Porphyry Copper-Gold - OREAS 503c - ColdBlock Technologies

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)

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

Strong Acid Digestion

Chiller temperature was set to -5°C
25g was weighed and placed into a ColdBlock™Digestion vessel
20 mL of Aqua Regia + 3mL HF was added
Sample was digested at 80% power for 20 minutes
20mL of 4% v/v Boric acid was added
Samples were digested again at 80% power for 10 minutes
Samples were cooled and bulked to 50mL using 2% HNO₃ + 5% HCl_v/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
Element	OREAS Certified 4-acid Value (ppm)	Low	High	Sample A	Sample B	Sample C	Average (ppm)	Stdev	% RSD	% Recovery vs certified 4-Acid value
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%

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