OREAS 263b

OREAS 263b was prepared from a blend of oxidised gold ores (from Sepon gold mine in Laos, Stawell and Boddington gold mines in Australia) and barren metasediments. Gold mineralisation at Sepon is localised in structural and stratigraphic fluid traps similar in style to the sediment-hosted gold deposits of the Carlin Trend, Nevada, USA. Mineralisation is finely disseminated and closely associated with decalcification and variable silica replacement of calcareous rocks along structures and at lithological contacts. The Sepon deposit is located approximately 40 kilometres north of the town of Sepon, in Savannakhet province of south-central Laos. At the Stawell gold mine in west-central Victoria, the Magdala lode is intimately associated with an intensely deformed package of volcanogenic sedimentary rocks. The Stawell ore samples were taken from basalt contact lodes and are strongly chlorite-altered (+/- silica, stilpnomelane) carbonaceous mudstones located directly on the western margin of the Magdala basalt dome. Mineralisation in the ore consists of a quartz-sericite-carbonate schist assemblage containing the sulphides arsenopyrite, pyrrhotite and pyrite. The Boddington gold mine is located within the Saddleback Greenstone Belt, 130 kms southeast of Perth, Western Australia. The Saddleback Greenstone Belt is a fault bounded sliver of Archaean volcanic and shallow level intrusive rocks, surrounded by granitic and gneissic rocks. The mineralisation is hosted in a complex of stockwork veining with chalcopyrite and pyrrhotite the dominant sulphides, and minor pyrite, sphalerite, cubanite, cobaltite, arsenopyrite and pentlandite. Thirty-one commercial analytical laboratories participated in the program to certify the elements reported below.

  • Gold by fire assay (25-50g charge weight) with AAS and ICP-OES finish;
  • Gold by aqua regia digestion (15-50g sample weight) with ICP-OES and/or ICP-MS finish;
  • Gold by cyanide leach (20-200g) with AAS or ICP-MS finish;
  • Gold by x-ray photon assay on ~350g sample weights (12 Chrysos PhotonAssay units at 7 laboratories with two rounds of data reported from each unit);
  • Full ICP-OES and ICP-MS elemental suites by 4-acid digestion;
  • Full ICP-OES and ICP-MS elemental suites by aqua regia digestion.

To confirm homogeneity, gold by instrumental neutron activation analysis (INAA) was undertaken on 20 x 85mg subsamples (see Table 6 in the ‘Homogeneity Evaluation’ section of the Certificate).

Analyte Certified Value 1SD Expanded Uncertainty Low Expanded Uncertainty High Method
Au, Gold (ppm) 0.214 0.012 0.210 0.219 Pb Fire Assay
Au, Gold (ppm) 0.211 0.026 0.205 0.217 PhotonAssay
Au, Gold (ppm) 0.191 0.016 0.185 0.197 Aqua Regia Digestion (sample weights 10-50g)
Au, Gold (ppm) 0.191 0.015 0.185 0.197 Cyanide Leach
Ag, Silver (ppm) 0.307 0.017 0.277 0.337 4-Acid Digestion
Al, Aluminium (wt.%) 6.30 0.219 6.15 6.45 4-Acid Digestion
As, Arsenic (ppm) 257 8 251 264 4-Acid Digestion
Ba, Barium (ppm) 479 14 466 492 4-Acid Digestion
Be, Beryllium (ppm) 2.16 0.136 2.06 2.26 4-Acid Digestion
Bi, Bismuth (ppm) 10.1 0.62 9.3 10.9 4-Acid Digestion
Ca, Calcium (wt.%) 0.294 0.009 0.284 0.305 4-Acid Digestion
Cd, Cadmium (ppm) 0.044 0.017 0.024 0.064 4-Acid Digestion
Ce, Cerium (ppm) 82 3.7 79 85 4-Acid Digestion
Co, Cobalt (ppm) 4.81 0.261 4.48 5.14 4-Acid Digestion
Cr, Chromium (ppm) 78 6.3 74 82 4-Acid Digestion
Cs, Caesium (ppm) 8.01 0.363 7.74 8.29 4-Acid Digestion
Cu, Copper (ppm) 75 3.5 71 79 4-Acid Digestion
Dy, Dysprosium (ppm) 3.21 0.282 2.95 3.47 4-Acid Digestion
Er, Erbium (ppm) 1.67 0.21 1.47 1.86 4-Acid Digestion
Eu, Europium (ppm) 1.02 0.082 0.93 1.11 4-Acid Digestion
Fe, Iron (wt.%) 2.68 0.098 2.62 2.75 4-Acid Digestion
Ga, Gallium (ppm) 16.6 0.61 16.0 17.1 4-Acid Digestion
Gd, Gadolinium (ppm) 4.26 0.240 3.90 4.62 4-Acid Digestion
Ge, Germanium (ppm) 0.12 0.01 0.09 0.14 4-Acid Digestion
Hf, Hafnium (ppm) 3.37 0.209 3.19 3.56 4-Acid Digestion
Ho, Holmium (ppm) 0.58 0.07 0.52 0.64 4-Acid Digestion
In, Indium (ppm) 0.081 0.007 0.070 0.092 4-Acid Digestion
K, Potassium (wt.%) 2.03 0.065 1.98 2.08 4-Acid Digestion
La, Lanthanum (ppm) 40.3 2.76 38.4 42.2 4-Acid Digestion
Li, Lithium (ppm) 37.9 1.73 36.8 39.0 4-Acid Digestion
Lu, Lutetium (ppm) 0.27 0.023 0.23 0.31 4-Acid Digestion
Mg, Magnesium (wt.%) 0.527 0.032 0.508 0.546 4-Acid Digestion
Mn, Manganese (wt.%) 0.017 0.001 0.017 0.018 4-Acid Digestion
Mo, Molybdenum (ppm) 2.36 0.173 2.21 2.51 4-Acid Digestion
Na, Sodium (wt.%) 0.115 0.008 0.110 0.120 4-Acid Digestion
Nb, Niobium (ppm) 10.1 1.2 9.2 10.9 4-Acid Digestion
Nd, Neodymium (ppm) 33.1 1.75 31.4 34.8 4-Acid Digestion
Ni, Nickel (ppm) 44.0 1.28 42.6 45.4 4-Acid Digestion
P, Phosphorus (wt.%) 0.029 0.001 0.028 0.030 4-Acid Digestion
Pb, Lead (ppm) 19.4 1.13 18.6 20.1 4-Acid Digestion
Pr, Praseodymium (ppm) 9.18 0.618 8.60 9.77 4-Acid Digestion
Rb, Rubidium (ppm) 132 4 127 136 4-Acid Digestion
S, Sulphur (wt.%) 0.029 0.005 0.026 0.032 4-Acid Digestion
Sb, Antimony (ppm) 11.3 1.07 10.5 12.1 4-Acid Digestion
Sc, Scandium (ppm) 10.9 0.57 10.4 11.4 4-Acid Digestion
Sm, Samarium (ppm) 5.86 0.372 5.47 6.25 4-Acid Digestion
Sn, Tin (ppm) 11.6 1.05 10.9 12.4 4-Acid Digestion
Sr, Strontium (ppm) 52 2.4 50 55 4-Acid Digestion
Ta, Tantalum (ppm) 0.93 0.044 0.85 1.01 4-Acid Digestion
Tb, Terbium (ppm) 0.56 0.08 0.48 0.65 4-Acid Digestion
Te, Tellurium (ppm) 0.26 0.03 0.22 0.30 4-Acid Digestion
Th, Thorium (ppm) 15.1 0.71 14.5 15.7 4-Acid Digestion
Ti, Titanium (wt.%) 0.315 0.027 0.297 0.333 4-Acid Digestion
Tl, Thallium (ppm) 1.16 0.072 1.11 1.21 4-Acid Digestion
Tm, Thulium (ppm) 0.24 0.015 0.21 0.26 4-Acid Digestion
U, Uranium (ppm) 2.49 0.134 2.35 2.62 4-Acid Digestion
V, Vanadium (ppm) 76 1.8 74 78 4-Acid Digestion
W, Tungsten (ppm) 42.5 3.65 39.6 45.5 4-Acid Digestion
Y, Yttrium (ppm) 14.3 1.5 13.4 15.2 4-Acid Digestion
Yb, Ytterbium (ppm) 1.63 0.24 1.42 1.83 4-Acid Digestion
Zn, Zinc (ppm) 44.0 2.10 42.2 45.8 4-Acid Digestion
Zr, Zirconium (ppm) 110 9 104 117 4-Acid Digestion
Ag, Silver (ppm) 0.275 0.020 0.252 0.297 Aqua Regia Digestion
Al, Aluminium (wt.%) 0.967 0.060 0.907 1.028 Aqua Regia Digestion
As, Arsenic (ppm) 231 7 224 239 Aqua Regia Digestion
B, Boron (ppm) < 10.0 IND IND IND Aqua Regia Digestion
Ba, Barium (ppm) 68 9 61 75 Aqua Regia Digestion
Be, Beryllium (ppm) 0.68 0.047 0.63 0.73 Aqua Regia Digestion
Bi, Bismuth (ppm) 9.10 0.514 8.55 9.65 Aqua Regia Digestion
Ca, Calcium (wt.%) 0.162 0.005 0.154 0.170 Aqua Regia Digestion
Cd, Cadmium (ppm) 0.035 0.007 0.025 0.045 Aqua Regia Digestion
Ce, Cerium (ppm) 48.2 5.5 44.3 52.1 Aqua Regia Digestion
Co, Cobalt (ppm) 3.36 0.41 3.08 3.65 Aqua Regia Digestion
Cr, Chromium (ppm) 33.9 1.45 32.3 35.5 Aqua Regia Digestion
Cs, Caesium (ppm) 2.09 0.23 1.91 2.27 Aqua Regia Digestion
Cu, Copper (ppm) 73 2.9 70 76 Aqua Regia Digestion
Eu, Europium (ppm) 0.60 0.059 0.51 0.69 Aqua Regia Digestion
Fe, Iron (wt.%) 2.29 0.094 2.21 2.36 Aqua Regia Digestion
Ga, Gallium (ppm) 2.89 0.253 2.67 3.12 Aqua Regia Digestion
Hf, Hafnium (ppm) 0.37 0.031 0.34 0.40 Aqua Regia Digestion
Hg, Mercury (ppm) 0.10 0.03 0.07 0.13 Aqua Regia Digestion
Ho, Holmium (ppm) 0.27 0.022 0.24 0.30 Aqua Regia Digestion
K, Potassium (wt.%) 0.238 0.022 0.221 0.256 Aqua Regia Digestion
La, Lanthanum (ppm) 23.2 3.2 21.1 25.3 Aqua Regia Digestion
Li, Lithium (ppm) 8.03 0.533 7.45 8.61 Aqua Regia Digestion
Mg, Magnesium (wt.%) 0.182 0.014 0.169 0.195 Aqua Regia Digestion
Mn, Manganese (wt.%) 0.013 0.001 0.013 0.014 Aqua Regia Digestion
Mo, Molybdenum (ppm) 2.15 0.132 2.03 2.28 Aqua Regia Digestion
Na, Sodium (wt.%) 0.019 0.002 0.018 0.021 Aqua Regia Digestion
Nb, Niobium (ppm) 0.13 0.02 0.11 0.15 Aqua Regia Digestion
Ni, Nickel (ppm) 37.9 1.43 36.4 39.4 Aqua Regia Digestion
P, Phosphorus (wt.%) 0.023 0.002 0.022 0.024 Aqua Regia Digestion
Pb, Lead (ppm) 12.9 1.24 12.0 13.9 Aqua Regia Digestion
Pr, Praseodymium (ppm) 6.43 1.51 4.36 8.51 Aqua Regia Digestion
Rb, Rubidium (ppm) 20.9 1.30 19.6 22.3 Aqua Regia Digestion
Re, Rhenium (ppm) < 0.001 IND IND IND Aqua Regia Digestion
S, Sulphur (wt.%) 0.027 0.005 0.023 0.031 Aqua Regia Digestion
Sb, Antimony (ppm) 7.35 1.27 6.67 8.03 Aqua Regia Digestion
Sc, Scandium (ppm) 2.33 0.172 2.16 2.49 Aqua Regia Digestion
Se, Selenium (ppm) 0.45 0.09 0.29 0.61 Aqua Regia Digestion
Sn, Tin (ppm) 1.69 0.117 1.56 1.83 Aqua Regia Digestion
Sr, Strontium (ppm) 17.3 3.3 15.2 19.4 Aqua Regia Digestion
Ta, Tantalum (ppm) < 0.010 IND IND IND Aqua Regia Digestion
Tb, Terbium (ppm) 0.37 0.07 0.28 0.47 Aqua Regia Digestion
Te, Tellurium (ppm) 0.22 0.020 0.20 0.25 Aqua Regia Digestion
Th, Thorium (ppm) 10.7 0.95 10.1 11.3 Aqua Regia Digestion
Ti, Titanium (wt.%) 0.015 0.004 0.013 0.017 Aqua Regia Digestion
Tl, Thallium (ppm) 0.43 0.034 0.40 0.46 Aqua Regia Digestion
U, Uranium (ppm) 1.31 0.094 1.23 1.38 Aqua Regia Digestion
V, Vanadium (ppm) 22.0 1.11 20.8 23.2 Aqua Regia Digestion
W, Tungsten (ppm) 14.8 1.41 13.2 16.3 Aqua Regia Digestion
Y, Yttrium (ppm) 6.20 0.378 5.79 6.61 Aqua Regia Digestion
Zn, Zinc (ppm) 30.0 2.74 27.9 32.0 Aqua Regia Digestion
Zr, Zirconium (ppm) 15.7 1.03 14.8 16.6 Aqua Regia Digestion
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