdBlock Digestion Pro Series Technology.

Instrument:

ColdBlock CBM & CBL sample digesters, chiller, HF compatible liners, ICP-MS & ICP-OES

Published:February 2023
Digestion Time:20 Minutes (Aqua Regia) & 30 Minutes (Strong Acid)
Acid Used:Aqua Regia & Aqua Regia, HF & H3
BO3
Average ColdBlock Recovery vs. CRM:

  • 101% Gold

  • 99% Arsenic

  • 101% Copper

METHODOLOGY

Aqua Regia Digestion (GOLD)

  1. Chiller temperature was set to -5°C
  2. 30g was weighed and placed into a ColdBlock™Digestion vessel
  3. 120 mL of Aqua Regia was added (HNO3 was added first, followed by HCl)
  4. Sample was digested at 80% power for 20 minutes
  5. Samples were cooled and bulked to 200mL using 20% HClv/v

Strong Acid Digestion

  1. Chiller temperature was set to -5°C
  2. 25g was weighed and placed into a ColdBlock™Digestion vessel
  3. 20 mL of Aqua Regia + 3mL HF was added
  4. Sample was digested at 80% power for 20 minutes
  5. 20mL of 4% v/v Boric acid was added
  6. Samples were digested again at 80% power for 10 minutes
  7. Samples were cooled and bulked to 50mL using 2% HNO3 + 5% HClv/v

DISCUSSION

Aqua Regia Digestion

  • If the Sulfide content of your sample is > 10 %
  • reverse the ratios of Aqua Regia and use 1:3, HCl:HNO3
  • Always add HNO3 first, slowly, in small (Reddish brown NO2 fumes might form) If a reaction occurs wait until it settles before adding the HCl.
  • ICP-MS was used for analysis of Gold – see Table 1 for results

Strong Acid Digestion

  • The addition of Boric acid will help re-solubilize any insoluble fluorides and will help neutralize any remaining HF in solution
  • If Silver precipitates out of solution as AgCl, bulk up with >10% HClv/v
  • If the Sulfide content of your sample is > 10 %
  • reverse the ratios of Aqua Regia and use 1:3, HCl:HNO3 – always add the Nitric acid first (reddish brown NO2 fumes might form)
  • See table 2 for

Figure 1 – After Bulk-up using Strong Acid Digestion

Figure 2 – After digestion using Aqua Regia digestion

OREAS 503c was prepared from a blend of porphyry copper-gold ore, barren granodiorite, and a minor quantity of Cu-Mo concentrate. The ore was sourced from the Ridgeway underground mine located in the Cadia Valley Operations (CVO) situated in central western New South Wales, Australia. ore.com.au

OREAS 503C; Porphyry Copper-Gold-Molybdenum; COA-1313-OREAS 503c_2; Ore research & Exploration; Melbourne, Australia (June,2018)

Results

Table 1 – OREAS 503c by 30g Aqua Regia Digestion

OREAS 503c – Porphyry Copper-Gold

Method:

30g

120mL Aqua Regia, digested 80% for 20 minutes

Element

Certified Fire Assay Value

95% Confidence Limits

Sample A

Sample B

Sample C

Average (ppm)

Stdev

% RSD

% Recovery vs certified Fire Assay

Low

High

Au

0.698

0.693

0.703

0.697

0.694

0.716

0.702

0.04

4.1%

101%

Table 2 – OREAS 503c by Strong Acid Digestion

OREAS 503c – Porphyry Copper Gold

Method:

0.25g

20mL Aqua Regia + 3 mL HF digested at 80% for 20 minutes, add 20mL of 4% Boric Acid – and digest again at 80% for another 10 mins

Element

OREAS

Certified 4-acid Value

(ppm)

95% Confidence Limits

Sample A

Sample B

Sample C

Average (ppm)

Stdev

% RSD

% Recovery vs certified 4-Acid value

Low

High

Ag

0.83

0.788

0.871

0.87

0.82

0.83

0.84

0.04

4.1%

101%

Al

73700

72400

75000

71285

71285

72526

71698

585.10

0.8%

97%

As

34.5

33.8

35.2

35.1

33.2

34.1

34.1

0.76

2.2%

99%

Ba

985

965

1004

1093

1095

1221

1137

59.91

5.3%

115%

Be

2.65

2.59

2.71

2.63

3.54

2.72

2.96

0.46

14.7%

112%

Bi

0.6

0.58

0.62

0.6

0.7

0.6

0.6

0.07

10.6%

104%

Ca

26300

25800

26900

26685

26712

27314

26904

290.26

1.1%

102%

Cd

0.22

0.19

0.25

0.22

0.22

0.2

0.21

0.01

4.4%

97%

Ce

63

61

64

61

61

63

62

0.71

1.2%

98%

Co

14.6

14.4

14.8

14.3

14.6

13.6

14.2

0.42

3.0%

97%

Cr

68

66

70

74

71

71

72

1.36

1.9%

106%

Cs

10.3

10.1

10.4

10.9

11.1

11.2

11.1

0.13

1.1%

107%

Cu

5380

5330

5430

5200

5223

5309

5244

46.63

0.9%

97%

Dy

4.21

3.97

4.46

3.99

3.94

4.25

4.06

0.14

3.3%

96%

Er

2.37

2.31

2.43

2.38

2.37

2.46

2.40

0.04

1.7%

101%

Eu

1.26

1.18

1.34

1.21

1.26

1.14

1.20

0.05

4.1%

96%

Fe

51700

50800

52500

50408

50680

50284

50457

165.42

0.3%

98%

Ga

18.5

18.3

18.8

17.9

18.1

17.3

17.7

0.32

1.8%

96%

Gd

4.75

4.48

5.01

4.69

4.8

4.89

4.79

0.08

1.7%

101%

Hf

2.4

2.36

2.44

2.5

2.1

2.3

2.3

0.20

8.7%

96%

Ho

0.85

0.84

0.86

0.8

0.83

0.82

0.82

0.01

1.5%

96%

K

31800

31300

32300

31156

31085

31041

31094

47.19

0.2%

98%

La

32

31.3

32.7

33

31

32

32

0.79

2.5%

100%

Li

31.1

30.5

31.8

31.3

31.4

31.6

31.5

0.14

0.4%

101%

Lu

0.34

0.32

0.35

0.32

0.32

0.34

0.33

0.01

2.9%

96%

Mg

15000

14800

15300

15275

15286

15284

15282

4.54

0.0%

102%

Mn

540

530

540

560

546

553

553

5.65

1.0%

102%

Mo

318

313

322

321

328

326

325

2.90

0.9%

102%

Na

19900

19700

20200

17338

16982

17027

17116

158.43

0.9%

86%

Nb

16.6

16.1

17

17.7

17.9

18.8

18.1

0.48

2.6%

109%

Click here to download the Application Note in PDF format.

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info@coldblock.ca.